ge - Forgotten Books

H isto r ic , a rch ived do cume n t

0 not assume content reflects curre

ntific knowledge , po l ic ies ,o r p racti

o n Q A

scl en t l fic

“a

(an aster i sk

dman . £950.

36-38,

‘

by V ictor

Saun der s ~ 1 968 k30

‘

p .

I

0 II

fi t Q A

1 969. 1 93 p .

1 08 p

xby Ka

l

i lW . K enyon;l éég

T H E SEA O T T ER

IN T H E

EA ST ERN PACIFIC OCEAN

By K a r l W. K enyon ,Wi l dl ife Bi o l og i st

Di v i si o n o fWi l d l i fe Research

BUREAU OF SPORT FISHERIES WILDLIFE

NUMBER 68

UNITED STATES

DEPARTMENT OF T H E INTERIOR

Wa l ter J . H i ckel , S ecr etar y

Lesl i e L. Gl asgow, Assi stan t S ecr etary for

Fish and Wi l d l i fe, Par ks, and Mari n e Resour ces

FISH AND WILDLIFE SERVICE

Charles H . Meacham, Commi ssi on er

BUREAU OF SPORT FISH ERIES AND WILDLIFE

John S . Gott schalk, Di r ector

Nor th American Fauna, Number 68Publ i shed by

Bur eau of S p or t Fisher i es an d Wi l dl i fe

August 1 969

U.S . GOVERNMENT PRINT ING OFFICEWASH INGT ON 1 969

For sale by the Super in ten den t of Documen ts, U.S . Gover nmen t Pr in t in gOffice Washin gton , D C. 20402 Pr ice

PREFACE

This report is the result of studies conducted from 1 955 to 1 967

by the D ivision of Wi ldl ife Research of the Bureau of Spo rt F isheries and Wildl ife . In addition to field data gathered primarily inthe Aleutian Islands , many unpublished repor ts , letters, and memor an dums in U.S . F ish and Wi ldl ife Service files were used . As abiologist working on studies of the Pribilof Islands population of

northern fur seals from 1 947 to 1 955, I developed an interest inthe sea otters of the Aleutian Islands . I was therefore p leased to

be assigned as project leader of sea otter studies.

Many people contributed help in the field and laboratory. The

fo l lowing undertook special studies and have kindly permi tted meto include their resu lts . Dr . D . G. Chapman ( statistical studies of

phases of pop u lat ion dynamics ) Dr . F . H . Fay (parasitism ) MissNeva K ar r ick (nutrit ional values of foods ) ;Dr . J . K . Ling ( skin

str ucture ) ;Dr . R. L. Rausch (par asitism) Dr . E . C . Roosen-Runge

(rep roduction in the male ) ;Dr . R. P . Scapino ( jaw muscles andjoints ) Dr . V. B . Scheffer (pelage and dentition ) and Dr . D . B .

Scott (dental attrition ) .

J . E . Burdick col lected specimens and analyzed stomach contents .

It wou ld be impossible to l ist all those who assisted in other ways ,but the following have been notably helpful:J. J . Al les , G . Baines ,A . W . F. Banfiel d , V . D . Berns, A . Bezezekofi

'

, F. Bezezekofi’

, K . L .

Binkley, E . L. Boeker , R. A . Boo l oot i an , J . W . Brooks, C . A . B-ros

seau , D . V . Brown , J . J . Burns , J . G. Carlisle , C . E . Carlson , C . H .

Conaway, I . MeT . Cowan, K . W. Cox , L. W . Croxt on , S . V . Dor ofeev

(deceased ) , Y. E . Dawson (deceased ) , M . A . Edwards, C . H . F iscus ,R . M . Gilmore, I . Go l odofi

‘

, C . J . Gui guet , E . Gunther, W . J . Hami l

ton, Jr . , G . D . Hanna, S . J . H arbo , A . C . Har tt, L . G . Her tlein ,

C . L . Hubbs , A . Jensen , A . M . Johnson , E . J . Johnson , M . L .

Johnson , R. D . Jones , Jr . , M . C . Keyes , J . G . King, C . M . Kirk

patrick , D . R. Klein , E . G . K l i n khar t , H . R. K r ear , W . S . Laughl in ,

D . L . Leedy, C . J . Len si nk , P . T . Macy, E . G . Magee , L . Margol is ,V . F . Mart in , P . A . McLaugh l i n , E . D . Mitchel l , H . W . Mossman ,

K . A . Nei l an d, U. C . Nelson , I . M . Newel l , T . P . O’

Br ien ( deceased ) ,R . T . Orr , R. L. Peterson , R. G . Frasil , J . Radovich , J . Rankin ,

C . A . Repenning, F . Richardson , A . Y . Rop pe l , L . V . Sagen , E .

Sczuck , A . H . Seymour , A . A . S inha, A . G . Smith , T . A . Smith ,

IV PREFACE

D . L. Spencer, R . Thomas, J . S . Vania, F . Vincenzi, A . D . Welander,N . J . Wi l imovsky, L . Wi ll iams, V. L. Yadon , C . E . Yunker, andM . Zhan .

The cooperation of Game Biologists of the A laska Departmentof F ish and Game was of particular value . Reproductive tracts ,stomachs, other specimens, and information contributed by themfurnished much of the material upon which this report is based .

The Woodland Park Zoo, Seattle , and the Point Defiance Aquarium, Tacoma, generously furnished facilities and care for captive

otters and routinely recorded certain observations on behavior,molt, and food consumption .

The help of Mrs . Ethel I . T odd, . n ot only in typing the manu

script but in assisting in many other phases of its preparation ,was indispensable .

A ll or a substantial part of the manuscript was read and editorialassistance was given by P . A . DuMon t , C . Larson, R. H . Manville,D . W . Rice, V . B . Schefi

'

er , K . Schneider, D . W . S later, and F .

Wi lke .

Weights and linear measurements of animals were taken ineither the metric or the English systems . The orig inal measure

ment is shown first, fo l lowed by the conversion in parentheses .Nautical charts show distances in nautical miles ( 1 naut ical

mi le equals statute or land mi le ) . In the present report,“mi les”means nautical mi les unless otherW 1 se specified . Depthsare usually given in fathoms ( 1 fathom equals 6 feet) because oftheir use on nautical charts . Depths are given in meters when

depth bears no particular relation to nautical charts . Maps are

adaptations from U. S . Coast and Geodetic Survey charts .

Trade names referred to in this publication do not imply en

dor semen t of commercial products .

Much work on the biology of the sea otter remains to be done .

Many of the studies included in this report are prel iminary ap

p r oaches to subj ects that will require years of future study .

CONTENTS

r efacen t r oduct ion

Systemat icsPhysica l char acter ist icsIden t ificat ion of the r iver ot ter an d the sea otter

Pelage an d

Feedin g mechan ismsAg e determin at ionT he sen ses

Habita t r equir emen tsGen er a l behaviorDa ily cycle of act ivityLocomot ion . .

S leep in g

Han dedn essTool-usin gDefen se an d escapeMater n a l an d fi lia l behaviorRelat ion to other an ima ls

Food an d feedin g behavior

What food i s eaten

Wher e food i s eaten

Stomach an alysesFeca l an a lysesFood quan t it ies r equir edRelat ive va lues of sea otter foodsDeplet ion of food r esour cesUnusua l food itemsCon clusion s

D ist r ibut ion an d number sOr ig in a lModer nSummar yHome r an geTer r itor ia lity

Repr oduct ionSex r at ioSegr egation of sexes

Br eedin g behaviorRepr oduct ion i n the femaleRepr oducti on in the male

c c c c c c c c c

VI CONTENTS

Limit in g factor sNatur a l mor ta l ityPr edat ionEn vi r onmen ta l pollut ionPoachin gSummar y

In capt ivityCaptur eEn vir onmen ta l n eeds of capt ivesFood an d feedin g of capt ivesDa ily cycle of act ivityCauses of death i n capt ivityDrug useTr an spor tat ion of capt ivesTr an splan t attempts

Man agemen t

Refer en cesAppen dix 1— Field studies of sea otter s, 1 954-66

Appen dix2 - Tabular summar y of sea ot ter s

studied fr om 1 955 thr ough 1 965

ILLUSTRATIONS

F IGURE1 . Pelage appear an ce shor t ly after a sea ot ter

emer ged fr om the water an d shook h imself2. Fr on t feet of the sea otter

3 . T he exter n a l ea r of the sea otter r esembles theea r of an ota r i i d sea l

4. Dor sa l an d ven tr a l views of a n ewlybor n fema le sea otter

Adult ma le r iver otter

6 . A sma l l adult fema le sea otter

7. E ight sea otter s asleep i n a kelp bed at

Amch itka Islan d8. Plan ta r sur face of the left hin d foot of an adult

ma le sea otter

9 . T he ske leton of an adult fema le sea otter to

show the gen er a l locat ion an d shape of th e bon es1 0. T he baculum of an adult male sea otter

1 1 . Adult ma le sea otter

1 2. Adult fema le sea ot ter eat in g the head of a lar gecodfish

1 3. At bir th the claws a r e wh ite an d cur ved1 4. Ha ir fr om the mid-back of adult ma le sea otter

1 5 . Plast ic impr ession of pelage shear ed n ear skinsur face fr om mi dback of adult ma le sea otter

1 6 . Hor izon ta l sect ion thr ough skin n ear sur face,midback , adult ma le sea otter

1 7. Shear ed sur face showi n g skin an d distr ibut ion of

por es fr om which ha ir bun dles emer ge

S"

CONTENTS VI I

Cr oss sect ion of pelage n ea r m idback ,

adult ma le sea ot ter

Hor izon ta l sect ion thr ough the sea otter skin showin gdeeper layer

T he shed pelage of an adult ma le ot ter was co llectedfr om the dr a in of h i s poo l at 7-day in ter va lsFr esh youn g adult den t it ion i n the late juven ile or

ear ly subadult stage of developmen t

Den t it ion of n ewly bor n ma le sea otter

Complete juven ile den t it ion of a fema leag e 2 to 3 mon thsDen t it ion at bir th“Ol d”adult den t it ion

In termediate juven i le-adult den t it ionDen ta l att r it ion an d bon e damage i n the adultsea otter

Cr oss sect ion of r ight upper can in e tooth of anadult fema le sea otter

Favor ed sea otter habita t i n the A leutian Islan dsTh r ee adult ma les i n typica l swimmin g att itudeDur at ion of 87 timed food dives made by a matedpa ir of otter s

Because the fifth digi ts of the h in d flipper sar e lon g, the sea otter wa lks with a somewhatclumsy r ollin g ga itAdult sea otter s, sta r t led on a favor itehaulin g-out beach at Amchitka Islan d

Otter s usua lly attempt to fin d a she lter edkelp bed befor e sleep in gA dr owsy otter pr een s i ts cheeks with i tsfor epaws befor e go in g to sleepWh ile dozin g on the sur face of her pool , a capti vefema le sea otter lan guidly gr ooms the fur of her

chest an d sidesT he sea ot te r cur ls i ts lon g flexible body in to

a ball an d r eaches between the h in d flipper s tog r oom the tail an d lower backUsin g i ts left p aw, a gr oomin g sea otter pulls theloose skin fr om i ts r ight side over the r ightfor eleg in or der to pr ess water fr om the pelagean d lick away the moistur eWh ile gr oomin g, water i s squeezed fr om the fur

of the for eleg un der pr essur e an d by rubbin gwith the pa lm of the p aw

Wh ile dr yin g i ts pelage , a fold of skin i s pr essedbetween the pa lms of the for epawsA mother otter rubs the t0p of her head with on e

p aw an d her elbow with the otherNear the en d of a gr oomin g per iod the sea ot te r

r ests belly down a t the sur face, ben ds the hea dto the be lly, an d vigor ously blows a i r in to the fur

VII I CONTENTS

Dur in g the gr oomin g per iod, befor e haulin g out ,

the sea otter may beat the water to a fr oth withthe fr on t legsAfter haulin g out , the otter usua lly r ests on i ts

back while gr oomin g an d dr yin g i tsfur befor e sleep in gA capt ive adult ma le sea otter fr om Amch itkaIslan d poun ds a clam, held between hi s for epaws,aga in st a r ock r est in g on h i s chestA capt ive otter poun ded her r in g aga in stthe cemen t edge of her p ool

A juven ile sea otter , cor n er ed on an Amch itkabeach, pr epar es to r ear backwar ds

In the defen sive posit ion a sea otter

l ies on i ts backWh en closely appr oached a cor n er ed sea otter

hisses, exten ds i ts st iffen ed for e legs, an dr ear s back as f ar as possibleAfter a feedin g per iod an d befor e takin g her 3to 4-week-o l d pup ashor e, the mother sea otter

scr ubs an d gr ooms her fur with her for epawsA capt ive mother sea otter leads her 3 to

4-week-o l d pup fr om the water

T he mother i s solicitous of her youn g f or a lon g per iodT he mother sea otter car r ies her pup high on herchest , clasped by both fr on t pawsThis mother sea otter an d her la r ge juven ilewer e sur pr i sed on lan d

Af ter dr agg in g her pup on to a r ock , a mother sea

otter pr een s an d dr ies her fur wh ile she suppor tsthe head of her nur sin g pup with a h in d flipperA pup , pr obably about 2 mon ths o l d, swims

beside i ts mother

T he mother sea otter has just emer ged fr om a

feedin g diveAn immatur e Glaucous-win ged Gull wa its expectan t lyf or fish scr aps discar ded by a feedin g sea otter

A capti ve sea otte r poun ds a clamon the cemen t edge of her poo lClams wer e br oken open by poun din g on e

aga in st an other held on the chestA Wild otter accepts a fish head fr omInn oken ty Go l odoffA capt ive adult fema le sea otter clasps on e p ieceof fish to her chest un der her left for eleg whileshe r eaches with her teeth to g r asp an other

At fr equen t in ter va ls the sea otter stops eat in gan d r olls about i ts lon gitudin a l axis thr ough 360°

Food taken fr om a sea otter stomachIn tact sea otter food or gan isms and par t ia llydigested fr agmen ts of the same speciesr emoved fr om stomachs

CONTENTS IX

Con ten ts of a lar ge sea otter feca l depositD istr ibut ion of the sea otter i n 1 741 an d 1 965,

a lso showin g the locat ion s wher e r emn an t

colon ies sur vived i n 1 9 1 1

Begin n in g i n 1 957, aer ia l sur veys of sea otter

habita t wer e un der takenA gr oup of 1 57 sea otter s r est in g i n a kelp bed inK ag a l ask a St r a itPar t of a gr oup of 440 sea otter s i n Kujul i k BayT he sea otter was extermin ated fr om the NearIslan ds dur in g the late 1 800’s or ear ly 1 900’s

T he Rat Islan ds gr oup , except Bul di r Islan d ,wher e 1 5 otter s wer e r ecor dedChan ges i n populat ion den sity on the n or th an dsouth coasts of Amchitka Islan d, 1 936-59Est ima ted cur ve of the Amch itka sea ot ter

populat ion 1 909—65

T he De l a r of Islan ds of the wester n An dr ean of

Islan ds wer e appar en t ly amon g the f ew A leut iana r eas wher e sea otter r ema in ed i n 1 9 1 1

T he Adak—Gr eat S i tk i n Islan d ar eas i n the cen t r a lAndr ean of s wer e r epopulated dur in g the 1 950’san d ear ly 1 960’s

T he colon ies on the souther n exposur es of Atka an d

Amlia Islan ds, i n the easter n An dr ean of Islan ds,appear to be augmen ted fr om the lar ge populat ioni n the cen tr a l An dr ean of sPopulat ion s of sea otter s at sever a l Aleut ian Islan dshave in cr eased to maximum size an d then cr ashedbetween 1 936 an d 1 965

T he colon y at Sama l g a Islan d an d i n the vicin ity of

Cape Sagak, Umn ak Islan d, i s a sma ll butperman en t on e

Th e San ak—Caton Islan ds an d San dman Reefs ar eas

wer e last sur veyed on 8 Apr i l 1 962This gr oup of 1 28 otter s slept on the open sea about2 miles off the n or th coast of Un imak Islan dJohn Nevzor ofl' holds an adult female sea otter

T he southeaster n en d of Amchitka Islan d showin gthe most favo r ed ma le an d female haul in g gr oun dsA gr oup of 39 otte r s sleepin g at S t . Makar ius Po in tEast , Amch itka Islan dRifle Ran ge Poin t , a fema le haul in g gr oun dAdult ma les sea r ch in g f or est r ous fema les i n ar ea s

habitua lly fr equen ted by feedin g fema les oftenswim be lly downA pa ir of sea otter s r est an d gr oombeside each other shor t ly after mat in g

An adult ma le an d fema le slept beside each otheron a t ida l r ock

XII CONTENTS

Volume an d classificat ion of food foun d i n 309 sea

otter stomachs fr om Amch itka Islan d, AlaskaS ea otter stomachs examin edFr equen cy of occur en ce of food species i n 309 sea otter

stomachs fr om Amchitka Islan d, A laskaStomach con ten ts of two ma le sea ot ter s fr omS imeon of Islan d, Shumag in Islan ds, A laskaStomach con ten ts of thr ee sea otter s taken i n 1 5—20fathoms of water i n the Ber in g S eaAn a lysis of 422 feca l samp les fr om AmchitkaIslan d Februa r y to Apr i l 1 959An a lysis of 75 feca l samples fr om the Shumag in Islan dsPr oximate an a lysis of impor tan t sea otter foodspecies (aver ages )Summar y of sea otter s obser ved an d est imated i n AlaskaSummar y of aer ia l sur veys of sea otter s, 1 957—65

Rat Islan ds gr oup , sea otter populat ion den sity,est imated fr om aer ia l sur vey coun ts, 1 9 May1 959 an d 2—3 May 1 965

Rat Islan d sea otter populat ion den sity i n 30 squar emiles of feedin g hab itatAmch itka Islan d sea otter populat ion den sity i n 1 1 0squar e miles of feedin g habitat

De l ar of Islan d sea otter populat ion den sity estimatedfr om aer ia l sur vey coun ts of 26 May

1 959 an d 2—3 May 1 965An dr ean of Islan ds coun ts an d est imate of sea otter s

obta in ed on thr ee aer ia l sur veys to show movemen t

of otter s

T an ag a Islan d sea otte r populat ion den sity i n 83squar e miles of feedin g hab itat

K an aga Islan d sea otter populat ion den sity i n 95squar e miles of feedin g habitatAdak Islan d sea otter populat ion den sity i n 75squar e miles of feedin g habitat

K ag a l aska Islan d sea ot ter populat ion den sity i n1 5 squar e miles of feedin g hab ita tNumber s of sea ot ter s obser ved an d est imatedpopula t ion in the Fox Islan ds gr oupNumber s of sea otter s obser ved an d est imatedpopulat ion in the San ak Islan ds an d San dman

Reefs ar eas

Number s of sea otter s obser ved an d est imatedpopulat ion in the Shumag i n Islan dsNumber s of sea ot ter s obser ved an d est imatedpopulat ion a lon g the A laska Pen in sulaNumber s of sea otter s obser ved an d est imatedpopulat ion in the K od iak Islan dsNumber s of sea otter s obser ved an d estimatedpopulat ion i n the K en a i Pen in sula , Pr in ceWill iam Soun d, an d K ayak Islan d ar eas

CONTENTS XIII

Est imated wor ld populat ion of sea otter s

Chan ges i n sea otter populat ion den sity i n s ix ar eas

Pr esen t an d pr ojected sea ot ter populat ion s i ncer ta in Alaska ar eas

Sea otter s tagged a t Amch itka Islan d , A laskaRecover ies of tagged sea otter s at Amch itka Islan dPr en ata l sex r a t io at Amchitka Islan dSexr at io of sea otter s killed at Amch itka Islan ddur in g exper imen tal har vests

S exan d ag e of sea otter s taken i n seven ar eas

fr equen ted most ly by fema les at Amch itka Islan dS exan d ag e of sea otter s taken i n thr ee a r eas

fr equen ted most ly by ma les at Amchitka Islan dAct ivit ies of a mated pa ir of sea otter s dur in gobser vat ion s on 1 9 , 20, an d 21 August 1 955Adult fema le sea ot ter r epr oduct ive tr acts fr omAmchitka Islan dPhases of r epr oduct ion i n the fema le sea otter as

shown by status of ovar ies an d size of con ceptusFr equen cy of pr imipar ous an d mult ipar ous sea otter s

Ute r in e hor n of pr eg nan cyWeight dist r ibut ion of embr yon ic an d feta l sea otter s

Repr oduct ive status of adult n on pr egn an t sea otter s

Sea otter s coun ted a lon g km . of shor elin eK i r i l of a r ea , a t Amchitka Islan d , A laskaPer cen t of fetuses i n each weight classFr equen cy of un implan ted an d implan tedpr egnan cy, by season

Mor ta lity of sea otter s, by ag e an d sex, at

Amch itka Islan d , Alaska , 1 956—63

Ag e an d sexof otter s foun d fr eshly dead onAmchitka beachesAbn o rma l con dit ion s foun d in sea ot ter s that diedon beaches of Amch itka Islan d, A laskaSumma r y of obser vat ion s fr om 83 sea ot ter s foun ddead at Amchitka Islan d , Alaska , 1 959

S ea otter mor ta lity i n r elat ion to populat ion coun ts

an d ava ilab le habita t , easter n ha lf of Amch itkaFoods offer ed to capt ive sea otter s

Food con sumpt ion of a 39- l b . kg . ) sea otter

( Susie ) at the Sea tt le ZooAct ivity of a capt ive sea otter i n daylight hour s,summer ( 1 957 ) an d wi n ter ( 1 960)Con dit ion s dur in g sea otter obser vat ion s a t the

Seatt le ZooCompa r i son of da ily act iviti es of wi ld an d capt ivefemale sea otter s i n summer

https://www.forgottenbooks.com/join

2 NORTH AMERICAN FAUNA 68

On my first brief visit to Amchitka in the late fall of 1 947,Dr . V . B . S chefl

’er and I found dead otters on the beaches . E lmer

Hansen , who was stationed there, found and sent us additional

specimens . These were mailed wrapped, without preservative,inside weather balloons and, as the assistant who cleaned the

bones , I had a strong and unforgettable introduction to the

sea otter .

In the 1 949—53 period, R. D . Jones, Aleutian National Wi ldlifeRefuge Manager, observed winter

“die-offs”at Amchitka . In1 950—5 1 he led an expedition there to capture and transplant

otters to other areas . Al l captive otters soon died, and it becameevident to h im that the sea otter adapted poorly to captivity under

field conditions . This experience demonstrated that until further

knowledge of the animals ’ biological needs was gained,transplant

ing attempts wou ld be futile .

As a first step toward a better understanding of sea otterbiology, Dr . Robert L . Rausch went to Amchitka to study strandedanimals, dead or dying, and Dr s . C . M . Kirkpatrick and D . E .

S tul l ken , wi th the aid of R. D . Jones, F . Wilke , C . J . Len si nk , and

D . Hooper went there in the winter of 1 954 to study sea otter

physiology and the responses of otters to captive conditions . Much

useful knowledge was gained through these studies, but fai lure ofa further effort to transplant otters from Amchitka to the PribilofIslands in March and Apri l of 1 955 showed that st i ll more knowledge was necessary .

It was now clear that the species was no longer endangered .

Anticipating a public request that the resource be utilized, thesecond or long-term study phase of management was begun bythe U.S . Fish and Wild l ife Service in 1 954 and 1 955 . An annotatedaccount of field studies is in appendix I . Early in this period itbecame apparent that several island populations were at or nearmaximum size and that experimental harvests cou ld be made .

When A laska became a State in 1 959, the statehood act providedthat jurisdiction over the exploitation of game and fur-bearingmammals, including the sea otter, should pass to the State .

1 Soon

State officials decided to harvest sea otter pelts . The third phase

of management began at Amchitka in the W inter of 1 962 whenan experimental harvest was taken by Alaska Department ofGame and U.S . Fish and Wildlife Service biologists . Subsequent

harvests were taken by State biologists at Amchitka in 1 963 and

1 Feder a l r eg ula tion s g over n the explo ita tion of these a n ima ls on Na tion a l Wil dl ife Ref ug elan ds but n ot i n S tate wa ter s adjacen t to them . T hus, the sea otter i s un der Feder a l jur isdictionwhen it comes on shor e on a N a tion al Wildl ife Refug e an d when it g oes to sea beyon d ter r itor i a l boun dar ies.

THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 3

1 967, and at Adak in 1 967 . One thousand pelts were avai l able forthe first publ ic auction ( since 1 9 1 1 ) on 30 January 1 968, at

Seattle, Wash .

The harvesting of otters served the dual purpose of furnishing

a financial return to the publ ic and making specimens availablefor bio logical research . Many of the facts thus obtained are pre

sented in this report.

Biologists of the State of Alaska, particu larly K . Schneider,under the direction of J . Vania ar e progressing in management

studies, especially in transplanting otters from areas of abundanceto vacant parts of their former range . Concurrently, bio logistsof the State of Cal ifornia are studying the population there . Inthe Soviet Union , long continued sea otter studies , principally in

the Commander and Kuri l Islands , have added much to our knowledge. A comprehensive review of publ ished information on thesea otter is given by Harris

Wise conservation pract ices based on biological knowledge willassure not only that the sea otter wil l once again be an article ofcommerce, but also that this interesting member of our wildlife

community will flourish as an esthetical ly and scientifical ly valuable part of our environmental heritage .

SYSTEMATICS

Evo l ut i on

It has been supposed that the sea otter derived from an Atlantic

Ocean early Pleistocene ancestor Lutr a r eevei (Newton ) (T hen ius

and Hofer, 1 960, p . Recent findings in Cal ifornia of sea otterremains from the early and late Pleistocene demonstrate that this

supposition is incorrect . M itchel l ( 1 966 , p . 1 908 ) studied all avail

able paleontological material . In his exhaustive review of the

fossils and literature he stated

Because these o lder Nor th Pacific fossi ls a r e con sider ed to be con speci fic withthe livin g sea otter , i t i s obvious that the Lutr a r eevei tooth can n ot r epr esen ta dir ect an cestor of E

’. lu tr i s. T he sea otter may pr obably be con

si der ed as a st r ict Nor th Pacific en demic autochthon , just as McLar en ( 1 960)has assumed i t to be .

Taylor ( 1 9 1 4) studied the osteology and aquatic adaptations of

the sea otter and the river otter and concluded that the two otters

are fundamental ly alike and probably descended from a common

ancestral form. Because the fossile record is incomplete, it ispossible only to specu late where the sea otter originated . Dr .

Charles A . Repenning suggests ( letter, 3 March 1 965 )

I would guess that En hydr a deve loped fr om the otter s of the Pliocen e of

In dia an d easter n Asia an d moved n or thwa r d a lon g the wester n shor e of the

Nor th Pacific with the accen tuat ion of globa l cl imat ic zon a lity. All of the

otter s of Nor th Amer ica ( in cludin g En hydr i odon ) seem t o be der ived fr omAsiat ic stock an d seem to have a r r ived i n Nor th Amer ica i n the Pliocen e an d

ea r ly Pleistocen e .

T axon omy

The sea otter is the only member of the genus En hydr a . It is

the largest (to 1 00 lb . [45 member of the family Mustel idae,which includes nearly 70 species— river otters, skunks , weasels,and badgers , among others . Unl ike other mustelids , it has no funct i on a l anal scent glands . The sea otter is the most specialized of

the group , being adapted to a narrow ecological zone in the marine

environment . Besides being the smallest marine mammal , it isthe only one in the order Carn ivora . Among mammals it sharesthe marine environment with , the pinnipeds (seals ) , cetaceans

(whales and porpoises ) , and sirenians (manatees and dugongs ) .

M iller and Kellogg ( 1 955 ) and Hal l and Kel son ( 1 959 ) recognizea norther n race , En hydr a lutr i s lutr i s Linn . , formerly ranging

THE SEA OTT ER IN THE EASTERN PACIFIC OCEAN 5

from Vancouver Island to the end of the Aleutian Islands chain ,and a southern race, E . l . n er eis Merriam, ranging from the Straitof Juan de Fuca southward, formerly into Baja Cal ifornia, Mexico .

The southern race was described on the bas is of one sku l l .Bar abash-Nikiforov ( 1 947 ) reviewed available data and says “wear e justified in drawing conclusions on the sea otter based on the

slight amount of material we succeeded in collecting.

”He recogn i zed three races:E . l . l a tr i s Linn . , the Commander-AleutianNorth American sea otter”;E . l . g r aci l i s Bechstein,

“The KurilKamchatka sea otter”;and E . l . n er ei s Merriam,

“southern Califormia sea otter .

”

After superficial examinat ion of several hundred sea otterstaken at Amchitka Island ( as mentioned elsewhere ) , and afterobserving the variation in color and body size among animals ofthis local popu lation , I agree with Scheff er and WilkeThey studied specimens from Cal iforn ia and the Aleutian Islandsand reviewed the basis for establishing a racial division . They

concluded that “Neither on the basis of demonstrable variationnor on the grounds of geographical isolat ion is there support for

a southern subspecies of the sea otter .

”

A careful study of specimens from the several geographica l

areas occupied by sea otters is now required before any racial

differences in these popu lat ions can be recognized . Because of the

variation among animals I have seen , the meager specimen ma

teri al used to date in defining races, and the similarity of habitatsoccupied by the sea otter throughout i ts geographic range , it is

not possible, without further study, to distinguish racially distinct

populations which might exist .

PH YSICAL CH ARACTERISTICS

The sea otter’s characteristics include the following:( 1 ) A coat

of sparse guard hair and dense insu lating fur which protects itfrom cold as blubber insulates other marine mammals . A blanketof air remains trapped at all times among the fur fibers of the

sea otter so that the skin is never touched by the water of its chilly

environment (fig. (2) Flattened hind feet or fl ippers for pro

pulsion . (3 ) Retracti le claws on the front feet (fig. 2 ) (but noton the hind feet ) , the only member of its family so adapted . The

forepaws are used to groom the fur, to gather and grasp food, to

break the shel ls of mo l lusks and crustaceans against a rock heldon the chest, and to pas-s food to the mouth . (4) A loose flap or

pouch of skin under each foreleg, extending partially across thechest, is used to ho ld food organisms after they are gathered fromthe bottom until they are consumed while the otter floats on its

back at the surface . In the wild it never voluntarily consumes

food on land . (5 ) Flattened and rounded molar teeth having no

cutting cusps . These are used to crush the shells , external skel e

tons, and flesh of food organisms . (6 ) A horizontally flattened tail

aids propulsion . (7 ) A manner of swimming under water, similarto cetaceans, by means of vertical undulations of the hind flippers

and tail . (8 ) An external ear (fig. 3 ) that resembles the ear of

an otar i id or eared seal more than it does the ear of a land carnivore

or of its closest relative , the river otter .

The body of the sea otter is relatively long and heavy, makingprogress on land clumsy and slow . Although highly adapted tothe marine environment, the sea otter is special ized to occupy thenarrow zone of shallow water near shore . Apparently it cannot(or at least is not known to ) obtain pelagic food where the sea isdeep . It does not undertake seasonal migrations . If removed

from its natural environment, i .e . , water, and kept in a dry pen ,it shows great distress, perhaps because it instinctively senses

that its fur may become soiled and through eventual wettingcause chil l ing and death . Also , in captivity when water is not

available, heat prostration and death may occur unless environ

mental temperatures are carefully controlled .

At birth the sea otter is covered with dense brownish fur andlong silky ye l lowish-tipped guard hair . Th e head is a light buflt

‘


FIGURE 1 .— Pelage appear an ce shor t ly after a sea ott er emer ged fr om the

water an d shook himself. On ly the t ips of the fur a r e wet an d thus st icktogether to form poin ts . Ben eath

,the un der fur i s dr y, in sulat in g the

otter’s skin an d en ablin g i t to ma in ta in i ts body temper atur e . (KWK

59- 8—1 )


FIGURE 2 .— Fr on t feet of the sea otter . In the r elaxed positi on the claws ar e

r etr acted (A an d B ) . T he claws ar e exten ded (C an d D ) dur in g feedin gwhen food i s gr asped an d , with the he lp of the teeth , tor n in to sma ll bitesized chun ks. Much gr oomin g i s don e with the claws r et r acted, but occa

si on a l l y dur in g this act ivity they may be exten ded . Note that the thir d an d

four th digits ar e closely join ed . T he paws ar e highly sen sit ive . When an

otter gr asps a human fin ger between i ts for epaws, the mobile digits can

be felt movin g like fin ger s in side a mitten . (KWK 64—1 —8)


1 0 NORTH AMERICAN FAUNA 68

F IGURE 4.—Dor sa1 ( left ) an d ven tr a l ( r ight ) views of a n ewly bor n fema le

sea otter taken on 6 Apr il 1 949 on Amchitka Islan d;weight g. (4 1b .

6 len gth 560 mm. (22 i n . ) specimen BDM 378. T he lon g, silky,yellowish-t ipped n ata l pelage of the body an d typ ica l l ight bufl’y head an d

n eck ar e demon str ated. T he n ear ly black fur of the feet i s soft an d wooly.(KWK 500 an d 501 )

THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 1 1

For this reason,observers often report the presence of sea otters

when they have actually seen river otters . To help in correctidentification of these two species , the fol lowing comparison ofdiagnostic physical and behavioral characterist ics is presented(see also figs . 5 and 6 )

Fi e l d obser va t i on

S ea O tter

1 . Occur s i n A laska fr om Pr in ce W illiam Soun d , a lon g the A laska Pen in sula ,

i n the A leut ian s, an d n ear Mon ter ey, Ca lif. Is cur r en t ly exten din g i ts r an gean d should be looked f or i n Pacific coasta l ar ea s .

2. Foun d a lon g open -sea coast i n salt water on ly .

3 . On sur face usua lly swims belly up , for epaws on chest wh i le paddlin gwith hin d flipper s. Floats high i n water .

4. Clumsy on lan d , seldom seen on shor e except i n isolated A laskan ar eas.

5 . Eats while float in g on back , n ever eats on shor e .

E

l liS leeps (usua lly ) i n kelp beds or ca lm water whi le float in g on i ts back

g. 7

7 . Bear s sin gle youn g which i s car r ied on the mother ’s chest as she swims

on her back .

River O t ter

1 . Occur s on r iver s an d a lon g seacoasts i n the Un ited States, Can ada , an dAlaska . Often swims sever a l miles i n sa lt wa ter between islan ds.

Foun d i n sa lt or fr esh water .

On sur face usua lly swims belly down , back n ear ly submer ged .

Ag ile an d gr aceful on lan d , often seen on lan d .

B r in gs food ashor e to eat .

Sleeps on lan d , usua lly, i n den s, n ever wh ile float in g on i ts back .May have up to four youn g, does n ot car r y them on chest whi le swimmg .3

TI

F’

SJ‘

P

P

N

Sp ec imen O bse r va t i on

S ea O tter

Maximum weight 1 00 lb .

Maximum len g th i n .

Fur lon g an d soft , guar d ha ir del ica te an d spar se .

Claws of for epaws shor t an d r et r act i le.

Hin d feet decidedly fli p p er l i k e an d webbed to t ips of toes. Pads visib leon ly at t ips of toes (fig. 8 ) T he fifth or outer digit i s lon gest (fig . 96 . Tai l somewhat flatten ed an d does n ot thicken mar kedly at base , less than176 of body len gth .

7. Eyes a r e open at b ir th .

8. Last upper mo lar iform tooth br oad an d flat ten ed , about 94 in ch or mor e

i n gr eatest width .

9 . Baculum of adult about 6 in ches i n len gth (fig.

Ri ver O t ter

P‘

F

SR

N!‘

Maximum weight 30 lb .

Maximum len gth 50 i n .

Guar d hair coar se an d den se, cover in g fur completely .

For ec l aws lon g an d n ot r et r act ile .

Hin d feet webbed but n ot fli p p er l ike. Pads cover much of pa lm an d digits.

T he fifth digit i s n ot elon ga ted .

6 . Ta i l n ear ly r oun d i n cr oss sect ion an d heavily thicken ed at base, mor ethan 96 of body len gth .


F IGURE 5 Adult ma le r iver otter . When compar ed with the sea otter , the

r iver otter’s ta il i s lon g, heavy at i ts base, an d taper ed . T he hin d feet ,

a lthough webbed,a r e r elat ively sma ll , an d the body i s less elon gate than

that of the sea otter . ( Specimen VES 1 322, len gth 1 22 cm . [48 weightlb . taken 8 December 1 945 n ea r For ks, Wash . ) (VES

1 940)

THE SEA OTT ER IN TH E EASTERN PACIFIC OCEAN 1 3

FIGURE sma l l adult fema le sea otter . White dots ma r k the umbilicusan d mammae . T he r elat ively shor t , flatten ed ta il of n ea r ly un iform widththr oughout i ts len g th , br oadly flatten ed an d webbed hin d feet , an d elon ga tebody a r e obvious char acter ist ics which differ en t iate the sea otter fr om the

r iver otter . ( Specimen KWK 61 —2 [Susie ] , weight i n life 40 lb . [ 1 8. 1

len gth 1 27 cm. [50 Captur ed 4 September 1 955 , Amch itka Islan d , died27 October 1 961 i n Seatt le zoo . ) (KWK 6 1 —42—1 6 )


FIGURE 7 .— E ight sea otter s asleep i n a kelp bed at Amchitka Islan d dur in g

a midday r est per iod . In the for egr oun d a la r ge juven ile r ests i ts head on

i ts mother ’s abdomen . (KWK 55— 1 8—1 8 )

7. Eyes do n ot open un t i l ag e 25-35 days.

8. Last upper molar iform tooth n ot br oadly flatten ed an d gr eatest widthless than l/z in ch .

9 . Baculum of adult about 4 in ches i n len gth .

FIELD RECOGNITION OF T H E SEXES

The sex of a l iving sea otter in the field may be recognized at areasonable distance if p revailing weather condit ions offer good

light and visibil ity . The fact that the sea otter habitually rests

on its back and floats high in the water facilitates recognition of

the sexes . If the sea otter is wet , so that the fur is sl ick , the penialbulge of the male (fig. 1 1 ) and the two abdominal mammae of

the female (fig. 1 2) may be visible with binoculars up to a distance

of about 1 00yards . When the fur is dry and fluff y, these definitivecharacters are less distinct but are visible at close range .

No instance is known of a male otter carrying a pup on i ts chest


F IGURE 8.— Plan tar sur face of the left hin d foot of an adult ma le sea otter .

T he outer (fifth ) dig it i s lon gest , a con dit ion n ot foun d i n other mam

mals. This adaptat ion in cr eases efli ci en cy of pr opulsion by the foot whenthe otter swims on i ts back . Pad developmen t at the t ips of the toes i s

min ima l . T he vest igia l pads n ear the cen ter of the foot ar e n ot visible on

some in divi dua ls. (KWK 62—23—26 )

or abdomen . Thus, all animals carrying young are recognized as

females . Large juveniles, still with their mothers , may approach

an adult male and romp with h im . Thus care is necessary during

observation to differentiate between the mother and a “visit ing”

male .

It was shown that the adult male averages larger than the

female ( see Body Measurement s ) but because of overlap , size

alone is not usefu l in recognit ion of the sexes .

The head and neck are heavier and more muscular in appearance

in the adult male than in the female . If a mated pair is observed ,this difference is apparent. Because of individual variation , how

ever, much observation and field experience is necessary beforethis relatively slight difference becomes a usefu l character in therecognition of sex .

In its behavior, the male sea otter is relatively bold . If a human

approaches a group of males and females hauled out near each


F IGURE 9 .— T he skeleton of an adult fema le sea otter No . KWK 61 —2 ) showsthe gen er a l

locat ion an d shape of the bon es. T he last join t of each di

g i twas r emoved with the sk i n an d i s missin g. T he elon gate fif th digit of theh in d foot i s demon str ated . (VBS 4954)



F IGURE 1 2.— Adult fema le sea otter eat in g the head of a lar ge codfish

(Gadus macr ocep ha l us ) . Note the two abdomin a l mammae an d that thehead an d n eck ar e r elat ive ly of lighter str uctur e when compar ed with thema le. Also, fema les float somewhat higher i n the water than do ma les.

This i s an un usua lly light -color ed an ima l (a lbin ist ic ) , but the ext r emit iesan d eyes wer e n orma lly pigmen ted. (KWK 59—1 3—2)

other, the females usual ly take alarm and depart before themales do .

On several occasions we pursued sea otters in an outboardpowered dory in order to capture them in a dip net. Females

attempted to leave the vicinity bymaking long dives . The relativelyfearless males often tried only to avoid the immediate vicinity ‘

of

the boat . One individual surfaced repeatedly in the same general

area . After about an hour of fruitless pursuit, we abandoned thechase and the otter began diving for food near the place we first

saw h im.

The difference in color between adult males and females wasnot quantitatively determined . In general , females appear quite

black when their fur is dry and fluffy. Males, in general , appearbrownish under the same conditions . Black males and brown ishfemales

,however

,are seen . Both sexes tend to become white

headed with age . Dark-headed individuals, however, were exami n ed which had worn teeth , indicating advanced age . Among a

group of 1 0 captive juveni le otters , the animals having the lightestcolored heads were males . In general , this diff erence tends

‘

to

prevail also in older animals .

Examination of the photographs and this discussion of diag

nostic characteristics, indicate that the sex of many otters may


be recognized in the natural environment. Seldom, however, maythe sex of all adult or subadult otters seen during a period of

observation be positively identified .

During hunting it was demonstrated that recognition of sex inthe field is impractical when obtaining skins is the primaryobjective. Between 3 1 Ju ly and 3 August 1 963 , officials of theAlaska Department of Game shot 20 sea otters of adult size .

Mothers accompanied by pup s were omitted from the kill in the

hope that a high proportion of males would be obtained . Only

one male (5 percent of the kill ) was taken in the “female areas”where this collection was obtained .

Body Measur emen ts

Stul l ken and Kirkpatrick ( 1 955 ) described some of the physical

characteristics of the sea otter and repor ted on physiological

studies of captive otters . My observations are intended to supple

ment theirs .

Body weights and lengths of sea otters captured or found deadon Amchitka beaches, or shot in waters near Amchitka, and ofotters taken in other Alaska areas are discussed in this section .

Because no anatomical feature is known to reveal the exact age

of a sea otter, juveni les and subadu lts ar e omitted and only datafrom newly born and adult animals are presented . Sea otters

were recognized as adu lts by observations of adu lt dentition , sutureclosure and sagittal crest development of the skull , and of thebaculum size in males .

Total length was obtained by meas uring, with a steel tape, each

animal from tip of nose to tip of tail as it lay flat on its back .

Only the total length is considered in the following discussion .

(The mean tail length was found to be percent of the total

length . The range in 1 0 adult males was to percent and

in 1 0 adult females to percent. ) Some animals killed

during the Alaska State harvesting operations could not be measur ed immediately after death . When an animal in rigor mortiswas measured, an attempt was made to stretch i t to full length .

Some of these , however, were probably measured as being sl ightlyshort er than they wou ld have been when relaxed .

The scales most frequently available were spring scales of50 and 1 00- l b . capacity . The data as shown in tables were con

verted to kilograms . Smal l young were usual ly weighed on a1 5-kg . capacity balance .


NEWBORN YOUNGThe data on body size of the youngest sea otters obtained are

reported in table 1 . The umbilical scar was fresh on each indi

vidual l isted and al l showed litt le or no wear of the fetal clawtips (fig. The two smallest, a male weighing lb . kg. )and a female weighing lb . were both dead when

obtained, one from the beach and the other from a mother that

was netted on the beach while carrying her dead pup . Among

the seven largest fetuses (four males and three females ) , collectedat Amchitka in 1 963 , the largest, a male , weighed lb .

kg. ) and measured cm . in length . The mean weight was

lb . kg. ) and the mean length cm . Thus it is

probable that the two smal lest newborn young were stillborn ,being abnormal ly smal l at birth . Al l of the others had receivedat least some nourishment in the form of milk from their mothers

before capture, thus were heavier than when newly born . The

l iving young examined indicate that a healthy newly born sea ottermay weigh as little as 3 lb . But the fetal material studied

( see Reproduction in the Female ) and larger newborn young indicate that larger body size of lb . kg. ) to 5 lb . kg. )and 61 cm. (24 in . ) in total body length is p robably normal .

ADULTS

Analysis of the weights and lengths of 84 adult males and 258adult females that were shot, are given in tables 2 and 3 . Animals

TABLE 1 .—Wei g ht an d l en g th of n ewbor n p up s taken a t Amchi tka Is l an d ,

A l aska

[T he umbil ica l sca r or adher in g fr agmen ts of the umbil ica l cor d wer e fr esh . Al l except the twodea d pups con ta in ed small quan tities of mil k]

Col l ection n umber Weig ht Len g th

Ma l es

32- 56

1 Fr eshl y dea d p up taken fr om the mo ther when she was n etted .

9 Fr eshly dea d p up foun d on beach .

3 Mother an d p up n etted an d r eleased . T he p up was n ot tag g ed because it was obviously n ewbor n (umbil icus stil l a ttached an d fr esh ) .


F IGURE 1 3— At bir th the claws ar e white an d cur ved . Soon after bir th theyoun g otter attempts to gr oom i ts fur , an d the soft t ips ar e lost . (KWK62- 1 6—2 1 )

found dead on beaches (table 4) and those which died in captivity(tables 5 and 6 ) ar e compared and the differences are discussed

below.

Scheffer ( 1 95 1 ) published information on the body size of threeadu lt sea otter specimens which he measur ed . The present data

confirm that the maximum length of the adu lt male sea ott er isabout 1 48 cm. that the adult female is 1 40cm. (55

The adult male may reach a maximum weight of about 1 00 lb . (45

kg. ) and the adu lt female may reach a weight of at least 72 lb.

It is indicated in other sect ions (see Food and Feeding Behavior ,Mortality Factors , and D istribution and Numbers ) that at Am

chi tka Island a dense sea otter population has depleted food

resources . Additional evidence for this is revealed by comparingthe body weights of Amchitka sea otters (table 2 ) with animalsfrom a sparse populat ion (table

NORTH AMERICAN FAUNA 6822

wN.

v

N

mNfi

Nb

.“cw

."3.wfl

aw

m

3“

N.

an

«6

wv

a

vwa

Nb

."o

n

:

ame

maw

v

ma

N.

an

an

N.

mN.

wag

aca

”ma

ma

ma

NN

a

ma

wma

ma

wv

mwNfi

N

S“3:

amm

w.oN

m

3”

wma

ma

QN

mwmN—H«

NA

mma

ma

v

N.

cm

a.

ma

a

wN

mw

o

mma

wua3;

mmN.

mwN

wfiN

wmm

ab

mmwmm

.“rma

Nvfi

w&w

fl

mm

mfiN

wmm

mm

wm

N.

Nina

was

mva

mmN.

N.

mm

a

mm

0

mm

mm

m

33

wNa

ova

we

N.

N

wN

N.

NN

n

ma

«N

a

$2

a

v

N.

mm;

mwa

mva

emN.

N;

mm

N.

NN

wmm

ma

P1 61 0) !

THE SEA OTTER IN T H E EASTERN PACIFIC OCEAN 23

3 .— T ota l l en g th an d body wei g h t of adu l t sea otter s k i l l ed i n a r eas

of sp ar se p op u l a ti on

otter s wer e shot i n 1 960 i n the Shumag i n Islan ds off Un imak Islan d an dA dak Isla n d ( l ) ]

-kilog r ams

beaches a t Amchi tka Is l an d , A l aska

combin ed i n this table:1 956 1 959 1 962 an d 1 963

[We ig ht i n k il ogr ams ]

TABLE 6 .— Wei g h t l oss of seven adu l t fema l e sea o tter s tha t di ed i n cap ti vi ty

[Weig ht i n k i log r ams ]

D—7


Scheffer ( 1 955 ) concluded that a reduction in body size wascorrelated with increasing population or crowding in the northern

fur seal (Ca l l or hi nus ur si nus) . T he data presented below indicatethat adult sea otters from a crowded population weigh less thananimals from a sparse popu lation . The length of adult otters fromsparse populations fell within the lengt h range of otters from the

crowded Amchitka popu lation ( tables 2 and However,an

insufficient number of animals from sparse populations were

available to demonstrate a statistically significant diff erence at theconventional level ofA lthough few adult sea otter specimens (five males and four

females ) are available from areas where sea otter populations aresparse, the differences in body weight between these animals andthe Amchitka collection are noteworthy. Among 79 adu lt malesthat were killed at Amchitka, the mean weight was lb.

and the heaviest weighed 85 lb . Among five that

were killed in sparsely populated areas , however, the mean weight

was lb . kg. ) and the heaviest weighed 99 lb .

The difference between the mean weights of these two samp les is

lb . This indicates that adu lt males in a sparsepopulation may average about 28 percent heavier than those in

crowded populations . The difference is significant at the per

cent level . The mean weight of four females from sparsely p op u

lated areas was about 1 6 percent greater than the mean weight

of 254 Amchitka females . When the animals were collected in

sparsely populated areas , no eff ort was made to select large

individuals .

Th e lesser body weights of the Amchitka animals appear to

confirm conclusions drawn from food habits and mortality studiesthat a large popu lation there has created ecological conditionswhich are below the optimum. B cause the sample of adult otters

from sparsely populated areas is / mal l , a more thorough statisticalevaluation of the apparent differences in mean body weight between crowded and sparse populat ions must be delayed until moredata are gathered .

Most of the sea otters killed at Amchitka were taken duringthe late winter to early spring period of environmental stress when

many of the otters were dying. Thus, it appears appropriate to

compare the animals killed at this season with others taken atAmchitka in the fal l when body condition would be expected tobe optimum. Unfortunately, the only fall ( 1 962) sample of adults

i s smal l, consisting of 3 males and 1 6 females . Comparison of the

mean weights of these animals with those taken in the late winter



than emaciated individuals which die on beaches in a denselypopulated area . Animals in captivity, taken in a densely popu latedarea (Amchitka ) , lost about 25 percent of their body weight atcapture, before death .

M ISCELLAN EOUS MEASUREMENTS

S k i n l en gth an d body l en gth

The skin of the sea otter is loose and stretches considerably

after it i s removed from the animal, as shown by the followingfigures:

S pecimen

Mill imeter s In ches Mil l imeter s In chesQ 40349 7294d‘

67 179

Thus, a skin freshly removed from the animal may easily bestretched 1 44percent and a tanned skin 1 1 6 percent of the animal’sbody leng th . It is concluded that measurements taken from skins

are of l ittle use in establishing body size in the sea otter .

In test i n e l en gth

Length of intestine in four adu lt sea otters is shown in table 7 .

Shortly after death , the intestinal tract was removed, laid on flat

ground, and measured . An effort was made to obtain the relaxedleng th (not the stretched leng th ) . The mean leng th of the small

intestine was times body length (tableIn general

,carnivores have shorter intestines than herbivores

but the variation among strictly car nivorous mammals is great.

TABLE 7.— In testi n e l en g th of adu l t sea otter s

[Len g th i n cen timeter s ]Ra tio , sma ll

Sma l l in testin e toin testin e 2 body l en g th

Mean

1 Fr om stomach to an us .

9 No ca ecum i s pr es en t i n the sea otter . T he small in testin e gr adually expan ds in to the lar g ein testin e. T he appr oxima te len gth o f the la r ge in testin e i s 60 cm . T his amoun t i s subtr actedfr om the tota l in testin e len g th to obta in the appr oxima te len g th of the smal l in testi n e .


Among pinnipeds, which subsist entirely on flesh , the ratio

(small intestine leng th )

nose-tail length

Mi r oun ga (King, The sea otter, which subsists on marine

invertebrates and fish , fal ls within this general range . Apparentlyanimals which feed primari ly on warm-blooded vertebrates haverelatively shorter intestines . The above ratio is 5 for the dog and

cat (King,

ranges from in Mon achas to in

O r ga n we i ghts

The relative sizes of body organs may give a clue to the adap

tat i on s of an organism to i ts environment . I have undertaken no

physiological studies , but the following comparisons of the relativesize of selected body organs of the sea otter with those of other

mammals indicate that such studies wou ld be interesting anddesirable .

Organs were weighed on a balance having a maximum capacity

of 1 5 kg. Sample organ weights were obtained from six adult

male and nine adu lt female sea otters that were shot while ap

p ar en t ly in normal health at Amchitka Island and other areas(table Comparison of the organ weight expressed as percent

of body weight indicates that in some respects the sea otter is quite

TABLE 8 .— Wei g hts of body or g an s i n n i n e adu l t fema l e an d six adu l t ma l e

sea ot ter s

[Weig ht i n g r ams . Al l appa r en tly hea lthy adults shot a t Amch itka Islan d, except 60-4 to 60—8which wer e sho t i n the S humag i n Isla n ds an d o ff Un imak Islan d ]

Heart Kidney Sp leenPercent Percent Percent Percentof body of body or body of body

Weight weight Weight weight Weight weight Weight weight

Mean

Mean . .

Mea n ,


similar to other mamma ls but in other respects it may be unique .

Among mammals in general (but with exceptions ) total bodyweight increases at a greater rate than organ weights . It is pre

sumed in the fo l lowing comparisons that the reader will keep thisgeneralization in mind .

Li ven — To remain healthy the sea ott er must consume aboutone-sixth to one-fourth of i ts body weight in food daily . Ap

p ar en t ly the air blanket in its fur is a less efficient means ofinsulation in its chilly habitat than the blubber of other marinemammals . The need for a relat ively large amount of food i ndi cates an unusual ly high metabolic rate in the sea otter . S l ijp er

( 1 962 ) be l ieves that marine mammals, and particu larly cetaceans,have a high metabol ic rate . S ince the l iver is an important organfor the production and storage of energy-producing substances,it is not surprising that the sea otter’s l iver is relatively verylarge;the mean is about percent of body weight . In this respect

it surpasses fur seals of comparable body size (mean to

percent;Scheffer, porpoises percent) , and dolphinspercent;S l ijp er , and the river otter percent;

Jensen, letter , 30Nov. although the river otter is a smaller

animal .H ear t — T he heart of the sea otter constitutes about

percent of body weight . The ratio is similar to that of fur seals

of comparable size (about percent of body weight;Scheffer,and to dolphins percent;S l ijp er , As Jensen

( 1 964) points out, sea water gives more support than fresh water

and therefore the sea otter may not need as large a heart as the

river otter percent of body weight ) .

K i dn ey — The marine environment may account for a large

diff erence in relative size between the sea otter kidney, mean

percent of body weight, and that of the river otter , percent

of body weight . The sea otter appears to have overcome the physi

ological problem of the marine environment by developing a

lobu late kidney relatively twice as large as that of the river

otter . I have observed sea otters in captivity drinking sea water .

2

A study of the physiology involved has not been undertaken . That

the sea otter obtains l iquids of appreciably less salinity than seawater from food is improbable , since body fluids of invertebrates ,

9 T he ca ptives wer e held for 2 mon ths on dr y beddin g a t Amchitka . Fr equen tly when I hel da p an of sea water befor e them they placed their mouths i n th e wa ter an d sucked an d lappedit up with the ir ton g ues . In the ir eager n ess to dr in k, they a lso placed the ir for epaws i n the

dish an d even tua lly spilled an d splashed so much of the wa ter tha t I did n ot measur e the quantity that was actually dr un k . When given a cho ice of sea o r fr esh water they dr an k e itherun selectively. Except for on e exper imen tal o ff er in g of fr esh wa ter the ca p t ives wer e given on lysea water .


upon which some otters feed almost exclusively, are isotonic, ornear ly so, with sea water (Sverdrup, Johnson, and Flemming,

Fisler ( 1 962 ) demonstrated that even a mouse (Per omyscus

that was adapted before capture to a salt marsh environment, survived when given sea water exclusively .

S l ijp er ( 1 962, p . 3 1 4) considers that the kidneys of cetaceans

(from percent to percent of body weight) are, because

of great body size, exceptional ly large . In general , a large kidney

appears to const itute an important aspect of mammalian adap

tat ion to the marine environment.

S p l een — In the sea otter the spleen is about percent

of total body weight, which is simi lar to percent in most

other mammals” (S l ijp er , 1 962 ,p . In 62 female fur seals

similar in size to the sea otters studied , Scheff er ( 1 960) found

that the spleen was from to percent of body weight .

Thus, in the sea otter and river otter percent, Jensen, 1 964)the spleen is relat ively large .

Although the mean percentages of organ size to body weightof al l sea otters studied were used in the foregoing general discussi on , it appears that in the male , which is larger than thefemale ( see Body Measurements ) the kidney i s relatively larger

than in the female . Also , the spleen of the female is slightly largerthan in the male (table

Body temp e r a tur e

The body temperature of two apparently healthy animals, a

juvenile male ( 59— 1 56 ) and an adult female ( 59 were ob

tai n ed when both had lost consciousness after injections of“Letho l

”(proprietary name for a compound containing N-amyle

thyl-bar bi tuate, sodium sec-butyl ethyl -bar bi tuate, isopropyl alco

hol , and sodium carbonate ) . The deep body temperatures ( intra

cardiac insertion of the thermometer before cardiac activity

ceased ) and rectal temperatures were the same . Th e temperature

of the juvenile male was C . ( 1 00° F . ) and that of the adult

female was C . (99°

Body temperature may drop before death under cert ain con

di t ion s. On 1 April 1 959 , at Amchitka Island , an emaciated adu ltfemale ( 59—98 ) was lying on a bed of grass above the hight ide line , breathing but unconscious . H er intracardiac temperature

was C . (84°E ) . An autopsy revealed extensive enteritis .

During an experimental transplant, observations were made ofa juvenile subjected to unusual stress . The otter , a female about


1'

year old and weighing 22 pounds, was liberated in cold water

(0°

C . ) on 9 April 1 955 . The fur had become saturated with filth

after 8 days in captivity. Within 1 minute after entering the

water the otter uttered loud distress screams and swam toward

our dory. After she was retrieved she was placed on dry straw.

When we returned to the ship , about 20 minutes later, the otter

was unconscious . The rectal temperature was C . (86°

In a warm room, the fur was vigorously rubbed and dried with a

towel and consciousness was restored . At 0700 the fo llowingmorning the rectal temperature was C . (99

° F . ) the animalappeared weak but ate . She was kept in a warm room (about22° to 24° C . or 72° to 75° F . ) and given almost constant attentionuntil she died on 1 5 April . During this period her body temperature

fluctuated erratically each day from 30° to 36 ° C . (86

° to 96°

When her temperature was low, I recorded that she was“almost

in a coma .

”Apparently after chilling, the temperature controlmechanism of this otter was upset.

B l ood quan t i ty

An approx imation of the blood content of sea otters was obtainedfrom five freshly killed animals (table Al l appeared to be innormal health when ki lled . The technique used in each case was

the same:After capture the animal was given a lethal injectionof Lethol . When the animal lost consciousness , it was weighedand measured . The thoracic cavity and heart were opened . The

animal was suspended, by means of lines attached to each leg,over a container into which the blood drained . In all cases the

heart was still beating when the incisions were made . The bloodweight and volume were measured directly.

The percentage of blood weight to body weight of four of the

TABLE 9 .— Bl ood quan ti ty i n sea otter s

[T he we ig ht of bl ood i s m in imal . T he blood was dr a in ed fr om an imal dir ectly in to a con ta in er .

0 co r r e<

it i on was added f or the slight amoun t tha t was sp illed . or for the blood r ema in in g

i n tissues

Adul tJuven il eA ul t

1 Appa r en tly this an ima l was abn orma l . Pa thologica l con dition s such as hydr othor ax an d

hear t fa ilur e occur i n other mamma ls . T he la r g e quan tities of fluids that accompan y these con

d i t ion s may be difli cul t to distin guish fr om blood .


animals (mean percent) fall wi thin the expected range (rabbit,percent;dog, percent;and horse, percent (Dukes,

1 943 ) and walrus,

percent (Fay, 1 958 ) In the fifth animal,the blood constituted nearly one-third of the body weight. This

animal, when captured , was sleeping on the beach and behavedin a normal energetic way. I noted , however, that it appeared“fat”and the abdomen was round and fir m . I suspected then

that it was pregnant, but found later that it was not.

There was no food in the gastrointestinal tract . In addition to

the blood quant ity, the only abnormality found were two cysts(congenital ? 1 .5x1 cm . and 1 .5x1 . 5 cm . ) containing clear , yel lowish fluid, on one kidney. T he gross appearance of blood was

normal . Why this animal retained such a large amount of fluid is

unknown . There was no mistake about the quantity of fluid

(table

Pelage an d Sk in

Preliminary descriptive studies of the pelage, skin , and molthave been made .

PELAGEVictor B . Scheffer (Marine Mammal Biological Laboratory,

U.S . Fish and Wi ldlife Service ) has made a cursory examinationof pelage samples from three sea otters and has kindly offered thefollowi ng notes ( in letter, 1 3 August Unless otherwise

stated, the notes are based on a sample from the mi dback of“Pappy, an adult male

,specimen D22—57 , which died in Seattle

Zoo on 1 6 December and was autopsied on 1 7 December 1 957 .

T he pelage i s an ext r emely fin e wool or fur with the t ips of thin lyscatter ed guar d ha ir s pr ot r udin g fr om i t . It i s light smoky gr ay n ea r the

skin , dar ken in g gr adua lly to smoky br own a t the sur face of the pi le . T he

la r g er g uar d ha i r s a r e dar k;their t ips make a layer about 34 mm . i n . )fr om the skin . T he sma l l er g uar d ha i r s a r e mor e n umer ous than the lar geron es;thei r t ips make a layer about 28 mm . i n . ) fr om the skin . T he

under fur ha i r s ar e by f ar the most numer ous;their t ips make a layerabout 23 mm. ( 1 i n . ) fr om the skin . T he outer sur face of the un der fur layeri s n ot dist in ct;the soft , wavy t ips of the fur ha ir s blen d with the t ips of

the sma ller guar d ha ir s (fig.

T he p e l ag e un i t con sists of :a bun dle of man y un der fur ha ir s an d on e

guar d hair at or n ear the an ter ior side of the bun dle (fig. a sebaceousglan d on r ight an d left sides of the bun dle, join ed at the an te r ior side;acoiled sweat glan d ben eath an d par t ly adjacen t to the follicles of the bun dle;an d other min or st r uctur es . Ther e i s appar en t ly n o ha i r -er ect in g muscle .

T he guar d ha ir s var y widely i n diameter an d len gth , though they fa ll in to


FIGURE 1 4.— Ha ir fr om the mi dback of adult ma le sea otter D22—57. T he outer

sur face of the un der fur layer i s n ot dist in ct;the soft , wavy t ips of the

f ur ha ir s blen d with the t ips of the sma ller guar d ha ir s. (VES 571 0)

two over lappin g gr oups which I ca ll “lar ger an d sma ller , with f ew in termediates . For example, her e a r e the diameter s of 1 0 r oots i n on e field of viewun der the micr oscope:1 4, 1 5, 1 6, 1 8, 20, 25, 26, 33 , 38, an d 64 micr on s (cf .

fig. Cr oss sect ion s of the guar d ha ir r oots ar e ova l to n ear ly r oun d i nout lin e;they var y i n diameter fr om 1 3 to 64micr on s (aver ageIn five bun dles I coun t 60 to 80 (aver age 7 1 ) un der fur r oots p er bun dle.

T he coun ts i n two other specimen s a r e:(KWK 59—1 3 , ol d fema le,9 Febr uar y

1 959 ) 79—1 1 0 (aver age (KWK 59—51 , youn g ma le, 7 Mar ch 1 959 )40—45 (aver age Compr ehen sive studies of pe lage samp les fr om diff er en tseason s an d diff er en t ag e gr oups of otter s wi ll be n ecessar y befor e the ex

ten t of holdover of pelage ha ir s can be eva luated . Cr oss sect ion s of the un derfur r oots a r e r oun dish ova l , smooth , fa ir ly un iform, an d to micr on s(aver age i n diameter (fig.A disc of skin -with-pelage cut by t r eph in e fr om the forma lin -pr eser ved ,

mi d-back specimen measur ed cm”. It con ta in ed 520 bun dles or p er

cm2

(fig’

. [That ther e i s con sider ab le var iabil ity i s demon st r ated by thefin di n g

'

by J . K . Lin g (MS ) of fo llicle bun dles p er em2on a sample of

facia l skin ] On the basis of 71 un der fur ha ir s an d 1 guar d ha ir p er bun dle ,(ha ir s p er em2

72 x 1 400 or p er i n?

) an d an est imateda r ea of cm2 for the tota l ha ir -cover ed sur face of the body, the pelage of

an adult ma le sea otter would con ta in about 800million ha ir s.

Above the sur face of the sk in , the shaft of each la r ger guar d ha ir i s a

typica l awn or shield ha i r , flatten ed in to a blade n ear the t i p . A t a level 1 0



F IGURE 1 6 .— Hor izon ta l sect ion thr ough skin n ear sur face , mi dback , adult

ma le sea otter D22—57, an ter ior at top . T he lar ge guar d ha ir i n each pelageun it may measur e 64micr on s i n diameter . T he fur ha ir s aver age micr on si n diameter . A t this leve l the ha ir s ar e r oun d to slight ly oval in cr oss

sect ion . (VES 571 6 )

ha ir s, r esembles the patter n i n a l l pin n ipeds, especia lly i n the fur sea lsCa l l or hin us an d A r ctocep ha lus. Dead un der fur ha ir s pr obably accumulatefr om on e year to the n ext i n the bun dles of older an ima ls as they do i n

Ca l l or hi nus. T he on ly eviden ce i s that the coun t i n a youn g sea otter i s 43 as

compa r ed to 71 an d 9 1 i n two adults. This “r eluctan t sheddin g,”if actua llya featur e of sea otter pelage, would help to ma in ta in a heat-in sulat in g coat


“W I ‘ W

Q Q's."l

F IGURE 1 7 .— Shea r ed sur face showin g skin an d dist r ibut ion of por es fr om

which ha ir bun dles emer ge, an ter ior at top . Sample i s fr om mi dback , adultma le D22—57 . Magn ificat ion x24. (VES 5721 )

dur in g molt . T he un der fur ha ir s seem to be equa l i n diameter , though twiceas lon g, as those of Ca l l or hi n us ( Scheffer , 1 962 , p . 22 an d On a disc cut

fr om the fr esh skin of an adult fema le fur sea l ther e a r e 939 bun dles an d

about in dividua l ha ir s ( Scheffer , On a disc of the same a r ea ,

though fr om pr eser ved skin , of the adult male sea otter“Pappy”ther e a r e

bun dles an d about ha ir s. Because of samplin g var iables, h owever , i t can n ot be said con clusively that the fur of the sea otter i s twice as

den se as that of the fur sea l .

SK IN

John K . Ling (Department of Zoology, Massey University , Palmerston North , New Zealand ) contributed the fol lowing de

scription , based on examination of a smal l sample of skin fromthe facial region of one animal (D22T he forma lin -fixed sk in was sect ion ed pa r a l lel an d at r ight an gles to the

skin sur face a lon g the hai r follicle axes an d sta in ed with haema toxylin , eosin ,

an d picr ic acid . Measur emen ts a r e un cor r ected f or p ost mor tem chan ges an d

a r e to be r ega r ded as appr oxima te on ly .

T he skin i s 3 mm thick fr om the sur face to the pan n iculus car n osus;theepidermis aver ages 50micr on s i n thickn ess, the pap illar y layer of the dermis


F IGURE 1 8 .— Cr oss sect ion of pelage (by Har dy device ) about 1 0 mm . fr om

sur face of skin ,n ear mi dback , adult ma le sea otter D22—57. T he lar ge

gua r d ha ir s a r e ova l i n cr oss sect ion at th is level , an d their sur face i s

cr enulated . T he much sma ller an d n umer ous fur ha ir s ten d to be 3 or 4

sided . Magn ificat ion X 430. (VES 571 2 an d 571 3 )

a lso 50micr on s, an d the r et icular layer makes up the r ema in der . T he lon gestun der fur ha i r s measur e up “

to 22 mm i n len g th , of wh ich 1 9 mm may pr ot r udebeyon d the sur face por e of the ha ir can a ls.

F ive layer s, st r atum cor n eum, st r atum gr an ulosum, st r atum lucidum,

st r atum spin osum an d str atum germin a t ivum, a r e r ecogn izable i n the spidermi s. T he gr anular layer i s n ot un iformly den se thr oughout an d pigmen t i sabsen t . T he ep idermis i s thr own in to a ser ies of fo lds wh ich a r e r e

flected by simi lar foldin g of the papi lla r y zon e of the dermis. Collagen fibr esi n the deeper dermis ar e or ien ted both r an domly an d par a llel to the skinsur face. Ar r ector p ili muscles a r e absen t .

Ha ir follicles a r e ar r an ged i n bun dles an d a r e a lig n ed a t an an gle of about70

°

to the sk in sur face . Each bun dle compr ises a gua r d ha ir follicle an d

un der fur fo llicles, which a r e sepa r ated fr om each other n ear their base butar e he ld together closely at higher levels . In cr oss sect ion ther e i s some

suggest ion s of t r io gr oup in g with a cen t r a l gua r d ha ir follicle between two

other guar d ha ir fol licles. T he un der fur follicles open in to the gua r d ha ircan a l an d a l l ha ir s emer ge at the skin sur face thr ough a common por e

[fig .

Cutan eous glan ds associated with each guar d ha ir fo llicle an d Open in g in tothe bottom of the gua r d ha ir can a l compr ise a bi lobed sebaceous glan d an d a

gr eat ly coi led apocr in e sweat glan d . T he sweat duct open s poster ior to , an dslight ly h igher than the common sebaceous duct formed by the un ion lowerdown of separ ate ducts fr om each glan d . K er atohya lin gr an ules aboun d n ear


the exter ior en ds of the cutan eous glan d ducts. Ther e ar e n o glan ds Open in gin to the un der fur fo llicles (fig .

Adaptat ion s of the sea otter in tegumen t to an aquat ic habit in clude ( 1 )on ly per iodic occur r en ce of the gr anular layer wh ich may con fer upon the

hor n y layer differ en t pr oper t ies fr om those a r isin g fr om the con t in uouspr esen ce of gr anules

,ther eby con t r ibut in g to i ts water -r esist in g fun ct ion;(2 )

the fla tten ed gua r d ha ir s;an d ( 3 ) the absen ce of ar r ector p ili musclesen ablin g the ha ir s to l i e close to the skin sur face when the an ima l en ter s thewate r . These fea tur es a r e exemplified by the fur sea ls an d they may be

common to a l l semi-aquat ic mamma ls. In common with other den sely fur r edspecies the sea otter has la r ge fun ct ion in g apocr in e sweat glan ds associatedwi th each guar d ha ir follicle .

S en so r y vi br i ssae

Sensory vibrissae are in three locations:mystacial , superciliary,and nasal . The numbers of vibrissae are for the left side onlyof an adu lt male . There were 8 rows including 62 mystacial vib

r i ssae tota l both sides 1 24 mystacial vibrissae ) . The largestwas 53 mm. long and the shortest 2 mm . Th ere were four super

ciliary vibrissae , the largest (dorsal ) was 33 mm . and the three

others were about 1 2 mm . long. There were three nasal vibrissae(along the dorsal anterior nasal area ) , each about 1 4mm . long.

The mystacial vibrissae are the most import ant as sensory

organs . They are vo luntarily control led and are frequently extended forward . In this posit ion they are used as sensory aids

when walking among rocks or when examining a strange object .

Presumably they are used when exploring the bottom of the sea

for food . In the wild they are often worn off short but in captivity,where a search for food is not necessary, they may reach a length

of 1 00 to 1 20mm.

MOLT

Maynard ( 1 898 ) wrote that Their fur is considered equally

good at al l seasons;hence they are hunted throughout the entireyear.

”S imi lar statements were ma de by many other authors .

The lack of an observable mo lting season may perhaps be ex

plained by analogy with mo lt in the fur seal . Scheffer and Johnson( 1 963 , p . 32 ) found that

“Th e number of underfur fol l icles per

bundle in the first adult-typ e pelage remains unchanged

throughout life but that the number of fibers in each bundleincreases with age .

“The rise in the fiber count means that up to60 percent of the fibers are not shed in late molt but remain fastin the bundle .

Scheffer demonstrated earl ier in the present report that a young


FIGURE 1 9 .-Hor izon ta l sect ion thr ough the sea otter skin showing deeper

layer,n ear ha ir r oots, with on e complete pelage un it . A— con n ect ive t issue,

B— swea t duct , C— sebaceous duct , D— sebaceous glan ds, E— la r ge guar dha ir

,F— lar ge un der fur ha ir , G— sma ller un der fur ha ir s. (JKL photo )


sea otter in its first adu lt pelage had fewer fur fibers (43 ) perbundle than two adults (adu lt male 7 1 and adult female That

the fiber popu lation is denser in the sea otter than in the fur seal(adult female 5 1 , adu lt male 68 ) is not surprising . Insu lation inthe fur seal i s provided by both blubber and fur but the sea otter,having no blubber , must depend for insulat ion only on its fur . It

seems reasonable to conclude that fur fibers are retained in thesea otter as they are in the fur seal , thus “masking”the periodof molt .

John Vania, Leader , Marine Mammal Studies , Alaska Department of Fish and Game , visited the Marine Mammal Biological

Laboratory in Seatt le from 8 to 1 9 November 1 966 to work with

V . B . Scheffer on the examination of skin samples from sea otters .

Of 26 sea otters taken in winter and 20 taken in summer , all

showed evidence of molt in some of the fiber roots . Th is evidence

is puzzling;the molt deserves further study . A tentative con

elusion is that, throughout the year , at various p laces on the body,individual fibers are in mo lt while others are at rest.Observations of captive sea otters also suggested that the period

during which fur is shed is pro longed . In al l seasons fur fibers

were seen on the paws of otters during grooming activity and

quantities of fur accumu lated at the drain of their pool .

To estimate the periods of maximum and minimum molt, Cecil

Brosseau , D irector, the Tacoma Aquarium, collected samples offur for me from a screen over the drain of a pool that held anadult male sea otter (Gus ) . The uniformly col lected samples consisted of the accumulation of fur and guard hair for a 1 5-hour

period at 7-day intervals from October 1 967 through October 1 968.

The samples were dried , cleaned manual ly (fish scales, fragmentsof bone , and other debris were removed ) , and weighed on a beam

balance to the nearest g . The mean weights of the samples

for each month show that shedding is maximal in late spring andsummer (mean of 4 August samples 59 cg . ) and minimal inmidwinter (mean of 4 January samples 25 cg. ) and that ap

p r eci ab l e shedding occurs in all months ( fig.

This study suggests that the sea otter exhibits one period of

maximal foll icular act ivity (molt ) annual ly in the spring and

that i t may be simi lar to the European otter (Lutr a lutr a) whichis said to mo lt almost imperceptibly during a prolonged period(Novikov, as does the po lecat (McCan n ,


F M A M J A S O N

MO NT H S [ 96 7 4 9 6 8

F IGURE 20 T he shed pelage of an adult ma le sea otter was collected fr omthe dr a in of h i s pool at 7-day in ter va ls fr om October 1 967 to October1 968 . T he mean weights i n cen t igr ams of thr ee to five samp les ( foursamples wer e disca r ded ) co llected each mon th a r e in dicated by dots. T he

cur ve shows maxima l an d min ima l per iods of sheddin g dur in g the yearan d suggests on e an nual maxima l per iod of molt .

T H E PELT IN COMMERCE

Pr ocessi n g

Concerning the processing of sea otter skins, Poland ( 1 892)stated:“The skins ar e occasionally smoked, and are also dyed ortopped . To clarify the meaning of this statement I wrote to Dr .

J . L. Stoves of Martin-Rice Ltd . , fur processors , London , England ,and received the following information ( letter, 7 May 1 963 )

S ea otter fur was dr essed i n the 1 9th Cen tur y by the con ven t ion a l method ,i .e. fatty t issue was r emoved by scr apin g or flesh i n g after wh ich the skin swer e smea r ed with gr ease or o i l (butter r ejected f or human con sumpt ion



count of the State of Alaska . Among available skins, 905

were considered acceptable for commercial use and were offeredfor sale .

To prepare them for sale the skins were cased ( skinned through

a single slit along the hind legs from heel to heel ) and dried onframes . The pelts were cleaned and brushed and displayed fur

side out. They were divided into 1 97 lots . The lots ranged in size

from one to eight skins matched according to size and color . The

bid price for a single skin determined the price for al l skins inthat lot.

Skins taken in 1 962 and 1 963 and held since then were lessvaluable, because of depreciation of quality in storage, than peltstaken in 1 967 . The earlier collection so ld for an average price ofabout $80 each . The more recently taken skins averaged $280

each . One lot of four skins was sold at the maximum price of

per skin .

The auction was attended by buyers representing 33 companiesfrom 7 states and 6 foreig n countries . Al l skins offered for salewere sold .

Feedin g Mechan isms

Dr . Robert P . Scapino , Department of Oral Anatomy, Un iversity of I llinois, has undertaken continuing study of the jaw

mechanics and feeding behavior in carnivores . He accomplished

a preliminary study of the sku l l and musculature of the sea otterand kindly contributed an anatomical description, excerpts fromwhich are quoted below ( letters , 1 963 and H e plans an

extensive publ ication on his studies of carnivore feeding mechamsms.

MASTICATORY MUSCLESI have completed gr oss dissect ion of the mast icator y musculatur e i n

En hydr a . T he descr ipt ive termin ology used i s somewhat differ en t than whatyou will fin d i n wor ks on Lu tr a (Fisher , 1 942;Schumacher , however ,the terms used to design ate the var ious muscles a r e per fect ly acceptable an d,

i n my View, the most useful . My division of the sup e r ficia l tempor a l musclein to super ior an d in fer ior heads i s somewhat un usua l an d later , when I haveexamin ed the muscle i n a sufficien t n umber of other mustelids, I may decide tolabe l i t diff er en t ly . But r ight n ow the sepa r at ion seems wa r r an ted, at leastfr om an an atomica l stan dpoin t .

T he masseter muscle of ca r n ivor es i s usua lly descr ibed as havin g i n comp l ete l y dist in ct super ficia l an d deep par ts, but i n the sea otter these division sar e even mor e in dist in ct than usua l .T he an atomy of the jaw muscles i n En hydr a i s essen t ia lly the same as i n


other ca r n ivor es. Two featur es of the tempor a lis, however , a r e n otewor thy.T he super ficia l tempor a lis i n most other ca r n ivor es a r ises fr om the en t ir eun der sur face of the super ficia l apon eur osis an d i s n ot con fin ed to the an ter iorpar t as i n En hydr a . Of the car n ivor es I have examin ed the on ly two that ar elike E n hydr a i n th is r espect a r e the min k an d r iver otter .

T he in fer ior head of the super ficia l tempo r a lis i s wel l developed i n

En hydr a an d dist in ct fr om the super ficia l head . In other car n ivor es thismuscle seems r elat ively sma ller an d blen ds with the super ior head . T he fun ct i on a l sign ifican ce of these differ en ces i s n ot clear .

MANDIBULAR JOINTS

Most ca r n ivor es have th r ee jaw jo in ts. T he two tempor oman dibular join tsa r e obvious, but the thir d , the symphysea l join t has escaped the ser ious a t

ten t ion of compar at ive mor phologists. My studies in dicate that the latter join thas cr ucia l fun ct ion s i n car n ivor e jaw mechan isms .

T he mor phology of the tempor oman dibular join ts i n ca r n ivor es i s dist in ct ive .

T he con dyle of the lower jaw takes the form of a tr an sver sely or ien tedcylin der that a r t iculates mor e or less snugly i n a t r ough-l ike glen oid fossa .

T he tempor oman dibular join t of E n hydr a does n ot appear sig n ifican t ly differen t fr om that of other ca r n ivor es.

T he symphysea l join t of ca r n ivor es i s mor e var ied . This join t con sisten t lyshows h igh mobi lity high mobi lity f or car n ivor es ) i n those lar gecar n ivor es that a r e power ful crusher s. T he mobile type of symphysis typica llyhas r elat ively flat a r t iculat in g pla tes that ar e separ ated by a well-developedfibr oca r t i l ag en ous cushion a lon g thei r a n ter osuper ior bor der s. T he symphysisof En hydr a fits this model . A lso i n E n hydr a , the ar t iculat in g p lates a r e

boun d together by stout cr uciate ligamen ts below an d behin d the fibr ocar t i l ag e .

T he mobi le typ e of symphysis seems to fun ct ion to faci litate fitt in g theteeth to the object that i s to be cr ushed an d the fibr ocar t i l ag e cushion as a

shock absor ber to r educe the bit in g for ce that i s t r an smit ted to the skull whenthe r esistan ce of the object i s over come ( Scapin o , T he cr uciate ligamen ts a llow symphysea l movemen t , but stab il ize the jo in t by pr even t in gdir ect later a l sepa r at ion of the a r t icula t in g pla tes .

T he teeth an d symphysis of E n hydr a appear to be pr ima r i ly adapted f orcr ushin g har d objects. T he sea otter easily cr acks the shells of mol lusks withi ts poster ior teeth (K ir kpat r ick et a l . , T he combin at ion of a loosesymphysis wi th bun odon t teeth i n this an ima l i s a lso obser ved i n other la r gecar n ivor es that a r e cr usher s.

DENT ITION

The teeth of the sea otter, particu larly the molars , are flattened

and rounded . They are n ot adapted to cut or shear flesh but to

crush invertebrates , the preferred food . Even the canines are

rounded , having a blunt point and no sharp edge (fig. Be

cause these are used to open the valves of such organisms as therock oyster (Pododesmus) the tips are often worn or broken .

Fisher ( 1 941 b ) described the dentition of the sea otter on the

basis of fragmentary material (particularly from younger ani


FIGURE 21 .— Fr esh youn g adult den t it ion i n the late juven i le or ear ly subadult

stage of deve lopmen t . Note th e r oun ded, blun t can in es an d spade—shapedlower in cisor s which a r e used to scoop in ver tebr ate or gan isms fr om theirshells. Foun d dead on the beach , 5 Mar ch 1 962, Amchitka Islan d, A laska ,weight 24 lb . kg. ) len g th mm. (KWK 66— 9—9 )

mals ) then available . For this reason , the present description of

premature dentition differs somewhat from hers .

In the following discussion, the terminology of Scheffer andKraus ( 1 964, p . 296—298 ) is used . The ages at which individual

teeth erupt are approx imations and are based primarily on bodysize. A l imited number of specimens was studied to determine theprogression of tooth eruption from birth to the adu lt dentition .

A detailed study of dental development remains to be undertaken .

In a newborn sea otter (fig. weight about kg.

the four canine teeth, two upper incisors and two lower first and

second pairs of p ostcan i n e teeth are erupted from the gums . Atbirth there are a total of 26 deciduous teeth of which 1 0 are

Visible ( see formula) . The fate of the fetal teeth that are erupted

from the bone at birth but are not gingivally erupted is not known ,but it appears that they are exfo l iated without becoming funct i on al .

T H E SEA OTTER IN THE EASTERN PACIFIC OCEAN 45

F IGURE 22 .— Den t it ion of n ewly bor n ma le sea otter (62 taken at

Amchitka Islan d , 1 8 Febr uar y 1 962 , weight kg. len gth 528mm. T he can in es an d on e pa ir of upper in cisor s a r e clea r ly shown . T he

bar ely er upted fir st p ostcan i n e i s vi sible an d the secon d p ostcan i n e i s i nd i cated by an a r r ow. T he youn g sea otter p up pr obably r ece ives most of

i ts n ut r it ion fr om mother ’s milk but soon after bir th i ts mother gives i tsoft bits of solid food . (KWK 62—1 4—28 )

The complete juvenile dentition (fig. consisting of 44

teeth of which 26 are gingival ly erupted, is obtained within aboutthe first 2 to 3 months after birth when the young otter hasreached a body weight of about 4 kg. (8—9 This mixed or

transit ional dent ition is retained for several months .

The comp lete permanent or adu lt dentit ion (fig. 21 ) consisting

of 32 teeth is attained toward the end of the first year of l ife andbefore sexual maturity is attained .

The den ta l formu lae given be low were determined from skulls

that appeared to be typical of the stages of development . Th ese

sku l ls were chosen after examining several dozen specimens .

D en ta l fo r mu l ae

Figur es r epr esen t the n umber of teeth p r esen t on on e side;those i n

par en theses ar e n ot yet gin giva lly er upted . Lower case z deci duous tooth;


FIGURE 23 .— Complete juven ile den t it ion of a fema le aged 2 to 3 mon ths,

weight lb . len gth 720 mm . , captur ed 1 2 Mar ch 1 959 . T he

perman en t in cisor s have a l l er upted an d the perman ent fir st p ostcan i n esar e er upt in g an d displacin g their feta l an teceden ts. T he secon d an d thir dpa ir s of deciduous p ostcan i n es a r e well developed . No in dicat ion of mola rer upt ion i s visible but the t ips of the er upt in g can in es a r e visible (a r r ow) .

(KWK 66—1 1 —1 1 )

upper case z p erman en t tooth , ( I z i n ci sor ;C z can i n e;PC: p ostcan i n e;molar ) .

Newbor n (fig. 24 an d fig. 22)1

(2 ) 1

Tota l on on e side, 4+ (9 ) tota l teeth , 26 .

Juven ile (mixed or t r an sit ion a l ) (fig. 23 )I 3 C ( 1 ) PC M ( 1 )i c 1 p c 2

i c 1 p c 2

I 2 C ( 1 ) PC M (2)

Tota l on on e side, tota l teeth , 44.


F IGURE 24.— Den t it ion at bir th . T he t in y feta l teeth ar e n ot er upted fr om the

gums. T he can in e teeth , a pa ir of upper in cisor s, an d the fir st an d secon dpa ir of lower p ostcan i n e teeth ar e er upted fr om the gums at bir th .

Fema le, captur ed with mother , Amchitka Islan d , Alaska ,weight kg .

len gth 521 mm ., umbilica l cor d attached . (KWK 66—1 1 —2 )

Adult (fig. 21 )

1

1

Tota l on on e side, 1 6;tota l teeth , 32.

In ci sor s

At birth the deciduous caniniform incisors (No . 3 pair) are

erupted (fig. These are the first funct ional teeth to be lost ,and are replaced after the two central pairs of permanent upperincisors and the two pairs of permanent lower incisors haveerupted gingi vally at about 2 or 3 months after birth . T h e four

pairs of central incisors are the first permanent teeth . Their ante


cedents are small and nonfunctional;they are probably shed whenthe permanent incisors erupt.

As Hildebrand ( 1 954) has pointed out , the spade-shaped and

somewhat protruding permanent lower incisors are used to scoop

food organisms from their shells when the sea otter is feeding. In

older animals they show wear (fig.

The sea otter is the only member of the order Carnivora with

only two pairs of lower incisors . In this respect, it resembles the

pinnipeds, most of which also have only two pairs of lower i nci sor s. The walrus has no lower incisors in the adu lt dentition .

C an i n es

At birth the deciduous canines are erupted . They are shed and

replaced following the loss and replacement of the deciduouscaniniform incisors at about 5—6 months of age .

F IGURE 25 .— “O l d”a dult den t it ion . No method of determin ing chr on ologica l

ag e has been foun d, but an ima ls with sever ely wor n teeth like this wer eclassified as

“o l d.

”T he wor n lower in cisor s an d can in es an d sever ely

er oded p ostcan i n es an d mola r s r esult when har d-shelled or gan isms ar e

cr ushed by the teeth . This ma le , we ight 55 lb . (25 len gth mm . ,

was captur ed on a beach at Amchitka Islan d , 1 4 Mar ch 1 959 . (KWK664 2—1 0)



Mo l ar s

The upper and lower molars have n o antecedents . They erupt

in the late juvenile period somewhat later than the permanentcanines and somewhat earl ier than the permanent p ostcan i n es.

Many young are born in the late winter-spring period . In the

following late winter and early spring period of stress, the food

intake of these large juveniles is inhibited by the eruption of the

permanent p ostcan i n e teeth and the accompanying loss of deci du

ous teeth . In the crowded Amchitka popu lation where food resources are heavi ly exploited, such young, stil l dependent on theirmothers for much of their food, are deserted and die at this time .

Apparently, the mothers are unable to supply the food needs of

both themselves and their large young during this season of stress .

Because poor occlusion , as described above, was obser ved . i n

many young otters found dead of starvation on beaches, it wasassumed that this condition was a factor in their failure to survive

( see Morta l ity Factors ) .

D en ta l a ttr i t i on

The teeth of many sea otters at Amchitka Island show severe

tooth wear (fig . In order to learn something of the nature

of this damage, sample sku l ls with worn teeth were sent to Dr .

David B . Scott, Chief, Laboratory of Histology and Pathology,National Institute of Dental Research . After he and his associateshad examined the teeth they contributed information in a letterof 23 May 1 963 . Excerpts are quoted

Non e of us feels that the p itted an d wor n ar eas have the r equisite char acter i st i cs of den ta l car ies. T he a lter at ion s ar e quite cur ious. S in ce we wer en ot famil ia r with the den t it ion i n the otter , we r emoved an un er uptedperman en t tooth an d un cover ed two other s fr om un der the deciduous teethof a juven i le ma le (KWK 59 an d a lso r emoved on e of the mor e in ter esti n g atypica lly pitted on es fr om an adult fema le (KWK 59 On e of the

former teeth split well en ough f or us to g et an idea of the en amel th ickn ess;taken together with the appear an ce of the other perman en t teeth i n this youn gskull the impr ession i s ga in ed that deep pitt in g i s n ot a featur e at the outset .

T he most in ter est in g an d con fusin g con figur at ion i n the pitt in g of the typefoun d i n the tooth fr om KWK 59—1 1 , i s the t ips of the cusps. As seen i n the

sect ion ed tooth , the hole i n the un der lyin g den t in i s actua lly br oader thanthe open in g thr ough the en amel , r esult in g i n a sor t of un dermin in g . [Exami

n at ion of man y teeth in dicate to me that these pits a r e formed when a pieceof har d san d i s pr essed in to a n ewly formed br eak i n the en amel . Movemen t

of the san d gr a in an d pr essur e on i t when food i s chewed cause i t to r otate

an d cr eate a cavity i n the den t in lar ger than the hole thr ough which i t en

ter ed . ] Th is i s n ot expected i n att r it ion , but a l l of us fee l that the classica lsign s of ca r ies ar e n ot pr esen t . Ther e i s quite a deposit of secon dar y den t in

T H E SEA OTTER IN T H E EASTERN PACIFIC OCEAN 5 1

F IGURE 27 .—Den ta l att r it ion an d bon e damage i n the adult sea otter . Adult

otter s foun d dead on beaches at Amch itka Islan d often have sever ely wor nteeth . Bon e r esor pt ion ( in dicated by a r r ows ) an d per iapica l abscesses ac

compan y sever e tooth att r it ion . All teeth showin g sever e wear wer e loose .

T he cr ushin g of har d-shelled or gan isms,such as mussels an d sea ur chin s ,

i s a suggested cause of sever e tooth wea r . (KWK 66— 1 4—1 0 above , 66— 1 3 -20

be low)


i n the pulp chamber ben eath the lar ge p i t that has r esulted i n ob liter at ionof the pulpa l hor n . Th is phen omen on i s or din a r ily con sider ed as a defen ser eact ion aga in st t r auma or car ies. Lookin g at these pits an d the mor e ad

van ced damage i n the other skulls,we a r e tempted to con clude that some sor t

of peculiar att r it ion a l sequen ce i s r epr esen ted . T he la ter flatten in g can be

mor e easi ly expla in ed i n the usua l terms of wea r an d tear . I suspect that a

r ather lar ge-sca le study would be r equ ir ed befor e the facts could be a scer

ta i n ed as to how the ea r ly pitt in g occur s .

Ther e i s a good bi t of ca lculus on the teeth . T he bon e r esor pt ion i n an adultfema le (KWK 59—1 53 ) suggests that ther e may have been per iapica l ab

scesses i n th e lower left molar r egion , pr obab ly as a r esult of pulp exposur efr om the att r it ion . T he bon e damage i n the upper left poster ior r egion couldbe expla in ed i n the same way, or equa lly well as an outcome of per iodon ta ldisease . Ther e a r e a lso other ar eas of bon e damage.

Tooth attrition and its relationship to feeding habits andmortality at Amchitka Island are discussed elsewhere . It is ap

parent that a dense otter population at Amchitka has resulted ina shortage of soft-bodied invert ebrate food species . Hard-shelledforms are eaten in large quantit ies . Sea otters often chew mussels

(Myti lus) and sea urchins (S tr on gyl ocen tr otus) . The sounds of

shel ls crushed by the teeth are often audible for many meters .

Also, sand is ingested with food organisms and sand grains areoften found imbedded in teeth .

Dental attrition is less prevalent in sea otters from areas having

uncrowded popu lations than from the crowded Amchitka area.

A captive female sea otter that was fed primari ly on soft foodsshowed no dental attrit ion when she died at the age of about7 years . It is thus concluded that dental attrition of the kind foundat Amchitka is the result of a diet that includes many hardshelled organisms with which abrasive sand , and even rocks are

taken ( see Food and Feeding Behavior )

Age D ete rm in ation

The chronological ages of certain wild animals may be as

cer ta i n ed from anatomical specimens . In pinnipeds the teeth show

rings or annuli (Scheffer , l 95oa ) which are related to cycl icalannual phases of fasting and feeding. S imi lar growth layers arefound in the ear plugs and baleen plates of whales ( Ichihara, 1 966 )and in bones (Chap sk i i , To a l imited degree of accuracy ,eye lens weights may indicate age in long- l ived mammals , such asthe fur seal (Bauer, Johnson , and Scheffer ,

In any study of age determination in mammals it i s desirableto have a col lection of known-age specimens . The isolation of sea


otter popu lations,problems yet unso lved in keeping a captive

colony, and the fact that a regular annual harvest of wild animalshas not been taken

,have prevented the accumu lat ion of known

age specimens .

Lacking such basic material , but drawing on his experience inthe study of teeth for indications of growth layers and age estimation , V . B . Scheffer studied a number of sea otter teeth fromyoung and old animals . Techniques that reveal growth layers in

teeth of other mammals revealed nothing that cou ld be related tothe annual growth cycle in the sea otter .

Dr. A . F . For z i at i and Mrs . M . P . Kumpula, Research D ivision

of the American Dental Association , National Bureau of Standards, Washing ton , D C , undertook a study of sea otter teeth .

Teeth were sectioned and subjected to techniques such as X-ray

photography and exposure to ultraviolet radiation . These and

other techniques usefu l in revealing growth layers in other mam

mal ian teeth showed faint l ines (fig. 28 ) but gave no usefu l i ndi cat i on of annual growth layers .

In a further effort to “mark”stages of tooth growth , three

capt ive sea otters on Amchitka Island were inj ected periodical lyduring a 3 -month period with al izarin red S dye . It was hoped that

visible growth lines wou ld be formed . When the teeth of theseanimals were studied by Dr . For z i at i and Mrs . Kumpula, how

ever , no consistent markings were revealed . Further studies of

structures that may indicate age in the sea otter are reserved

for the future .

Karl Schneider, Alaska Department of Game ( letter , Nov.

tells me that he experimented with a number of different stains

and techniques and is now able to differentiate cementum layers

which appear to indicate age .

The sea otter is a permanent resident in a relatively uniform

environment . It requires a dai ly food intake of uniform amount

(a capt ive consumed 1 5 lb . k g . ] of food per day during al lseasons ) . There is no abrupt molt or distinct period of fast ing.

In the absence of marked seasonal environmental changes orperiodic metabol ic changes during the sea otter’s l ife, i t is notsurprising that the usual indicators of chronological age are notevident .

One captive otter (Susie ) was about 1 year old when capturedand died of abnormal causes after 6 years in captivity. H er teeth

and bone structure at death appeared to be those of a young adult .

On this basis i t is est imated that in ideal habitat a wild sea ottermi ght be expected to l ive for from 1 5 to 20 years . A captive river


T H E SEA OTTER IN T H E EASTERN PACIFIC OCEAN 55

otter l ived to the age of 1 4 years and 4 or 5 months (Scheffer,

T he S en ses

The various senses are mentioned or discussed in context under

different subject headings in other parts of the text . A brief

summary of observations of the use of the senses is given below .

SIGHT AND SMELL

The sense of sight appears moderately well developed but, on

land at least , is less important than smel l as a warning sense . The

fol lowing observation illustrates this:I appr oached a disper sed gr oup of 25 otter s sleep in g on the r ocks. T he S . W .

br eeze of ca . 4—6 kn ots was such that I could appr oach cr oss win d . I movedquiet ly to within about 1 0 feet of a gr oup of six sleepin g an ima ls an d made a

n oise to awaken them . T he an ima ls looked at me but wer e n ot a la rmed . Aftertak in g photos I made some quick movemen ts an d they became mi ldly a larmedan d wen t slowly to the water wh ich was i n a chan n el about 1 5 feet wideamon g the r ocks . Her e they pr een ed— n ot a larmed . Then they swam slowlyto a poin t di r ect ly down win d of me . As they g ot my scen t , a l l dived i n gr eata larm an d swam fr an t ica l ly away un der water .

O n e o l d ma le awoke of hi s own accor d an d wa lked leisur ely over the r ockson my upwin d side . H e was on ly 3 feet away . H e looked at me with n o

r ecogn it ion — I moved slowly an d took a pictur e , the click star t led him but he

was n ot a la rmed an d ambled ar oun d behin d me , to a poin t downwi n d of me .

When he caught my scen t he took ext r eme a la rm an d scr ambled fr an t ica llyover the r ocks, dived in to the water , an d did n ot come up un t il 1 00 feet away .

(Field n otes, 1 2 Mar ch 1 962, East Cape , Amchitka Islan d , Alaska . )

When otters feeding or resting in the water are approached bya human observer and the wind is blowing from the observer to

the otters , they become rest less . Feeding and rest ing animals rise

high in the water and sniff the air . Although there is no rapidmovement s or indication of alarm, it is general ly true that allanimals wi l l leave the area within about 1 0minutes after the ob

server’s arrival . In the same locations , when the wind blows fromthe otters toward the observer

,the otters remain unconcerned even

though the observer moves about on land in clear View .

As mentioned under “Food and Feeding Behavior ,”sight underwater may be usefu l in finding food . Gentry and Peterson ( 1 967 )demonstrated that a sea otter was capable of quite a high deg ree ofaccuracy in dist inguishing, under water, the size of experimenta l

disks .


HEARINGNo observation that I know of demonstrates that the sense of

hearing is either particu larly acute or poor . The sound of a camera

shutter clicking at a distance of 3 to 5 m . usual ly causes an otterto glance alert ly about, but does not cause alarm . Both wi ld andcaptive otters soon become accustomed to routine sounds of human

activity .

TASTE

Captive otters, when given a variety of foods , often licked each

item, then went back to eat first the food which they apparentlyconsidered most tasty . Certain foods were obviously preferred,presumably because of their taste .

TOUCH

The forepaws and vibrissae appear to be very sensitive , andthey are important in finding food ( see Food Gathering and

Sensory Vibrissae ) .



F IGURE 29 .— Favor ed sea otter habitat i n the Aleut ian Islan ds i s cha r acter ized

by havin g exten sive un derwater r eefs to a depth of about 20 fathoms, kelpbeds, an d poin ts of lan d or offshor e r ocks that give shelter dur in g storms.

Th is photogr aph shows an example of favor ed habitat on K i r i l of Bay at

Amchitka Islan d, Alaska . (KWK 55— 1 6— 35 )

GENERAL BEH AV IOR

Observations o i the habits and characteristic behavior of sea

otters were obtained in their natural habitat and in captivity .

Quantitative studies of behavior and experimental studies wereundertaken in only a l imited way (Gentry and Peterson , 1 967;and in section “In Capt ivity Certain characteristic habits and

behavioral traits are discussed in context as they relate to varioussubjects in other sect ions of this report .

D a ily Cycle of A ctivity

It was shown in the section In Captivity that when an abun

dant food supply was avai lable a captive animal spent relativelyl ittle t ime feeding as compared to a wi ld otter . It appears that the

abundance of food in the wild also strongly influences the dailycycle of act ivity of otters in diff erent areas of the Aleut ian Islands .

In general , at Amchitka, otters begin to dive for food withinthe first hour after sunrise . Feeding, interspersed with short

periods of grooming and rest , then cont inues until mi d or latemorning . Somet ime between 1 1 00 and 1 300 the otters sleep ordoze, usual ly while float ing on their backs in a kelp bed . The dura

t ion of this rest period usual ly varies from about one-half to threequarters of an hour . One mated pair rested from 1 225 to 1 302 (37

minutes ) . After this nap , feeding, interspersed with short rest

periods for preening and grooming the fur,cont inues unt i l m i d

afternoon when the otters may sleep soundly, usual ly while floating, but in male areas a number of animals may haul out for the

afternoon nap . This nap usually cont inues for about an hour . The

same pair mentioned above rested from 1 446 to 1 548 (62 minutes ) .

After this rest period , feeding again occurs and may continue

until sunset or after . At dark or shortly before , some animals haulout to sleep

,usually within a meter or two of the water but on

rare occasions as far as 75 m . up on the beach . Others spend part

or al l of the night sleeping in a kelp bed whi le floating on the

back .

In areas where popu lations are less crowded than at Amchitka ,and presumably food is more abundant , general observations i n


di cate that rest periods are of longer duration because food needsmay be satisfied in a re lative ly short time .

Mothers accompanied by young, especial ly large young at Amch i tka , often cont inued to dive for food long after al l other ottersin the general vicinity had retired for the night. On several occasions I watched mothers feeding unti l they were obscured by darkness . This is another indication that food species in the Amchitkahabitat have been overuti l ized by that local population . To obtain

sufficient food for herself and her young, a mother must search forit after other otters have retired .

The general daily cycle of behavior described above continuesthroughout the year . When pro longed storms create violent waveaction, the daily cycle is disrupted and animals unable to obtainsuff icient food die ( see Mortal ity Factors ) .

Locomot ion

SWIMMINGMe thods of swimm i n g

Taylor ( 1 9 1 4, p . 49 1 ) pointed out t hat the outer or fifth digit

of the sea otter’s hind foot is the longest (fig. In this respect

the sea otter diff ers from its nearest relative the river otter, from

seals, and from most if not al l land carnivores . He considered that“extra support” (presumably in walking) is furnished by thisunusual feature . Howell ( 1 930, p . 284 however

,after study

ing the musculature of the pelvic l imbs , surmised that the seaotter swims by means of vertical undulations of the posterior partof the body;that i t uses the hind fl ippers held in the horizontalp lane, palms up , in combination with the tail to present in a satis

factory degree the lunate rear border theoretical ly desirable .

”

Thus, the long fifth toes wou ld form the outer borders of theswimming organ . He was unable to confirm this theory by obser

vation . He felt some doubt as to its validity because“It is true thatno other mammal is known ever to have employed this method ofswimming.

”

On many occasions , from boats and cliff s, and in captivity, I

have watched sea otters swimming in clear water beneath the sur

face . H owell’s deductions were ent irely correct.

Whi le the sea otter is swimming beneath the surface or diving,vertical undu latory movements of the body, as described above,furnish propulsion . While near the bottom, maneuvering and

T H E SEA OTTER IN THE EASTERN PACIFIC OCEAN 6 1

searching for food, stroking or paddl ing movements of the hindflippers are also used .

Unl ike other marine mammals , the sea otter habitually swimson the surface when it is moving from one area to another . It

usual ly swims on its back and paddles with alternate strokes ofits hind flippers (fig. In this position the long fifth digit dips

most deeply into the water and in combination with the otherwebbed digits produces forward motion .

Thus , the fifth digit is a usefu l adaptation to two unusual

methods of swimming in a mammal :( 1 ) Progression beneath thesurface through undu lat ions of the hind flippers and tail in the

vert ical p lane , and (2 ) progression on the surface by paddlingwhile rest ing on the back . Whether the fifth digit became elongatedas an adaptat ion to swimming beneath the surface or as the

dominant member used in surface propu lsion is difficu lt to surmise .

The sea otter infrequently swims bel ly down at the surface,with the head and shou lders above the surface (fig. At such

FIGURE 30.— Thr ee adult ma les i n typ ica l swimmin g att itude . T he for epaws

a r e folded acr oss the chest or pr essed p a lmsi de down aga in st the chest .

Forwar d pr ogr ess i s obta in ed by alter n a te st r okes of the hin d flipper s.

Maximum susta in ed sur face speed i s about km p er hour kn ots) .

(KWK 62—27—1 4)


times the hind feet are used to deliver paddling strokes simi lar to

the stroking movements employed when swimming on the back .

Progr ess on the surface appears to be slower when swimming onthe bel ly than whi le swimming on the back .

The front feet are not used in swimming either on the surface

or beneath it. They are pressed p a lmsi de down against the chestor folded across the chest when not in use to manipulate food or

to preen the fur or hold young (fig .

The tail i s flattened in the horizontal plane an d'

tap er s only

sl ightly, so that it presents a broad surface for most of its length .

The tail of an adult female measured 3 1 7 mm . long, 44mm. thick,and 64mm . wide near its base . In addition to its use in conjunction

with the hind fl ippers in underwater swimming, the tail is used as

a “sculling oar . S light alterations of positions are made whenthe otter is floating on its back . Frequently I observed resting

otters floating in this position with front and hind feet folded on

the chest and abdomen . Norma lly the tail floats on the surface

while the otter rests, but if i t wishes to make sl ight movements, forexample to face away from a light breeze , the ta il is projected

downwards and by means of circular sideward movements the

body is rotated in the desired direction . Also , when captives wereeating and they wished to pivot about on the surface to avoid food

pilferage by other otters, the tai l was used in scu l l ing to assist thestroking hind flippers .

Swimm i n g sp eed a n d ag i l i ty

The sea otter is a slow swimmer but it moves more rapidly

beneath the water than on its surface . Two methods were used

to measure swimming speed:( 1 ) From the shore, otters traveling

from one area to another were timed as they passed beach points .

The distances were then measured on nautical charts and the

speed computed . 2 ) Otters were pursued with a motor-driven dory

while they swam beneath the surface . In clear water the otters

could sometimes be seen as they attempted to escape pursuit.

Presumably, at such times they moved at maximum velocity . The

speed of the dory was measured by timing its passage over a

known distance .

Examples , surface speed:( 1 ) An adult female swam parallel

to the coast of K i r i l of Point on a nearly windless day . For the most

part she swam on her back but occasionally she rol led over andporpoised”(exposing the back ,

but not leaving the water ) for

1 0 to 1 5 yards . During the observation period she made one food

dive and when she emerged ate the several urchins she had


gathered whi le she cont inued on course at the surface . In 44

minutes she covered exact ly 1 nautical mi le, thus her speed waskm. per hour knots ) . (2 ) An adu lt female , carrying a sleep

ing pup on her chest, moved hurried ly and steadi ly on the surface

from an area where a rising wind caused rough water . The wind

was from her side , so she was neither swimming with or against

it. She passed over a measured distance of about 800 m . in 20

minutes , or at the rate of km. per hour knots ) . (3 ) Afteremerging from a food dive with a fish (weighing aboutan adu lt male swam on his back while he consumed the fish and

moved with moderate speed to another area. H i s departure from

the feeding area was apparently prompted , to some degree atleast, by the presence of three Glaucous-winged Gu l ls (Lar usg l aucescens) which swam beside or flew above him while theyretrieved discarded fish scraps . The otter was able to outdistance

the birds that al ighted beside h im on the water . In 675 seconds

he traversed a measured distance of 300 m . at an average speed

of km. per hour knots )

The top speed of our dory was approximately 1 1 km . per hour

( 6 knots ) . On many occasions we chased sea otters in order to

catch them in a dip n et . When the water was clear and smooth ,

we cou ld watch the otters swimming beneath the surface as theyattempted to escape . It appeared that their top speed for brief

intervals,less than 1 minute

,was not more than km . per hour

(5 knots ) and probably somewhat less . When we were unable tosee otters beneath the surface

,we often overran them . Occasionally

during escape attempts,otters wou ld porpoise clear of the water

ahead of the boat . When this was done they were most readilycaptured .

Th us it appears that when an otter moves from one area to

another on the surface , its near maximum sustained rate of travel

may approach km . per hour and the underwater , briefly main

tai n ed (up to about 1 minute ) , maximum escape speed is about

9 km . per hour . This compares with a near maximum, briefly

sustained (3 to 5 minutes ) , escape speed of the northern fur seal ,which we pursued in a vessel having a maximum speed of 26 km .

per hour ( 1 4 knots ) , of about km . per hour ( 1 0 knots ) . APacific bottlenose porpoise ( Tur si op s g i l l i ) sustained a speed of 29km. per hour knots ) for seconds (Lang and Norris ,

Although a slow swimmer , the sea otter is remarkably agi le .

On one occasion I plunged the dip net direct ly in the path of anotter as i t swam just ahead of the dory and at a depth of about

m . The otter, unable to avoid entering the n et , rol led forward ,


comp leted a 1 80° reversal of course, and escaped before I couldpull the net from the water .

DIVINGD ur a t i on of food d i vesIn water depths ranging from about 2 to 25 m. food dives were

timed with a stop watch from observation points on the cliffs of

Amchitka . Several factors render such observations somewhat

difficu lt to obtain and evaluate . Usually several otters were divingfor food in an area under observation . Although an otter maymake

several food dives in a rather l imited area, perhaps 1 5 m . in diam

eter, the animal may unexpectedly move 1 00 m . or more beneath

the surface to a new feeding locat ion . Also , a nearby otter may

move to the vicinity of an animal that is being timed , causing confu-sion . The positive identification of the sex of a diving otter issometimes difficu lt to ascertain at the distances and with thefrequent poor visibil ity caused by weather conditions .

General observations indicate that the duration of food divesby adu lt males exceeds that of adu lt females . The fo llowing dataprobably exaggerate this difference because the females’ diveswere, to a greater extent than the males’, in shal low water:

Dur a tion of food dives (secon ds )

A dult maleA dult female

The few observations presented are not strictly comparable ,because water depth varied and the animals under observationmay have had differing food preferences which caused some of

them to search longer for a part icular item . Males feed on fish to

a greater extent than females . Among 50 stomachs of adu lt maleswhich contained food, 82 percent contained fish , and 62 percent

of 1 78 stomachs of adult females contained fish . The search for

and capture of fish would probably require more time than the

gathering of invertebrates .

The best data on the duration of dives of the female were oh

ta i n ed on 20 and 21 August 1 955 . On these two days a mated pair

of otters remained in a smal l cove at Amchitka and no other ottersfed in the area . During the period of mating the two otters dived

and emerged from their food gathering dives simultaneously. Be

cause the male fol lowed the female closely, the duration of her



face . The longest dive lasted for 250 seconds minutes ) and

the shortest 30 seconds . The last timed dive of 205 seconds

indicated that the animal had not become exhausted and we

abandoned the chase as futile . Barabash-N ikiforov ( 1 947 ) saysthat the longest time that the sea otter can submerge is not morethan 6 minutes .

”My conclusion is that the maximum duration of

a dive is probably less than 6 minutes .

D ep th of di v i n g an d. d i stan ce fr om shor e

The maximum depth to which a sea otter may descend to gather

benthic food organisms is not definitely known . Consideration of

the historical record along with modern observations and data,however, indicate certain tentative conclusions .

The greatest diving depth I find in the historical record isquoted from Chase Littlej ohn , a sea otter hunter of the 1 9th

century . He said “There is a [p lace] about 50 fathoms deep

where they go to the depth of the water to feed (Hall ,Other otter hunters indicate lesser diving depths . Snow ( 1 9 1 0,p . 281 ) stated that the sea otter appears to prefer to get its foodat depths of 1 0—25 fathoms .

Captain C . L . Hooper ( 1 897 ) studied the sea otter and problems

of conserving it in Alaska during the latter part of the 1 9thcentury. It was his conclusion that banks of 30 fathoms of waterare its feeding grounds .

”Further, he concluded

that the pr in cipa l par ts of the pr esen t sea otter gr oun ds ar e a lr eady withinthe ter r itor ia l water s of the Un ited States. suitable r egulat ion s by theUn ited States Gover nmen t , pr oper ly en for ced , will fur n ish amp le pr otect ionf or the sea otter , as n ot en ough can be taken outside of these l imits to en

cour age hun t in g to an y exten t .

This statement implies that otters seldom ventured to depths

greater than those found relatively near shore .

Modern observations tend to confirm the early sea otter hunters’information , except that in certain areas where shallow water isfound far from land sea otters appear to find suitable feeding

grounds beyond the 3-mi le limit .

During seven seasons (Apri l through August, 1 957—63 ) A . C .

Hartt and B . F . Jones recorded all sea otters sighted beyond 3

miles from shore . Their primary mission was offshore fisheries

investigations during which their ships operated near various

Aleutian islands, in the passes between them, and as far as 200

mi les from land in the North Pacific and Bering Sea .

Their observations of otters over deep water (table 1 0) are of

interest, because in each case the otters were near areas where


shal lower water was only a few mi les distant. Also , the obser

vat i on s were in areas where strong tidal currents are prevalent.

These could quickly move an otter sleeping on the surface several

mi les from a feeding area .

The observat ion of two otters 32 mi les west of Kiska in the55-mi le wide pass between Bul di r and Kiska Islands on 27 May1 959 (A . C . H artt, letter, 1 960) is of particular interest. Theirpresence there may be explained by the fact that they were nearan underwater mountain ridge , Bul di r Reef, which is about 20

nautical miles long and over a mi le wide , and which offers cons ider ab l e area having depths of from 1 7 to 30 fathoms .

The only avai lable authentic record of an otter far from shore

and away from passes between islands was recorded by G . T . Joyn t

( letter, Whi le flying as a naval aviator in the Aleutians inthe spring of 1 943 , Joyn t saw an otter

a litt le over 50 mi les due south of East Cape on Amch itka Islan d . On th ispar t icular day the open ocean was as smooth as a mi ll pon d This an ima lwas obser ved at ver y close qua r ter s an d iden t ity was cer ta in because of the

r a r ity of an yth in g on the sur face makin g a wake so f a r fr om lan d . I haveoften con jectur ed that th is par t icula r an ima l could have been a vict im of an

un in ten t ion a l r ide i n a la r ge fr ee-float i n g kelp r aft . When ever sea otter

wer e obser ved mor e than a half-mile fr om the n ea r est kelp patch i t wasusua lly a sin gle an ima l an d they wer e most fr equen t ly i n the st r a its betweentwo of the la r ger islan ds. On these occasion s they wer e usually headed toon e islan d or the other an d n ot a imlessly swimmin g about .

Joyn t was a trained bio logist before becoming a naval aviatorand gathered much usefu l information about sea otters in theAleutians .

The large amount of time spent by the several observers (table1 0) in offshore areas and the dearth of observations of sea otters

at an appreciable distance from depths of 20 to 30 fathoms ,demonstrate the tendency of otters to remain in shallow water .

On 1 0 Ju ly 1 960, an adult female sea otter (KWK 60—1 9 ) was

shot 9 nautical mi les north of the A laska Peninsula N . lat . ,

W . long . ) in water 20 fathoms ( 1 20 ft. ) deep . Th e stomach

contents ( see Food and Feeding Behavior ) consisted of benthic

organisms . During aerial surveys of the area off the north coast

of Unimak Island and south of Amak Island on 8 April 1 962, themajority of 81 1 otters recorded were seen between 3 and 1 0milesfrom shore in water from 1 0 to 25 fathoms deep . The majority

were near or inside the 20-fathom curve . Th e 20-fathom curve

where this large number of otters were seen ranged from 5 to 8

mi les from the north shore of Unimak Island . I presumed that


domwa

sm

no

Euwo

m

so

53mm

.

vo

>~wmno

Ecan

Ema

m

commmuv

fio

83m

am

woo

.“was

6

300

fl

oo

cv

fimov

aw

A

55mm

326

.

H

“Jam-

4ma

son

no

zoommuv

fio

vvumfiao

m

Avmmvb

Scum

maven-o

Snowman

mvnou

aa

fluxunma

de—rm

mamamc

3A

933”Scum

35

8cm

25?zoo

m

doomoun

$50

afluxwfimfiwo—hE4

m

co

do

mmlafi

NN

loN

373.

ocm

do

oalob

oomloo

w

ooo

fi

fi fl fl fl w


light -colored objects seen on the chest of some of these animals

were food items .

Aerial observat ions of most of the Alaskan areas populated bysea otters indicate that otters prefer to feed in depths of 5 to 1 5

fathoms and that most of them, except off Unimak Island , are

within about one-half mile of the shore . Weather conditions and

lack of time prevented aerial examination of al l shal low banks

far from land where otters might be expected . On 3 May 1 965 ,however

,Tahoma Reef N . lat. , E . long . ) Middle

Reef (52° N . l at .

, 1 76° E . and Bul di r Reef N . lat. ,

E . long ) , respect ively, 30, 20, and 20 mi les from the

nearest land (Bul di r Island ) and having considerable water areasfrom 3 to 20 fathoms in depth

,were examined . Observat ion con

di t i on s were excellent . We saw a number of birds and sea lions,particu larly in the kelp beds over Tahoma Reef, but sea otterswere absent .

Numerous observations of feeding otters near Amchitka Island ,at al l seasons, indicate a preference there for depths of 5 to 20fathoms . Also , during rough winter weather otters are inclinedto search for food to a greater degr ee near shore . When the

weather is mi ld they tend to move offshore to the vicinity of submerged reefs .

Several otters were observed over deep water and far from

shore in the vicinity of drift ing patches of float ing kelp . This

suggests that the otters could obtain food organisms that gathered

in the shelter of the kelp . It is known that pelagic fishes accumulate under and around float ing objects in the sea . That sea otters

might rarely adapt to pelagic feeding is intimated by Snow ( 1 9 1 0,p . 280)

On on e occasion I foun d the stomach of an otter I killed some 8 or 1 0 mi lesoff shor e filled with the r ema in s of a quan t ity of sma l l fish with n o sign s of

the r ema in s of an y cr ustacean s .

He does not, however , identify the area or state the depth of

water where this otter was taken . Mar ak ov ( 1 965 , p . 21 4) also

reports sea otters up to “1 5 mi les from the coast in comparat ivelydeep places .

”No authentic record , however, indicates that the sea

otter is capable of adapting itself to the capture of pelagic organisms where g reat depth prevents food gathering from the bottom.

In consideration of al l the data avai lable,i t is my conclusion

that sea otters feed in shal low water ( 1 to 1 5 fathoms deep ) whensufficient food is avai lable there . When food resources are moreabundant offshore and part icularly in mild weather , they move tofeed in depths of 20 or , rarely, 30 fathoms . Food dives to depths


as great as 50 fathoms for food may be possible but otters are

rare ly seen in water as deep as 30 fathoms ( 1 80 i t ) . No specimen

is available to give positive evidence of food gathering at depths

gr eater than 20 fathoms ( 1 20

O ur observations tend to confirm the conclusion of Barabash

Nikiforov ( 1 947 ) that“the greatest depth to which it can go is

50meters [ 1 64 ft . ]

WALK ING AND RUNNINGProgression on land is simi lar but less agi le than in other muste

lids . The long, outer 5th digits of the hind flippers, which par

t i cu l ar ly aid progression when the ott er swims on its back , hinder

progress on land . Snow ( 1 9 1 0, p . however, exaggerated this

hindrance when he wrote

T he use, however , of the h in d limbs i s ver y limited , the toes appear to lacka l l muscular power , an d the otter can n ot place i ts hin d-feet flat upon the

gr oun d;when i t attempts to wa lk , the toes ar e doubled back un der the soles.

As figure 32 i l lustrates , Snow’s statement is not true . He

probably received his impression from otters that were cornered

F IGURE 32.— Because the fifth digits of the hin d flipper s a r e lon g, the sea otter

wa lks with a somewhat clumsy r ollin g ga it . It moves somewhat mor e slowlythan n orma l human wa lkin g speed . (KWK 62—1 0—29 )


on land and trying frantical ly to escape the clubs of hunters . H isimpression that the toes of the hind flipper were doubled backunder the foot when walking was so strong a conviction that hefigured this unnatural posit ion in the frontispiece of his book .

When the sea otter walks unhurriedly on land, it moves with arolling gait, raising one foot at a time and with the back arched(fig.

When animals some distance from the water are startled , they

arch the back and bound or hop , moving both forefeet then bothhind feet forward in rapid succession (fig. Juveniles andyoung adults are more agi le than large, heavy adults . Some large

animals seem unable to raise their bodies from the ground and

slide, with the help of the feet , across the beach on the belly.

S leep in g

The sea otter may sleep while floating on its back (fig. 34) or

when hauled out on shore (fig.

F IGURE 33 .— Adult sea otter s, sta r t led on a favor ite haulin g-out beach at

Amchitka Islan d , boun d towar d the wate r i n a typica lly muste lid man n er .

Speed of movemen t i s somewhat less than the r un n in g speed of a n orma llyagi le man . (KWK 1 027 )


F IGURE 34.— A— Otter s usua lly attempt to find a shelter ed kelp bed befor e

sleepin g. After gr oomin g i s fin ished , the hin d feet ar e folded on the abdomen .

T he for epaws may be placed over the eyes or aga in st the side of the heador folded acr oss the chest wh ile sleepin g. (KWK 56—4—4) B— This r ecen t lyawaken ed otter i s swimmin g lan guidly fr om i ts r est in g place while attempti n g to keep the head an d for epaws dr y. After awaken in g, otter s appea rr eluctan t to immer se the feet an d head. (KWK 56—4—1 9 )



usually the last to be immersed as the otter swims leisurely fromits resting p lace (fig.

When sleeping on land , an otter usually spends a variable timelanguidly preening its fur before entering the water. Then it mayfollow the procedure described above to delay wetting the feet,head, and tail .

Gr oom in g

Pelage care is of primary importance to survival in the sea

otter . Grooming is essential to maintain pelage cleanliness and

waterproofness, and thus insulation against the chi lly marinehabitat. A blanket of air remains trapped among the dry underfurfibers which serves as insulation . A captive female sea otter spent48 percent (about 7 .5 hours ) of the dayl ight hours grooming her

fur and a wi ld female,observed for about hours

,spent 1 1

percent of the time in grooming activity (table 64, Comparison of

daily activities of wild and captive female sea otters, see In

Captivity ) .

Grooming takes place either in the water or on land . Energetic

grooming is done before rest periods and languid grooming (fig.

36 ) at intervals during a resting period and at the end of a restperiod . Grooming may be divided into two primary phases , ( 1 )washing the fur and (2 ) drying the fur .

Grooming is accomplished primarily by rubbing the fur withthe palms of the forepaws, but the hind flippers may be rubbedtogether or against the fur of the abdomen and sides . The fur of

al l parts of the body is rubbed by the forepaws . To accomplish

this and reach remote parts of the body, the otter may twist and

squirm within its loose-fitt i n g skin, so that areas of the mi d-back

can be reached . The flexible body may be rolled in a ball so thatthe forepaws reach beyond the root of the tai l to the lower back(fig. Also , loose skin of the sides and belly may be rolled overa foreleg while water is pressed from the pelage and removed

with the tongue (fig.

Water may be pressed from the fur by the palms of the forepaws (fig. A fold of skin and fur may be pressed between theforepaws

,squeezing water from the fur and the moisture removed

with the tongue (fig. The fur may be rubbed in a circularmotion or by rapid strokes in many directions . The retractile

claws (fig. 2 ) ( see Physical Characteristics ) are occasional ly extended to aid in grooming but usually they remain retracted .

Figure 41 , i llustrates a typical grooming posture .

T H E SEA OTTER IN T H E EA STERN PACIFIC OCEAN 75

F IGURE 36 .— While dozin g on the sur face of her pool

,a capt ive fema le sea

otter lan guidly gr ooms the fur of her chest an d sides. (KWK 61 —1 0—34)

The fur is washed by rubbing submerged parts of the body with

the forepaws and by rol l ing, head first, over and over at the surface . Ro l l ingmay be accompl ished just prior to s leep on the water ’ssurface . It smooths the fur and leaves a thin film of water in the

outer pelage tips .

In the final stages of a grooming session the otter may rest belly

down at the surface, the head bent under the body while blowingair into the fur . S imultaneously the sides and belly are rubbedvigorously with the forepaws (fig . The fur may also be

aerated by a rapid churning mot ion of the forepaws , beating the

water to a foaming froth (fig.

If the otter intends to rest on land , i t swims to a point near the

desired resting place . H ere i t goes through a 5 to 1 0-minute

grooming routine before leaving the water . After hauling out, the

otter energetically rubs and dries its fur (fig .

In general , females tend to be more thorough than males ingrooming their pelage . I somet imes saw males , but not females ,after hauling out, that failed to thoroughly groom and dry their

fur before sleeping .


F IGURE 37.-T he sea otter cur ls i ts lon g flexible body in to a ba ll an d r eaches

between the hin d flipper s to gr oom the ta il an d lower back . (KWK 1 028 )

Casual observers of grooming sea otters often misinterpret

grooming for “scratching”and ask if sea otters have lice . They

do not.

Vo ice

BABY CRY

This cry is uttered from birth unti l the large juvenile stage ispassed . The pup cries when in distress or when it wants attention

from its mother . The sound:a sharp , high pitched“waah -waab .

”

This may be repeated constantly for long periods if the pup is

T H E SEA OTTER IN T H E EASTERN PACIFIC OCEAN 77

F IGURE 38.— Usin g i ts left p aw, a gr oomin g sea otter pul ls the loose skin

fr om i ts r ight side over the r ight for eleg i n or der to pr ess wa ter fr om the

pelage an d l ick away the moistur e . Moistur e i n the t ips of the fur give thepelage a sl ick , wet appear an ce except on the head wher e dr y, lightcolor ed un der fur i s exposed by par t in g of the wet t ips. (KWK 61 —1 0— 1 9 )

separated from its mother and no tranqui l izer is given . The sound

resembles the cry of a young gull . The mouth is open wi de whenthe cry is uttered .

SCREAM

This is uttered ( 1 ) when an adult is in severe distress— as when

held in unsatisfactory captive condit ions . Often i t indicates that the

animal is near death . It is not uttered when an animal is captured .

(2 ) When a female has lost her young, as when the pup straysbehind a rock

,she screams repeatedly . This cry is the adu lt version

of the baby cry . It is ear sp l itting at close quarters and can be heardat a distance of to mi le in the wild and as far away as200meters when an animal is in a closed building. The mouth is

open wide when the otter screams .

WH ISTLE OR WHINE

This is uttered to denote frustration or mi ld distress . Captives


F IGURE 39 .— Whi le gr oomin g, water i s squeezed fr om the fur of the for eleg

un der pr essur e an d by r ubbin g with the pa lm of the p aw. (KWK 61 —1 0—25 )

whistle when the feeding schedule is delayed, and when they arecarried on a truck or aircraft. The sound is uttered by adults andsubadu lts primarily and to a lesser degree by juveniles . Th e

whistle is loud enough to be heard to a distance of about 200

meters . It is a high p itched vocal sound that resembles a human

whistle and is uttered with the mouth slightly open .

“Wheeeewheeee repeated often and of varying duration .

COOINGFemales coo during premating and postmating behavior and

also when grooming and fondling young. The coo appears to come

from the throat and to denote satisfaction and contentment.

Females coo whi le eating if the food is particularly p leasing. The

mouth appears to be closed when it is uttered . Cooing can beheard up to a distance of about 1 5 to 30 m. on a quiet day. The

sound“ku-ku-ku”may be continued for considerable periods either

steadily or intermittently.

SNARL OR GROWL

This sound appears to origi nate deep in the throat and is uttered


F IGURE 40.— While dr yin g i ts pelage , a fold of sk in i s pr essed between the

pa lms of the for epaws. Water expelled fr om the fur i s r emoved with theton gue . (KWK 6 1 —1 0—1 0)

when a newly captured animal is attempting to escape from a net.The snarl or grow] is audible only a few meters away .

H IS S ING (NONVOCAL )

Females hiss during capture, after capture , and before becomingtame . The sound is simi lar to a cat’s hiss (as noted by Steller in hisJournal ) but more exp losive and of short duration . The sound is

characteristic primarily of females and juveni les . If a person ap

pears unexpectedly near a caged otter the hiss may be uttered in

the first moment of fright .

GRUNTINGWhen a hungry animal is eating voraciously it utters soft grunt

ing sounds that appear to denote satisfaction . In the male thisappears to be equivalent to the cooing of the female .


F IGURE 41 .— A mother otter r ubs the top of her hea d with on e p aw an d her

elbow with the other . Both paws a r e i n con stan t mot ion dur in g gr oomin g.

After gr oom in g her own fur , the mother took her pup on to her chest an d

gr oomed an d dr ied i t befor e a llowin g i t to nur se fr om her two abdomin a ln ipp les. (KWK 57—29—1 4)

BARK

A yearl ing male during pool cleaning, while trapped in theempty pool and resenting thus being “cornered,”uttered a staecato bark which trai led off into the whist le, apparently to denote

frustration .

COUGH ING , SNEEZING, AND YAWNINGSounds as in other animals .

H an dedn ess

During many hours of watching wild sea otters feeding, I notedthat when the animals emerged from a food gathering dive the

food items were carried to the surface under the left forelimb.

Only if a large quantity of food was brought to the surface, i .e. ,



FIGURE 43 .— Dur in g the gr oomin g per iod, befor e haul in g out

,the sea otter

may beat the water to a fr oth with the fr on t legs, per haps aer at in g the furto some degr ee . (KWK 55—1 9—3 )

test was broken comp letely around the oral orifice before the teeth

were emp loyed to remove the broken shell .From these observations I have concluded that the sea otter is

right-handed . In hundreds of animals observed I have never seenfood items brought to the surface under the right forelimb unless

the quantity was too great for the left limb to accommodate .

Handedness in other animals is variable . Warren ( 1 953 ) dem

onstr ated that in the Rhesus monkey the right and left hands areused with about equal frequency. Lane ( 1 946 ) indicated that birds

of prey tend to be left-footed, and parrots (Friedman and Davis,1 938) are simi lar. Pigeons, Fisher ( 1 957 ) concluded, tended to beright-footed .

Further study under experimental conditions may reveal if sea

otters invariably exhibit right-handedness .

T ool-usin g

The use of a rock or hard-shel led mollusk held on the chest asan“anvil”for breaking the shell of a clam held in the forepaws is

discussed under Food and Feeding Behavior . Chest pounding with

the forepaws commonly occurs as an apparent expression of f r us


F IGURE 44.— After haulin g out , the otter usua lly r ests on i ts back whi le

gr oomin g an d dr yin g i ts fur befor e sleepin g. (KWK 57—32—4)

tr at i on , as when an otter has been robbed of i ts food by another

otter . Perhap s the pounding of a hard-shel led mo l lusk againstanother origi nated because of frustration when the otter could

not break , with i ts teeth , the shell of a food organism . At Amchitka ,where the shells of mussels are crushed by the post-canine teeth ,

food pounding behavior is not observed . Where feeding was ob

served in Alaska, hard-shel led clams were not eaten and mussels(Myti lus) do not grow as large as those in Cal ifornia where theyare commonly pounded against a hard object (Hal l and Schaller,

When captive otters from Amchitka were presented with clamsthat could not be broken with the teeth or crushed between thepaws, they broke them against a rock or another clam on the chest(fig. 45 ) or by pounding them on the cement edge of the pool

(fig. A female also pounded smelts (Osmeridae ) , and herring(Clupeidae ) which she did not particularly rel ish (fig. and

she pounded a rock on the edge of her pool . Thus , animals thatcame from an area where food organisms were not observed to

be broken by pounding, used this technique when frustrated by


F IGURE 45 .—A capt ive adult ma le sea otter fr om Amchitka Islan d poun ds a

clam,held between h i s for epaws, aga in st a r ock r est in g on h i s chest .

Usua lly the head i s held er ect (above ) but n ot in fr equen t ly i t i s exten deddur in g food poun din g behavior (below) . (KWK 67—1 5—7 above, 67—1 4—30below)

hard-shelled organisms or by fish they did not care for . Also

(Kenyon , a sea otter pounded a drain cover with a rockwhen the cover frustrated a desire to explore the drain . I consider

the sea otter’s tool-using behavior, as derived from chest-pounding,



break the shells of clams and mussels by carrying them aloft and

letting them fall on a rocky beach .

D efen se an d Escap e

ON LAND

When a sea otter on shore finds itself cornered and cut off fromescape to the sea it stiff ens, faces the approaching intruder, and

begins to rear backward (fig. If the intruder continues to

approach, the otter flop s onto its back (fig . If it is approached

more closely, it may hiss and the stiffened forelegs are extended

(fig. The animal may attempt to bite any object extended

toward it, whi le using the forepaws to push it away. I have never

seen a cornered animal attempt aggressively to attack humanintruders . Defense and escape are the only reactions .

IN T H E WATER

When a sea otter is surprised at close quarters by an intruder

it first rises high in the water . It faces the intruder and extends

F IGURE 47 .— A juven ile sea otter , cor n er ed on an Amchitka beach , pr epar es

to r ea r backwar ds to assume the defen sive postur e i llustr ated i n figur e48. (KWK . 62—1 0—1 0)


FIGURE 48 .— In the defen sive posit ion a sea otter l ies on i ts back , faces the

sour ce of dan ger , an d i s a ler t to r epe l an attack . If an advan ce i s made totouch an an ima l i n this posit ion

,i t attempts to bite an d to push the adver

sar y with i ts for epaws. T he for epaws may a lso be used to a i d i n br in gin gthe teeth in to con tact with the adver sa r y . (KWK 62—1 0—26 )

its forelegs , stiffly , palms of the forepaws outward toward theintruder . It then submerges vertically, pushing the forelegs abovethe head . It sinks backward beneath the surface , rather than

plunging forward as in a normal dive .

Mater n a l an d Filia l Behavior

DURATION OF DEPENDENT PERIOD

The p lace of birth is discussed under “Reproduction in theFemale . In her paper on the “Early l ife of a sea otter pup ,”Fisher ( l 94oa ) described many aspects of the behavior of mother

and pup . Other writers have remarked on the unusual care of themother for her young.


FIGURE 49 .—When closely appr oached , a cor n er ed sea otter hisses, exten ds \

i ts st iff en ed for elegs, an d r ear s backwar ds as f ar as possible. No aggr essivebehavior i s disp layed . (KWK 59—8— 6 )

The period of dependence is unusually long. This was not ascer

ta i n ed directly from known individuals, but indirectly through

various observations at Amchitka. Female reproductive tracts

from there indicate that the maj ority of young are born from early

spring to summer ( see Reproduction in the Female ) . In the fall

and early winter , large juveniles are numerous . During the late

winter and early spring period of high mortal ity (March to May) ,most of the j uveni les that die weigh 20 to 30 lb . (9 to 1 4

At the end of the annual “die-off”few large j uveni les can befound alive . Observations during this period of juveniles crying

and swimming about, apparently in search of their mothers , plus

data compiled under “Mortal ity Factors”and “Home Range i n

di cate that most of these young animals are abandoned by mothers

in the period of stress caused by storms and dep leted food r e

sources .It is assumed that this group of young, most of which were

dead by May, were the young that were born in the previous spring



F IGURE 50.— (Above ) After a feedin g per iod an d befor e takin g her 3 to

4-week-ol d p up ashor e, the mother sea ot ter scr ubs an d gr ooms her fur wi thher for epaws. T he p up at th is stage i s un able to swim. By a imless str okesof i ts hin d flipper s i t may move about i n a cir cle or attempt to r oll over(as shown her e ) to gr asp a kelp st r an d . Whi le she washes an d gr ooms, themother seldom moves mor e than a meter fr om her p up an d usua lly staysclose beside i t (be low) . She watches i t con stan t ly . (KWK 55- 1 9—7 an d 9;1 1 September 1 955 )


F IGURE 5 1 .-A capt ive mother sea otter leads her 3 to 4-week-ol d pup fr om

the water . This appear ed to be a“wa lkin g lesson .

”At other t imes the

mother ca r r ied her a lmost helpless p up fr om the water i n her mouth .

(KWK 57—27- 8 )

up because of her wounds, the hunters started to return to theirship and later that same night, Snow wrote :

We had t r aveled some distan ce, when a l l at on ce , r ight un der our ster n , we

hear d the most un ear thly cr yin g imagin ab le; an other cr y a lon gsideshowed us the da r k form of th e otter we had been chasin g. It was n ow

followin g the boat , lamen t ing the loss of her off spr in g .

The possessiveness of the mother sea otter is evident from birth

until the young one is one-half to nearly two-thirds the mother’s

size (fig. Virtual ly the only t ime that the mother is apart fromher pup is while she is diving for food , while preening, or whenswimming beside the pup . On one occasion I watched a mother

wi th a juveni le nearly as large as she . Th ey rested together on a

rock until the energetic young one began to exp lore nearby. Whenit went to the water as if to depart , the mother rol led forward ,grasped the juvenile’s hind flipper in her teeth , and did not release

it until the young one turned and resumed its posit ion near her .

Many observations of mothers and young at Amchitka indicatethat the ties between them may be strong but that the strength of

the mother-young bond varies with each individual .


F IGURE 52.—T he mother i s so licitous of her youn g f or a lon g per iod . A— A

lar ge juven ile , pr obably weighin g about 20 lb . ( 9 kg . ) an d about 8 mon thso l d, n ur ses wh ile i ts mother pr een s i ts fur . B— Alarmed by the p hotog r apher , the mother gr asps her youn g on e by the side of the head an d , C ,

plun ges with i t in to the water . (KWK 62—1 9- 3 1 , 32 , an d 37 )

On 6 May 1 959, a juvenile (about 1 6 l h . , 7 k g . , in weight) ,sleep ing beside its mother on rocks near deep water, was capturedin a dip net after the mother awoke and escaped . Three times

within the next 5 minutes , while a metal tag was being attached



flipper . As soon as she was r eleased, he r ushed to her side an d then followedher to the water . After a dive of about 50meter s, the two came up . T he p up

immediately clasped h i s mother about the n eck an d she pul led h im towa r dher with her for epaws. This wa s a hea lthy, en er get ic p up .

Fright during capture may temporarily upset the normal behavior of a pup towards i ts mother (F ield notes, 27 March 1 962 )

Today we captur ed i n the same n et a mother with a lar ge pup as they sleptbeside each other on the cobble beach a t Rifle Ran ge Poin t (Amchitka Islan d ) .

After the n et was placed over them, they both began to st r uggle vio len t lyan d the p up attacked the mother , b it in g h er wher ever i t could . T he motherpaid litt le atten t ion to the p up except that when i ts hea d came n ear her s she

attempted to gr asp the back of i ts n eck i n her teeth— as if to car r y i t off withher . We r emoved the p up fr om the n et an d tagged i t . It was r eleased about2 feet fr om the st r ugglin g, st ill n etted mother . It r ushed to her an d b i t her

on the side i n sever a l places. T he mother ign or ed the b ites an d st r uggled on

with the n et . After taggin g, the mother was r eleased . As she r an to the water ,the pup fol lowed her . T he mother swam r apidly f or about 1 00m. , then stoppedan d the p up sur faced beside her an d p ut i ts for epaws ar oun d her n eck whileboth looked back at us befor e swimmin g out together — their fr ight apparen t ly for gotten .

ATT ENTION T O DEAD YOUNGMothers were occasionally seen carrying dead pups . I watched

a mother carrying a dead, watersoaked pup while she emerged

from the water and rested on kelp-covered rocks . For nearly an

hour she licked the water from the pup’s pelage and groomed its

fur with her forepaws . When it was fluffy and dry,she went to

sleep with it on her chest . H ow long a mother will attend a deadpup is not known but one was observed in which patches of skin

and hair were slipping from the body, indicating that it had beendead for several days . A dead pup was removed from beside asleeping captive mother after she had '

car r i ed the carcass with

her for 3 1 hours . On several occasions we attempted to take deadyoung from mothers seen resting on tidal rocks . Mother otters ,

however, are wary and in each instance , the mother escaped ,

carrying the carcass with her .

Although mother otters carry their pups beneath the surface

during escape dives , they normally leave the young one float ing on

the surface when they dive for food . Dead pups, however , were

carried by the mother while food diving . Unanswered questions

are:Di d the pup die because the mother carried it while diving for

food ? or did the mother carry it to avoid its loss because the furbecame watersoaked causing it to sink after the pup died ?


MOVING YOUNGWhile swimming on her back, the mother sea otter carries her

pup clasped between her forepaws (fig. After a feeding orpreening period, when the pup floats near its mother, she maygrasp the pup with her forepaws and lift it onto her chest or she

may roll on her side , clasp the pup to her chest and then roll again

onto her back . If a mother with a pup is frightened or pursued ,she holds the pup t ight ly with her forelegs and g rasps the side ofits head in her teeth as she turns to dive . Small young may drownduring escape dives if the mother must dive repeatedly at short

intervals ( see D iving ) .

On land the mother otter grasps the side or back of the pup’shead in her teeth and drags i t . The pup is l imp and relaxed , as ifdead, whi le i t is being dragged . Large juveni les usual ly walk beside the mother when they hau l out but if alarmed , the mothergrasps the youngster by the head and drags it . Although a juve

F IGURE 53 .— T he mother sea otte r ca r r ies her p up high on her chest

,clasped

by both fr on t paws. White sca r t issue was seen fr equen t ly on the n oses of

adult fema les but r ar ely on juven iles or adult ma les. It i s pr esumed thatthese sca r s a r e in flicted by the ma le dur ing ma t in g when the n ose of the

fema le i s gr asped by the ma le ’s teeth , usua lly causin g i t to bleed . (KWK57—29—27 )


ni le weighing 1 5 to 20 lb . (7 to 9 kg. ) may be at least as agi le onland as i ts mother, it relaxes complete ly when grasped by themother and al lows itself to be dragged, even over rough terr ain ,making no effort to assist in i ts own prog ress (fig.

NURSING

The mother sea otter nurses her pup from two abdomi nal nip

ples, usually whi le floating on her back . Nursing may also take

place on land (fig. When the pup is smal l it usual ly rests onthe mother

’

s chest and abdomen whi le nursing, both on land orwhile the mother is floating. If the pup becomes hungry and crieswhile i ts mother is feeding, she grasps i t around the chest with

her forepaws and rolls it onto her chest, then turns it around,pushing it headforemost toward her abdominal nipples, allowingit to nurse .

As the pup g rows larger i t nurses while floating belly down , itsbody at right angles to that of i ts mother . Nursing periods are

short, lasting 2 to 5 minutes . The pup kneads its mother’s abdomen

whi le nursing. It was difficu lt to time the durat ion of the nursingperiod because pups often fe l l asleep within 5 minutes and theactual duration of the nursing period was in doubt .

F IGURE 54.— This mother sea otter an d her lar ge juven ile (est imated weight

20-22 l b.,9-1 0 kg. ) wer e sur pr ised on lan d . Although the p up was capable

of r un n in g at least as fast as the mother , she gr asped the side of i ts headi n her teeth an d dr agged i t . On the r ough ter r a in the p up boun ced an d

caught i n cr evices but i t r ema in ed r elaxed an d limp . When the two

r eached the water the p up was a llowed to swim fr ee of i ts mother ’sgr asp. (KWK 62—1 7—37 )



Large juveniles often attempt to nurse . When the mother i s

reluctant, she rolls over . If the young otter is persistent and clasps

her firmly with the forelegs , she may rol l on a horizontal axisrapidly through 5 to 1 0 rotations , which usually dislodges it .

SWIMMINGAt an early age , while the pup is still nearly helpless, the mother

occasionally lifts it from her chest, places it in the water, then

swims slowly away from it. The pup swims bel ly down paddlingclumsily with al l four feet. During these early swimming sessions,the pup frequently cries . The mother may remain just beyond the

pup ’s reach for 50m. or more before she allows it to overtake herwhen she again ro l ls or l ifts it onto her chest . By the time the pup

reaches an estimated age of 2 to 3 months, swimming ability is

improved and i t appears more at ease, crying less when swimming.

When the mother swims near the pup it does not attempt frantically

to reach her but swims quietly beside her (fig. At this stagethe pup apparently has not learned to swim on its back . Swimming

on the back appears to develop slowly. While the mother is resting

the pup often plays , swimming and making shallow dives near

her . During these periods the pup appears to develop the ability

to swim on its back .

DIV ING AND FOOD GATHERINGAfter a pup learns to swim, it attempts to dive . Its first dives

barely take it beneath the surface and considerable effort over a

period of time is required to overcome the buoyancy of its air

fil l ed fur . When the pup finally learns to reach the bottom in

shallow water it brings up star fishes, bits of kelp , and pebbles .

Seldom does it obtain edible items . Even after the pup is nearly a

year old and about three-quarters as large as its mother , and may

obtain much of its own food by diving, it continues to depend on

its mother to satisfy its food needs .

From the time of birth the young otter is able to consume solidfood which its mother gi ves to it . In the early weeks of l ife , however, stomach examinations indicate that milk predominates inits diet . After the pup is a month or two old it frequently pestersits mother for food . When she emerges from a food dive , the pupcl imbs onto her chest to beg for and receive part of the food shehas brought to the surface (fig. Large j uveni les

,able to dive

well but unable to satisfy their food needs,may snatch food for

cib ly from the tolerant mother whi le she is floating on the surface

and eating.


F IGURE 56 .— This p up , pr obably about 2 mon ths ol d

,swims beside i ts mother .

T he mother r emoved the pup fr om her chest , placed i t i n the water , thenswam slowly away wh ile the p up followed . Swimmin g session s, such as this,wer e seen often at Amchitka . They usua lly lasted f or fr om 3 to 5 min utesan d termin ated when the mother aga in lifted the youn g on e on to her chest .

(KWK 1 022 )

SLEEP

Resting and sleeping are more frequent on the water than on

land but mother otters may bring their young ashore to sleep .

Newly born young often sleep while pressed against the mother’sneck, under her chin . As the pup g rows , it usual ly sleeps sprawledfarther down on her chest or abdomen . When the young has

reached a weight of about 1 0 lb . (4+ the mother holds thesleeping juveni le ’s head on her chest or abdomen (fig. 7 ) whi lei ts body floats at right angles to hers . Large juveni les sleep floating close beside and paral lel to the mother . When mother andyoung rest on land

,s leeping posit ions are simi lar (fig.


F IGURE 57 .— A— T he mother sea otter has just emer ged fr om a feedin g dive .

Whi le she eats, her pup (about 2 to 3 mon ths o l d ) cr awls on to her belly .

B— T he pup t r ies to take food fr om the mother ’s p aw. C— T he motherr eaches forwar d, placin g food (a sea ur chin ) i n the pup ’s mouth an d paws .

D— After fin ishin g her food the mother r ises ver t ica lly i n the water whi lein ha l in g befor e r ollin g forwar d i n an other food dive . T he p up con t inuesto eat the food obta in ed fr om i ts mother . (KWK 65—24—1 3 , 1 4, 1 5 , an d 1 6;3 1 October 1 965 )

GROOMINGShortly after birth the sea otter pup makes uncoordinated at

tempts to rub and groom i ts fur . Young animals are, however ,dependent upon their mothers to keep their fur fluff y and dry .

After a feeding period and before resting,the mother otter first

grooms and washes her own pelage thorough ly while her pupfloats nearby (figs . 41 and When she has finished

,she either

takes her pup on her chest to preen and dry i ts pelage or drags itashore . She licks the pup’s fur thorough ly, then fluff s it and rubs it



however, the two slept in close proximity and when alarmed by a

human visitor or unexpected noise they clasped each other withtheir forelegs.

An adult female and two juveni les of about the same size werenetted together on a beach at Amchitka Island on 2 Apri l 1 955 .

The adult showed maternal attention to one pup and tolerated

the other, allowing both to nurse . The adult, however , groomed

only one juvenile and my conclusion was that the other was astray or an orphan that had joined company with the mother andpup . Additional evidence that this may have been the situationwas observed on 9 April . The pup presumed to be the mother’soffspring died short ly before this group of sea otters was to be

liberated at the Pribilof Islands . The surviving juvenile and the

adult female were l iberated together . In the water, the juvenile

attempted to cl imb onto the adu lt but she ignored it and swamquickly away . We then retrieved the screaming juvenile .

The above observations indicate to me that under cer tain condi t i on s a tolerant adu lt otter might contribute to the survival ofan orphaned juvenile . It appears, however, that under conditions

of stress and during times of food shortage an adult might give

littlemore than companionship toward the survival of an“adopted”juvenile .

Re lation to O ther A n imals

Within its usual habitat,which includes the beach, off shore

rocks, and water out to a depth of about 30 fathoms (60 the

sea otter is often near other mammals and birds . Two species, the

Bald Eagle and ki l ler whale, are discussed under “Predation .

”

Harbor seals and sea otters often haul out on the same rocksand rest or sleep near each other . Each species appears to ignorethe other;no i n ter sp ecific strife of any kind was ever seen . In

general , harbor seals and sea otters appear to prefer sl ightlydiff erent resting places . At St . Mak ar ius Point on Amchitkaseveral large rocks are located a few meters offshore . Some of

these were habitually used by sea otters and others by harborseals . If a sea otter found a harbor seal on a favorite resting spot,it selected another place . On several occasions a harbor seal wasseen to cause a sea otter to move . When the moving seal jostledthe sea otter in attempt ing to pass , the otter got up and moved .

In ter sp ecific competition for food is probably negligible . The

harbor seals at Amchitka feed primari ly on octopus and Atkamackerel (Kenyon, l 965a ) . Both of these species may be taken


by sea otters but our fishing operations indicated that fish p opu

l at i on s at Amchitka are large . Also , sea otters tend to feed onsedentary fish that were not found in seal stomachs .

S teller sea l ions seldom chose places that were favored by seaotters for resting on land . When sea lions passed near sea otters

that were diving for food, the otters usual ly raised themselves

high in the water to stare at the sea lions . Otherwise the two

species ignored each other .

Parasitic worms ( T er r an ova deci p i ens, for example ) which com

mouly infest the harbor seal and sea l ion , enter the encysted stage

in fishes . Sea otters that eat fish also become infested . H a l ar achn e

mi r oun g ae, a nasal mite commonly found in harbor seals, wererarely found in wild sea otters . These may have been picked up by

the sea otters at a location commonly used by the two species .

In the wild these pinniped parasites seemed not to seriously aff ectsea otters .

Glaucous-winged Gu l ls frequently obtained scrap s from otters

whi le they fed on fish . I did n ot see gulls attempt to take fish

away from a feeding otter but they swam close to feeding ottersor hovered above them ready to take scraps (fig. When wewere searching for sea otters during census studies, we found

that gul ls were a usefu l indicator of the locat ion of feeding otters .

A group of gu l ls sitt ing together on the water usually markedthe location where an otter would emerge from a food-gathering

dive .

Unlike many other mammals, sea otters at Amchitka did notappear to recognize the cal ls of birds as possible indicators ofapproaching danger . On a number of occas ions , B lack Oystercatchers (H aematop us bachman i ) and Emperor Geese (Phi l actecan ag i ca) were alarmed by our approach when we were stalkingsea otters that were hauled out on the beach . Although the callingbirds sometimes flew direct ly over the otters, they appeared to

pay l itt le or no attention to them.

Rats (Rattus n or veg i cus) introduced to Amchitka during WorldWar II often entered the sea otter enclosure to search for foodscraps . On one occasion a r at approached a sea otter that was

grooming its fur whi le resting on i ts back beside the pool . Aftersniffing at the sea otter’s side

, the r at suddenly jumped onto theotter’s chest . Quickly the otter struck the rat with i ts forepaw,

knocking it a distance of nearly a meter .

In general , i t did not appear that the sea otter was in serious

compet ition with other mammal and bird species within its environ


F IGURE 58.— An immatur e Glaucous-win ged Gull wa its expectan t ly f or fish

scr aps disca r ded by a feedin g sea otter . Gr oups of two or thr ee gulls sitt in gtogether on the sur face i n the A leut ian a r ea usua lly in dicated the locat ionof a sea otter feedin g on fish . While the otter was ben eath the sur facethe gulls wa ited n ear the locat ion wher e they expected i t would emer gefr om a food-gather in g dive. (KWK 57—31 —2 )

ment at Amchitka or that any i n ter sp ecific strife existed . Perhaps

in periods of food scarcity, survival of gu l ls is enhanced throughtheir util ization of the otters ’ discarded food scraps .



That certain individual animals would learn to feed on pelagicforms and thus divorce themselves from the necessity of remaining

in relat ively shal low water is improbable . Observations indicate

that the sea otter subsists only on benthic organisms . Wide, deep

passes between is lands, which prevent bottom feeding, appear to

act as a barrier to the spread of sea otter populations . (See D i str ibution and Numbers . )

Food Gather in g

Many observations indicate that the sea otter uses its forepaws

primarily to gather food and that the tactile sense is important

in locat ing food organisms . A captive female with good eyesightwas offered food in a bucket about half fu l l of turbid water . In

one instance the bucket contained about 200 small crabs (Pachyg r ap sus) , 4 blue mussels (Myti lus edu l i s) , and a number of p ebbles of various sizes . The otter had eaten both organisms beforebut showed a preference for mussels . When the bucket was presented to her, she immediately reached to the bottom with bothforepaws, her chin on the edge of the bucket, and within a few

seconds retrieved the four mussels . She made no attempt to place

her head in the bucket or to look into i t . Thus , she demonstrated

a high reliance on her tactile sense in selecting the mussels from

among pebbles and crabs .

Numerous observations of Susie , during the 6 years that shelived at the Woodland Park Zoo, indicated that she relied heavily

on her tactile sense while retrieving food placed in her pool . She

was blind in her right eye when captured and bl ind in both eyesfor over a year before death . During this period of total bl indnessshe continued to find food and to select the most desired kinds,using her paws to select it . I have observed several healthy wildotters that were bl ind in one eye but have seen only one that wasapparently blind in both eyes . This animal was emaciated andnear death . Existence without sight among breakers in the harsh

coastal environment would probably be impossible even if foodcould be found.

Wild otters normally terminate feeding activities before darkand do not begin morning feeding until after sunrise . Mothers

which must provide for their young, however, may continue diving

for food after dark . I watched a mother diving one evening until

darkness prevented further observations . During the period

shortly before visibility was lost, the otter continued to bring fooditems (mostly sea urchins ) to the surface in the usual quantities .


I thus inferred that '

she rel ied primarily on her tactile ability tofind food .

S ight under water, however, is apparently sometimes used in

locating food . Captive otters on Amchitka often searched the

bottom of their pool by swimming on the surface, head submerged .

Food items on the bottom were quickly located visually in thismanner and retrieved .

The vibrissae may also aid in the search for food . Captive otters ,having an abundance of easi ly located food , abrade the vibrissaeto aminor degree;theymay reach a length of 1 0to 1 2 cm . (fig .

The vibrissae of wi ld otters may be worn off short , to a leng th ofabout to emf Presumably the abrasion occurs during thesearch for food among rocks .

F IGURE 59 .— A capt ive otter poun ds a clam (Pr oto thaca ) on the cemen t edge

of her pool . This otter came fr om Amch itka wher e br eakin g shel ls of foodor gan isms by poun din g was n ot obser ved . T he wh isker s of capt ive otter s

gr ow lon g, as i llust r ated her e . In the wild the whisker s a r e usua lly abr adedan d shor t . Pr esumably wea r occur s dur in g the sear ch f or food amon gr ocks. (KWK 57—24—1 6 )


It wou ld appear that under usual circumst ances the sea otterdoes not use its teeth under water . On many occasions I have seen

sea otters come to the surface clasping l iving fish to their chests

with their forepaws . After surfacing, each otter grasped the fish’s

head in its j aws and kil led i t , suggesting that the teeth are notused to kill fish beneath the surface .

That otters may use their teeth beneath the surface when

necessary to obtain food was demonstrated at Amchitka . In Con

stan t i n e Harbor the otters apparently learned that our net floatsmarked an abundant supply of fish . We often saw an otter on the

surface, eating, near the floats . When we pu l led the nets, we foundfish that the animals were unable to remove but which they hadpartly eaten underwater . Usually about half the fish was left, butoccasionally only the head and pectoral girdle remained . The fish

were not bitten off cleanly;they were chewed, leaving strips ofskin and tooth-marked shredded flesh attached to the entangledportion . The frequency with which we saw otters eating fish on

the sur face near the nets indicated that they were able to remove

a considerable number . Rarely did otters become entangled in thenets and drown .

The stomach of one adu lt male contained a number of large clamsiphons . The siphons, with adhering fragments of mantle and

muscle tissue , appeared to have been ripped from the clams by theotter’s paws or teeth . Visceral material from these clams waslacking in the stomach . Presumably the siphons protruded -from

the sea’s floor and the remainder of the clam was not dug out .Fisher ( 1 939 ) postulated that the sea otter used either a rock

or its canine teeth to remove abalones from the bottom. Cox

( 1 962 ) presents convincing evidence that the sea otter uses a

rock to break the abalone shel l;that the otter then removes theviscera and

,after the abalone dies and releases its ho ld on the rock

bottom, brings it to the surface where it eats the muscle from the

remainder of the shell . Th e behavior of a captive otter , which

persistently pounded a rock against an underwater drain cover

unti l it was able to damage the fastening and remove it (Kenyon ,

lends strong support to the use of a rock rather than theteeth in obtaining abalones . The canine teeth are probably not ofsufficient streng th to remove any but smal l abalones from the

bottom.

A unique habit related to feeding in the sea otter, that of pound

ing hard-shel led mollusks against a stone or other mollusk held onthe chest, has been given much attention , most recently by Halland Schaller A lthough this habit is frequently observed


1 1 0 NORTH AMERICAN FAUNA 68

What Food i s Eaten

The food of the sea otter consists predominantly of benthic i nvertebrates and fish . At Amchitka Island fish predominate (50

percent by vo lume ) , mo l lusks are second in importance, and

echinoderms (mostly sea urchins ) third (table In other areas,mollusks and echinoderms are found to predominate .

That the feeding habits of the sea otter vary in different areas,in accordance with the abundance of food organisms, is indicated

by the statements of Snow who claimed to have examined

hundreds of stomachs . He stated that he did not find clams amongthe food species eaten by the sea otter and that

I have n ever n ot iced an y t r aces of the shells of clams, or limpets, or musselsi n the stomachs I have examin ed , but foun d as a r ule, the r ema in s of cr abs,sea ur chin s, sea-squir t s, an d wha t looked like fish spawn .

He also said that he very seldom found any remains of ordinary

fish , the bones of which would immediately prove its presence .

He adds that the sea otter “finds no difli cul ty in chewing up goodsized crabs , which judging from the contents of the many stomachs

I have Opened and examined, appear to be its chief food .

”Mr .

H . P . Hansen , a king crab (Par a l i thodes p l atypus) fisherman told

me ( 1 964) that in the An dr ean of Islands he“often sees sea otters

eating king crabs , sometimes quite large ones .

”

Although a large variety of organisms is eaten , individual otters

appear to have certain food preferences .

“Individual sea ottersoften prefer a certain food in the assortment of food characteristic

to them”(Barabash-Nikiforov, Some adult males at Amch i tka subsist primarily on fish and rarely eat sea urchin s . In

general , at Amchitka it appears that the otters fall into twogroups— those eating mostly fish and those eating mostly invertebrates . The fish eaters, as would be expected , show a higher deg ree

of infestat ion with certain parasites (principally T . deci p i ens)

TABLE 1 1 .— Vo lume an d c l assifica ti on of food foun d i n 309 sea otter stomachs

fr om Amchi tka Is l an d ,A l aska

[On ly stomachs con ta in in g food . a r e con sider ed . T he samples in clude 1 07 stomachs collected i nJan ua r y an d Febr ua r y 1 962, 20 stoma chs collected i n October 1 962, an d 1 82 stomachs collectedi n Ma r ch an d Apr il 1 963 ]

T ota l volume Per cen t ofFood item (millil iter s ) tota l volume

An n el id wormsCr abs, shr imp , etc._

Echin oderms (mostly sea ur chin s )T un icatesVer tebr a tes

T H E SEA OTTER IN THE EASTERN PACIFIC OCEAN 1 1 1

than those subsisting primari ly on invertebrates . Also , the bonesof “fish -eaters”are white but the bones of those otters utilizinginvertebrates— including many sea urchins— are stained purpleby the biochrome p o lyhydr oxyn ap hthoqui n on e (Scott, i n Fox , 1 953 ,footnote p .

Much indigestible material is swallowed incidentally in the consumption of nourishing food . Part of the test of almost every seaurchin eaten is crushed by the p ostcan i n es and swallowed . Many

stomachs contain scraps of red and brown algae . Seaweeds, as

Barabash-Nikiforov ( 1 947 ) and F isher ( 1 939 ) indicate, cannot be

considered an otter food . This material appears in the feces un

altered i n appearance , except for the wear and abrasion en

countered during passage . I have often seen such scraps of kelp

eaten when entangled among the spines of sea urchins . Its occur

rence in stomachs is accidental .

Smal l pebbles , gravel , and bits of hard clay occurred in 1 4 percent of 475 stomachs from Amchitka . One stomach contained 325

smal l stones . Stones are also commonly found in the stomach offur seals and sea l ions (Eumetop i as and Za l op ha s) and no sure

exp lanation of their presence is known . Although the “gastro l iths”of pinnipeds are usual ly waterworn or smooth , the stones wefound in sea otter stomachs often looked as if they had beenfreshly broken apart;they were seldom waterworn or smooth .

No reason for the swal lowing of this indigestible material isknown .

After food has been selected from the substrate , it is stored for

transportat ion to the surface in fo lds of loose skin (fig. 1 1 ) which

extend from the axi l la across the chest ( see Kirkpatrick et a l . ,

1 955;Barabash-Nikiforov,

If only enough food is gatheredto fi ll the pouch on one side , it is stored under the left foreleg and

paw. If a large quant ity is gathered, it may be stored and carried

in the chest pouches under both forelegs .

When an otter captures a large octopus or fish and satisfies its

appet ite before it consumes the entire organism, it often sleeps onthe water

’

s surface with the remains of such an uneaten meal

clasped to i ts chest . After sleeping for awhile, the otter awakensand continues to eat . Uneaten food , however , is not retained for

an extended period . After the animal has nibbled i ts food intermi tten t l y for perhaps 2 hours , and then begins to groom, the food

is forgotten and al lowed to sink . Capt ives retrieve discarded food

and again eat after g rooming and resting.

On occasions when we have pursued otters with an outboard

motor-powered dory we have interrupted their feeding. When this


occurs, the otters do not rel inquish food rema ining in the chestpouches . In one instance we interrupted a feeding adu lt male andpursued h im for nearly 2 hours . H e invariably evaded us by sur

facing at unpredicted p laces . We finally abandoned as futile oureffort to capture h im and he immediately continued to eat the

sea urchins he had carried under his left foreleg during the entirechase .

When captive otters are given food on land, the items are

transferred to the chest pouch under the left foreleg with the

assistance of the right paw. The otter then walks on three legs to

return to the water with the food . If the quant ity of food exceeds

the capacity of the pouch under the foreleg, additional food may

be grasped and carried in the jaws .

A captive, restin g on her side near her pool , was able to place 1 8clams (Pr otothaca) , ranging from about 3 to 4 cm. in greatest

diameter, under her left foreleg. When a 1 9th was added , most ofthe other s fel l out. E ight clams were easily carried under the leftforeleg whi le the otter walked on three legs about 3 m . to the pool .

Wher e Food i s Eaten

Sea otters normally bring food items to the surface and , usingtheir forepaws , pass the food to the mouth and eat while floating

on their backs . Hooper ( 1 897 probably misinterpreted a statement by Steller ( 1 75 1 ) when he stated that “the otter haul outupon the land to feed on the sea urchins and the other shel lfishexposed at low water . Wi ld sea otters do not carry food from the

water to exposed rocks or beaches and normally do not emergefrom the water to obtain food . I know of no record of a wild ottervoluntarily consuming food on land .

A wild otter that habitually frequented the inshore water near

our fish -cleaning platform quickly learned to take fish scraps fromour hands . After several weeks he often left the water to beg forfood while fo l lowing us about. Even though he accepted p ieces offish as far as 25 m. from the water (fig. he always carried

the food back to the water before eating it .

Captive otters, if they are denied access to water , wi l l eat whilelying on a dry surface , but usually reluctantly . Captives having

free access to water and dry areas , voluntarily leave the water to

obtain food when they are hungry (fig. 62 ) but return to the water

to eat it.

Periodically (usually at intervals of 20 to 30 seconds ) whileconsuming food at the surface , the sea otter stops eating and rol ls



FIGURE 62 .—A capt ive adult female sea otter clasps on e p iece of fish to her

chest un der her left for eleg while she r eaches with her teeth to gr aspan other . After r eceivin g a l l the food she could ca r r y un der the for eleg an di n her teeth

,she r etur n ed , wa lkin g on thr ee legs, to the wa ter befor e she

con sumed her food . T he lon g outer or fifth digit of the hin d foot i si llustr ated . (KWK 59—1 3—1 0)

TABLE 1 2 .— S ea otte'r stomachs exami n ed

[T his l istin g in cl udes an imals pr esumed to be healthy . Most of them wer e shot. An imals foun ddead an d dyin g on beaches a r e excluded ]

S tomachs empty T o ta lLoca tion Number Per cen t Number Per cen t i n ed

6—1 0 Jun e 1 960 S humag i n Islan ds_8—1 0 July 1 960 Ber in g S ea 1

.

22 Jan .—9 Ma r ch Amchitka Islan d_

26—29 O ct . 1 9621 4Mar ch—2 Apr il -do

1 O tter s wer e taken a t sea o ff the n or th co ast of Un imak Islan d .


F IGURE 63 .— A t fr equen t in ter va ls, while float in g on the sur face an d con

sumi n g food , the sea otter stops eat in g an d r olls about i ts lon gitudin a l axisthr ough This act ion washes food slime an d scr aps fr om the chest .

It i s an impor tan t behavior a l cha r acter ist ic tha t helps to keep the fur

clean an d water pr oof . Food slime dest r oyed the water -r esistan t an d

in sulat in g qua lit ies of the fur of capt ive otter s that wer e n ot given access

to water . In n atur e , sea otter s eat on ly i n the water — n ever on shor e .

(KWK 1 021 )

After removal from the p ickl ing bath , they were packed in widemouthed, 5-gal lon cans and shipped to the Seattle laboratory .

After removal from the stomach , the weight and volume of the

contents were measured, the food species were identified, the

percentage composition of each species was evaluated, and all

pertinent data for each specimen was entered on a 3-by-5 card .

A co l lect ion of identified invertebrates and fish,accumu lated at

the Seattle laboratory for the study of marine mammal foodhabits, aided identificat ion of food species . Food organisms that

could n ot be ident ified local ly were sent to specialists who examinedthem and made ident ifications whenever this was possible .

If a feeding otter swal lows the test, she ll , or bony parts of afood organism, the identification of food species may not prove

difficu lt . Such hard parts are usual ly not crushed sufficiently toobliterate al l diagnost ic characteristic-s. Often, however , the feed

ing ott er discards most or al l of the hard par ts , making i den t i


ficat i on of food species diffi cult or impossible . As the stomachswere examined, a collect ion of unknowns was accumulated . Food

organisms found in various stages of mutilation in different

stomachs eventually furnished material that made possible the

recognition of small fragments or badly mutilated food in otherstomachs . The food species found in sea otter stomachs taken at

Amchitka are shown in table 1 3 and a general account of theseorganisms and the sea otter’s habits relating to their consumptionfollows .

Annelid worms were usually torn into pieces several centimeters long and the pieces swallowed with minor damage frommastication . Considerable slimy mucus accompanied annelid r e

mains .

Crabs were torn to pieces and usually the carapace was not

among the stomach contents . The larger legs and chelipeds were

usually thoroughly crushed .

Among the mollusks that were found , various techniques of

ingestion were indicated . Small chitons were slightly crushed andoften swallowed near ly intact . Large ones (Cr yp tochi ton stel l er i )were thoroughly crushed and torn , reducing them to small pieces .

The flesh of l impets was scooped from the shell and swal lowednearly intact and the shel l discarded . Rarely was a fragment oflimpet shell swallowed .

TABLE 1 3 .— F'r equen cy of occur r en ce of food sp eci es i n 309 sea o tter stomachs

fr om Amchi tka I s l an d , A l aska

Number of stomachs havin g itemO f 1 07 O f 20 Of 1 82

stomachs stomachs stomachsFebr uar y O ctober Ma r ch

Food or gan ism Apr il 1 962 1 962 A pr il 1 963 T o ta l Per cen tAn n el idaR ibbon worm Emp l ecton ema

S an d worm N er eis sp

Lug worm A r en i col a sp

T o ta lA r th r op odsCr ustacea

O l ive g r een isopod Idothea(Pen t i dotea )

Amphipods ( pr obabl yin ciden tal )

Shr imp S cl er ocr an g onbor eas

H ermit cr ab Pag urusCr ab:Can cer sp .

T elmessus ch ei r ag on us

Pa r al i thodes? ( l ar val )Pl acetr on wosn essen alciH ap al og as ter sp

Un iden tifiedShr imp



Snails were recognizable in stomachs because the tough muscul ar foot was usually little aff ected by chewing and often thechitinous opercu lum remained intact and attached to the foot . The

shells of small snails (Bucci num sp . ) were often swallowed butthose of large ones (Ar g obucci num or eg on en si s) , except the opercul um, were not.

C lam shells , except those from smal l individuals,were seldom

present in the stomach . One stomach contained about 2 l iters ofclam meats, the foot and viscera of many almost intact, but notone scrap of shel l . The shell of thin-shelled clams (S er r i p es g r oanl an di cus) were fragmented and swal lowed in considerable quantity.

The small mussel Musculus ve'r n i cosa , which was consumed in

large numbers, was usual ly swal lowed whole . Individual musse lsmay appear in the feces with the valves st i l l intact. Many fragmen ted shells of larger mussels

,such as Vo l sel l a vo lsel l a, some

times appeared i n feces . Often , however, stomachs having a numberof mussels contained little or no shel l . The viscera were r ecog n i zable by their orange color and attached byssus .

The pearly monia (Pododesmus macr oschi sma) appeared in 50

stomachs, often in considerable quantity but only a few tiny

fragments of shell were found . Observations of feeding otters

revealed that, after slightly loosening the valves with one caninetooth, the two valves were twisted horizontally past each other

between the paws so that the viscera could be quickly scoopedwith the lower incisors and tongue from the half shell to which

it adhered . Seldom are the shel ls broken during this procedure .

S ince few hard parts of this species are ingested , it is not r e

vealed as an important food species in fecal examinations .

Octopuses are eaten with particular enthusiasm by captive ottersand wi l d otters also appear to relish them . Because of its size

( commonly 2 to 4 the octopus constitutes an excellent food

source at Amchitka. Apparently otters are not disturbed by thewrithing tentacles of this mollusk . Pieces of arms are bitten offand eaten when one moves within range of the paws and mouth .

Other tentacles wrap themse lves about the otter’s head, legs, andbody while the otter continues to tear off and swal low chunks offlesh (fig. Occasionally a sucker attaches itself to the otter

’

s

palate but it is quickly torn loose by the extended claws of theforepaws . A large octopus may furnish sufficient food for more

than one feeding period . The chitinous beak of the octopus may

or may not be swallowed . Even if it is, fecal examinations do not

reveal the importance of this food species .


FIGURE 64.— Food taken fr om a sea otter stomach:A— fr agmen t of octopus

jaws;B— sma ll pebbles;C—b ctop us ten tacles an d man t le;D— a scar idworms (pr obably T er r an ova deci p i en s ) E— fin s, skin , an d oper cular spin esof the r ed I r ish lor d (H emi l ep i dotus hemi l ep i do tus ) . T he sea otter

’s

teeth a r e n ot adapted to cutt in g;the tough octopus flesh i s swa llowed i nchunks that show litt le effect of chewin g . ( T he pen ci l i s 1 2 cm . lon g . )

(KWK 1 01 3 )

A captive otter was fed 5 lb . kg. ) of squid (Lo l i g o) daily.

Before beginning to eat each squid he removed the pen by grasping

its tip between his incisors and drawing it from the mantle . He

then discarded it over his left shou lder by turning his head quicklyto the side.

Starfish of several species are of minor value as a sea otter food .

Although a number of stomachs ( 1 1 1 ) contained starfish remains,the volume was small . I have seldom observed a feeding otter thatate an ent ire starfish . The otter usual ly tears off and eats one ortwo arms of a star fish , then loses interest and discards the r e

mai n der .

Fecal and stomach examinations indicate that the green seaurchin (S tr on gyl ocen tr otus dr obachi en sis) is frequently eaten and

this food has been considered the most important, if not essential ,item in the diet of the sea otter . With capt ive sea otters , Shidl ovskaya ( 1 947 ) stated that

“Longer interrupt ions than 5 days in


feeding sea urchins shou ld not occur . Evidence that this as

sumption is not always true is presented under “Relative Valuesof Sea Otter Foods .

”

The method of ingesting green sea urchins varies according to

the size of the sea urchin and also somewhat according to thehabits of individual otters . Stomach examinations and observationsof feeding otters indicate that some animals habitually ingest

more of the test than others . Small urchins are crushed by themolars and usual ly at least part of the test is swallowed (fig.

Lar ge urchins may first be bitten with the p ostcan i n es on one side,

F IGURE 65 .— In tact sea otter food or gan isms ar e shown at the top of column s

A to E , an d par t ia lly digested fr agmen ts of the same species r emovedfr om stomachs a r e shown below. A— six-r ayed star (Lep taste'r i a s sp . ) B

gr een sea ur ch in (S tr on gy l ocen tr otus dr obach i en si s ) C— sea cucumber(Cucuma r i a sp . ) D— pea r ly mon ia (Pododesmus macr oschi sma ) E

mussel (Myti lus edu l is ) ;F— fr agmen ts of mar in e a lgae . A lgae, which i svoided un digested i n the feces, i s n ot a food species but i s eaten acciden ta lly.(KWK 1 01 1 )



mastication ( seals and sea l ions may,however

,tear chunks from

a fish that is too large to swallow intact ) . The sea otter apparently

captures fish with its paws and al l fish flesh found in stomachs had

been torn into chunks that were crushed before swallowing. No

fish were swal lowed who le .

Thus, the sea otters’ manner of capturing and eating fish is

unique among marine mammals . After the fish was brought to the

surface and killed by a crushing bite at or near its head, it washeld in the paws and chunks were torn from it, masticated to a

moderate degree and swal lowed . Some chunks of fish found instomachs measured about 3 x 4 x 5 cm . Eating usually began at

the fish’s tail and often all or most of the head (particularly of thecottids ) and viscera were discarded . Strong adu lt males claspedthe fish body firmly with the forepaws and extended claws , then,starting at the anterior end ripped the skin with the canines andincisors from first one side, then the other . The flesh and bones

were then rapidly eaten l ike a candy bar . Gl obefish , being scale

less and having soft bones, were consumed almost in their entirety .

In the Shumag i n Islands four adult male and one adult femalesea otters were taken on 6 and 7 June 1 960 at S imeon of Islandand one female on 1 1 June at Little K on iuji Island . Four stomachs

were empty. The stomach contents of two males are shown in

table 1 4.

Of interest is the fact that among the contents of the two

stomachs which had a combined vo lume of liters

mostly clam meats, there were no scraps of clam shell . For this

reason , the species eaten could not be positively identified . Dr .

G . D . Hanna did , however, tentatively identify the large siphons

as belonging to the Washington clam (S chi zothaer us nutta l l i i ) .

Perhaps this large clam was not removed from the sand bottom

or the she l l could not be broken or opened by the otter . About 1inch of the siphons appeared to have been bitten or ripped from

the clam bodies . A captive otter demonstrated that clams , evenlarge horse clams (S chi zothaer us) , are cracked either against a

TABLE 1 4.— S tomach con ten ts of two ma l e sea otter s fr om S imeon of Is l an d ,

S humag i n I s l an ds, A l aska

Volume

S pecimen an d food item (mill il iter s ) In dividualsKWK 60—6:Cl am feet 2 425

KWK 60-8La r g e clam syphon sSma ll clam feet.H o r se musselWhelk oper culum


rock or against another clam resting on the otter’

s chest (fig.

It is thus inferred that clams which are buried are not dug fromthe bottom.

In the Bering Sea on 8 and 1 0 July 1 960, one adult male and

two adult female otters and two pups were taken miles off the

north shore of Unimak Island in a depth of 1 5 fathoms and 9 mi lesnorth of the Alaska Peninsu la in 20 fathoms . The food habits of

these individuals are of particu lar interest because no otherstomach specimens of otters which habitual ly remain off shore areavailable . The foods found in three of the stomachs are shown in

table 1 5 . All food items (clams, crabs , and a hexag r ammi d fish )are benthic forms . This indicates that here , as in other areas, the

sea otter is predominant ly a bottom feeder ( see D iving) . The lack

of feces on the beaches of nearby Amak Island in July 1 96 1 and1 963 indicates that otters in this area seldom come ashore .

Feca l An a lyses

Studies of sea otter food habits prior to 1 962 were based

primarily on analyses of fecal remains (Wi ll iams , 1 938;Murie ,1 940;1 959;Jones , Al l of these studies indicated that thesea urchin was the dominant food species .

About 95 percent of 422 fecal samples I examined at Amchitkacontained sea urchin remains (table Stomach examinations,however, as wel l as other studies discussed elsewhere ( see Relative Values of Sea Otter Foods ) , indicate strongly that mollusksand fish are essential foods and that in some areas sea urchins

may be of relatively minor importance and then primari ly duringtheir season of reproduction .

The examination of feces may contribute certain qualitative

TABLE 1 5 .— S tomach con ten ts of thr ee sea o t ter s taken i n 1 5—20 fa thoms of

wa ter i n the Ber i n g S ea

V olume

S pec imen an d food item (mill il i ter s ) In dividua lA dul t fema le (KWK 60—1 6 )

Cl i n oca r di um ci l ia tum .

S ur f clam ( S p i sul aFish ( H ez a g r ammos

Pup (EWK 60—1 8 )

A dult female ( KWE 60—1 9 ) 1

018 1 1 1 ( S er r i p es g r oen l an dicus )T an n er cr ab ( Chi on ecetea ba i r di )H erm it cr ab ( Pa g ur usCr ab , un iden tifiedMus cul uc n i g er

1 Both stomach an d in tes tin a l con ten ts in cluded .


TABLE 1 6 .— An a lysi s of 422 feca l samp l es fr om Amchi tka Isl an d, Febr uar y

to Ap r i l 1 959

[T he samples wer e exam in ed on seven habitually used haul in g -out beaches ]

Food or g an ism 1

A r thr opodaCr abs Cr ustacea )

Mo l l uscaChiton s (Amphin eur a )S n a ils ( Gastr opoda )Limpets A cmea

H or se mussel Vo l sel l a volsel l aMussel Myt i l us edul usVa r n ished hor se mussel Muscul us ver n i cosaPear ly mon ia Pododesmus macr och i sma

Clam (Pelecypoda )Pecten ( Pelecypoda )Octo pus Cephalopoda )

Echin oderma ta:3S ea ur chin S tr on g yl ocen tr otus dr obachi en sisChor da ta :Fish

1 Non food mater ia l , clay, g r avel , etc . , was foun d i n seven feca l samples .

2 Fr equen cy r efer s to the n umber of samples havin g th e item , n ot the n umber of in dividua l spr esen t.3 S ta r fish wer e pr obably br oken in to fin e p ieces an d thus n ot detected.

information concerning the food habits of sea otters but, becausehard parts of some food species are not ingested, information de

rived from fecal examination contributes distorted informationon both the qualitative and quantitative aspects of food habits .

Otters must defecate on land if fecal samples are to be studied.In many areas otters defecate on land infrequently or not at all .Weather conditions, geographical features ( such as sheltered

beaches above the tide line ) , and the presence of a human pcpu

lation appear to influence the frequency with which sea otters haul

out on land . Like al l other marine mammals , and unlike manyterrestrial ones , the sea otter is not selective in choosing a de

fecat i on site . When sleeping or resting on land , the otter usuallyrises to i ts feet and expels the feces at the edge of its restingplace . As it changes position for comfort during several hours onshore, feces may be deposited in several locations around the resting spot and the animal may, in changing position , l ie in its ownfeces . Defecation in the water is also a random function and mayoccur while the animal is eating, swimming, or resting on its backon the surface . Although , as noted above, defecation on land isfrequent, I have often noted that captive otters, after a rest period

beside their pool, may defecate immediately upon entering the

water.



TABLE 1 7 .— An a l ysis of 75 f eca l samp l es f r om the S humag i n Is l an ds

[ 1 5 samples wer e taken at S imeon of Islan d, 5—9 Jun e 1 960 an d 60 at Eagl e H ar bor , Nag a iIslan d on 1 6 Jun e 1 960]

Food or g an ism

A r thr opodaCr abs ( Cr ustacea )

Mol lusca:Sn a il s Gastr opoda )H or se mussel Vo l sel l a vol sel l aMussel Myt i l us edul usClam ( Pel ecypoda )Subtota l

Echin oderma taS ea ur chin S tr on g yl ocen tr otusChor da ta:

such as high winter morta l ity, indicates that the sea otter pcpu

lation has approached its maximum size in the Shumag i n Islands

as it has at Amchitka . It might therefore be concluded, in thelight of al l avai lable evidence ( see Relative Values of Sea OtterFoods ) , that the sea otters of Amchitka consume a large numberof sea urchins because other food resources have been depleted .

In areas where otter popu lations have not yet approached maximum size, food species more nourishing than sea urchins are

sti ll abundant and the sea urchin may be eaten to a minor degree .

The fecal analyses presented here give useful qualitative i n

formation on food habits . They show that the food habits of ottersin a crowded popu lation diff er from those in areas where crowdingis not a factor . It is, however, evident that stomach analyses are

necessary to reveal the food habits in their proper perspective . Adiscussion of the method of ingestion of each group of food

organisms indicates in more detail why fecal examinations are of

only limited use in food habits studies of the sea otter .

Food Quan tities Requir ed

The food requirement of the sea otter is great. Captive juveniles

held on Amchitka Island during the 1 957-59 study periods r e

quired from 25 to 30 percent of their body weight of food per day.

The quantity of food consumed by captive adult otters did not

vary according to season . The required amount for an adult male

and female was similar, about 20 to 23 percent of the body weightper day. The data are discussed in the section on the sea otter

In Captivi ty.


Re lative Va lues o f Sea O tter Foods

Miss Neva L . Kar r i ck , Assistant Laboratory D irector, Food

Science P ioneer Research Laboratory of the Bureau of CommercialFisheries at Seatt le, has furnished proxima te analyses of certainrepresentative sea otter foods (table From these data and

the known quantit ies of food consumed by captive otters and data

obta ined from stomach examinations, it is evident that the sea

urchin is seldom as important a food item as previously supposedand that the sea otter is primarily dependent for survival on

other foods with more calories and higher protein content .

A capt ive sea otter weighing about 40 pounds required an

average of about lb . of food, primarily r ockfish , per day (24

hour period ) . This diet supplied about calories (about 89

calories per 1 00 grams of fish ) . Sea urchins with g ravid gonadscan supply roughly 58 calories per 1 00 grams of gonads and 1 6calories per 1 00 g rams of viscera. If large gravid sea urchins wereavailable

,about 200 would be required to supply calories

to a sea otter in a 24-hour period .

Most of the sea urchins now avai lable at Amchitka are small .The reason appears to be that a large sea otter population is over

util izing this food resource ( see Depletion of Food Resources ) .

Mature gravid green sea urchins , weighing about 1 1 5 g. each ,

were obtained for analysis from an area at Go l d Bay, A laska,where there are no sea otters . At Amchitka, the size avai lable ingreatest quantity weigh about 6 to 1 0 g. These are consumed in

large numbers , particu larly by juvenile otters . The gonads in

these immature sea urchins are almost microscopic . The amount

of visceral material available in them is small and is a poor

TABLE 1 8 .— Pr oxima te an a lysi s of imp or tan t sea o tter food sp eci es

[Aver ages . T h e e da ta wer e fur n ished by Bur eau o f Commer c ial Fisher ies T echn o l ogica l Labo r a to r y, S ea ttle, Wash . ]

Pr o tein Ca lor iesMo istur e Oi l X N . Ash p er 1 00

S peci es ( per cen t ) ( per cen t ) ( per cen t ) ( per cen t ) gr ams 1

Dun gen ess cr ab mea t Can cerma g is ter .

Butter clam S axi domua n ut tal l iO ctopusS ea ur chin S tr on g yl ocen tr otua

1 Calor ies p er 1 00 g r ams aver age per cen t o i l X 9 plus ave r age per cen t p r ote in X 4.”al

S ea

egt ter s usua l ly disca r d most or a l l of the viscer a of octopus;ther efor e on ly the flesh was

an yz


nutritional source . Because of the general depletion of inverte

brates and the apparent inabi l ity of juvenile otters to obtain anadequate number of fish and mollusks , these young animals are

compelled to eat the abundant and easily obtained immature sea

urchins . An otter would have to consume nearly of these immature urchins daily to supply the calories which appear

to be required .

D ep letion of Food Resour ces

The requirement for large amounts of food by sea otters hasbeen discussed . Feeding grounds are limited by depth to relativelyshallow waters and tag returns indicate that individual sea otters

do not range wide ly along the coast (see Home Range ) . Because

of these circumstances which concentrate feeding activities in

rather limited areas, it appears probable that a large population

of sea otters could seriously deplete food resources within their

home range . Evidence is available that this does in fact occur .

SEA URCH IN DEPLET ION

McLean ( 1 962 ) presents convincing evidence that the sea urchinS tr on gyl occn tr otus fr an ci scan as has been nearly exterminated in

a particular area on the California coast which is occupied by a

considerable number of sea otters . Of the area he studied he says

(p . 1 01 )“the large sea urchin was totally absent, although sp ines

and test fragments were present in gravel samples .

”

Indirect evidence from Amchitka Island, where a large sea otterpopulation exists, indicates that sea otter predation has drastically

reduced certain food species there . Small green sea urchins areabundant. It is not possible, however, to find large individuals in

the intertidal zone and I seldom saw an otter eating an urchin

that approached in size the large individuals which are abundantin other A leutian areas where the sea otter is scarce or absent.Bottom samp les obtained by R . D . Jones, while diving with

SCUBA equipment, both at Amchitka and in comparable areasat Adak (where at the time few sea otters occurred ) , showed thatsea urchins at Amchitka are relative ly scarce and smal l .In a recent letter ( 1 6 December Jones reported on a

subsequent visit to the Adak area he had explored prior to thetime that it was occupied by a large number of sea otters

In 1 957 the gr een sea ur chin was numer ous an d obvious i n this ar ea , an d thist ime I saw n on e. I have n o quan t itat ive data because I had n either the equip



str ated that the local abalone beds were seriously decimated butnot entirely eliminated by sea otter predation .

In a publ ic statement, additional information was given byCox (California Senate , 1 963 )

In 1 956 we wen t in to Shelter Cove r ight off Mon ter ey an d over a per iod of

sever a l days tagged 51 3 aba lon e. On e yea r later we came back i n the a r ea an d

we spen t appr oximately thr ee days sea r chin g an d we foun d five aba lon eon e of wh ich had a tag . T he ar ea wher e we wer e able to co llect five hun dr edaba lon e i n an hour we couldn ’

t fin d any. On on e dive I br ought up over twodozen br oken shells char acter ist ic of br oken on es of the sea otter s. We

wer e told by the car etaker , that a her d of sea otter s had spen t thewin ter i n this cove I had been ca l led to task f or n ot r epo r t in g this:However , I felt th is was n ot an adequate exper imen t .

In a recent study of sea otter feeding habits on the California

coast, Ebert ( 1 968 ) concluded that “sea otters exert a profoundinfluence upon benthic communities .

During 1 963 , abalone fishermen in San Luis Obispo County,California, comp lained that sea otters were destroying the abaloneresource - of that area . C laims of spectacular damage to abalone

beds appeared in many newspapers . In response to these com

plaints a hearing was held at the C ity Hall, San Luis Obispo, on1 9 November 1 963 . At this hearing Mr . Harry Anderson , DeputyDir ector of the California Department of Fish and Game, presentedtestimony to the Cal ifornia Senate Fact F inding Committee onNatural Resources . He compared commercial landings of abalonesin cer tain areas before and after sea otters were present in these

areas . In 1 96 1 when sea otters were present “the catch was overpounds, by far the largest catch of any year in the

1 0-year period .

”He indicated further that competition amongabalone fishermen has increased greatly . In 1 928 there were 1 1

l icensed commercial abalone fishermen in California . The numberhas increased to 505 in 1 963 . S ince the abalone resource is limited,it becomes apparent that the individual fishermen can expect toobtain fewer abalones than when competition among them was

less . It was concluded that “all the evidence we have indicatesthat the sea otter has not seriously harmed or threatened the

abalone resource .

”

The data indicate that the depletion of food resources at Am

ch i tka has resulted in an abnormally high winter die-off of seaotters as well as a population of undersized animals ( see Mortality

Factors and Body Measurements ) . Evidence from California r e

veals that when sea otters feed for an extended period in a limitedarea they may seriously deplete local populations of their prey

species .

THE SEA OTTER IN T H E EASTERN PACIFIC OCEAN 1 3 1

Un usua l Food Items

BIRD SOn 27 March 1 962, at Amchitka Island , I watched an adult

female sea otter through a 50-power telescope whi le she consumed what appeared to be a shearwater (Puffinus) or Fu lmar(Fu lmar us) . When first seen she was carrying the carcass on her

chest . She stopped in the shelter of an islet to g room, leaving thebird floating beside her . After about 5 minutes of grooming shepicked up the bird and tore flesh from the breast . She alternatelygroomed and ate for about 30minutes . While she ate , the bird’sintestines streamed out across her chest and feathers littered the

water around her. After apparently satisfying her appetite sheswam away carrying the carcass , bloody sternum erect, on her

chest.

On 1 3 November 1 957 , I found sea otter feces at East Cape ,Amchitka Island , which consisted of feathers, skin, fat, and flesh

(breast muscle ) of what appeared to be a cormorant (Pha l acr ocor ar p e l ag i cns) . The chunks which were torn from the bird

showed l ittle indication of having been affected by passage throughthe digestive tract.

Hungry captive otters consumed Emperor Goose (Ph i l acte

can ag i ca) flesh (Kirkpatrick et a l . , 1 955 ) but Jones told me that

the meat passed undigested through the al imentary tract .It appears that the flesh of birds is eaten only under the stress

of hunger, part icu larly in winter . Also , the sea otter , adjustedto a diet of fish and invertebrates, seems unable to derive nourishment from the flesh of birds .

MISCELLANEOUSOn several occasions sea otters were seen to eat unusual food

items that zoo visitors threw into their pool . These included a sl iceof white bread, a marshmal low, and peanuts . The animals ap

p ear ed to suffer no i l l eff ects from ingest ing these items but thekeeper reported that the peanuts passed through the animal un

digested .

C on clusion s

It is evident that fecal examinations give less adequate i n formation about sea otter food habits than similar studies for otherspecies . Certain food species ( clams and certain fishes ) may not


appear in recognizable form at all in droppings because shells are

n ot swallowed and the bones of some fish (Cycl op ter i chthys) are

soft and are digested . On the other hand, when sea urchins are

eaten some part or all of the test may be swallowed . The important

quantities of high protein food contained in mollusks and fish can

not be evaluated by the examination of feces.

It has been wrongly assumed that sea urchins held fir st -rankimportance as a sea otter food . Barabash-Nikiforov ( 1 947 ) bel i eved that sea urchins were essential to survival . There can beno question but that where and when mature g ravid sea urchins

are avai lable they are an important food source . That they are not

essential to sea otter existence is demonstrated by: 1 ) A captivesea otter was given no sea urchins for a period of 4 years and

remained in good health;2 ) numerous captives held on Amchitkarefused to eat urchins after being introduced to a diet of fish;(3 ) each winter many juvenile sea otters (apparently incapable

of obtaining fishes ) died of enteritis (probably induced by shockor stress accompanying starvat ion ) and were found to have the

remains of considerable numbers of sea urchins in the intestines;(4) feces and stomachs of sea otters taken , for example, in the

Shumag i n Islands, contained few, if any, sea urchin remains (al

though sea urchins occur there ) .

My con cl us10n i s that sea urchins may, during their season of

reproduction in areas of abundance, rank high in import ance as

a sea otter food source . Where an abundance of mollusks andfish may be obtained, however, the sea urchin is at no time an

essential food species . The food value of the sea urchin may vary

from poor to good, depending on maturity and the season of r e

production . Mol lusks and fish , however, when available and to

those animals able to obtain them , furnish an adequate and con

si sten t l y nourishing diet. Mol lusks (37 percent) and fish (50 percent ) , relatively high i n calories, account for 87 percent by volumeof the sea otters’ food at Amchitka .




Barabash-Nikiforov ( 1 947 ) and Nikolaev ( 1 960) indicate that

on the east coast of S iberia the sea otter may have ranged to

64° N . The records , however, are vague . Gu l in ( 1 952 ) photo

graphed the skin of a sea otter said to have been taken by localhunters at Lavrentiya N . lat .

,1 7 1

° E . long . ) near Bering

Strait on the Chukotsk Peninsu la . No date or other specific dataare given . S uch a casual report in a popular magazine of a seaotter so far north of the usual range must be regarded withskepticism.

Specific records as far north as 64° do not appear to be available .

Gr ibkov ( 1 963 ) says that the known boundary of the sea otter’

s

range is 57 ° N . on the east coast of Kamchatka but mentions that

in 1 960 sea otters“were bagged north of this point .

The occurrence of a permanent sea otter population in the

northern Bering Sea or Arctic Ocean where the sea freezes isquite unlikely . That a stray otter might have traveled north withpack ice in spring from the lower l imit of winter drift ice insouthern Bristol Bay and the southeastern shore of Kamchatka,i s a possibil ity. Retreat ing winter ice might account for the pres

ence of three sea otters at the Pribi lofs in 1 889 , 1 892, and 1 896(Preble and McAtee, 1 923 ) long after they were extirpated there .

A sighting in Norton Sound (64° N . ) in June 1 941 , was reported

by Frank Glaser ( i n Len si nk ,

In general i t is true today, as it was in early times , that theprosperous sea otter colonies are south of areas where sea ice

forms regu larly and remains for long periods in winter months .

The environmental factors that control the southern limit ofdistribution , other than predation by man and environmental

pol lut ion caused by h im today , are unknown . Additional sourcesof information on aboriginal distribution are cited by BarabashNikiforov

POPULAT ION REDUCT IONTH ROUGH EXPLO IT AT ION

Intensive exploitat ion of the sea otter by Europeans began withthe voyage of Vitus Bering in 1 741 and continued unregulated for1 70years . Exploitat ion was halted and protection was given to thesea otter by internat ional treaty in

8 Con ven tion between the Un ited S ta tes , Gr ea t B r ita in ,Russ ia , an d Japan fo r the pr eser va

t ion an d pr otecti on o f fur seals . P r ocla imed 1 4 December 1 9 1 1 an d a ppr oved 24 August 1 9 1 2.

A r t icle V o f th is Con ven tion exten ded pr otection to the sea otter . Fur ther pr otection was ex

ten ded by th e “P r es iden tia l P r oclama tio n f o r the pr eser va tion an d pr o tection o f f ur seals an d

sea otter , sign ed by Woodr ow W ilson on 3 1 May 1 9 1 3 , an d a n“Executive o r der r eg a r din g

the pr otection of fur seals an d sea otter s , sign ed by Ca lvi n Cool idge on 1 4 Jan ua r y 1 929

(U .S . Bur eau o f F isher ies ,


The sea otter was then commercial ly extinct and nearly extinctas a species . The number of sea otters that were taken during theperiod of unregu lated exploitation is not known because properrecords were not kept . Most records are vague concerning where

skins came from, except that they came from the New World .

F isher ( l 94ob ) states that her summary is not complete but listsrecords of skins taken between 1 740 and 1 91 6 . Between

1 745 and 1 867, sea otter skins were reported as having

been shipped from Alaska”and from 1 868 to 1 905 the take was

skins (U.S . Bureau of Fisheries, From 1 906 to1 9 1 0, 240 skins are recorded taken by U.S . and Canadian hunters

(U.S . Bureau of F isheries, 1 907 through Thus the total

recorded number of skins taken in waters off Alaska, prior to1 9 1 1 , was Skins taken by hunters of other nationalitiesare not recorded . Len si n k ( 1 960) presents figures and broad estimates which place the take of sea otters from Alaska at over

animals .

PO ST ULATED SIZE OF ABORIGINAL PO PULAT ION

From data gathered during recent studies , some idea of the

possible take may be postulated . Today it appears that about

sea otters occupy approximately one-fifth of the originallineal coastal range of the sea otter . Some of the presently occupied

habitat is of superior quality . Islands contribute more usable

habitat than do unbroken cont inental coastl ines . Thus , it is prob

able that the population of sea otters in 1 740 may have been no

more than five times the present number, probably betweenand animals . If the annual increment that could

be cropped on a sustained yie ld bas is was about percent per

year ( the approximate annual yield of the Pribi lof fur seal (Ca l l orhi nus ur si nus) herd is 5 percent per year and fur seals normally

bear one pup each year;2 years elapse between sea otter pups ) ,then the take in 1 70 years could have been between and

if cropping had been rational . The kill ing of sea otters,however, was unregu lated and for periods of many years the takewas at the expense of the popu lat ion “capital .”Probably certainpopulations were wiped out during an early part of the exploitation

period . Thus the yield over the entire period was less than it wouldhave been if only the annual increment had been taken . Reasoning

on this basis, it appears that the probable take of sea otters between

1 740 and 1 9 1 1 was less than a mi ll ion and more likely about ahalf mi llion animals .

In the following section, sea otter population studies in Alaska




of unregulated hunt ing are indicated by ( 1 ) areas where large

populations are found today, and (2 ) areas where sea otters were

taken shortly before and after 1 9 1 1 . Fragmentary data on otters

that were taken between 1 906 and 1 936 are reviewed briefly

below.

Records of the U.S . Bureau of F isheries ( 1 907—37 ) indicate that

at least 302 otters were taken in Alaska from 1 906 through 1 936 .

Of these, 240 were taken between 1 906 and 1 9 1 1 and 62 from

1 9 1 2 to 1 936 . For 21 3 skins ( 1 86 before 1 9 1 1 and 27 after 1 9 1 1 )no location of origin is given , but many apparently came from theAleutian

,Sanak

,and Kodiak Islands areas . The specific locations

of origin of the remaining skins were often not stated clearly. It

appears,however

,that the remaining 89 skins may be al located to

the fo l lowing areas:Aleut ians, 7 (4 in 1 9 1 0 and 3 in

Southern Bristo l Bay and Bering Sea north of Unimak Island, 1 5(al l before 1 91 1 ) Alaska Peninsula, south coast (about 56 °6 ( 1 9 1 8 , 2;1 929 , 2;1 93 1 , Sanak Island area, 3 ( 1 926, 2;1 934, 1 ) Shumag i n Islands , 1 ( 1 9 1 0) Kodiak area, 52 (3 1 before1 9 1 1 and 21 after 1 9 1 1 ) Prince Wi l l iam Sound and Kayak Islandarea, 5 ( 1 9 1 0, 3;1 924, Within these areas otters probablysurvived along exposed coasts that offered few if any anchoragesand where off shore reefs made hunt ing hazardous . Such areasalso offered otters feeding habitat wel l offshore .

The map (fig. 68 ) and table 1 9 summarize moder n field counts

and estimates of sea otter popu lations in Alaska and indicate thatmost of the popu lat ion is concentrated in an area about 500mileslong which includes the Rat and part of the An dr ean of Islands

observed , 1 965 , table From the present spearhead of

population expansion in the central An dr ean of s eastward to the

next small colony at Atka (228 observed, 1 965 , table 25 ) is about75 miles . The next colony ( 1 59 observed , 1 965 , table 25 ) is 50miles farther east, near the east end of Aml ia . Moving eastward30 miles , the next colony (28 observed , 1 965 , table 25 ) is at

Seguam. From here to the smal l Sama l g a-Umnak colony (9 ‘

ob

served , 1 965 , table 30) is 1 40 mi les . The next smal l colony (32observed , 1 965 , table 30) is at T i g al da Island 1 75 miles to the east .

From here to the Unimak—Amak—Port Moller colony oh

served, 1 965 , table 30) is 75 miles . Along the south side of theAlaska Peninsu la and northeastward to the Kayak Island area, adistance of about 800mi les , the colonies observed , table 36 )are not separated by any known geogr aphic barriers .

After the publ icat ion of population and distribut ion studies byLeusink ( 1 960) considerable field work was undertaken . The data


TABLE 1 9 .—S umma r y of sea otter s obser ved an d est ima ted i n A l aska

[S ee tables i n section s f or coun ts by islan ds . Most a r eas have n ow been sur veyed sever a l times .

T he hig hest coun ts which wer e made un der Optimum con d ition s wer e selected f or this sumobser ver s, D . L . S pen cer , C . J . Len s i n k , an d K . W . Ken yon ga ther ed most oft ese ata

Aer ia l sur veys

A r ea Yea r

Near Islan dsRat Islan dsDel a r of Islan dAn dr ea n of Isla n dIslan ds of the Four Moun ta in sFox Islan dsBog osl of Islan dS an dman ReefsS an ak Islan d ar ea __

S humag i n Islan dsPavlov Islan dsA laska Pen in sulaS emi di Islan dsKodiak ar eaPr in ce Will iam S oun d

an d Kayak Islan d 1 004

T o ta l1 S ee Aer ia l Sur veys for method of estima tin g .

2 Pr ojected i n the r eg ion s wher e g r owth was obser ved on the assumption that th e in cr ease isat the ra te of 5 per cen t p er yea r .

3 T ota l

now avai lable indicate that in significant areas sea otter p op ul ations have decl ined and are less than the est imates wh i ch Len si nkcomputed on the basis of figures then available to h im. Len si nk

( 1 960) considered that sea otter feeding habitat included waters

to a depth of 50 fathoms, but no evidence is avai lable that theydescend to this depth ( see D iving) . Because of this assumption a

greater area of available habitat and greater population potentialwas postulated by Len si n k than is indicated by information nowavai lable . A lso , Len si n k ’

s ( 1 960) estimates for a large sea otter

population at Amchitka do not agree with the modern or historicaldata for this area . The rate of popu lation g rowth which he postulated is greater than indicated by the data now avai lable . In addi

tion, as shown later, the Amchitka population “crashed in the

1 940’

s and now fluctuates annually near a population about onehalf its max imum size .

A er i a l sur veys

The most extensive aerial surveys consumed about 200 hours of

flight time in a DC—3 aircraft ( table A ir speed was maintainedat 1 20 knots and flight altitude varied from 200 to 400 feet, de

pending ou winds and nearby terrain . Two observers counted

otters from the aircraft’s cockpit . Some groups were so large that



al l individuals cou ld n ot be counted in the time avai lable . In such

groups we counted a sample of 1 0 to 50 animals . We then visually

divided the remainder of the group into sectors equivalent to the

counted sector to obtain an estimate of the total number of animals .Aerial photographs were taken of unusually large groups to ascer

tain the accuracy of the fie ld estimates ( see Aerial Photography ) .

The flight path was divided at the center l ine of the aircraft. Oneobserver stood behind the pilot and the other behind the cop ilot .Otters were seen to a distance of at least 1 mile on each side of the

aircraft during excellent survey conditions and to at least mi le

under good conditions .

The width of the survey track was ascertained by flying at survey

height over an air strip of known length . In this way each observer

obtained a reference point on the wing of the aircraft, which from

his position in the aircraft during surveys delimited a known dis

tance on the surface .

Observation conditions were evaluated during the surveys andwere classified as followsExce llen t— n o win d , high over cast (water glassy an d n o glar e ) .

Good— light win d (to 6 or 8 kn ots) an d over cast;or n o win d (glassywater ) but sun glar e pr esen t .

Fai r— light win d to 1 0 kn ots an d sur face glar e or win d 8 to 1 5 kn ots an d

sky over cast .

Poor — win ds over 1 0 kn ots an d glar e on water , or win d over 1 5 kn otsr ega r dless of sky cover .

When possible, survey operations were suspended during fair

or poor conditions, because too few otters could be seen and the

errors in the census could not be properly evaluated .

Observations were recorded by one of the biologists , or by athird person assisting h im. Each observation was immediately

p lotted on a U.S . Coast and Geodetic Survey chart .

Several aerial surveys which supplemented the comprehensivesurveys were conducted from single engine aircraft and from a

Grumman Widgeon . Also , the U.S . Navy cooperated by sending

F ish and Wi ldl ife observers on survey fl ights in a UF—2 Grumman

A lbatross aircraft.Data were gathered in 1 959 to provide a factor for computing

estimated total sea otter populations from aerial counts .

In an effort to ascertain as nearly as possible the number of sea

otters occupying a particular coastal area at Amchitka Island ,inshore and offshore surface surveys were repeatedly conducted

by dory. A total of 1 7 survey counts were made along a 1 3-milesection of coast from (and including) Crown Reefer Point


N . lat. , E . long, ) to (but not including ) EastCape N . l at . ,

E . long. ) The surveys were

conducted in February,March

,and April of 1 959 ( see Kenyon and

Spencer ,These surface surveys differ from the others because an i n ten

sive effort was made in a l imited area to observe, by repeated trips ,the available sea otter habitat at close range in locations famil iarto the observer . The mean number of otters observed was 254. On

an aerial survey of the same section of coast in May 1 959 , 1 92

otters were counted . Thus , approx imately 76 percent of the number

seen from the surface was observed from the air .

If only the highest surface counts for the section of the coast

are considered, the total count for the area is 295 otters . Th is

figure would indicate that on the aerial survey about 65 percent

of the otters in the survey area were seen

Based on the premise that the maximum number of otters seen

on surface surveys failed by 1 5 percent to include al l those present,an aerial survey wou ld reveal 50percent of th e otters present . This

correction factor was used previously (Kenyon and Spencer,

The correct ion factor indicating that about 75 percent of the

otters were seen is a conservat ive one and is used to estimate total

popu lat ions in the following discussion for these reasons:( 1 ) Tagrecoveries at Amchitka revealed that the home range of a sea ottermay include about 1 0 mi les of coastl ine . It therefore appeared

reasonable to use the mean of counts for each part of the area

studied . In this way some compensation is made for the movements

of individual otters in and out of the study areas during intervals

between surveys . (2 ) Many observat ions during aerial surveys ,when the same locations were flown over repeatedly, indicated to

us that, in general , under excellent conditions we saw at least 75

percent of the otters present. In some places, having a minimum

number of rocks and kelp breaking the surface , where the shoreline was even and the band of water furnishing available feeding

habitat was narrow, we felt reasonably certain that, in calmweather, we saw more than 75 percent of the otters present .

(3 ) We found that water depths as shown on USCGS charts constituted a dependable guide to locations inhabited by sea otters .

A large majority occur within the 20-fathom curve (waters lessthan 1 20 feet in depth ) . Rarely do sea otters occur in water as

deep as 30 fathoms . Therefore we cons ider that no significant

number of sea otters was missed during the aerial surveys .

Future studies may show that we were unable to estimate the


error in our counts accurately. Nevertheless, the results of the

surveys are comparable and they establ ish the order of magnitudeof populations in the locations that were surveyed . For the

purpose of this report, comparabi l ity of field observations indifferent areas is more important than an estimate of absolute

population magnitude .

On calm days, when the sea was glassy and a floating otter could

be seen at a distance of more than a mile on each side of the

aircraft, we carefully examined many extensive offshore areas

between is lands . Where the water is shallow and otters occur innumbers well off shore (as off the north shore of Unimak Island)we systematical ly flew sectors through the area covering most

of the sea’s surface where otters occurred .

In areas of dense populat ion , the otters tend to gather in groups

or “pods”of variable size numbering from 1 0 to 30 animals .

Group s of 1 00 or more animals were infrequent (fig. 69 ) and

rarely were more than 200 otters together (the max imum observedwas 440, fig. In sparse popu lations, relatively fewer groups

F IGURE 69 .— A gr oup of 1 57 sea otter s r est in g i n a ke lp bed i n K ag a l aska

Str a it (between Adak an d K ag a l aska Islan ds) , Aleut ian Islan ds, Alaska .

F light a lt itude about 1 50 feet,a i r speed 1 20 kn ots;6 Apr il 1 962. (KWK

62—35—1 9 )



the field estimates of large concentrations were 1 2 percent belowthe number counted on photog raphs . The 1 965 field estimates,made after studying earlier results, however, averaged only about2 percent below the counts from photographs . Relatively few

groups as large as 1 00 animals were seen,therefore no general

correction factor is appl ied to the field count, as this would notmaterially affect the overall estimate .

Per cen t er r orLoca ti on i n fiel d es tima te

T otal _ .

1 Aver age .

S ur face sur veys

Surface surveys were made in limited areas from an outboard

motor-driven dory and by observers using binoculars and telescopefrom shore (Len sin k , 1 958;Kenyon and Spencer,A review of observations of sea otters from 1 933 through 1 962

in many Alaska areas indicates that observations of numbers ofanimals made from the surface are generally less useful than

aerial observations . When a local otter popu lation is smal l , surfaceobservers may miss the animals altogether . For example, on aerial

surveys in 1 959 , 1 962, and 1 965 Spencer and I were able to count8 to 1 0 otters in the vicinity of S amal g a Island and Cape Sagak,Umnak Island . Reports from Aleut hunters at nearby NikolskiVillage during the past 1 0 years indicate that this population ,

though small , is permanent . In 1 961 , R. Thomas and in 1 963 ,

G. Baines, fur seal research biologists , Bureau of Commercial

Fisheries, visited Sama l g a . They each spent a 24-hour period on

or near Samal g a and looked specifically for sea otters . Neither

saw otters or any indication on beaches that they were present.

Len sin k ( 1 958 ) counted otters in the Shuyak and Barren Islandsin the summer of 1 957 , first from the surface and then from the

air. Thesurface count was 21 1 otters . On an aerial survey of the

same area he recorded 5 1 5 otters , indicating that at least 59 per

cent of the otters in an area may be missed on a surface survey .

On the basis of these surveys , a correction factor of 60 percent

is applied to certain surface counts that are discussed .

A r ea of habi tat

Sea otter feeding habitat was ascertained to consist of waters


30 fathoms or less in depth ( see D iving) . Where population and

distribution surveys were made , the area of available habitat wasmeasured on U.S . Coast and Geodetic Survey charts . A modifiedacreage grid

, 64 dots per square inch , was used to obtain measure

ments which were converted to square miles of avai lable habitat.Estimates of populations (exclusive of pups carried by mothers )were app l ied to the square miles of habitat to obtain the populationdensities that are presented in the following discussion and tables .

The entire A leutian Chain , waters adjacent to the A laskaPeninsu la

,the Sanak Islands and Sanak Reef area, the Sandman

Reefs, and the Shumag i n Islands were surveyed one or more times

under good to excel lent observation conditions during our com

prehensive 1 959 , 1 960, 1 962, and 1 965 surveys . During these

surveys and those by other individuals in different Alaska areas ,(table 1 9 ) otters were observed . The highest count obtained

in each area surveyed was used to obtain this total .

As the aerial surveys and surface studies proceeded , it becameevident that the popu lat ion of sea otters in the various g eog r ap h ical ly separated areas exhibited different stages of popu lationdevelopment . For example , in the Rat and Del ar of Islands acrowded popu lat ion heavily exploited available food resources ( seeFood and Feeding Behavior ) , and in certain of the An dr ean of

Islands dense local popu lat ions were expanding into adjacent areasof vacant habitat . These observations are discussed in the per

sp ect ive of available data from earl ier observers under the geographical headings that fol low .

T he N ear Is l an ds

This Aleutian group (fig . the western extremity of U.S .

territory, i s separated from Bul di r , the westernmost of the Rat

Islands by 55 mi les of open water . Attu and Ag attu are the largestislands but Shemya is today more important because of its airfieldan d mi l itary base . A smal l mil itary base has been maintained onAttu since World War II . Early in the war, the native Aleut popul at i on was removed from Attu by the Japanese and was neverreestablished there (Go l odoff ,In the early years of sea otter exploitation , the Near Islands

yielded many furs . The Alaska survey expedition of the U.S . Navy

Department in 1 932 searched for sea otters at Attu but found none .

Informat ion was received , however , that“the Chief of the Attu

natives assured the commander of the expedit ion that there were

a few [sea otters ] at Ag attu which would soon be gone becausethe Japanese come frequent ly to take them”(H utchinson ,


F IGURE 71 .— T he sea otter was extermin ated fr om the Near Islan ds dur in g

the late 1 800’s or ear ly l 900’s. Pr obably because wide passes separ ate theseislan ds fr om the heavily populated Rat Islan ds, i t was n ot un t il July 1 964that the fir st authen t ic obser vat ion s of otter s wer e obta in ed i n the NearIslan ds. Our aer ia l sur vey of 2 May 1 965 r evea led that at least 27 otter s

ar e n ow established ther e .

Whether the remnant population was exterminated before 1 91 1 ,or by poaching in later years, is not known . Beals ( 1 943 ) visited

the Near Islands but was unable to find any clue that the sea otter

existed there . That the aboriginal sea otter population of the Near

Islands was in fact extirpated is beyond doubt .

In 1 956, Refuge Manager R . D . Jones moved five otters to Attu

from Amchitka on a U.S . Navy ship and liberated them. It is not

known whether any of these survived . Before our 1 959 aerial

survey, no surface observer had reported seeing otters .

Our aerial survey of 1 9 May 1 959 included all of the NearIslands and was conducted under excellent conditions . We maderepeated sweeps to inspect areas appearing to offer ideal sea otter

habitat but we saw no sea otters .

B . F . Jones, while a bio logist with the Fisheries Research Institute, told me that on 1 2 June 1 959 he sighted one otter one-four th

of a mi le off Chirikof Point at the eastern extremity of Attu. Anadditional report from R. D . Jones ( letter, 25 March 1 964) states



t icul ar l y in 1 964 and 1 965, and present day Defense Depar tmentAtomic Energy Commission weapons testing activity.

The Rat Islands are noteworthy because it was at AmchitkaIsland that the first indication of substantial recovery of a seaotter population was noted in 1 935 . An aerial survey covering al l

of the Rat Islands was conducted in 1 959 . Attempts to repeat the

survey in 1 962 failed because of prolonged harsh weather, but asuccessful survey was made 2 May 1 965 . The survey data are

recorded in table 21 .

Individual islands from which data of particular interest are

available are discussed below.

Ba l di r Is l an d — This island is 55 mi les west of Kiska and is themost isolated of the Rat Islands group . Apparently, for thisreason it was the last to be repopulated . No otters were seen

during an aerial survey 1 9 May 1 959 , but this survey was un sat i s

factory because of poor weather conditions (wind and fog) . T he

first modern report of sea otters at Bul di r was made by R . D . Jones

He saw an adult male and three females with young there

during a visit, 25—28 June 1 962 . In 1 963 , between 7 and 1 9 July,our party r ecorded five mothers with young and four lone adults

on a partial surface survey which included the north coast of the

island .

On 2 May 1 965 aerial survey conditions were fair (wind 1 0—1 5

knots and sun glare ) and 1 5 otters were seen . Numerous sea lions

were also present, making observations somewhat difficult. It seemsprobable to us that the total sea otter population does not exceed30 animals .

Murie ( 1 940 and and Wi l liams ( 1 937 ) did not find sea

TABLE 21 .— Ra t Is l an ds g r oup , sea otter p op u l a ti on den si ty,

estima ted fr omaer i a l sur vey coun ts, 1 9 May 1 959 an d 2—3 May 1 965

O tter s estima tedO tter s coun ted Estima ted to ta l S quar e p er squar e mile

Islan d habita t 1 1 959

Bul di r 9Kiska , L . Kiska ,

T an adak I . an d PassegulaPyr am id, Davi dof .KhvostovLittl e S i tk i nAmchitkaS emi sop ochn o i

1 S quar e n autica l miles of water 80 fa thoms or less i n depth .1‘At Bul di r Islan d i n July of 1 963, 9 otter s wer e coun ted fr om the sur face al on g 4 m i l es of

the 1 0-m ile shor el in e . T he estima ted to ta l i n that year was 25 o tter s .

THE SEA OTTER IN THE EASTERN PACIFIC OCEAN 1 5 1

otters at Bul di r . The present breeding population probably becameestablished there in recent years . This fact is important because

the sea otters must have crossed 55 mi les of open water to reach

Bul di r from Kiska. Bul di r reef, a 20-mile strip of relatively shallow

water, extends 20mi les west of Kiska to 1 5 mi les east of Bul di r .

It off ers depths of less than 30fathoms where food might be founden route

,and otters were seen in thi s area on 27 May 1 959 (A. C .

Har tt , letter,Th e observed absence of sea otters at Bul di r after intens ive

exp loitation ended in 1 91 1 , and their reappearance there in 1 962,furnishes another example that, given time, sea otters will find

their way from one island group to another across broad expanses

of deep open water .

Rat Isl an d .— The available observations of numbers of sea otters

at Rat Island are listed in table 22. These data indicate that p op u

lation changes at Rat Island followed a pattern simi lar to the

changes observed at Amchitka during the same period and inmore recent years in the An dr ean of Islands . No observations are

available from Rat Island to indicate that population reduction

there was caused by mortal ity . Presumably, though , as was oh

served at Amchitka, mortality at Rat Island caused populationreduction from a high of 3 1 otters per square mi le of habitat to

1 2 to 1 5 per square mile in recent years .

Amchi tka Isl an d — A number of surface and aerial counts andestimates of the Amchitka sea otter population have been madesince 1 935 . Estimates of the total popu lation , because of the varietyof methods used in obtaining the basic field data, are ap p r oxima

tions and are given to represent an order of magnitude . That these

approximations are within reasonable limits is indicated by thefact that they reveal a history of popu lation growth , decline , and

stabil ization (with annual fluctuations ) that is typical of animalswhen a “seed population is given complete protection in ideal

vacant habitat .

The first observation of significant recovery of a sea otter pcpu

TABLE 22.— Ra t Is l an d sea otter p op u l a t i on den si ty i n 30 squa r e m i l es of

feedi n g habi ta t

O tte r s p er Author ity an dYear Coun t squa r e m ile sur vey method 1

2 940 F . Bea l s an d G . T . Joyn t, aer ia lcoun t-estimate .

R . D . Jon es , aer i a l sur vey .S pen cer -Ken yon , aer ial sur vey.S pen cer -Ken yon , aer i al sur vey.

1 Al l un publ ished r epor ts i n U .S . Fish an d Wildl i fe S ervice files .Estima te based on the assumption tha t 75 per cen t of the otter s wer e r eco r ded .


lation was reported at Amchitka Island by Lt . H . B . Hutchinson ,Commander, A leutian Islands Survey Expedition , in a

memorandum of 21 June 1 935 . The investigation by Naval per

son n el at Amchitka was in response to a request by the U.S .

Department of the Interior . H utchinson ( 1 935 ) stated there are

more than one thousand adu lt animals and half that number of pups on the waters surrounding the island .

”Possible poaching of sea otters by the Japanese was suspected when a vessel

believed to be the H akyuo Mar u was observed attempting to enter

Constantine Harbor, Amchitka Island, on 24 June 1 935 (Hutchinson, 1 935 ) .

Also , unidentified men were seen on the island in August 1 936(Swicegood , Accordingly, buildings were erected on Amch i tka by the U.S . Bureau of F isheries in Ju ly 1 937 (U.S .

Bureau of Fisheries, Sea otter wardens were stationed thereintermittently during parts of each year from 1 937 through 1 940.

During World War II, specific observations of sea otters wererecorded by G . T . Joynt ( 1 957 ) and Beals Beginning in

1 949 , many observations were obtained from Amchitka . Selected

population counts and estimates that were made are shown in

table 23 . Other estimates not based on field counts are omitted .

The tendency of a sea otter population to expand to new areas

primarily at the periphery of a dense popu lation is illustrated byobservat ions from Amchitka .

Lt. Cdr . S . P . Swicegood commanding ofl‘i cer of the

Chel an , conducted field counts of otters at Amchitka on 1 4—1 6

August 1 936 . A lthough 804 otters were counted along 24miles ofthe Pacificcoast of the island , only 1 0were seen on the Bering Sea

coast . A - similar condition was observed in the summer of 1 937

when C . E. Loy and O . A . Fr i den ( 1 937 ) counted otters along

the Pacific coast of Amchitka and only 80 along the Bering Seacoast. The aerial count by Beals ( 1 943 ) when he recorded

otters along the Pacific coast and along the Bering S ea coast

indicates that between and 1 943 a movement of otters from

the Pacific to the Bering Sea coast of the island occurred , probablybecause the large Pacific coast population caused food depletionalong that side of the island.

A review of the field counts at Amchitka between 1 936 and

1 965 , summarized in table 23 , demonstrate that a dense population

existed on the south side of the island in 1 936 (42 otters per squaremile ) while a sparse one (3 otters per square mi le) occupied the

north side . Emigration was not rapid but it was appreciable by

the year 1 939 ( south side 40 otters per square mile , north side 1 4



otters per square mile ) . By 1 943 the population density was highon both north and south sides of the is land but nearly equal (43and 41 otters , respectively, per square mile ) . The difference oh

served i n 1 949 ( 1 0 otters per square mile of habitat on the south

side of the island and 1 9 on the north side ) probably resulted from

mortality and emigrat ion caused by depletion of food species that

must have occurred in earlier years when the population on the

south exposure was very dense (42 otters per square mile ) . By

1 959 the popu lation reached a condition of relative equil ibriumwith the popu lation evenly distributed ( 1 9 otters per square mile )on both north and south shores of the island (fig. By 1 965

considerable divergence again occurred, the density on the northside increasing to 25 otters per square mi le and on the south side

decreasing to 8 . Additional detailed studies over a period of years

will be necessary to understand the observed population fluctuations . It is possible that significant numbers of otters might moveacross Oglala Pass to Rat Island .

SOUT H S IDE AMCHIT KA I.

NORT H S IDE OF AMCHIT KA 1.

LL OF AMCHIT KA

I9 43 | 9 4 9

YEAR OF COUNT AND EST IMAT E

FIGURE 73 .-Chan ges i n populat ion den sity on the n or th an d south coasts of

Amchitka Islan d, 1 936—59 . Est imates of the populat ion den sity ar e based onfield coun ts (see table


Available information indicates that in the 1 909—1 1 period theAmchitka sea otter popu lation may have numbered about 1 00

animals (fig. and that this popu lation reached maximum size

of about otters in the early l 94o’

s and then “crashed”toabout animals by 1 949. A gradual increase to aboutotters apparent ly occurred between 1 949 and 1 959 , but mortal ityin the winter-spring period of environmental stress caused the

population to stabilize or possibly to decrease in the early 1 960’s.

A curve based on field counts and population estimates is shownin figures 73 and 74. An estimated rate of increase of 1 0 percent

5000

4000

I909'

so'

3 s'

42'

45'

48'

5 |

YEAR or ES T IMAT E

FIGURE 74.— E st imated cur ve of the Amchitka sea otter populat ion ,

1 909—65 .

No data ar e ava ilable befor e 1 936 . T he cur ve fr om 1 909 to 1 936 i s a p r o

ject i on back fr om the est imated 1 936 populat ion , assumin g that the p op ul at ion in cr eased i n this per iod at an expon en t ia l r ate of 1 0 per cen t p er year(see sect ion on Seguam Islan d ) . Poin t 1 :Populat ion est imate by Swicegood( 1 936 ) based on exten sive sur face coun ts an d obser vat ion s. Poin ts 2 an d3:Populat ion est imates based on the sur face coun ts of Loy an d Fr i den

( 1 937 ) an d Loy Poin t 4:E st imate based on aer ia l coun t by Bea lsPoin t 5:Est ima te based on aer ia l coun t by Jon es Poin ts

6 an d 7:Est imate based on aer ia l coun ts by K enyon an d Spen cer ( 1 960)an d K en yon


per year in early stages of growth (fig. 74) is based on the

observed growth rate in a part of the An dr ean of Islands (SeguamIsland ) where conditions seemed simi lar to the Amchitka area .

The field counts of otters by Loy and Fr i den ( 1 937 ) and Loy( 1 940) are proj ected to est imated totals on the basis of Len sink

’

s

( 1 958 ) data indicating that about 60 percent of the otters presentmay not be seen on a surface survey . These estimated totals assume

logical positions (Points 2 and 3 ) on the curve between the estimated totals of Swicegood Point 1 , and Beals

Point 4. The observations of mortality which occurred after the

Amchitka population reached a density of at least 42 otters per

square mi le are discussed under Limiting Factors .

Len si n k ( 1 960) estimated the total popu lat ion of sea otters atAmchitka on the basis of a field count of otters obtained during a

period of weeks in the summer of 1 956 . His count was otters

on the eastern half of the island and his total estimate wasto animals .

Our 1 959 and 1 965 aerial surveys for all of Amchitka weremade under excel lent observat ion condit ions and our total countswere and otters, respectively. Why were our total

counts much less than Len si nk ’

s partial count ? Two reasons aresuggested:( 1 ) The number of otters at Amchitka may have beenreduced between 1 956 and 1 959 . General field observations andobserved high winter-spring mortality indicated that population

reduction may have occurred . Emigration may also have occurred .

(2 ) Len si n k made many trips to different contiguous counting

areas during a period of weeks . It is possible that otters movedin the time between counts and the same animals were included

in more than one count . If Len si n k ’s ( 1 960) estimate of to

otters at Amchitka is accepted , it would mean that the p op ulation there was 55 to 73 animals per square mi le of feeding habitat .All other observations and studies made at Amchitka and in otherareas indicate that this est imate is very high— nearly twice as

large as the indicated maximum population observed by Beals

In summary, our studies conducted since 1 955 and intermittentsurveys made since 1 935 have indicated that the sea otter p op ul a

tion on Amchitka Island grew to a large size , causing over ut i l i za

tion of food resources during the mi d- l 94o’s. Population reduction

through starvat ion was then observed and a fluctuating population

in balance with the habitat resulted .

It was not surprising,therefore, that our 1 965 observation of

otters at Amchitka was less than our 1 959 tally of a



scouting fl ights around Semi sop ochno i Island and report that they

have never seen sea otters in that vicinity .

”

On the aerial survey of 1 9 May 1 959 , when observation conditions were excellent, we saw 393 otters ( 1 6 per square mile of

habitat) at S emi sop ochn oi Island . It thus appears that the animals

moved from Amchitka across nearly 30 mi les of open water tothis island after 1 943 , when the Amchitka population approachedmax imum size and population pressure st imulated emigration .

By 1 965, the popu lation at Semi sop ochn o i had decreased to anestimated 8 otters per square mile of habitat (table

D e l ar of Isl an ds

This small group (fig. 75 ) i s technically part of the An dr ean of

group (U.S . Board on Geographic Names, but is treatedas a separate unit here . The group includes a distance of about

33 mi les from east to west and is separated from T an ag a Island

FIGURE 75 .— T he Del a r of Islan ds of the wester n An dr ean of Islan ds wer e

appar en t ly amon g the f ew Aleut ian a r eas wher e the sea otter r ema in ed i n1 91 1 when i t was given pr otect ion. A lar ge populat ion developed her e an d

at K an aga an d T an ag a Islan ds by the late 1 940’s, but populat ion pr essur edid n ot cause r epopulat ion of n ea r by Adak un t il the m i d- l 95o’s. T he numberof otter s obser ved on aer ia l sur veys of 2 an d 3 May 1 965 , as shown on th ismap , was


on the east by 1 4-mi le-wide T an aga Pass and from the Rat Islandson the west by 50-mile-wide Amchitka Pass . The Del ar of s have

no human inhabitants .Murie ( 1 940) found a thriving sea otter population at Og l iuga

in 1 936 . Joyn t ( 1 957 ) says of his 1 943 aerial observations that

T he most den sely gr ouped of any p od of sea otter obser ved was on on e en d

of the san d bar s exposed a t ha lf t ide that lies between K ava l g a Islan d an d

Og l iug a Islan d i n the De l ar of Islan ds gr oup .

Data from the 1 930’s, as cited above , indicate that the Del ar of

and Rat Islands populations approached maximum size at about

the same time . Because of the width of Amchitka Pass (50miles ) ,i t appears probable, as pointed out by Len si nk that r em

nant populations remained in 1 9 1 1 in both the Rat and Del ar of

Island groups . The habitat at Amchitka and in the Og l iug a

K ava l g a Islands areas , is simi lar in having extensive shallowsdotted by submerged or partially submerged reefs . Although theseoffered feeding habitat and a place of refuge to the sea otter , they

presented considerable hazard to early sea otter hunters and wereprobably instrumental in preserving the species .

On 26 May 1 959 , our aerial observations (table 24) revealedthat the number of otters per square mile of habitat in the Del ar of swas the highest of any island group that we surveyed . This condi

tion is of particu lar interest because the Del ar of s were among thefirst Aleutian islands to be repopu lated . By May 1 965 , our observations indicated that the Del ar of popu lation had dropped by ap

proximately 50percent (table

It may be postulated that after the popu lation peak , which

probably occurred in the 1 930—40 period , emigration to T an aga

TABLE 24.— D el ar of Is l an ds sea otter p op u l a t i on den si ty estima ted fr om aer i a l

sur vey coun ts of 26 May 1 95 9 an d 2—3 May 1 965

Estima tedS qua r e

Islan d 1 965 1 959 habitat 1 1 959 1 965

“ M

375 2 77 529

Ul ak 1 48Ama t i g n ak

260

T ota l _ 653 89 Av . 21

1 In cludes wa ter of 30 fa thoms o r l ess i n depth as measur ed fr om U .S . Coast an d Geo deticS ur vey cha r ts .Closely associa ted is l ets an d islan ds .


took place . After the T an ag a popu lation exceeded the carryingcapacity of the available habitat, otters moved westward to theDe l ar ofs again as well as eastward to Kanaga and Adak . Thus ,we observed a second population peak in the Del ar of s in 1 959 .

This resulted in food depletion and a subsequent “populationcrash”bringing the popu lation dens ity from 21 down to about 1 0

otters per square mi le by May 1 965 (table Whether oi l fromthe San Patrick, which was wrecked on the south shore of UlakIsland during the winter of 1 964—65, was a factor in population

reduction is not known .

A n dr ean of Is l an ds

The An dr ean of Islands (figs . 76 and 77 ) (excluding the Del ar ofgroup ) extend for a latitudinal distance of about 230miles fromT an ag a on the west to Seguam on the east . Human populations

in this group are at the U.S . Naval Station on Adak, and Atka

FIGURE 76 .— T he Adak—Gr eat S i tk i n Islan d ar eas i n the cen tr a l An dr ean of s

wer e r epopulated dur in g the l 950’s an d ear ly 1 960’s by otter s fr om the

Del a r of an d K an aga an d T an ag a Islan ds. No otter s wer e foun d on a sur veyof A dak i n 1 952, but on an aer ia l sur vey i n 1 954 a coun t of 48 was obta in ed,an d by 1 965 the coun t in cr eased to On aer ia l sur veys of 25 an d 26

Apr i l 1 965, otter s wer e obser ved i n the ar ea shown .


NORTH AMERICAN FAUNA 681 62

v-‘QQ v-I P 'I

V V

wN

and.

25

cm

NN

mfi

nu

mm

mm

«6m55

MNw

mbw

ham

amb

é

mov

é

u

se"

mm

mm“

mm

mmw

Sma

mwN

mmw

m

8.

m

wad

fi

23

4

mm

and”

m2a

wNN

o

?mam

mom

waN

wan

;

vmo

fi

mmo

m&2.

am

mam

«A

ea

«AN

amN

owwd

mew

fi Q O O O gQ G fl fi'a

wwfi

mU“D

F 4

b'

l o


and was not surveyed in 1 962 ) increased from otters in 1 959

to in 1 962 (table a gain of 742 otters or percent in

3 years . In the next 3-year period ( 1 962—65 ) the same area gained

858 otters minus table 25 ) or percent.

Within the An dr ean of s, emigration occurred when islands became densely popu lated . For example, the Kanaga popu lation lost

otters minus table 25 ) between 1 959 and 1 962,

while nearby islands (Adak, K ag a l aska , Little T an ag a , Umak ,

An agaksik ,Great S i tk i n ,

and adjacent islets ) increased from

to (table a gain of otters or 86 percent .

Because immig rat ing otters may have moved into the availablevacant habitat surrounding the above named islands from T an ag a

as well as Kanaga, it is not possible to separate the increase r ep r esenting reproduction from that caused by immigration in these

areas . The conclusion is indicated that in the An dr ean of s the total

sea otter popu lation may grow at a rate of about 4 to 5 percent

per year and that in the 1 975 to 1 980 period the population there

may number over otters or about 1 4 animals per squaremi le of habitat .

T an aya Is l an d — Th e repopulation of T an ag a Island appears tohave been wel l underway by the mi d- l 93o’s. Wi ll iams ( 1 937 )mentions it along with Amchitka and Og l iug a as being one of the“most product ive”islands . D . H ooper ( i n Jones , 1 953 ) indicated

that the otter populat ion there was large in 1 953 . Until our aerial

surveys , no comprehensive quantitative assessment of the otter

population at T an aga was made . Available popu lation data aresummarized in table 26 .

Th e few observations available indicate that populat ion overflowfrom the Del ar of Islands repopu lated T an ag a during the 1 930’s,and that during the late l 94o’s or early 1 95o ’s the local populationreached maximum size . During the mi d or late- l 95o’s, the p op ul a

tion density probably became reduced through emigration to

Kanaga Island and remained stabilized from 1 959 to 1 962 at about

1 4 otters per square mile of habitat . The increase to about 1 7

TABLE 26 .— T an aya Is l an d sea ot ter p op u l a ti on den s i ty i n 83 squar e mi l es of

f eedi n g habi ta t

Otter s p er Author ity an d

Year Coun t squar e mile sur vey method

O . J . Mur ie an d V . B . S cheff er ,sur face sur vey .

D . H oover , sur fa ce sur vey ( i nLen s i n k ,

S pen cer an d K en yon , aer ia l sur vey .

S pen cer an d K en yon , aer ia l sur vey .

S pen cer an d K en yon , aer i al sur vey .


otters per square mi le in 1 965 may have resulted from emig ration

from densely popu lated Kanaga.

K an ag a Isl an d — The Murie expedition visited Kanaga in 1 936

and Wi ll iams ( 1 937 ) states that no sea otters were seen . Natives

r ep or ted‘ to h im, however, that otters did

“occur occasionally orsparingly”there . By 1 943 , Kanaga was apparently only sparselyrepopulated . Joyn t ( 1 957 ) says that in 1 943:

A f ew str ay an ima ls wer e obser ved a lon g the south shor e of K an aga but Ido n ot r eca ll ever obser vin g mor e than 6 or 8 an ima ls on the thr ee or fourflights over th is a r ea .

By 1 953 the population had increased g reatly. In June of that

year D . Hooper ( i n Jones, 1 953 ) spent 2 1 days on Kanaga . He

walked 40mi les of beach and counted 575 otters . After examininga number of inshore areas at T an aga he estimated that the otter

popu lations of Kanaga and T an ag a Islands were large, “probablynumbering several thousand”animals .

Data obtained on the 1 959 and 1 962 aerial surveys indicate thatthe Kanaga population was near maximum size in 1 959 . The

precipitous population drop from an observed total of otters

in 1 959 to 846 in 1 962 indicates that the estimated 1 959 population

of 26 otters per square mile of available feeding habitat may have

depleted food resources and precipitated substantial emigration

(and mortal ity ?) during the elapsed 3 -year period . By 1 965 a

slight increase , probably resu lting from crowding at nearby Adak ,

had occurred (table

On a dory survey in 1 957 along a 1 9-mi le sample of coast,Len si n k ( 1 960) recorded 566 otters . Along the same coastal sampleon our 1 959 aerial survey we recorded 549 otters and in 1 962 the

aerial count there was 404. The similarity of the 1 957 surface

TABLE 27.— K an ag a Is l an d sea otter p op u l a ti on den si ty i n 95 squar e mi l es of

feedi n g habi ta t

O tter s p er Author ity an dYear Coun t squa r e mile sur vey method

man y

1 3 000—5 000 32—53

1 822

1 Because this es tima te was made fr om da ta ga ther ed a lon g the south shor e , wher e mor e

habita t i s ava ilable than alon g the n or th shor e , the estimated upper l im it may be somewha t hig h .

G . T . Joyn t ( 1 957 ) flew r epeatedlyover a r ea .

D . H ooper ( i n Jon es . 1 953 ) wa lked40miles of beach an d coun tedotter s .C . J . Len si n k dor y sur veyalon g 1 9 m iles of coast .

S pen cer an d Ken yon , a er ia l sur vey,en tir e islan d .

S pen cer an d K en yon , aer ial sur vey,en tir e islan d .

S pen cer an d K en yon , a er ia l sur vey,en tir e islan d .



TABLE 28 .— Adak Is l an d sea otter p op u l a ti on den si ty i n 75 squar e mi l es of

feedi n g habi ta t

Estima te O tter s p er Author ity an dYear Coun t of tota l squa r e mi l e sur vey method

1 954

1 962—65 period . Al l available observations are listed in tables27 and 28 .

K ag a l aska Isl an d _ K aga l aska is uninhabited by man . Most of

the is land is precipitous . Although i ts coastl ine is about 35 mileslong, the band of shallow water surrounding it and offering sea

otter feeding habitats is relatively narrow . As at nearby Adak , sea

otters were apparently exterminated at K ag a l aska before 1 9 1 1 .

On the 1 959 aerial survey we recorded one otter there . Between

then and the 1 962 survey the influx from nearby Adak was rapidand had apparent ly passed its peak in 1 965 (table 29 and fig.

A tka Is l an d — The vil lage of Atka is the farthest west locationof a small Aleut popu lation today. The vil lage is on Nazan Baynear the eastern end of the 55-mile long is land .

Both R . D . Jones and I were told repeatedly by Aleuts living atAtka that during the l 94o’s sea otters were occasionally seen atVasi l i ef Bay near the east end of Atka . The 1 959 , 1 962, and 1 965

aerial surveys confirmed that a smal l and growing sea otter colonyi s resident in this area (table

Vasi l i ef Bay ofler s ideal sea otter habitat. The main body ofthe bay is dotted with rocks and islets . Numerous channels amongthem and irregu lar shores off er many areas that are sheltered

TABLE 29 .—K ag a l aska Is l an d sea otter p op u l a ti on den si ty i n 1 5 squa r e mi l es of

feedi n g habi ta t

O tter s p er Author i ty an dYea r Coun t squar e mi l e sur vey method

Len si n k , a er ia l sur vey.S pen cer an d Ken yon , aer ial sur vey.S pen cer an d Ken yon , aer ia l sur vey .

S pen cer an d Ken yon , aer ia l sur vey.

Ken yon field n otes . No otter s seen or

r epor ted seen .

R . D . Jon es , sur face sur vey, west sideon ly.R . D . Jon es, sur face sur vey en tir e isl an d.

0. J . Len si n k a i r sur vey. Al lo tter s seen o n wes t s ide of islan d .R . D . Jon es . Fir st r ecor ded sig htin g at

A dak Nava l S ta tion . on east side ofislan d .C. J . Leusin k ( 1 960) an d R . D . Jon es ,

sur face sur vey. Most otter s on west sideof isl an d .

S pen cer an d Ken yon , aer ial sur vey.S pen cer an d Ken yon , aer ial sur vey.S pen cer an d Ken yon , aer ial sur vey.

T H E SEA OTTER IN T H E EASTERN PACIFIC OCEAN 1 67

NAGA I

MCH IT KA I

ADAK

KAGALAS KA

S EMIS OPOCHNOI

I9 3 S'

3 7'

3 9'

4 9“57

‘

59

YEAR OF COUNT AND ES T IMAT E

FIGURE 78 .-Populat ion s Of sea otter s at sever a l Aleut ian Islan ds have i n

cr eased to maximum size an d then cr ashed between 1 936 an d 1 965 . E st imates Of otter s p er squa r e mile of habitat (water s within the 30-fa thomcur ve ) , wh ich a r e based on exten sive field coun ts, a r e shown as dots whichar e con n ected by solid lin es. Obser vat ion s Of

“f ew,

”or“man y,” or

“thousan ds”a r e shown by quest ion mar ks an d con n ected by br oken lin es .

(For data , see tables 21 Populat ion peaks appa r en t ly occur r ed betweenaer ia l sur veys at Adak an d K ag a l ask a Islan ds.

from wind and rough water in storms . This habitat apparently

attracted the occasional otter that wandered eastward from the

large popu lat ion in the western An dr ean of s, causing the colonyto form and to be augmented by further immig ration . In the 1 959to 1 962 period , the co lony increased by 86 percent and between1 962 and 1 965 by 375 percent . Repopulat ion of the north side OfAtka had n ot begun in 1 965 .

Aml i a Is l an d — It is 40 miles long, has no human inhabitantsand except near the west end is seldom visited by the Aleut iannat ives of nearby Atka Vi llage . T h e U.S . Coast and Geodet ic Survey has not as yet ( 1 965 ) issued a chart showin g soundings ofAm l i a

’

s inshore waters . T h e area of sea otter feedin g habitat ( table25 ) was est imated on the basis Of measurements taken at Atkabecause the two i slands appear simi lar .

Vague reports that I received from the hun ters of Atka dur ingthe l 94o

’

s and l 95o’s indicated that a smal l n umber of sea otters


was resident at Amlia for a number of years . The 1 959 aerialsurveys revealed that a smal l population occupied the south sideof the island, the greatest number being near the eastern extremity

(fig . 77 and table 25 ) The 1 962 survey confirmed that this p op ul a

tion is resident but time was n ot available then to resurvey thenorth coast. In 1 965 the entire coastline was surveyed but otters

were seen only on the south coast. The increase between 1 962 and

1 965 from 1 1 1 to 21 2, a doubl ing Of the popu lation, may in largemeasure be attributed to immigration from the west .If repopulation of this island proceeds in a way simi lar to

population spread Observed in other areas (Amchitka and Adak,for example ) the north coast can be expected to repopulate after

the present population on the south coast has increased

considerably.

S eguam Isl an d .— This is the easternmost island in the An dr ean of

group (U.S . Board on Geographic Names, It is separated

from Aml ia by Seguam Pass , 1 6 miles of deep water and strongcurrents . It has no human inhabitants .

The Murie expeditions did not find sea otters at this island butinformation from Aleutian natives indicated that otters had beenseen there (Wi l l iams , The first specific evidence that sea

otters occupied Seguam was found on our 1 959 aerial survey . The

1 962 and 1 965 surveys confirmed that the small population isresident and is g rowing slowly . An increase of approximately1 0percent per year (from 28 to 47 otters in 6 years ) may represent

the rate Of increase due to reproduction in an isolated, uncrowdedpopulation .

Because the popu lation today is so small (table it seems

unlikely that otters survived the period Of unregulated exp loitationin this location . It appears more probable that wanderers from

the larger populations in the west reached Seguam in recent years

and remained there either because the habitat is desirable or

because the width of Amukta Pass discouraged emigration to the

Islands of Four Mountains . The relatively slow rate of increase ,however, indicates that immigration is , as yet, not appreciable at

this rather iso lated location .

Is l an ds of the Four Moun ta i n s

From Amukta Island northeastward to K ag ami l Island on

Sama l g a Pass is about 70miles . There is no human popu lat ion inthis island group , therefore few surface Observations are available .

The survey of 3 March 1 960 covered al l coast l ines and was madeunder excellent conditions . On 7 April 1 962, survey conditions



FIGURE 80.— T he San ak— Caton Islan ds an d San dman Reefs a r eas wer e last

sur veyed on 8 Apr il 1 962. A ll other sur veys of the easter n Fox Islan dsshown on this map wer e made on 8 May 1 965 . T he tota l n umber of otter s

obser ved on these two sur veys i n the ar eas shown i s

separated, but apparently permanent, sea otter colonies and one

large population , but most of the available habitat is unoccup ied .

The small S ama l g a—Cape Sagak colony and the other on the northeast coast Of T i ga l da are apparent ly growing slowly. The large

Bering Sea population Off the north coast of Unimak Island andthe western Alaska Peninsula, already Of considerable size, is

possibly augmented by an influx Of otters from the SanakSandman Reefs areas in the North Pacific Ocean . R. D . Jones

( letter, 1 0April 1 964) reports that heObser ved an adult otter r ight smack i n the n ar r ows of the n or th en d Of

Fa lse Pass [Isan otsk i Str a it ] . I’ve n ever seen on e ther e befor e . H e was at

the t ime bein g swift ly car r ied in to Ber in g S ea by the t ide .

The avai lable sea otter habitat in the Fox Islands is at presentsparsely populated . Because of the large extent Of this area,repopu lation wi l l probably require many years .

T he wester n For Isl an ds — Human settlements include NikolskiVillage, a sheep ranch, and a DEWl i n e site near the south end Of

Umnak Island, and a sheep ranch and Reeve A leutian A irways’instal lation near Cape Tanak on the north end of 65-mile longUmnak . On Unalaska Island the village Of Unalaska is the largestof the extant native Aleut ian sett lements . There is also a DEWl i n esite at Driftwood Bay on Unalaska Island . Counts Of otters from


several sources and estimates of all otters in this area are sum

mar i zed in table 30.

Several Aleut ian nat ives who hunt and fish in the waters off the

south end Of Umnak and near the east end of Unalaska have givenme verbal reports over a period of several years ( 1 950 Fred

and Antone Bezezek off of Nikolski Vi l lage , Umnak Island , havetold me Of repeatedly seeing a small number Of otters in the

vicinity Of Sama l g a Island and Cape Sagak at the southwest endof Umnak Island . Their highest count was 1 4 otters (F . Bezezek off ,

letter 1 3 March The three aerial surveys of the Fox Islandsindicate that the smal l colony at the western extremity Of Umnak

Island is permanent but no increase is indicated . Apparently fewwanderers enter this extensive western Fox Islands area which is

iso lated from other populations .

NO one at Unalaska reported a sea otter sighting in the 1 950—62period . That sea otters are now repopulat ing Unalaska is indicated

by a recent report . On 1 9 and 20 July 1 968 , C . H . Fiscus , A . M .

Johnson,and H . K ajimur a (personal communication ) saw an otter

in K i sma l iuk Bay on the north coast of the island , and another OffTiderip Point at the island

’s southwestern extremity.

The available sea otter habitat adjacent to the islands fromSama l g a Island to Akutan Pass is about 570 square miles . If this

habitat can support about 1 2 otters per square mile , the estimatedfuture popu lation of this areamay eventual ly be about otters .

K r en i tzi n Is l an ds .— The K r en i tz i n Islands occupy a 45-mile

sector Of the Fox Islands from Akutan Pass on the west to UnimakPass . The vil lage of Akutan , on Akutan Island , is the only humansettlement in the K r en i tzi n s . Occasional otter sightings near

Akutan are reported by nat ive Aleut fishermen (Len si n k ,

TABLE 30.— Number s o f sea o tter s obser ved a n d est ima ted p op u l a ti on i n the

Fox I s l an ds g r oup

[T he man y islan ds , islets , an d r ocks wher e n o sea o tter s wer e obser ved ar e omitted ]

Islan d an d yea rS ama l g a-Umn ak

Egg an d Ol d Man Rocks:1 957 1

T i g a l da:1 960 2

Un imak-Amak2 892

T ota l (highes t coun ts )1 Leus in k ( 1 958 ) aer i al sur vey .

2 Sur fa ce sur vey of Jun e 1 960.


On 23 August 1 962, R . Thomas (fur seal research biologist)sighted one otter in Akutan Bay (personal communication ) .

On 3 and 4March 1 960, D . L . Spencer and I surveyed this island

group in detai l under good weather conditions . On 7 and 8 April1 962 and again on 8 May 1 965 , wind permitted us to make only

an inadequate survey of a smal l area Off T i g a l da Island, the only

place where sea otters were previously seen . Only three otters weresighted in 1 959 and 1 962 . In addit ion to the aerial survey data,I Obtained information during surface surveys by dory on 26—29June 1 960when I counted 1 1 adult otters and 6 young wi th mothers

at T i g a l da Island . During the 1 965 survey, in spite of wind and

rain, we sighted 32 otters there (tableDuring May and June Of 1 960 and 1 962, C . H . Fiscus (fur seal

research bio logist) spent considerable time in the K r en i tzin s whileconducting pelagic sealing investigations in Unimak Pass andBering Sea . The sealing vessel anchored on numerous Occasions

in different bays and bights and F iscus went along the shore by

dory in several areas . These included Avatan ak Strait, Akun,Seredka, and Trident Bays at Akun Island;Rootok Strait, DurbinStrait, Durbin Bay at T i g a l da Is land;Ug amak Strait

, Ugamak

Island;and the south shore of Akutan . Although a careful search

was always made for sea otters, Fiscus told me that none was

Observed . It therefore appears probable that the small colonyalong the northeast shore of T i ga l da Island is the only one in the

K r en i tzi n Islands and that otters reported occasionally from AkunStrait are wanderers .

The area Of sea otter habitat adjacent to the K r en i tzi n Islands

is about 200 square mi les . If it may support about 1 2 otters per

square mi le, the future otter popu lation may be about

Un imak an d Amak Is l an ds — Unimak Pass separates UnimakIsland from the K r en i tzi n Islands . The distance from UnimakPass to Amak Island is about 1 00 mi les . A Coast Guard Stationat Cape Sar i chef is the only human settlement in the study area .

The greatest number of sea otters in this area inhabit the shallowwaters Of the Bering Sea off Izembek Bay in the vicinity of AmakIsland and Off the north central port ion of Unimak . Depths of 20fathoms or less extend to about 8 miles from shore and the

30-fathom curve extends to about 1 5 mi les from shore . Th e ma

jor i ty Of the 81 1 ott ers observed on the 8 April 1 962 aerial surveywere seen near the 20-fathom curve . Observation conditions weregood to excellent during this survey and sectors were system

at ical ly covered between 1 and 1 5 mi les from the shore of UnimakIsland and the tip Of the Alaska Peninsu la . In addition, I conducted



FIGURE 81 .— This gr oup Of 1 28 otter s slept on the open sea about 2 miles Off

the n or th coast of Un imak Islan d, A laska . NO kelp beds ar e foun d i n thisOffshor e locat ion . Ava ilable evi den ce in dicates tha t an ima ls i n this ar ea

r ar ely come ashor e . (KWK 65— 1 7—8 )

three factors :( 1 ) An influx of otters from the Sanak IslandSandman Reefs area. (2 ) A north wind of several days’ durationbefore and during our 1 965 survey may have concentrated largenumbers of otters near shore from their extensive Offshore feedinggrounds . During the 1 962 survey of this same area, we found ottersmore scattered than in 1 965 . In 1 962 they were spread over many

square miles of open water . Possibly we failed to see many of

them in 1 962 . 3 ) A large number of mothers carrying young were

Observed during both surveys— Obviously reproduction accountedfor some but certainly not all of the Observed population increasein this area .

If the habitat (more than square miles ) may be populatedas densely as some of those of the A leutian Islands, the populationmight reach from to otters . NO quantitative study

of the marine invertebrate fauna of southwestern Bristol Bayhas been made . A qualitative study by McLaughl i n how

ever, revealed a variety Of crustaceans and molluscs in this area

and suggests that it is rich . T he large numbers and variety ofaquatic birds and marine mammals there indicate that food species

are abundant.We extended the 1 965 survey along the north shore Of the

Alaska Peninsula about 1 0 miles northeast of Port Moller butfound no sea otters beyond the mouth of that bay. Our Observations


suggest that Port Moller ( 56° N . lat. W . long. ) is near the

northeast extremity of the sea otter 3 range in Bristol Bay. A sea

otter taken near the Naknek R iver at about N . lat.

in northeastern Bristol Bay where they are rarely to be found

(U.S . Bureau Of Fisheries, 1 9 1 1 , p . 56 ) was probably a wandererfrom southwestern Bristol Bay.

S an ak Isl an d an d S an dman ReefsSanak Island (fig. which supports a small village , is ap

proximately 20mi les southeast Of the eastern extremity Of Unimak

Island . Between Sanak Island and the Alaska Peninsula the Sandman Reefs consist of extensive shallows having a number ofexposed rocks and islets .

Sea otters were reported in the Sanak Island-Sandman Reefsarea as early as 1 922 (McCr acken , but must have beenvery scarce at that time (Len si n k , The Murie expedition

received reports Of otters in this area in 1 936 but found none

(Wil l iams , Aerial surveys in 1 957 and 1 962 indicate thata substantial population now in this area is increasing (fig. 80

and tableAerial surveys in 1 957 by Len si nk ( 1 958 ) and my Obser vations

Obtained on dory surveys Of 20—23 June 1 960 indicated that fewsea otters occupied waters surrounding Caton Island and that theanimals were more numerous among the reefs Off the southeast

coast Of Sanak . Aerial surveys Of 1 0 April 1 962 , during excellent

weather conditions , confirmed these Observations . Th e majority

Of the otters Observed on both aerial surveys were concentrated

among reefs and islets off the southwest coast of Sanak Island

TABLE 31 .—Number s of sea ot ter s obser ved an d est ima ted p op u l a ti on i n the

S an ak Isl an ds an d S an dman Reefs a r eas

Aer ial sur veys Estimated1 957 1 1 962 2

Ar ea

S an ak a r eaS an ak Islan d an d associa ted r eefsCa to n Islan d an d associated

S an dman Reef sCher n i

Dee r Islan d an d a l l r eefs n o t n amed above

1 Aer ial sur vey by Len s i n k ( 1 958 ) on 1 9 July 1 957 .

1 A er ial sur vey by D . L . S pen cer a n d Ken yon on 1 0Apr il 1 962.


within the 20 fathom curve . Len si nk ( 1 958) saw no otters in the

relatively deep waters Off the northeast shore of Sanak and onlyone was seen there during the 1 962 survey.

Fl ights over the Sandman Reefs on 1 0 April 1 962 were undertaken when conditions were excel lent . We viewed the exposed rocksand islets and examined most Of the Open water . Otters could beseen on the glassy surface within a track about mi les wide .

Because Of the irregular bottom topog raphy of this area, it is

diffi cult to measure from charts the amount Of available sea otter

habitat. The approximate measurements obtained, however, indi

cate that the Sanak Island-S andman Reefs areamay furnish nearly900 square mi les Of feeding habitat . With about two otters per

square mile of habitat this area appears underpopulated .

S ince the surveys of 1 957 and 1 962 were undertaken underexcel lent Observation condit ions, they may be comparable . If the

total count in the Sandman Reefs area is projected forward at

an increase of 5 percent per year ( see An dr ean of Islands ) the

estimated 1 962 count wou ld be 637 . T he aerial count of 1 962 was

638 otters . The 1 957 survey may have missed a number Of otters

in the Sanak Island area, since Len si n k’s ( 1 958) figures when

projected to 1 962 at 5 percent per year fal l short of the countObtained in 1 962.

S humag i n Isl an ds

This group lies 1 00miles east of the tip of the Alaska Peninsulaand reaches its southern extremity at Cher n abur a Island about1 00miles south of the Peninsu la’s south shore .

Sea otters apparently survived the 1 741 —1 91 1 period of ex

p l oi tat i on in the Shumag in area where Off shore feeding areas

Off ered them refuge . Japanese poachers worked the area until at

least 1 9 1 0. An estimate Of otters in the southern Shumag in s

was made in 1 920, but this population was certainly reduced whena tanker and a freighter were wrecked and spi lled O i l in this area

during World War II (Kenyon ,

A smal l human population l ives at Unga Vil lage on Unga Islandand another at Sand Point on POp Of Island . Reports from surface

Observers at these locations indicate that occasional otters wander

to the vicinity of these two islands but that no sizable populat ionexists there . About half of Unga Island was surveyed in 1 962 andonly four otters were seen, confirming reports of surface Observers .

The sea otter popu lation Of the outer Shumag i n s is, however, large(table 32) Many shallow areas with underwater reefs, particularly



Pass to Cape Douglas at the mouth of Cook Inlet. The north shoreof the peninsula is discussed under“Unimak and Amak Islands.”D . L . Spencer has flown over the coastal waters of the peninsula

many times . Because Of his previous knowledge of sea otter dis

tr ibuti on and because of a shortage Of time, our 1 962 survey in

cluded primari ly those areas where a significant number of seaotters was known to ex ist.

O tters were counted in the Cape Kuml iun—Sutwi ck Island area

in 1 951 and 1 957 (table This area appears to be the center Of

the population along this coast . The 1 962 survey was made from

Cape Kuml iun northeastward . The greatest concentration of sea

otters was in Kujul ik Bay and around Sutwi k Island . One large

group which was photographed (fig. 70) contained 440 otters,by a count from the photograph , the largest assemblage that wasseen on the aerial surveys up to that time . From this area north

eastward the number Of otters seen decreased as shown in table33 . In 1 957 Len si n k ( 1 958 ) found none east Of Ch i g i n agak Bay .

Our Observation of five otters east of this point in 1 962 indicates

a slow population spread eastward .

The difference in distribution of otters in the area between Cape

K uml iun and Cape K unmi k , including Sutwick Island, betweenthe 1 957 and 1 962 surveys , probably indicates that this rather

large local population shifts about in this area in response toweather or food supply.

It is not possible from available charts to measure the square

mi les of sea otter habitat along the southeast coast of the AlaskaPeninsula. We believe, however, that the

"

i n cr easi n g population

may fill much vacant habitat in future years before maximum

population is reached .

TABLE 33 .— Number s of sea otter s obser ved an d estima ted p op u l a ti on a l on g

the A l aska Pen i n su l a

Sur veys Estima te1 951 1 1 957 2 1 962 8 tota l 4A r ea

Un ivi kshak Islan d ar eaKujul i k Bay CSutwi ck Islan d ar eaAn iakchak Bay an d Amber Bay ( C .Cape Kunmi k to Cape Ig vak ( 55Cape Ig vak to Cape Kul i ak ( 70miles )

T ota l1 A er ia l sur veys dur in g the May to Aug ust per iod by R . D . Jon es ( i n S ti les , 1 953 ) .

3 Aer ia l sur vey, 25 July 1 9573 Aer ia l sur vey, 1 0A pr il 1 962, by Ken yon an d S pen cer .

4 Estimated popul a tion as of A pr il 1 962.

THE SEA OTTER IN THE EASTERN PAC IFIC OCEAN 1 79

K odi ak Isl an d to C o ok I n l et A r ea

From the Trinity Islands, Off the south shore Of Kodiak, to theBarren Islands

,in the mouth of Cook Inlet , is about 1 80miles .

Records of confiscated sea otter skins in reports of the U.S .

Bureau Of Fisheries ( 1 91 2 to 1 936 ) and the observation Of four

otters near Afognak Island in 1 922 (Eyer dam, 1 933 ) indicated

that sea otters survived after 1 9 1 1 in the Kodiak area.

Len si nk ( 1 958;1 960;1 962) conducted both aerial and surfacesurveys in this area and reviewed the numerous report s available

from various individuals who l ived in or visited the area during aperiod Of many years . The historical record of 1 8th and 1 9th

century otter hunters , as wel l as midden excavations reported byLaughlin reveal that the sea otter was once numerous inthe Kodiak area . Today repopu lation is proceeding slowly . Th e

majority Of Observations of otters come from waters off the north

coast Of Afognak Island and nearby Shuyak Island or from the

Barren Islands . Leusink ( 1 958 ) says of the few Kodiak Islandreports that “The Observat ions Of otters on Kodiak are bel ieved tobe stray animals from the Shuyak area .

”

During the 1 957 surveys Leusink did not find otters in theTrinity Islands but reports that R. Lopp Observed 1 4 in 1 957

(Len sin k , The resu lts of surveys by Len si n k and W . Troyer

are shown in table 34. D . L . Spencer has flown over and visited on

the ground much of the coastal Kodiak area in recent years . He

told me in 1 962 Of reports from many local inhabitants . These all

indicate that the Kodiak area has not been repopulated to a si g n i f

ican t degree .

On the west side of Cook Inlet , in K ami shak Bay, Spencer ( letter ,1 957 ) Observed 40 otters at Augustine Island and one at ShawIsland .

K en a i Pen i n su l a , Pr i n ce Wi l l i am S oun d , an d K aya k Is l an d ar eas

Th e distance from the tip of the Kenai Peninsula to Kayak

TABLE 34.— Number s of sea otter s obser ved a n d estima ted p op u l a t i on i n the

K odi ak Is l an ds

[Data fo r 1 957 an d 1 959 a r e fr om Leus in k except the estima tes based on field obser vation s;1 965 da ta is fr om aer ia l sur vey by S pen ce r a n d Ken yon ]

Islan dAug usti n e an d Shaw Islan ds an d Cape Douglas a r ea A pr i l 1 965S huyak July 1 959


Island Off the coast is about 250miles. Sea otters are scarce alongthe coast of the Kenai Peninsu la. The center of the sea otter

population in this area is in Prince Wil l iam Sound .

Many reports Of otters, particularly from Prince Wil l iam Sound,were made during past years by personnel of the U.S . Fish and

Wildl ife Service, the A laska Department of Fish and Game, andthe U.S . Coast Guard (Len si n k , That the population is a

long-establ ished one is indicated by the seizure by the Governmentof two illegal ly taken skins at Seward in 1 924 (U.S . Bureau of

F isheries,

Aerial surveys made in 1 959 by Len si n k ( 1 962 ) furnish the bestmodern information on sea otter populations in this region (table

We did not con duct an aerial survey of the Kenai Peninsula

but a number of biologists have visited this coast . The lack of sea

otter Observations by them and by residents indicates that no

significant popu lation of otters occupy this area .

The long-established Prince Wi lliam Sound sea otter popu lationmay have reached maximum size some years ago followed by adecrease in recent years

,or

,possibly the surveys are not compara

ble (table The reason for the indicated decl ine is a matter ofspeculation . Itmay be that ecological conditions aremarginal . Much

of the coastal area is precipitous,furnishing only a narrow zone Of

shallow water where sea otters may Obtain food . The Prince

Wil l iam Sound population , being the most northerly in Alaska,may suffer during severe winter weather . Available food speciesmay be heavi ly infested with parasites to which the sea otter ispoorly adapted . F . H . Fay found an individual more massively i n

fested than any animals taken from other areas ( see Parasites and

Miscellaneous D iseases ) . Lastly, it is possible that the relatively

TABLE 35 .— Number of sea o tter s obser ved an d est ima ted p op u l a ti on i n the

K en a i Pen i n su l a ,Pr i n ce Wi l l i am S oun d ,

an d K ayak Is l an d ar eas

Aer ia l sur vey Estima tedobser vation s popula tion s

A r ea 1 959 1 1 964 2 1 959 3

Kayak-Win g ham Islan dsH i n ch i n br ook Islan dMon tag ue Islan dGr een an d L i ttle Gr een Islan dsLa touche an d E r l i n g ton Islan dsO ther , in cludin g un sur veyed a r eas

Q

1 Da ta fr om aer ial sur veys made i n A pr il an d August 1 959 usin g a Cessn a 1 80 a ir cr aft .2 John Van ia , lette r o f 30 O ctober 1 964. A er ia l sur veys made 1 an d 2 O ctober 1 964.

3 Estima tes , a lthoug h simila r to Len si n k’s estima te o f to ar e n ot taken

fr om h i s r epor t. Fo r the sake of un iformity i n this r epor t they wer e computed on the same

basis as other estima tes .



As previously suggested (Len si nk ,1 960) these may have

reached the Pribilofs on drifting ice from the Unimak—AmakIslands area . Preble and McAtee ( 1 923 ) mention the finding Of

skulls in subsequent years . I presume that these, l ike the ones

several other biologists and I have found since 1 947, had remainedburied under sand dunes since the l 7oo’s or even earlier .

The area Of availabl e feeding habitat— water 30 fathoms or

less in depth— around St. Paul Island is about 395 squareIf the population ther e was as dense in 1 786 as that now found at

certain Of the Rat and Del ar of Islands (about 1 6 to 1 9 otters per

square mi le ) , the total population at the Pribilofs could have been

about to in 1 786 . This estimate indicates that E ll iott’

s

( 1 875 ) statement is plausible .

In April 1 954 we attempted to transplant sea otters by shipfrom Amchitka Island to the Pribilofs . Al l 1 9 animals apparentlydied soon after liberati on on 9 April . None was subsequently seen .

Another transplant of seven otters by aircraft on 20 May 1 959was successful in that at least some of them survived . Residents

of the Pribilof Islands , bel ieved to be rel iable Observers , reported

the occasional sighting of one or two otters until the spring of1 96 1 . Although the sightings could not be verified, they do indicate

"

the possibility that at least some otters survived for 2 years ( seeTransplant Attempts ) .

Iso lated as this island group is by 240mi les of open sea fromthe nearest population , near Unimak and Amak Islands and thetip of the A laska Peninsula , there is probably l ittle chance thatnatural repopulation will occur in the near future . The possibilityexists that eventually otters associated with floating ice may reach

the Pribilofs from the Unimak-Amak-Alaska Peninsula area .

O ther wester n A l aska ar eas

The Pavlov Islands (55° N . l at . , W . long. ) ar e south of

the A laska Peninsula and northeast of the Sandman Reefs . In

1 957 (Len si n k , 1 958 ) and again in 1 962 the group was partially

covered during aerial surveys . On each survey four otters were'

seen near outer I l i asik Island . As the Sandman Reefs population

grows,otters will probably move from that area into the Pavlov

Islands .

The Semidi Islands N . lat . , W . long . ) l ie about.

20mi les south of Sutwi k Island . In the summer Of 1 957 Len si nk

( 1 958 ) recorded five otters there . This isolated group was not

subsequently surveyed .

Chirikof Island N . lat. ,W . long. ) is about 40


miles southwest of the Trinity Islands and was not included onsea otter surveys . D . L . S pencer told me in 1 962 that he flew

around Chirikof and saw no sea otters there .

S outheaste r n Al asha

Observers occasionally report sea otters from the vast complex

Of islands, passes, and straits Of Southeastern A laska. Enforce

ment Agent J . A . Kl ingbeil , Jr . , ( letter, 1 4 October 1 950) reported

four animal-s seen at Nakwasi n a Bay on 2 September 1 950, whichhe believed to be sea otters . He also reported a single otter seenat S ilver Bay, Baranof Island ( i n Len si n k , The possible

Observation of sea otters near Ketchikan was reported by J .

D itcher in 1 945 ( i n Len si n k , 1 958 ) and by L . W . Croxton in 1 96 1

( letter, NO Observat ion , however, has been confirmed byother Observers . It appears that until 53 were transplanted to

the area by the Alaska Department of Game in 1 965 and 1 966 few,

if any, sea otters existed in Southeastern Alaska .

Dall ( 1 870) indicates that exploitat ion of the sea otter in theAlexander Archipelago was intensive . Apparently this populationwas wi ped out before 1 900.

Maynard ( 1 898 ) indicates that otters were most abundant

along the coast as far as S itka . South of that point they were lessnumerous and were taken mostly from Queen Charlotte Islands .

”

There is no record that sea otters occur ed in the inland pas

sages of Southeastern Alaska and apparently they also shunnedparts of the outer coast .

BRIT ISH C OLUMBIA

The sea otter apparently became extinct on the British Columbiacoast during the l 920’s:

In a conversation , in 1 962, A . W . F . Banfiel d told me of a sea

otter skull , deposited in the National Museum of Canada, that was

found by Patch in the Queen Charlotte Islands in 1 9 1 9 . Later he

wrote ( lett er, 1 963 )

I discussed the specimen with [C . A . ] Patch some year s ag o an d was un derthe impr ession i t was a fa i r ly fr esh skull , when he picked i t up . T he

Nat ion a l Museum Of Can ada spon sor ed an expedit ion to the n or th en d Of

Gr aham Islan d dur in g the summer Of 1 9 1 9 . Con cer n in g the sea otter

he [Patch , 1 922] wr ites (p .

“I foun d a sea otter skull i n a deser tedcabin n ear Rose Spit . Ch ief Har r y Wi ah sa id that about a yea r befor e our visitan In dian shot at a sea otter which was r est in g on kelp n ear Nor th Isla n d .

H e a lso sa id that about th ir ty yea r s a g o h i s father , h i s wife ’s father an d

other In dian s— a tota l of n in eteen boa ts— g ot twen ty-on e sea otter s i n a

for en oon an d six i n the af ter n oon .


The most recent record is of a sea otter taken at Grassie Island,Kyuquot , in 1 929 (Cowan and Guign et, Concerning this

specimen Gui guet wrote in a letter ( 1 958 ) that

We have on e specimen r ecor d ( skin ) Of an adult sea otter taken at K yuquot

Soun d (Gr assie Islan d ) i n the autumn of 1 929 an d don ated to the P r ovin cialMuseum by the B . C . Game Commission . Ther e ar e f ew deta i ls, the an ima lwas n ot sexed, measur ed or the skull pr eser ved . S in ce that t ime we have n o

authen t ic r epor t , but man y sight”r ecor ds, an d of those in vest igated a l l

pr oved to be r iver otter . As f ar as we kn ow, the sea otter has yet to r e

establish on the B r it ish Columb ia coast .

WA SH INGT ONThe last authentic record Of sea otters on the Washington coast

is Of “several being killed at Wi llapa Harbor in 1 9 1 0 (Scheffer,

The river otter is frequently seen in salt water along the outer

coast and among the islands and inland waterways of Washington

State . Observers Often report these to us as sea otters . To date , all

sightings that cou ld be investigated proved to be Of river otters .

C . Van der sl uys of Friday Harbor, Wash . , who is famil iar with the

inland waters, wrote ( letter, 1 963 )

We did see a gr oup Of otter last summer , Off the S an Juan Islan ds. In fact ,th is an ima l seems to be in cr easin g i n number i n th is a r ea each year . Loca llywe ca ll them lan d otter , an d to my kn owledge, I have n ever seen a sea otter

a r oun d her e.

I have searched the outer coast Of Washington many times dur

ing the past 1 0 years but have never confirmed any report of seaotters there (Kenyon and Scheffer,Although originally numerous on the outer coast Of Washing ton,

it i s doubtful whether the sea otter ever occurred on inland waters

at any distance from the open-sea coast. Scheffer ( 1 940) says,“There are no authentic records Of the sea otter in Puget Soundor the San Juan Islands .

”Dr . E . Gunther ( letter, 1 963 ) told me:

Peter Puget ’s Jour n a l Of the explor at ion of Puget Soun d , May 7 to Jun e 1 1 ,1 792 [fr om] Pacific Nor thwest Quar ter ly, vol . 30, n o . 2, Apr i l 1 939commen ted on the absen ce of sea otter s i n Puget Soun d (p . [Fr om]Men zie ’s Jour n a l Of Van couver ’s Voyage:“We saw but f ew sea otter skin samon gst them [the n at ives] wh ich shows that these an ima ls do n ot muchfr equen t the in ter ior chan n els.

”

Dr. R. E . Greengo , Professor of Anthropology at the University

Of Washing ton , told me in 1 963 that he and his students have care

fully examined about 30 midden sites in the Puget Sound area.

Among the many bones found, only two, from Sucia Island in the



presence near the mouth of Bixby Creek, Monterey County, became general ly known (California Senate,The permanent population of sea otters on the California coast

is between Point Conception N . lat. ) and Monterey Bay

N . Here, during an aerial survey on 27 August 1 957,Boo l oot i an ( 1 96 1 ) Observed 638 otters . Because Of predation bythe sea otter on abalones (H a l i oti s sp . ) the Opinion was expressed

that sea otters were shot or ki lled with spears by fishermen

(H . Shelby, i n California Senate, T O ascertain the number

Of otters presently on the California coast, aerial surveys were con

ducted by the Cal ifornia Department of Fish and Game . Th e sur

veys included theareas surveyed by Boo l oot i an During thefirst, 26 to 29 January 1 964, 236 otters were Observed (CommercialFisheries Review, 1 964a ) . During the second, 1 3 February 1 964,the counts by two Observers were 339 and 351 (Commercial F isheries Review, l 964b) The most recent survey was on 8 June 1 966

when 6 1 8 otters were counted (J . G . Carlisle, Jr . , letter, July

[For recent inf ormation see page 200 and footnote 5, table

These surveys indicate that the Cal ifornia sea otter populationhas not increased in recent years . Other Observations, however,suggest that the population in the area sur veyed did not increase

because otters wandered to other areas .

R . G . Pr asi l searched National Park Service fi les on the Channel

Islands and found the following reports (J . C . von Bl oeker and

R . M . Bond, letter 28 May 1 940)

K en n eth E . Stager saw a sea otter asleep i n the r ocks on the n or thwest sideOf San ta Bar bar a on Mar ch 1 7th H e appr oached to within 30 feetof i t befor e i t awaken ed an d took to the water . H e i s familiar with thesean ima ls Off the Mon ter ey Coun ty coast (as I am a lso ) an d I see n o r eason to

doubt hi s r ecor d .

Another report was obtained by L . Sumner and R . M . Bond

( letter ) during a survey at Anacapa Island in 1 950. They inter

viewed a long-time island resident named Raymond (Frenchy)Ladr eau and wrote

Ladr eau told us that i n 1 943 two sea otter s came to the kelp beds Of the West

Islan d an d to the lan din g a r ea n ear by wher e he has hi s shack . H e sa id theywer e quite tame an d un afr a id an d r ema in ed ther e f or 2 or 3 days befor e di sappear in g. This i s the secon d r ecen t r ecor d Of sea otter s i n the Chan n elIslan ds a r ea an d in dicates that if un distur bed they may be expected to i ncr ea se i n that gen er a l r egion . Per haps some day, if pr otected fr om poacher s,they wil l r ema in perman en t ly ar oun d An acapa an d n eighbor in g islan ds.

Al lanson ( 1 955 ) reported seeing two otters at San Miguel

Island in the Channel Islands (34° N . ) in 1 954.

THE SEA OTTER IN T H E EASTERN PAC IFIC OCEAN 1 87

On 1 7 and 1 8 March 1 958, I visited Santa Rosa and San Miguel

Islands aboard the M/V T r i n i ty and Observed the inshore watersOf both islands from a dory. Much ideal sea otter habitat wasexamined but no otters were seen . This survey and reports from

other visitors to the Channel Islands indicate that, as yet, nosubstantial sea otter popu lat ion has developed there .

Orr and Poulter ( 1 964) recorded several observations at AfioNuevo Island N . lat. ) in the summer of 1 963 and Bentley( 1 959 ) noted two near Trinidad Head (41

° N . ) in December 1 956,indicating that individual otters are moving nor thward .

LOWER CALIFORN IA , MEX ICO

The aboriginal population Of sea otters reached its southern l imit

at least as far south as Morro Hermoso N . lat . ) (Ogden ,1 941 ) and Natividad and Cedros Is lands N . lat. ) (Anthony, 1 925;Scammon , Anthony indicates that the lastremaining colonies “in the region of certain kelp beds south ofEnsenada”were wiped out when about 50 were killed in 1 897

and an additional 28,“eight or nine years later at the same point .

The last record he gives is of one being “killed by fishermen in

1 9 1 9, at San Benito Island .

”

In April and May 1 946 and in January and February 1 965 Ivisited many Of the islands and inshore water areas along the

coast Of Lower California from Natividad Island to the U.S . border

I found no information that sea otters might still exist along thecoast and saw nothing to indicate their presence . The species was

probably ext irpated on the Mexican coast in 1 9 1 9 .

SOV IET UN ION POPULAT I ONSBarabash-Nikiforov ( 1 947 ) summarizes information on the dis

tr ibut i on Of sea otters in the Soviet Union . Information on modern

sea otter populations in areas under Soviet control became available only recently . The drowning Of Scientist S . D . Per el eshi n atPar amush i r Island in the Kuril Islands in 1 959 probably retardedsea otter studies . Per el esh i n

’

s successor, Scientist A . N . Belkin ,

accidental ly shot himself in 1 965 (pers . comm . , V . A . Ar sen i ev)but some of his work was published posthumously.

C omman der Is l an ds

Data obtained on a visit to the Commander Islands in July 1 961

and the available published information is summarized .

Geologically the Commander Islands (K oman dor sk ie Ostrova )


are part of the A leutian Chain . They are separated from Attu,

westernmost Of the Near Islands, by about 1 85 mi les of Open sea .

Permanent human settlements are Preobrazhenskoe (populationabout 300) on Copper Island (Ostrov Medny) and Nikolskoe

(population about 500) on Bering Island (Ostrov Bering ) .

Exploitation of the sea otter began at the Commander Islands

in 1 741 when Vitus Bering’s second expedit ion discovered them.

Barabash-Nikiforov ( 1 947 ) stated that in 1 902 the sea otter

popu lation there was “at least head”but because Of excessive killing“the herd numbered 700 head in 1 904. The numberat Medny

“in the winter 1 9 1 1 —1 9 1 2 was 63 head . After 1 924

he says that Importation Of animals was begun and still continues”and the number rose to “over 200 head in He also

says that “An increase in the number Of sea otters around BeringIsland was Observed after the autumn of 1 93 1 .

Informat ion now avai lable contradicts some of the data givenby Barabash-Nikiforov The current information is pre

sented .

Mar akov ( 1 963 ) says Of the Commander Islands that the sea

otter became rare early in the 1 9th century and then “disappearedentirely, first on Bering Island an d

'

then also on Medny Island .

They reappeared on Medny toward the end of the“century but

have never reappeared on Bering Island .

“Hunting continued onMedny Island unt i l 1 924. When it was completely banned , no

more than 350 individuals were left . The herd showed litt le or no

in crease during the following 30 years .

_Mar akov bel ieves that

various human activities,including the spill ing of petroleum prod

ucts in the sea, prevented popu lation growth . Mar ak ov ( 1 965 )states that “the herd of otters on Medny Island numbers morethan 1 000 adult individuals .

”

I Obtained additional information during a visit to the Commander Islands from 9 to 23 July 1 961 .

We saw six sea otters (five adults , one pup ) during our visit .

We found these near the southeast end ofMedny Island along aboutmiles of coast . Reefs projecting from the shore , outlying rocks ,

and extensive kelp beds provide excellent habitat in this area . The

green sea urchin is abundant at the locations we visited on Mednyand Bering Islands . Two sea otter droppings found among the

rocks at Medny consisted entirely Of sea urchin tests .

Certain of our hosts , the late Dr . S . V . Dor ofeev, G . A . Nesterov

(biologist) , and E . P . Skripnikov ( supervisor of seal ing activitiesat Medny and a resident of the Commander Islands for about 25years— 1 5 years on Bering Island and 1 0 years on Medny Island )


NORTH AMERICAN FAUNA1 90

h.

.

0

A.

SQ

AN

S:xnmmH

SQ

Sav

age

Emacs

WSPh

wmma

MEmso

Q

SQSQSQSQSQSQSQ

Sac

ha-m

Emuvd

m.

h

32

3352

82

Exam

coo

baa

.“woo

;

mNmJ

ma

OQ

o

wmaa

d

0

3k.wmafi

a.

we8

38

5.

cow

aha

voo

é

bfimé

OQ

wwb

fi

m

gr”

ma

m.”

arm

w

as“.

we

coo

;25

6

m

gNab

Nowa

35

a

me

vawwfiwJ

mmmfia

mowfi

mac

a

kin

dn

5a

moafi

Irmaa

mama

Nwafi

rmafi

Noafl

rmafi

amafi

ma

ma

ma

ma

mwma

mwafi

moafi

”L

lam

a

now

Iawua

a

id—ma

0

M

I

dasem

8253oo

cmuna

|l

|

nda

zmnmcofia

sa

n

d

?

3

Eso

m

a

ma

>0a

>ana

fim

wa

fln

fiw

aa

Evnaw-xa=aw

lit

l.

ma

id—ma

xo

h

wondwuvzda


D ISCUSSIONIn the for eg oi n g section , observation s of sea otter population s

obtain ed between 1 935 an d 1 965 i n several geographic areas were

reviewed . The data in cluded aerial an d surface coun ts , total

population estimates based on them, measuremen ts of available

habitat, an d population den sities i n differen t areas . The field

observation s an d the con clusion s derived from them ar e discussed

below.

Rate of p op u l at i on i n cr ease

Two methods may be used to ascertain the approximate rate of

in crease i n a sea otter population :( 1 ) The an n ual rate of repro

duction an dmorta l ity i n a population may be studied;or 2 ) otters

i n an isolated population may be coun ted at in terval s an d the

in cremen t foun d directly. The first method is treated elsewhere .

The results obta in ed by the secon d method ar e discussed below .

Because movemen ts of large n umbers of otters from on e islan d

to an other were recorded , it was eviden t that the area in cluded

i n population surveys must be sufficien tly large to in clude location swhere both emigration an d immigration occurred . The population

surveys i n the An dr ean of Islan ds furn i sh the best avai lable i n

formation on which to base a study of population growth . On the

east, this otter population i s i solated from the smal l population of

the Umn ak-Sama l g a Islan ds by 1 20miles , which in cludes AmuktaPass an d the unpopulated Islan ds of Four Moun tain s . On the west ,the study area is separated from the De l ar of Islan ds by 1 4-mi le

wide Tamaga Pass .

This sample area , about 2 1 0 miles i n len gth , in cludes den sely

populated islan ds adjacen t to others havin g un occupied habitat .

Aerial surveys of the An dr ean of s i n 1 959 , 1 962, an d 1 965 were

con ducted un der comparable con dition s by the same observers .

The smal l , semi- isolated population s at Atka an d Aml ia at the

eastern en d of the sample area showed a larger rate of in crease

than did the total An dr ean of population . Probably these colon ieswere augmen ted by wan derin g in dividual s that formed the van

guard of the massive eastward movin g population of the Kan aga

Adak-K ag al aska Islan ds segmen t of the sample area .

The rate of the An dr ean of population in crease of about 1 2+percen t i n each of two 3 -year periods or over 4 percen t per year ,i s less than the rate of in crease postulated by Soviet biologists .T he rate of in crease was at first presumed to be 1 0 to 1 2 percen t

per year by Barabash-Nikiforov ( 1 947 ) but he fin al ly con cluded

that thi s rate was n ot i n accord with his field observation s an d


placed the an n ua l rate of in crease of a population at 7 percen t.In the Comman der Islan ds, however, even this rate appeared somewhat high when compared with his “on the spot observation s .”Len si nk on the basis of his surveys, con cluded that therate of in crease of the An dr ean of Islan ds population was 1 0 to 1 5percen t per year . The more comprehen sive data gathered i n thesame areas after his studies were completed, however , in dicate

that the tota l population within the An dr ean of group is n ow i n

creasin g at a lower rate, probably because of den sity-caused

morta l ity i n the heavily populated areas .In a loca l area of sparse population

,the 1 959—65 data in dicate

the population may have in creased durin g that period at an an n ual

rate of at least 1 0 percen t . For example , the estimated populationat Seguam, the easternmost islan d of the sample area, in creased

from 28 to 47 otters (table 25 ) i n the 6-year period 1 959—65 or ata mean an n ua l rate of a l ittle more than 1 1 percen t . This conelusion is based on the assumption that Seguam Pass is a fa irlyeffective barrier to immigration .

After a large population i s produced, as it was, for example,at Adak ( i n the An dr ean of Islan ds ) i n the 1 954—62 period (table

the overa l l an n ual in crease of the An dr ean of population wasat the rate of about 4 percen t .The observed 4 percen t an n ual rate of in crease is a gen eral ized

figure . At islan ds where the population exceeded the carryin g

capacity of the habitat, i . e . , more than 1 0 to 1 5 otters per square

mi le of habitat ( see table population reg ression was observed .

Stress morta l ity ( starvation ) , as well as emigration , probably ac

coun ted for the loca l population decreases . Eviden ce to supportthis View was foun d on 28 April 1 965 durin g a brief examin ationof on e otter haulin g groun d at Shagak Bay, Adak . There I foun da large Juven i le otter dead on the beach . It exhibited a l l thecharacteristics of starvation that I observed at Amchitka . Probably the rate ofmorta l ity durin g the win ter-sprin g season of stressat T an ag a ,

Kan aga ,an d Adak i n the 1 962—65 period was con sider

ably greater than at the relatively sparsely populated islan ds east

of K ag a l ask a durin g this same period .

Thus, the rate of population in crease varies accordin g to p opulation den sity an d its relation to ecological con dition s an d may be

quite differen t from the rate of reproduction . E l sewhere it is

shown that about 1 6 youn g may be born an n ual ly per 1 00 i ndepen den t an imal s of both sexes an d a l l ages .

In gen era l , it is con cluded that an isolated population havin gample un used habitat may grow through local reproduction (n o



The Kan aga data in dicate that this level may be ma in tain ed forat least a 3 -year period . The Amchitka data in dicate that after thein itia l population “crash”a period of slow in crease, or adjustmen t, occurred (table Durin g the recovery period the p op u

lation approached a den sity of about 20 otters per square mile offeedin g habitat . That this is n ot an optimum population den sity isin dicated by the con tin ued an n ua l occurren ce of heavy mortal ityamon g juven i les an d old adults ( see Age Specific Mortal ity ) , bycomparatively smal l body size ( see Body Measuremen ts ) , by excessive den ta l attrition , an d by the fact that by 1 965 the populationhad fa l len to a den sity of 1 4 otters per square mile of habitat.Optimum population den sity i n the A leutian area , after a de

p l eted habitat has recovered from the damage caused by over

util ization of food resources, may be postulated at about 1 0 to 1 5otters per square mi le of habitat. Table 38 shows predictedpopulation s i n certa in Alaska areas based on data n ow available .

More data ar e n eeded, however, to properly estimate optimumpopulation den sity.

Geogr ap h i c ba r r i er s

Passes between areas of feedin g habitat aroun d islan ds , mayact to a varyin g degree as barriers to the spread of sea otterpopulation s . For example, Bul di r , Semi sop ochn o i , an d the Near

Islan ds were n ot repopulated for a n umber of years after theislan ds n earest to them supported high population s . The 55 milesof open water between Bul di r an d Kiska was an effective but n ot

a perman en t barrier . A few otters reached Bul di r from Kiska

betwen 1 936 an d 1 961 . Kiska was den sely populated by 1 959 an d

perhaps before that, but n ot un ti l the 1 959— 65 period were sma l l

colon ies establ ished i n the Near Islan ds , 65 mi les west of Bul di r .

TABLE 38.—Pr esen t an d p r ojected sea ot ter p op u l a t i on s i n certa i n A l aska ar eas

[Only the areas that have been most intensively studied a r e included . T he projections of futurepopulations a r e based on the assumption that a population of about 1 0 to 1 5 otters p er squarem ile of feeding habitat may be supported ]

AreaNear IslandsRa t IslandsAn dr ean of IslandsIslands of the Four Mountains

K r en i t zenUn imak-Amak Islands

S anak Island and S andman Reefs


The 30miles of deep open water between Amchitka an d Semi

sop ochn o i Islan ds was apparen tly a less effective barrier . No otters

had reached Semi sop ochn o i i n 1 943 (when the Amchitka populationwas n ear maximum size ) but by 1 959 the population at Semi

sop ochn o i was relatively den se ( 1 6 otters per square mi le ) . Movemen t to S emi sop ochn o i of a substan tia l n umber of otters , rather

than the slow in crease of a smal l breedin g n ucleus , durin g this

period is in dicated .

T he behavi or a l bar r i er

Con siderable data show that the reoccupation of vacan t habitat

is depen den t to an importan t degree on the inheren t behaviora l

characteristics of the sea otter .

The sea otter does n ot un dertake season al migration s . Recoveryof marked sea otters at Amchitka revealed that the home ran geof an in dividual otter in cludes on ly a few mi les of coast . Mar akov( 1 965, p . 21 2 ) al so foun d that otters i n the Koman dorski Islan dsbecome attached to a particular area .

Elsewhere ( see Amchitka Islan d ) it is shown that otters movein to areas of n earby but un occupied habitat on ly i n respon se to“population pressure”after a large loca l population has developed(table The Amchitka data in dicate that the reman en t colony

which repopulated the islan d was probably on the Pacific coastan d that sig n ifican t n umbers of sea otters did n ot move to theBerin g Sea coast un til 1 940 or soon thereafter (fig.

Substan tial population movemen t from den sely populated

Kan aga to n earby un populated Adak an d later from Adak ton earby islan ds east of it did n ot occur un til den se local population sbuilt up . In 1 959 the Adak population had reached a den sity of3 1 otters per square mile of habitat (table 28 ) but on ly on e otterwas observed at n earby K ag a l aska (table It thus appears

that otters ten d to main tain an established home ran ge un til theeffects of a den se population force movemen t.

Wan de r i n g i n di vi dua l s

Man y observation s of in dividual otters at great distan ces fromlarge loca l population s ar e available . That such wan derers eventual ly settle perman en tly i n a local ity that offers idea l habitat

con dition s is in dicated by the existen ce of smal l colon ies at great

distan ces from large population cen ters . The smal l colon ies foun din the Near Islan ds, Bul di r , Atka , Aml ia , Seguam, an d i n the

Umn ak-Sama l g a an d T i g a l da Islan ds areas i n the 1 950—65 period ,ar e examples .


It thus appears that vacan t sea otter habitat is repopulated bytwo mean s:( 1 ) Movemen t of large n umbers of otters from a

den sely populated area to adjacen t un populated habitat, an d (2 )wan derin g in dividua ls that accumulate to form colon ies where

habitat con dition s ar e ideal man y miles distan t from den se p opu

l at ion s.

Because of the in dicated 4 percen t per year rate of growth ofthe An dr ean of sea otter population , the repopulation of vacan thabitat at the periphery of a den sely populated area , is , today,the most importan t mean s by which the sea otter is reoccupyin gthe places from which it was extermin ated durin g the 1 8th an d

1 9th cen turies .

D i sp er sa l of sea otte r s an d p opu l at i on den si ty

Most an imal s in cluded i n taggi n g studies at Amchitka were

adults when marked an d the recoveries in dicated that they r e

main ed perman en tly alon g a l imited area of coast ( see H ome

Ran ge ) . By an a logy with other species it would seem probable

that wan derers, con tributin g to ran ge exten sion , might be com

posed mostly of subadult an ima l s . That this may be true al so ofsea otters i s in dicated by our fai lure to observe as man y mothersaccompan ied by sma l l youn g i n n ewly populated areas as i n otherareas . In 1 959 , we saw n o otters i n K ag a l ask a Strait, but in 1 962we observed 348 there . Aerial photographs of a group of 1 57an ima l s an d an other of 59 revealed n ot on e small pup amon g

them. In mi d-November of 1 965 , when this area was well behin d

the van guard of population expan sion , I spen t 2 days i n K aga l askaStrait an d saw a n umber of mothers accompan ied by youn g.

Two possible con clusion s con cern in g the otters which first app ear ed i n K aga l aska Strait ar e in dicated:( 1 ) Al l were males , an d(2 ) they were mostly subadults of both sexes an d had n ot born

youn g.

Estimates of population den sity, or the n umber of sea otters persquare mile of available habitat, were obta in ed i n several Aleutianareas . Amon g these were location s where substan tial population shave existed for man y years , an d a lso recen tly repopulated areas .

On the basis of geographical barriers an d population den sity,sea otter population s i n Alaska may be classified accordin g to fourgen era l categories (two den sities of isolated population s an d two

den sities of population s adjacen t to avai lable habitat ) .

l . D en se i so l a ted p opu l a ti on s

This category in cludes population s of sea otters that have



The rate of in crease of these three colon ies is related in verselyto their distan ces from the large western An dr ean of population

Annual rate o f increaseColony large papulation

Possibly the an n ua l rate of in crease of the Seguam colon y

represen ts the rate of in crease that may be attributed to localreproduction i n an un crowded population .

Summary

1 . In 1 741 when un reg ulated exploitation of the sea otter beg an , the species ran ged from cen tral Lower Ca l iforn ia, Mexico,n orth a lon g the coast of the North Pacific Ocean , through theA leutian an d Kuril Islan ds to the n orthern islan ds of Japan .

2. The n orthern limit of the sea otters’ ran ge overlaps butsl ightly the usua l southern l imit of wi n ter drift or pack ice i n theBerin g Sea. The farthest n orth colony i n Alaska is i n Prin ceWi l liam Soun d N . l at . ) where the sea does n ot freeze .

3 . The total population of sea otters in 1 740 was probablybetween an d an ima ls .

4. The n umber of sea otters taken durin g 1 70 years of unregulated exploitation i s n ot recorded but probably did n ot muchexceed on e-ha lf mi l l ion an ima l s .

5 . The tota l world population i n 1 9 1 1 , when exploitation ofthe sea otter was halted, probably n umbered between an d

an imals .

6 . Smal l sea otter population s apparen tly rema in ed i n 1 9 1 1

at the followin g 1 1 areas:Kuril Islan ds , K amchatka Pen in sula ,

Comman der Islan ds , Rat Islan ds , An dr ean of Islan ds, the Un imak,San ak Islan ds-San dman Reefs area , Shumag i n Islan ds, KodiakIslan d an d Prin ce Wil l iam Soun d area, i n the Queen Charlotte

Islan ds, British Columbia , on the coast of Ca l iforn ia n ear Monter ey, an d i n the San Ben ito Islan ds , Baja Cal iforn ia .

7. The first modern data on the recovery of sea otter p opul ati on s

'

Were obtain ed i n the Aleutian Islan ds i n the mi d-1 930’san d con siderable mi scel lan eous data were subsequen tly gathered

durin g the l 94o’s. Deta i led field studies of population an d di str i

but i on were begun by the Fi sh an d Wi ldl ife Service i n 1 954 an d

con tin ued through 1 965 .


8 . The sea otter is l imited to a relatively n arrow ban d ofwater aroun d islan ds an d a lon g main lan d shores where waterdepths do n ot exceed 30 fathoms . Un der the prevai l in g weathercon dition s when aerial surveys were made , sea otters were easilyobserved . We con cluded that i n most areas about 75 percen t of thesea otters presen t were recorded . Comparative surface an d aerial

surveys in dicated that about 60 percen t of the otters seen on

an aerial survey may be missed on a surface survey.

9 . Data obtain ed on aerial surveys i n the An dr ean of Islan dsi n 1 959 , 1 962, an d 1 965 in dicated that i n this area , havin g muchavailable an d unpopulated habitat, the population i s growin g at

an expon en tial rate of between 4 an d 5 percen t per year .1 0. Aerial surveys an d other studies con ducted between 1 954

an d 1 965 i n Alaska revea l that large areas of sea otter habitatar e n ot yet repopulated . In certain areas repopulation of vacan thabitat is proceedin g rapidly (the An dr ean of Islan ds ) . In i solatedareas the habitat may be heavily util ized by a den se population(the Rat Islan ds ) .

1 1 . In a l l observed areas where estimated sea otter population s

reached 20 to 40 otters per square mile of habitat, the population sdecreased to about 8 to 1 5 otters per square mi le of habitat . Thedecrease occurred through mortal ity (e . g . , Amchitka Islan d ) oremigration (e . g . , K an aga an d Adak ) . In years followin g a p op u

lation “crash”the population s at islan ds may fluctuate betweenabout 1 0 an d 20 otters per square mi le of habitat .

1 2. Reoccupation of ava ilable sea otter habitat is hin dered bywide , deep passes between i slan ds . Sea otters readily cross passesabout 1 0 miles wide . S ign ifican t n umbers may cross 30 miles of

open water (e . g Amchitka to Semi sop ochn o i ) . Passes 50 milesor more i n wi dth may be crossed by a few in dividual otters thatwan der great distan ces from den sely populated areas (e . g . , from

Kiska to Bul di r an d from there to the Near Islan ds ) . These in divi dual s may even tually con cen trate i n location s havin g un usual ly

desirable habitat .1 3 . The most sign ifican t factor that l imits the spread of sea

otter population s is the ten den cy of in dividual otters to occupya l imited home ran ge . Feedin g habitat on on e side of an i slan d , orat an islan d n ear an other havin g vacan t habitat , may become

den sely populated (to about 40 otters per square mi le of habitat )before a sign ifican t n umber of otters move in to adjacen t vacan t

habitat even at the home islan d . Where repopulation was observed,the south sides of islan ds were repopulated prior to the n orth exp osur es (e . g . , Amchitka , Atka , an d Aml ia ) .


1 4. In addition to the man y areas i n western Alaska off erin g

sea otter habitat which today i s un populated, approximately

mi les of coastlin e, in cludin g much sea otter habitat, separates thecolon y at Kayak Islan d, Alaska, from the sma l l cen tra l Cal iforn iacolon y.

1 5 . Severa l aeria l surveys were made i n 1 958 an d 1 964 to 1 966a lon g the Ca l iforn ia coas t . The highest coun ts i n 1 958 an d 1 966

yielded 638 an d 6 1 8 sea otters , respectively . Further surface an d

aeria l surveys , begun i n August 1 968, yielded a high coun t ofotters (Peterson an d Odemar

,in dicatin g a population

in crease sin ce 1 958 of about 5 percen t per year .

1 6 . The n umber of otters recorded durin g aerial an d l imitedsurface surveys i n Alaska was an d the tota l population i n

Alaska waters i n 1 965 is estimated to be about1 7 The most recen tly published Soviet tota l estimate of sea

otters in Soviet waters is

1 8. On the basis of a l l data ava ilable , the world population ofsea otters i n 1 965 was computed to be A gen eral estimate

of the world population , presumin g that some populated areas

have n ot been observed , is about to an ima ls .

1 9 . Measuremen ts of avai lable sea otter habitat, much of whichwas n ot occupied i n 1 965 , an d the observed population den sity ofrelatively stable population s ( 1 0 to 1 5 otters“per square mi le ofhabitat ) in dicate that the A leutian Islan ds an d closely related areasof the Alaska Pen in sula may even tual ly support a population of

about to sea otters .

H ome Ran ge

The purpose of perman en tly markin g sea otters is to obtain

from field observation s an d recovery of tags, over a period of time ,the followin g in formation on the life history of in dividual an imal s

( 1 ) Maturation , (2) agin g, (3 ) lon gevity, (4) reproduction , an d

(5 ) movemen ts an d home ran ge .

S ea otters were captured on shore with a sport fisherman ’s

lan din g n et (fig. 82) Whi le the n etted otter struggled to free itself,usin g forepaws an d teeth on the n et , on e rear fl ipper was graspedan d a cattle or sheep ear tag ofmon el metal (table 39 ) was clampedto the web of the hin d fl ipper with a specia l pl iers . Two men wererequired, on e to hold the n et an d the other to affix the tag . Colored

plastic strips were attached experimen tal ly to some tags, so thatin dividual an imal s might be recogn ized i n the wild .



TABLE 39 .— S ea otter s tag g ed a t Amchi tka Is l an d

, A l aska

Juven ile Adult T otalYear

EL 401 —409 1

EL 1 2908 and 1 29 1 021 2901 - 1 2903;1 29261 3000;3 EL 426 , 427,429- 43 1 , 433, 440-442,and 444.

EL 446—565EL 566- 572

T otal .1 T his series sheep-ear size.

2 T his series cattle-ea r size . T he high numbers to a r e the r esul t of usingtag remainders from Pribilof fur seal ser ies . T he prefix EL was hand stamped on only a f ew.

T he tags were obtained from the National Band and T ag Company, N ewport, Ky .3 Except two ruined.

on e an imal was recovered at a haulin g-out place, an d on e colormarked in dividual was observed repeatedly .

Two hun dred an d eight of the an ima ls were captured an d taggedat n in e tradition al haulin g-out areas;the remain in g 1 6 were

marked at scattered location s on Amchitka Islan d . Three haulin g

out areas ar e on the Berin g Sea coast, five ar e on the Pacific coast,an d on e i s at East Cape where the Berin g S ea an d Pacific coastsmeet. The min imum distan ce between the haul in g groun ds used as

taggin g location s is 1 mi le an d the maximum distan ce is 9 miles .Eight an ima ls tagged at on e haulin g-out place were subsequen tlyrecaptured at the n ext n earest on e.

Three females , tagged as adults an d recovered n early 3 years

later, were foun d an d 5 miles, respectively, from thelocation s of taggin g. On e fema le recovered 2 years after taggin g

was mile from the location of taggin g . Two fema les recovered

about 1 year after taggin g were an d 2 miles from the location

of taggin g an d two others were recovered at the location oftaggin g.

On e youn g adult ma le , whose tag bore a colored plastic flag ,was observed repeatedly . This an ima l visited the location wherewe discarded fish rema in s i n Con stan tin e H arbor, n ear K i r i l of

Dock. H e was presen t dai ly for a period of about a mon th an d a

half. H e became tame an d was captured by han d when he cameashore to accept food . Because of the art ificial food source , the

seden tary behavior of this an ima l may n ot represen t the n ormal

behavior of the adult ma le . On e juven ile male , tagged at East Cape ,was foun d dead 24 days later i n Con stan tin e H arbor , 9 mi les fromthe location of markin g. Amon g five juven i le males , recovered

within a mon th of taggin g, however, on ly on e was as far as 3

miles from the taggin g location .

203SEA OTTER IN THE EASTERN PACIFIC OCEAN

mmb b u b mma b mmmb b a mo mmmfioma mmmmm

0

E Ec

3 0 0 30mfi d d o O mm a O a d m O

EE gEo

bm a -afi fi o

S oc-1

vvav>

3w~a

co

mma-

H.

a

co

Scuo‘a

«c

a

c

s

2

se

a

an

”ac

am”

0

8ma

“we

0

8ma

se

a

m

38

av

g”

«e

a

O

Ea

awn

38

O

SmN

O

S«5

O

Eon

su

m

09

«an

a.

2

ne

w

ev

aa

E

5

a.

a

a

bs”

daw

n

mwlmlmw

mwlmlwa

Nwlmlw

Nwlmlw

Nwlmlb

mwlmlbw

mwlmlom

wo

lmlm

mo

lmla

m

mwlmlma

Nwlmtbw

Nwimlww

Nwlwlwa

Nwtmlma

Nwlmlwa

amlmlw

a

wlmlwa

wwIN|¢a

Nwln

lwa

moivlma

Nwlmlna

mmlv

lva

mmlv

lv

mmlv

la

a

amlvlm

amlmlou

vmlwa

la

a

wmlmla

n

wmlmlmu

mNwlmINN

Nwlmlb

awlmlb

Nwlmlv

Nwlmln

wwlmla

NwI

vN

awlwlvw

Nwlwlww

Nwlwlwa

Nwlwlma

amialma

Nwlmlma

awlwlma

amlvlwa

amlvlma

amlvlma

amlv

lw

mmlvlb

amlvlm

mulv

lw

aml

l

mmIV|N

mmlvla

amlmla

vula

a

wmlm

wmlw

comma

?

a

s

1a

m

6mm

Ana

dam

1a

m

dam

Qma

dfim

Ana

da

m

1a

m

Now

1a

m

23

Ana

Gav

QM

cmv

1a

m

6

3.

Am

Gav

1a

m

53.

Am

mmv

Jam

33

AM

oooma

dm

maawa

aanm

mmmwa

dma

wvawa

dm

mvmwa

dfl

a

vaNa

Ama

mbmwa‘

ama

Nbawa

wa

ma

NomNa

AH

momma

dm

a

maNa

Afi

oa

ama

dma

aov

1a

m

a

ov

Ana

non—c:

ma

y


The taggin g of n ewborn or very youn g pups was discon tin uedbecause the frighten ed mother, upon release, usual ly made severallon g dives . It seemed probable that at least some of these youn gpups may have died as a result of un usually lon g periods ofimmersion . Also, severa l mothers refused to accept their helplesspups when they were released an d later fai led to return for them.

D ISCUSSIONTo date the in formation from taggin g is meager . Man y of the

an imals which were captured on lan d were there because they were

ill or i n weaken ed con dition . For this reason ,the rate of survival of

tagged an imals is probably lower than for the population as a

whole . There is as yet n o reason to bel ieve, however, that the actof taggin g in creased the morta l ity W ithin the tagged segmen t ofthe population as compared to the un tagged segmen t ( except whenmothers with smal l pups were captured ) . D isturban ce of thean ima l s durin g taggin g was brief an d care was taken n ot to in jurethem. The tag placed i n the web of the hin d flipper had n o n oticeable effect on swimmin g. Marked an ima ls, i n the wild an d i n

captivity, ign ored their tags, except that certa in in dividuals

chewed the colored plastic flags attached to the metal tag .

The data an d gen era l field observation s lead to the followin gten tative con clusion s:( 1 ) The home ran ge of the female sea otterdurin g at least a 3-year period may in clude about 5 to 1 0miles ofcoastl in e . Soviet biologists foun d that the ran ge from the “basicstation i s 1 5 to 1 7 km. to mi l es]

’ f

(Nikolaev an d Skal k i n ,

(2 ) An imal s tagged on on e side of Amchitka did n ot move

aroun d to the other side of the islan d ( see Distribution an d

Numbers ) . 3 ) Males may have a larger home ran ge than females .

(4) In dividual otters may use more than on e of the tradition alhaul in g-out places .Addition a l in formation from tagged an imal s is foun d i n section s

on“Ag e at Sexua l Maturity,”“Age Specific Mortal ity,”an d

“Juven ile Sex Ratio .

Territorial ityIt i s difficult to say whether territorial ism exists i n the sea

otter i n the same sen se that it does i n other mammal s . Man y sea

otters , both male an d fema le , share much of the same home ran gewithin which the two sexes min gle to some degree . Also they may

segregate to haul out i n tradition a l ly established location s ( see

Segregation of Sexes ) .


REPRODUCTION

SexRatio

Because sea otters segregate themselves accordin g to sex, ther aw data from samples kil led, captured, or foun d dead on beachesat Amchitka Islan d must be carefully evaluated before drawin gany con clusion s con cern in g the sex ratio amon g differen t age

classes.

PRENATAL SEX RA T IOThree samples of fetal sea otters ar e ava ilable from females

kil led i n 1 962 an d 1 963 . The data ar e summarized in table 41 . Thesmallest fetus i n which sex was positively determin ed weighed

g. Amon g the 58 fetuses i n which sex was determin ed, theratio was 45 percen t males:55 percen t fema les . The fact that thetwo 1 963 samples show a n early ratio in dicates that un ti l a

larger sample is ava i lable the pren atal sex ratio may, for practicalpurposes , be con sidered to be about

JUVEN ILE SEX RAT IOData on the sex ratio of juven i le otters were gathered durin g

taggin g studies when sea otters were n etted, tagged , an d released .

This work was don e mostly before the period i n which highmorta l ity occurred . The youn g otters were i n the areas frequen ted

primarily by females with youn g. Man y of the youn g that werecaptured for markin g were stil l i n compan y of their mothers orrecen tly separated from them. Morta l ity amon g youn g i n company

with theirmothers is n ot kn own but apparen tly i s low or moderate .

TABLE 41 .— Pr en a ta l sex r a ti o a t Amchi tka Is l an d

Number Ratio ( percent )Date taken Males Female T otal Males Females

22 J an . Mar . 1 962

1 7—3 1 Ma r . 1 9633 1 July—3 Aug .


Little geographica l segregation of deser ted juven i les had ap

p ar en t ly occurred at the time tagging was don e . Th erefore , thi sclass of an imal s con tributes the best in dication of sex ratio amon gsea otters up to approximately 1 year of ag e . Amon g 1 1 7 j uven i les

that were captured an d marked , 58 males , 58 females, an d 1 ofunkn own sex were recorded (table 39 , section on H ome Ran ge ) .

This eviden ce suggests that the sex ratio is approximately 1 :1 dur

i n g the juven i le period .

ADULT SEX RAT IOThe areas i n which fema les predomin ated were the most accessi

ble to hun ters . Also, these areas ar e more exten sive than thelocation s frequen ted by males ( see S eg er g at i on of Sexes ) . Primarily for these reason s the sex ratio of an imal s taken durin g

croppin g Operation s i n 1 962 an d 1 963 were biased i n favor offemales . The take con sisted of 67 percen t females an d 33 percen tma les (table In the section on mortal ity it was shown thatthe sex ratio amon g juven i les foun d dead on beaches durin g thelate-win ter to early-spri n g period of stress was 58 percen t males

42 percen t females . These data suggest that amon g survivin g

adults, females outn umber males . The percen t by which femalespredomin ate amon g adults , however, can n ot be derived from theavailable data . The differen ce between the n umber of males an d

females taken durin g kill in g operation s is a result of sexual seg reg at ion an d is too g reat to be explain ed by the apparen t differen ce

i n male an d female mortal ity amon g juven iles .

Un til further studies ar e con ducted , it may be con cluded thata n early equal n umber of males an d females ar e con ceived an d

that the sex ratio remain s approximately un ti l juven i les ar e

deserted by their mothers . At this time , more ma les than females

die of n atural causes . T hus , amon g adults, fema les probably predomin ate over males . H arvestin g operation s ten d to con firm thi sbut more data ar e n eeded .

TABLE 42.— S exra tio of sea ot ters k i l l ed a t Amch i tka Is l an d dur i n g exp er i

men ta l harvests[Ratio , males to females ,

FemalesNumber Percent Number Percent number

Jam—Ma r .

Man - A p r . 1 963


Segregation of Sexes

Male an d fema le sea otters at Amchitka habitually segregatethemselves an d, a lmost a lways occupy distin ct geographical areasat al l season s . This con dition first became apparen t durin g obser

vat i on s when otters i n various areas were coun ted an d the n umbersof each sex recorded . Addition a l in formation was obtain ed whenotters were captured on beaches an d when those dyin g of n atura lcauses were recovered . Durin g harvestin g operation s i n 1 962 an d

1 963 , more quan titative data on the degree of segregation becameava i lable (tables 43 an d The terms “ma le area an d

“femalearea”refer to the geographica l location s used predomin an tly (butn ot exclusively) by each sex . Mar ak ov ( 1 965, p . 21 3 ) n oted sexualsegregation amon g otters at Medny Islan d, Comman der Islan ds,US S R .

FEMALE AREAS

These ar e more n umerous an d less discrete than male areas

(fig. 83 , map ) . S even female areas ar e l isted i n table 43 . At theseplaces the adult females usua l ly haul out i n favored shelteredplaces n ear the extremities of poin ts . In gen eral , they appear less

boun d to a l imited haulin g out location than the males . Certain

location s, however, such as St . Makar ius Poin t W Rifle Ran gePoin t, an d Con stan tin e Poin t, ar e more favored than others . T agrecoveries reveal that females may use more than on e of thefavorite haulin g groun ds ( see H ome Ran ge ) . T he kil l of adultfema les reveals that they ar e gen era l ly distributed a lon g the coastwhen feedin g. Man y were taken a kilometer or more from favoredhaul-out location s . Observation s as well as data from the ki l l in dicate that females n ot on ly avoid the male haul-out location s butalso avoid the feedin g habitat adjacen t to them. Amon g 242 adultotters ki lled i n female areas, 93 percen t were females . When 20

an imals , n ot accompan ied by a pup but i n female areas , were

ki lled selectively (3 1 July to 3 August 1 963 ) i n an eff ort to take

males, on ly on e male was obtain ed . This sample may in dicate thatmales con stitute on ly 5 percen t of the an imal s i n female areas .

MALE AREA S

Thr ee location s on the eastern half of Amchitka (fig. 83 , map )ar e used a lmost exclusively by ma les;the southeast tip of St .Mak ar ius Poin t (SMPE ) about 800m. of beach, the n orth beachan d tip of East Cape (EON ) about 500 m. of beach, an d Crown

Reefer Poin t (CRP) about 600 m . of beach . Alon g each of these



884717

102

37


F IGURE 83 .-T he southeastern en d of Amchitka Islan d showi n g the most

favored ma le an d fema le haulin g groun ds. In dividua l an ima ls may haulout at a lmost any location a lon g the shore . At the location s in dicated on themap , however , aggregation s of sea otters a r e habitua lly formed when num

bers of an ima ls come ashore to rest at a l l season s.

beaches the majority of an imals habitua l ly haul out on 40 to 50

m. of beach . A few in dividual s may haul out in discrimin ately at

various distan ces from the most favored location . When a n umber

of otters ar e hauled out, they usual ly con gregate i n g roups , often

sleepin g i n con tact with on e an other (fig. Amon g 1 02 adultotters killed i n these areas , on ly 2 were females (table

It appears that the males, except those actively seekin g to mate ,

l imit feedin g activities to a radius of several hun dred meters fromthe haul-out location . If they did n ot do this , more than 7 percen tmales (table 43 ) would have been shot i n the female areas durin g

kill in g operation s . When matin g activity was observed ( see Breed

i n g Behavior ) , males actively sought estrus females an d matin g

was observed on ly i n female areas . Thus , it is reason able that a

higher proportion of males was foun d i n the female areas than

females i n male areas .


F IGURE 84.— A group of 39 otters sleep in g at St . Makar ius Poin t East,

Amchitka Islan d , a favorite haulin g groun d f or ma les. T he man y sleepin gposition s ar e demon strated . Some l i e on their backs, others on the belly or

side, or curled n ose-to-ta il . (KWK 65—27—34)

JUVEN ILES

The foregoin g parag raphs dea lt primarily with adults . Segreg at ion of sexes is more pron oun ced amon g adults an d subadultsthan amon g in depen den t or n ewly wean ed juven i les . Amon g 35

juven i les taken i n ma le areas, 80 percen t were ma les (tableIn female areas, amon g 84 juven i les examin ed 63 percen t werefema les (table

S in ce juven iles ar e or were recen tly associated with theirmothers, it might be expected that a larger n umber would be

foun d i n the fema le areas than i n the male areas . The percen t ofjuven i les taken i n both ma le an d female areas was, however, thesame, about 26 percen t ( see footn otes, tables 43 an d This mayin dicate that in depen den t juven i les wan der to a l l areas an d min gle

with any group of adults . It also appeared , however, that juven ileswere more attracted to areas occupied predomin an tly by adults

of their own sex (20 percen t fema le juven iles on the male areas

an d 37 percen t male juven i les on fema le areas ) . Perhaps becauseof the recen t mother-youn g relation ship the proporti on of youn gmales on the fema le area was greater than the proportion of youn g

females i n the male ar eas .



in other islan d population s . Kn owledge of the degree of segregationof sexes an d the location s of areas where ma les con cen trate mayprove useful i n man agemen t operation s .As men tion ed elsewhere (Breedin g Behavior ) , ma les oftenpatrolled fema le feedin g areas an d attempted courtship with al l

females presen t . In the course of 3 or 4 hours , two to four malesmight pass separately through such an area .

Breedin g Behavior

Observation s at Amchitka ar e often hin dered by den se fog. Th isfact an d the ten den cy of mated pa irs of otters to occupy offshorerocks, have preven ted me from followin g any on e pair of ottersthrough a l l phases of the breedin g cycle . I have, however, recordedobservation s of 41 mated pairs i n the wild . Amon g these, copu

lation was in itiated by 1 3 males which were n ot successful i n

completin g it . Copulation was completed , apparen tly successfully,i n eight cases . The rema in in g 20 observation s were of pairedan imal s i n close compan y which, as explain ed later, exhibited thebehavior typi ca l of mated pa irs . Excluded from the records ar eobservation s? of un successful attempts at courtship by males

toward un receptive females . The data on various aspects of thebreedin g cycle were obtain ed from man y pairs obser ved brieflyan d from the observation of on e pa ir which remain ed for about

days i n a sheltered cove (table These observation s i ndicate that the cycle of breedin g behavior is rather un iform. A

description of behavior durin g the differen t phases of the breedin gcycle follows

C OURTSH IP OR PREC OPULATORY PERIODAs men tion ed elsewhere , adult ma les an d adult females segregate themselves to a con siderable degree . When a ma le seeks a

TABLE 45 .— A cti vi ti es of a ma ted p a i r of sea o t ter s dur i n g obser va ti on s on

1 9 , 20, an d 2 1 Aug ust 1 955

1 9 August, 1 634-1 81 0. T he ma le an d fema le rema in ed in close compan y at

a l l times.

E lapsed time

Number (m inutes )Activity periods On land In water m inutes


TABLE 45.— Acti vi ti es of a ma ted p a i r of sea otters duri n g obser va t i on s on

1 9 , 20, an d 21 Aug ust 1 955— Con t i n ued

20 August, 1 542-1 91 0. T he male left the fema le restin g on the rock when hecon tinued food divin g, but he remain ed close to her while she was i n the

water.Elapsed time

Number (minutes )Activi ty periods On land In water m inutes

MaleFeed ingGroom andS leep and rest.S exual behavior ( play )Investigate strange female

FemaleGr oom andS exual behavior ( play )

T otal

21 August, 1 052—1 820. T he ma le left the fema le restin g on the rock when hecon tinued food divin g

,but he rema in ed close to her while she was i n the wa ter .

Elapsed time

Number (m inutes )Activi ty periods On land In water minutes

MaleFeedi ng 1 0

Groom and wash 5S leep and 2

S exual behavior ( play ) 5

S n i fi 1

FemaleGroom and washS leep andS exual behavior ( play )

On 22 August a den se f og preven ted deta i led observation s.

Summary of activities of mated pa ir of otters on 1 9 , 20, an d 21 August 1 955,durin g three observation periods tota ling 749 minutes ( 1 2 hours, 29 minutes ) .

T otal elapsed time

Male FemaleActi vi ty Minutes Percen t Minutes Percent

Investigate strange female _


fema le i n estrus, he usua l ly swims bel ly down an d rapidly on thesurface (fig. 86 ) an d seldom dives for food . H e closely skirts

favorite haulin g-out rocks, an d he may rise high i n the water tolook on to the rocks, or leave the water to wa lk quickly about,sn iffin g the rocks . If he sees a feedin g female floatin g on her

back he swims directly to her . H e may come up ben eath her an dattempt to put his forelegs aroun d her chest from behin d, hisforepaws restin g i n or n ear her axi l lae . Or he may rise up besideher . H e may rub an d p at her chest, belly, an d gen ital area withhis forepaws, or he may n uzzle an d appear to sn iff them with hisn ose . If the female is un receptive , she rolls away from h im an d

pushes h im away with her fl ippers an d paws, or sn aps at h im.

Before departin g he may sn atch whatever food items she has on

her chest .If she is receptive, the two may roll an d frol ic together . Durin g

F IGURE 86 .—Adult ma les actively searchin g f or estrous fema les i n areas

habitua lly frequen ted by feedin g fema les often swim belly down ratherthan i n the more usua l inverted position . (KWK 1 026 )



on the female’s head with his jaws, an d the two an imals , l inked

together by their heads, spun rapidly over an d over i n the lon gitudi n a l axis on the surface . The spin n in g con tin ued for on ly a fewsecon ds . Then the female became limp, the male again align ed

his body with her back an d grasped her with his forelegs, an dcopulation con tin ued for an addition al min utes . When the

male released his grip after an elapsed time of min utes , thefemale’s n ose was gashed an d bleedin g. The two an imal s im

mediately began to groom an d scrub their fur . Then , the femaleleadin g, the pair swam to an d hauled out on the rock where theyhad previously en gaged i n courtship . H ere they con tin ued togroom an d dry their fur for 1 0min utes . The female was p ar t i cul ar ly vigorous i n this activity. Durin g this period an d subsequen tperiods of association with the male on the chosen rock, the femalea lmost con stan tly uttered a soft chucklin g soun d . After dryin g

their fur, the pair wen t to sleep curled up close beside each other .The time was late aftern oon an d presumably, as was observed on

other occasion s , they slept i n this location un til after sun rise then ext day.

Whi lem ost observation s in dicated that the male in itiated matin g activities , estrous females were observed to tease or stimulatea reluctan t ma le . In on e in stan ce (7 May 1 956 at 1 7 1 5 local time )I“saw a male an d fema le sleepin g close beside each other i n a kelp

patch . They appeared to be a mated pair, an d I presumed thatcopulation had occurred . While I watched, the female awoke an dbegan to n uzzle the ma le about the head an d abdomen . The male

was slowly aroused from sleep an d at first appeared in diff eren t to

the atten tion of the female . Within about 30 secon ds , however ,he clasped her with his forepaws , then grasped the side of herhead i n his jaws . The female then became rigid (as described

elsewhere ) an d copulation was accomplished . Un fortun ately, after

copulation had con tin ued for 1 1 min utes , their motion s carried

them behin d rocks, an d it was n ot possible to obtain further observat i on s of the pa ir .

In on e case , a secon d copulation occurred about on e-half hourafter the first . Various observation s of behavior in dicate that morethan on e copulation may be usual .

Copulation usual ly occurs in the aftern oon . I have 21 obser

vat i on s of copulation an d attempted copulation durin g the after

n oon,but on ly 1 recorded for morn in g

Barabash-Nikiforov ( 1 947 ) says that durin g coitus the pa irclin g to each other, in tertwin in g belly to belly, an d revolve

aroun d the lon gitudin a l axis .”Murie ( 1 940) also said position


apparen tly bein g with the ven tral surfaces opposed, although ofthis I could n ot be positive .

”In al l n in e cases of completed copu

lation that I observed, the male clasped the female from behin dan d remain ed dorsa l to her but sl ightly to on e side of her mediandorsal l in e durin g copulation . Because of the position of the female,lyin g rigidly on her back with forepaws exten ded, immediately before coitus , i t would seem un usual that the position of the male

would be other than dorsa l to her body durin g copulation .

POSTCO PULATORY PERIODIn on e case this period was observed to last for 3 days ( 1 9

through 22 August 1 955 , table The pair fed , groomed , an d

rested i n close compan y (fig. Occasion al ly they en gaged i n

short periods of play, an d the ma le sometimes attempted copu

lation . The female, however, appeared to be un receptive durin gthi s period . The pair rested periodical ly on the chosen haulin g-outsite an d slept beside each other durin g the n ight .

F IGURE 87.— A pa ir of sea otters ( fema le on left ) rest an d groom beside each

other shortly after matin g . T he light colored head i s more typica l of malesthan fema les. As shown here, fema les ten d to be more alert an d wa tchfulthan ma les . Ma les ten d to be phlegmatic an d take a larm less easily thanfema les. T he n ose of the fema le was grasped i n the teeth of the ma le durin gmating an d i s swollen . T he broader an d heavier head an d n eck of the ma lei s eviden t. (KWK 975 )


The male fol lowed the female closely, often bein g i n con tactwith her while the two con sumed food, side-by-side on the surface .

When the fema le dived for food the ma le quickly followed, often

discardin g a food item that he had n ot fin i shed eatin g. When thefema le surfaced, the ma le emerged a fraction of a secon d behin dher .

Durin g this period the ma le left the fema le’s side on ly after thetwo had emerged an d groomed followin g a feedin g period . While

the female remain ed on the chosen rock to groom an d sleep, themale dived for food n earby. While eatin g he swam back n ear thechosen haulin g-out rock to eat , an d often glan ced at the femalebefore divin g.

On the third day of the matin g period the ma le exhibited less

in terest than previously toward his mate , an d several times stolefood from her . Also , he followed her i n food dives less promptly.

The pair had left the cove by shortly after dayl ight on the morn in gof 23 August .

T H E SEPARATION PERIO DThe breakin g of the pair bon d was observed on severa l occasion s .

The female, i n each case, deserted the male . Probably because themale is larger than the fema le he requires more food, an d as a

gen eral rule he return s to the water to con tin ue feedin g while thefema le rests on lan d . In on e in stan ce , the food dives of the male

gradua l ly carried h im about 50m . from the female’s restin g place .

She watched h im in ten tly an d, sudden ly, while the male wasben eath the surface gatherin g food, she slipped quietly in to thewater an d swam rapidly away ben eath the surface . Apparen tlythe visual acuity of the ma le was in adequate to detect immediatelyfrom his feedin g station theabsen ce of the fema le . When the ma lereturn ed for on e of his periodic visits to his mate on the chosenrock an d foun d her gon e, he left the water an d walked rap idlyabout, sn iffed the spot where the fema le had rested , an d looked

quickly at possible hidin g places n earby . Apparen tly satisfied thatthe fema le was gon e, he en tered the water an d swam hurriedly

to severa l n earby haulin g-out places , risin g high i n the water tolook on to them. H e a lso rose high in the water to look across the

surface i n differen t direction s . Although I observed several suchepisodes, I n ever saw a male relocate the female after her departure .

In gen era l , it would appear that durin g the postcopulatoryperiod the female exhibits less in terest i n retain in g the pair-bon dthan does the male . The female may, however, exhibit sexual



F IGURE 88.—A— An adult ma le an d fema le slept beside each other on a tida l

rock (ma le right, fema le T he more a lert fema le was aroused by theclick of the camera an d started to leave the rock . T he ma le con tinued tosleep soun dly. (KWK 62—1 9—6 ) B— T he fema le return ed an d prodded thema le with her forepaws an d then climbed on top of him , pressin g h i s headan d chest with her paws. T he ma le ra ised hi s paws to push her away.(KWK 62—1 9—5 ) C— T he ma le, fin a lly aroused , looked about sleepilywhi le the fema le stared i n a larm at the camera . T he fema le nudged thema le toward the water . (KWK 62—1 9—3 )

their mothers, may attach themselves temporarily to an adult,either male or female, or to an other juven i le . T he two an imals

may play together, an d when frighten ed may clin g loosely together

with their forepaws .Figure 90 shows a juven ile which took refuge behin d an adult

male, beside which it slept . After bein g disturbed by my presen ce,


F IGURE 89 .—A— F in a lly aroused , the ma le moved ahead of the fema le while

she prodded h im toward the water from behin d . (KWK 62— 1 9— 1 ) B— As

the pa ir slid in to the water the fema le grasped the still drowsy ma le an d

gazed over h im at the camera . (KWK 62—1 9- 43 ) C— F in a lly completelyaroused

,the male stared i n mild a larm whi le the fema le cla sped h i s back

i n her forepaws. Shortly after the last photograph was taken the pa ird ived an d made their way through a n arrow chan n e l to open water beyon dthe tida l rocks. (KWK 62—1 9—40)

the two swam off together . S in ce an impregn ated female separates

from the male shortly after copulation , an d fami ly groups in clude

on ly the mother an d her youn g, it appears improbable that suchan association as il lustrated would in volve family ties .

As a gen era l rule , lon e females an d females with youn g ar e

observed apart from adult males . But a courtin g male, after a

period of attempted courtship with a fema le an d her youn g, may


F IGURE 90.— This adult male was toleran t of a deserted juven ile which slept

beside h im an d sought she lter behin d him when frighten ed . When the adultfin a lly became a larmed , en tered the water , an d swam off , the juven i lerema in ed i n close compan y with h im. (KWK 62—25—24)

sleep n ear them i n a kelp bed, or the three may haul out on a rock

to groom, rest, an d sleep i n close association . It Would appear thatsuch an association is an expression of gregariousn ess . On on e

occas ion I watched an adult male an d female play roughly together

for about 1 5 min utes . The fema le was accompan ied by a large

pup, which durin g the play period attempted to participate, orswam about n earby an d occasion al ly cried . Although the maleten tatively attempted copulation , the female was n ot receptive .

After the thr ee had hauled out an d the male had groomed an d

rested beside the mother an d pup for about 20min utes , he en teredthe water an d left the vicin ity. In this case it was apparen t that,a lthough the ma le was sexual ly motivated , the association of themale an d female was casual , an d they were n ot a mated pa ir . T he

association described above might lead an observer to form er

r on eous Opin ion s con cern in g breedin g habits .

Reproduction i n the Femal e

In this section,data from female reproductive tracts , the con

cep tuses they con tain ed , an d field coun ts of depen den t youn g an d



TABLE 47 .— Phases of r ep r oducti on i n the fema l e sea o t ter as shown by sta tus

of ovar i es an d si ze of con cep tus

[ Information from genital tracts collected from 1 954 through 1 963 i s combined]S eason of sample collection

Jan —Feb . Man —A p r . May—Aug .

1 S ept.—Dec .

Num Per Num Per Num Per Num Per n umber cent ber cent ber cent ber cent ber

Un implanted blastocyst_ConceptusesClass 1ClassClass 3Class 4Class 5

T otal conceptuses . .

T otal pregnantNot pregnant 2

T otal tracts1 T he 1 9 adult female sea o tters taken between 3 1 July and 3 August 1 963 were kill ed selec

t ivel y , mothers accompan ied by pups were spar ed . T hus . the percentage of postpartum n on

p

éieg n an t specimens in this sample i s less than it woul d have been if the kill had been n on

s ect ive .

2 S ee table 51 f or more deta ils .

TABLE 48.— Fr equen cy of p r imi p ar ous an d mu l ti p ar ous sea otter s

Primiparous Multiparousexamined Number Percent Number Percent

T otal

TABLE 49 .— Uter i n e hor n of p r eg n an cy

Uterine horn pregnantRight

examined Number Percent Number Percent__ I

THE SEA OTTER IN THE EASTERN PACIFIC OCEAN

O O CQN Q‘

w tb v-‘Q CD1-1a

1

227


TABLE 5 1 .— Rep r oducti ve sta tus of adu l t n on p reg n an t sea otters

[N ine an imals, adult in body size but be ing null iparous and showing n o foll icular activity, ar e

excluded ]

S amples co llected i n

S pring 1 963,Man —Ap r .

Nonpregnant Num Per Per Numtracts ber cent cent ber T ota l

Postpartum, inactive ovar iesPup presentPup absent .

Inactive ovaries 2

Active ovaries 3_T otal

T otal tracts examined and percentn ot pregnant1 An imals were k il led selectively to exclude all mother s accompan ied by young . T he objective

was to take as many male skins as poss ible in a female ar ea . Among 1 9 independent an imals ,only 1 male was taken .

2 Multiparous but n o t showing positive evidence of being r ecently postpar tum .

3 Estrus and proestrus .

total n umbers of specimen s ar e shown because n ot al l specimen s

could be used for every aspect of this study . I did n ot examin e a l l

collection s an d samples . Those that I did examin e presen ted ade

quate in formation for certa in aspects of this study.

The reproductive tracts were removed from the an imals from a

few min utes to several hours after death,depen din g on field con

di t i on s. They were then fixed en tire for 24 hours i n AFA solution

(95 percen t a lcohol , 30 percen t;commercia l formal in,1 0 percen t;

glacia l acetic acid, 1 0percen t;water , 50percen t ) . After fixin g, the

tracts were stored for later study i n 70 percen t isopropyl a lcohol .

S in ha et a l . ( 1 966 ) expla in how certain aspects of reproductive

tract studies were con ducted . I examin ed ovaries with a 1 OX Loupeafter slicin g them in to section s about 1 mm . i n width .

FIELD C OUNTS OF SEA OTTERS

Field coun ts of sea otters were recorded when ever possible . The

primary obj ectives were to obtain in formation on 1 ) the season

of birth , an d 2 ) the an n ua l rate of reproduction .

Observation s were limited by: ( 1 ) En vironmen ta l con dition s

such as win d , precipitation ,an d rough water;2 ) a variable degree

of sexua l segregation amon g in depen den t an imals,in cludin g

mothers with youn g;(3 ) the often in distin guishab i lity of sexesan d ag e classes;an d (4) the con stan t movemen t of an ima ls to an d

from loca l areas . In spite of these factors , useful field observation s

were obta in ed .



It can thus be said that the fema le sea otter does n ot mature sexua l ly un ti l after 2 years of ag e.

The mean «weight of 39 pregn an t fema les was 50 lb . kg. )

(extremes 36 an d 70 lb . ) Amon g 21 primiparous fema les , the meanweight was 43 lb . kg. ) (extremes 35 an d 52 If themarked 33-l b .

,2-year-old had con tin ued to grow durin g her third

year at the rate she did i n her secon d,her weight would have ap

p r oximated the mean weight of the primiparous females . Thissuggests that the fema le may become sexua l ly mature at 3 years ofag e.

Amon g n orthern fur sea ls on the Pribi lof Islan ds,the pregn an cy

rate i n 4-year-olds is about 3 percen t an d i n 5-year-olds about 40percen t (Fiscus an d K ajimur a , If we assume a somewhatsimi lar con dition i n the sea otter, it is in dicated that a smal l percen tage of females may become pregn an t after attain in g 3 years ofag e, i .e. , i n the fourth year , an d that an ima ls 5 or more years of ag econ stitute the importan t reproducin g segmen t of the population( see also “Impl ication of Other Observation s, p . 245

PREGNANT FEMALES

Table 47 an d figure 9 1 summarize data from 1 78 females show

i n g eviden ce of pregn an cy . Amon g pregn an t an ima ls , un implan tedpregn an cy reached maximum frequen cy ( 1 00 percen t) i n the fa l lsample . Implan ted preg n an cy in creased i n sprin g an d reached

maximum frequen cy 69 percen t) i n summer . The high frequen cy

of large (weight class 5 ) fetuses i n summer (50 percen t, table 50)an d con curren t low frequen cy of un implan ted pregn an cies (3 1

percen t, table 47 ) in dicate, as do the field coun ts of depen den tyoun g

,that parturition reaches a peak i n summer . Although the

fa l l sample of tracts is smal l,it demon strates that parturition i n

the fa l l an d win ter accoun ts for a min ority of births .Amon g 1 37 pregn an t fema les from two samples for which data

ar e avai lable ( table it is in dicated that an n ual ly 1 7 percen tof the pregn an t an ima ls became pregn an t for the first time an d

that 83 percen t ar e multiparous .

Locat i on of p r egn an cy

A record of the uterin e horn of pregn an cy is avai lable for 97an imals . A lthough the sample is sma ll , it was gathered un sel ec

t ively an d demon strates that pregn an cy occurs with equa l f r equen cy i n the right an d left uterin e horn s ( table T he location

of implan tation of the con ceptus is usua l ly within the cen ter on ethird of the uterin e horn .


—FETALWT . C L. 5

UN IMPLANTEDPREG .

NO T PREGNANT

F M A M J J A 8

MO N T H S

FIGURE 91 .— Phases i n the reproductive cycle of the fema le sea otter as r e

vea led by ovary an d feta l examin ation s of four samples of reproductivetracts. Although some of the samples a r e sma ll , they illustrate that largefetuses an d implan ted pregn an cies predomin ate i n summer an d thatpregn an cy i s a t a maximum i n late wi n ter an d sprin g.

C on cep tus si z e an d deve l opmen t

To compare the con ceptuses that were recovered from r ep r oduc

tive tract samples,the embryos an d fetuses were classified ac

cording to five arbitrarily chosen weight classes followin g a

logarithmic scale ( table The con ceptuses ran ged i n weight

from a fraction of a gram to g . (4 When the weights of

fetuses taken i n differen t seas on s ar e compared , it is shown thati n win ter con ceptuses of smal l size predomin ate an d i n summer

large fetuses predomin ate . Th e series of photographs (figs . 92 an d

93 ) i llustrate stages of developmen t . The comparative sizes of thecon ceptuses i n the samples from diff eren t season s were useful i n

in dicatin g the timin g of certain phases of th e reproductive cycle

(see Chapman’s an alysis that follows ) .

The morphology of the female reproductive tract was studied


F IGURE 92.— Early feta l stages of the sea otter . Sexcould n ot be determin ed

i n either specimen by gr oss examin ation , an d the ag e of the fetuses i s n ot

kn own . D ifferen tiation of the fron t an d hin d limb buds has barely beguni n the larger fetus. Specimen s from Amchitka Islan d , 1 8 an d 1 9 March1 963:Left— Specimen JEB 63—52, weight g . , crown -rump len gth 1 7mm. (KWK 65—1 8—1 5 ) Right — Specimen JEB 63—67, weight gcrown -rump len g th 24 mm . (KWK 65—1 8

an d described i n detai l by S in ha The developmen t of thefeta l membran es , their structures , an d evolution ary relation shipswere studied an d described by S in ha an d Mossman Thegen era l appearan ce of the gravid reproductive tract is shown i nfigure 93 .

N ONPREGNANT ADULT FEMALES

Sp r i n g samp l e

A lthough two sprin g samples ( 1 962 an d 1 963 , table 46 ) offemale sea otters from Amchitka were taken ,

I studied on ly the1 963 specimen s .Between 1 5 March an d 2 April 1 963 , 1 25 adult fema le sea otters



mothers, may be some distan ce m. ) from them an d thus notassociated with the mother by the hun ter’s observation s . Also,large young may have recen tly become in depen den t.Amon g the eight remain in g n onpregn an t fema les

,four showed

n o foll icular activity or positive eviden ce of bein g post partum.

On e of these was diseased . It possessed a large ovarian cyst(3 1x1 5 mm. ) The rema in in g four were multiparous ( en largeduterin e horn s ) but did n ot show eviden ce of bein g post partuman d appeared to be approaching estrus (follicles en larged ) or tohave recen tly ovulated .

S ummer samp l e

Amon g 1 4 sexually mature sea otters taken between 3 1 July an d

3 August 1 963 at Amchitka , 5 (36 percen t ) were n ot pregn an t .

Three of these were post partum. Non e was accompan ied by a

pup . (As explain ed elsewhere, thi s collection was selectively takento exclude mothers accompan ied by pups . ) Two were multiparousin active but their reproductive tracts revea led n o eviden ce of bein grecen tly post partum ( table

Fa l l samp l e

Amon g 1 7 sexual ly mature females taken between 1 2 Octoberand 3 November, 1 3 (76 percen t ) were n ot pregn an t . Amon g

these, eight ( 61 percen t) were accompan ied by youn g an d on e was

lactating, in dicatin g that a pup had recen tly been lost. Of the five

remain in g, three showed n o follicular activity or in dication of hav

i n g recen tly lost a pup . On e showed foll icular activity in dicatin g

a proestrus con diti on (table

FIELD COUNTS

An effortwas made to record n ewly born youn g separately fromolder depen den t youn g. Because of variable field con dition s , theresults were in con sisten t an d n ot useful to this study . Th erefore,a l l youn g with mothers were grouped as dep en den t an imals .

Coun ts were made i n man y areas but on ly i n a con sisten t wayduring a l l field season s i n the Con stan tin e H arbor

,K i r i l of Poin t to

K i r i l of Bay areas . After a l l of the data from severa l other areaswere studied , it became apparen t that because of diff eren t condi ti on s i n each area the results of coun ts i n on e area were n ot

comparable with those made i n an other . A lso, coun ts made froma cliff top can n ot be compared with coun ts made from a dory .

Fema les with youn g amon g coasta l rocks may be missed durin g an


offshore dory coun t . Also , the n umber of ma les , i .e . , the degree ofsexual segregation ,

varies i n differen t areas ( see table 43 , Segregation of Sexes ) .

I made the field coun ts from K i r i l of Poin t an d vicin ity from thesame observation station s at a l l season s (table Because theywere made i n differen t years , they can n ot be con sidered strictlycomparable but they do con stitute the best material avai lable an d

gen era l con clusion s ar e based on them.

In the summer of 1 955, K i r i l of Poin t (on the Berin g Sea shoreof Amchitka ) , boun ded on the east by Con stan tin e H arbor an d on

the west by K i r i l of Bay an d havin g a shorelin e of about km.

(3 n autica l miles ) , was chosen as a study area . I soon foun d thatit was frequen ted primarily by females , an d especial ly motherswith youn g ( see Segregation of Sexes ) . Coun ts i n this area were

thus n ot represen tative of the ratio of depen den t youn g to in de

pen den t an imals l n the Amchitka population ,but were biased i n

favor of a high ratio of depen den t youn g to in depen den t ( in cludes

both sexes an d a l l ages other than depen den t youn g) an imals .

PH ASES OF REPRO DUC TIONBr eedi n g season

Mating behavior (mated pairs , attempted copulation ,or copula

tion ) was observed i n a l l mon ths except October an d December .

H arsh win ter weather reduces visibility an d I have spen t less timei n the field i n the fal l an d win ter season s . Barabash-Nikiforov

TABLE 52.—S ea ot ters coun ted a l on g km. of shore l i n e K i r i l of area ,

a t

Amchi tka Is l an d,A l aska

[T his area included parts of Constantine H arbor, all of K i r i l of Po int, and part of K i r i l o f Bay .

T his loca l ity i s frequented primar ily by females and young . Complete counts of K i r i l of Po int,as well as counts from par ts of the area , a r e included in this ta ble ]

S easonNumber Inde Percent mean

0 pendent dependent percentcoun ts an imals T ota l young young

January 1 959FebruaryMarch , 1

59

959 andApr il 1 95May 1 956- “m a m

July 1 956_August 1 955_S eptemberOctober 1 957


( 1 947 ) did n ot observe copulation durin g October an d December .Data from field observation s of breedin g behavior an d from

reproductive tracts give con flicting in dication s of the period ofmaximum matin g activity . Field observation s appear to in dicatethat most breedin g activity occurs i n Jun e . By mon ths , observation s of breedin g behavior were as followsJan uary -1 May

February Jun eMarch JulyAp r i l August

Field observation s of behavior ar e hampered i n fall an d win terby stormy weather con dition s . Because comparative field observa

tion time was n ot avai lable i n a l l season s, I con sider that field

observation s of matin g activity ar e n ot quan titatively useful .They ar e qual itatively useful , however, i n demon stratin g thatbreedin g activity does occur i n a l l season s .

Because the frequen cy of p regn an cy i n our samples in creasedfrom 27 percen t i n early fal l (October ) to 70 percen t i n theJan nary-February sample (table 47 the avai lable data in dicatethat maximum breedin g activity occurs i n the late fa ll to win terperiod . Further studies, particularly of reproductive tracts tak eni n fall an d win ter mon ths, ar e n eeded to revea l with certain tythe period of maximum breedin g activity.

Gestat i on p er i od

S inha et a l . ( 1 966 ) demon strated that after fertil ization i n thesea otter the blastocyst en ters a period of rest, i .e. , un dergoes“delayed implan tation .

”Thus, presen ce of a corpus luteum in dicates pregn an cy whether or n ot a con ceptus is visible on gross

examin ation of the tract . When the “restin g stage”is completed,the blastocyst becomes implan ted i n the mucosa of the uterin ehorn an d proceeds through embryon ic an d feta l stages of g rowth .

To gain some kn owledge of the len gth of the gestation period

an d the duration of its un implan ted an d implan ted stages, datawere obta in ed from the ovaries an d con ceptuses of 275 r ep r oduc

tive tracts (table 47 an d fig.

On e method of estimatin g the gestation period of the sea otteris to assume that durin g the period of implan ted pregn an cy therate

‘

of fetal growth may be comparable to that of the Europeanriver otter (Lutr a lutr a) an d American river otter (L. can aden si s) .

(A more sophisticated method, given below, i s employed by Chapman . ) The European an ima l diff ers from the American river otteran d sea otter i n that the blastocyst does n ot un dergo a delay i n



less than a week old were 285 an d 290 g. (Jen sen , If thesmaller of the two is presumed to approximate the birth weightan d its cube root is plotted accordin g to the method of H uggettan dWi ddas ( 1 95 1 ) for a gestation period of about 62 days, a fetalgrowth rate lin e is established (fig . If the full-term fetusweighin g 1 32 g . , that was recovered by H ami lton an d Eadie

is plotted on the same growth sca le as the European otter,it i s in dicated that the period of implan ted pregn an cy i n theAmerican river otter may be less than 2 mon ths . Liers ( 1 951 )states that “The eyes open when the youn g ar e about thirty-five

days old .

”This in dicates that at birth the river otter is i n an

early stage of developmen t compared to the sea otter which isborn with the eyes open .

To obta in an approximation of the period of implan ted pregn an cy i n the sea otter, it appears reason able to compare its fetalgrowth rate with that of its closest relatives . If the cube root ofthe sea otter weight at birth (gen era l ly at least g . , see Body

Measuremen ts ) i s plotted on the same lin e of growth, then thein dicated period of implan ted gestation is at least 4mon ths . Datafrom reproductive tracts in dicate that maximum breedin g activity

probably occurs i n the fa l l to wi n ter period an d that the maximum

n umber of births occur i n the summer to early fal l period . The

samples in dicate that the period of un implan ted gestation i n themajority of an imal s (table 47 ) exten ds in to the Jan uary to Aprilperiod, i .e . , to last for about 6 to 8 mon ths . This would in dicatethat the total gestation period may be about 1 0 to 1 2 mon ths .Because matin g an d parturition occur durin g a l l mon ths , thismethod of estimatin g the gestation period from the ava i lable data

do n ot permit a more precise defin ition .

Pup p i n g season

Birth may take place at any season . Th is was stated by man yearly sea otter hun ters , an d con firmed by modern observers

(Barabash-Nikiforov, 1 947;Fisher, 1 940a;Murie , 1 940;I have han dled an d examin ed n ewly born youn g i n a l l mon ths .Man y of these n ewborn were captured with their mothers durin gtaggin g operation s an d were return ed to the mother when shewas released after taggin g.

Scheffer ( 1 95 1 ) rai sed the question whether there was a seasonof birth:“The eviden ce of five specimen s . i s that the youn gar e born i n April an d May, rather than the year aroun d . Data

from our samples in dicate that there is a season of maximum

birth frequen cy. The data i n table 52 demon strate that the per


cen tage of depen den t youn g i n the population i s relatively lowi n the win ter an d sprin g. After the late-win ter to early—sprin g

season of storms, which is accompan ied by much morta l ity amon g

juven ile otters ( see Limitin g Factors ) , an in creasin g n umber of

births is demon strated i n the field coun ts . A summer peak i n the

frequen cy of births is confirmed by high frequen cy of large fetusesrecovered i n that season from reproductive tracts (table

The frequen cy of n early full-term fetuses i n the samples i n

creased from n on e i n the Jan uar y-February sample to 6 percen t

i n the March-April sample an d to 3 1 percen t i n the May-August

sample (table 47 The n umber of depen den t youn g with mothers

al so in creased throughout the sprin g an d summer ( see table 52,

Field Coun ts ) .

In the smal l midsummer sample (August ) the fetuses were

large , i n weight classes 3 , 4, an d 5 , n on e were i n weight classes 1an d 2 (table

These data stron gly suggest that birth frequen cy in creases i nearly sprin g an d reaches a peak i n summer . Our samples from theSeptember through February period were too smal l to confirm

the field observation s of n ewly born youn g i n every mon th .

Although the Steller’s sea cow (H ydr odama l is g i gas) is a very

differen t an imal from the sea otter , it was a l so a residen t in shoremarin e mammal . It is in terestin g that Steller n oted ( i n Stejn eg er ,1 936 , p . 355 ) that the sea-cow brin gs forth their youn g at a l l

season s , gen eral ly however i n autumn , judgin g from the man y

n ew-born seen at that time .

”The fact of bearin g youn g at a l l

season s, while havin g a season of maximum birth frequen cy, may

be a case of convergen t evolution related to the habitat i n whichthese an imals were sympatric .

Pl ace of bi r th an d fe ta l or i en ta t i on

There is n o record that the birth of a sea otter has ever been

observed . Fisher ( 1 940a , p . 1 32 ) presumed that“The births of the

youn g otters take place on the kelp beds . This in fers that theyoun g ar e born i n water . Barabash-Nikiforov ( 1 947, p . 97, En glishtran slation ) , however, saw a mother with a n ewly born youn g on

shore an d recovered the still warm afterbirth .

The place of birth i n marin e mammal s may be related to fetalorien tation at birth . For example , i n cetacean s birth a lways occurs

i n water. S l ijp er ( 1 956 ) summarized data on the position of the

cetacean fetus at birth . In 22 observed births, a l l youn g were born

ta il foremost . Presumably caudal presen tation is a survival factor


i n an a i r breathin g mamma l bor n un der water (Essap i an ,

S l ijp er however, does n ot subscribe to this theory.

If cauda l presen tation is a survival factor i n aquatic birth an d

it were the rule i n the sea otter, it might be supposed that birthwould occur in the water . Amon g 43 fetuses for which feta lorien tation were recorded, delivery would have been cepha l ic i n22 (5 1 percen t ) an d cauda l i n 21 (49 percen t ) . T hese data in dicatethat selective evolution for cauda l presen tation at birth, an d by

in feren ce for birth i n water, has n ot taken place i n the sea otter .

By comparison , the fur sea l is more specia l ized for l ife i n themarin e en vironmen t than is the sea otter but emerges from thewater before parturition . Peterson ( 1 965, p . 1 36 ) recorded thati n 61 percen t of 1 1 2 observed births the youn g emerged headforemost. It i s thus in dicated that birth i n the sea otter, as i n

the fur seal n orma l ly occurs on lan d .

Per i od be tween bi r ths

Figure 9 1 an d table 47 demon strate that durin g the win ter an dsprin g when the maximum n umber of sea otters ar e pregn an t,on e-third of the tracts i n our samp l e were n on pregn an t . I stron glysuspect that a l l reproductive tract samples ar e biased toward a

low frequen cy of n on pregn an t an imal s . This assumption is basedon three observation s: 1 ) that n o female kn own defin itely to beaccompan ied by a pup was foun d to be pregn an t, (2) that femaleswith youn g ar e more wary an d secretive than females withoutyoun g an d ar e thus less avai lable to hun ters , an d (3 ) that durin ghun tin g operation s I n oted a degree of reluctan ce in hun ters toshoot a female accompan ied by a pup if an imals without pups werepresen t . Thus, an unkn own degree of bias i n favor of sin gle an imals, i .e. , a high percen tage of pregn an t an ima l s, is in cluded i nal l samples . The July to August 1 963 sample is particularly biased ,sin ce sin gle an imal s on ly were selectively kil led . At this season then umber ofmothers accompan ied by pups is approachin g the an n ualmaximum ( see table Thus , the percen tage of n onpregn an tan imals i n the adult female population would also approach maximum n umbers at this season . This is shown by the sample (fig. 9 1 )but it would be much more apparen t had the sample beenun selective .

Because the summer sample of reproductive tracts was takenselectively to exclude mothers accompan ied by pups it is , i n somerespects, n ot comparable with the sprin g an d fal l samples . Neverthel ess, the followin g con clusion s con cern in g n on pregn an t femalesea otters i n our samples ar e in dicated . ( 1 ) Females accompan ied



percen t. S in ce the youn g sea otter rema in s with its mother forabout a year, the an n ual rate of reproduction is 1 4 percen t, orabout 1 6 youn g born per 1 00 in depen den t an ima ls per year .

From Chapman ’s an a lysis ( see later section ) it is shown thateach 1 00 adult fema les i n the breedin g population produce 50youn g per year . Thus, i n the adult population (male an d female )there ar e theoretica lly 25 depen den t youn g per 1 00 adults of bothsexes . Itwas calculated that 3 1 percen t of the in depen den t an imal sobserved durin g field coun ts ar e juven iles . Thus, 69 percen t ofthose observed ar e adults . It follows that, with a g roup of 69adults there ar e 1 7 25 percen t ) depen den t youn g, or

Depen den t youn gIn depen den t an imalsJuven i lesAdultsTota l

In formation from reproductive tracts, from field coun ts ofdepen den t an d in depen den t an imal s, an d the ratio of males to

fema les i n the kill ar e used i n two ways to demon strate that thean n ual rate of reproduction of the Amchitka population i s about1 4 to 1 5 percen t .

T wi n n i n g

Barabash-Nikiforov ( 1 947 , p . 98 ) an d Sn ow ( 1 9 1 0) reportobservation s of mothers with two youn g, an d reproductive tractscon ta in in g two fetuses . Our observation s in dicate that twin n in g

is un usual . In 278 reproductive tracts taken i n 1 954—63 , 1 78 of

which showed an in dication of pregn an cy, n o twin fetuses werefoun d . On e specimen (No . JEB 63—1 66 ) taken at Amchitka on

25 March 1 963 , had well-defin ed corpora a l bi can t i a i n both ovaries

an d darken ed scar tissue (placen tal scars ) i n both uterin e horn s .This female was n ot , however, accompan ied by youn g.

That activity i n both ovaries is n ot n ecessarily an in dication

of twin n ingwas shown by on e specimen (ADFG Both ovaries

con tain ed well-defin ed corpora lutea but on ly the left uterin e horncon tain ed a con ceptus .In early April 1 955 , a fema le an d two large youn g (each about

1 8—20 lb . ) with her were captured on shore at Amchitka . They

were held i n captivity an d l iberated at the Pribilof Islan ds . Durin gthe days that the three an ima l s remain ed i n captivity, the adultal lowed both youn g to n urse . She appeared equa l ly permissive toboth . She groomed on ly on e of the pups, however , an d when the


three were l iberated together, she ign ored on e an d took on herchest the on e she habitually groomed . It was our con clusion thatthe deserted pup was an orphan toward which this motherexhibited toleran ce .Large youn g, still depen den t on their mothers , will frequen tlyplay together for lon g periods whi le their mothers ar e divin g forfood . If on e mother should desert her youn g at such a time, it i spossible that an association such as we observed could occur .

Although it i s possible that a mother may bear twin s, I believe it i sdoubtful that a mother could feed an d groom an d successfullybring two youn g to the stage of in depen den ce .

In the n orthern fur seal (Ca l l or h i nus ur si nus) which , l ike thesea ott er, n ormal ly bears on e youn g at parturition an d is highlyspecialized to marin e existen ce , twin n in g is rare . Peterson an d

Reeder ( 1 966 ) summarize data derived from Fi scus, Bain es , an d

Wilke ( 1 964) demon stratin g the in ciden ce of twi n implan tation

in the fur seal at percen t amon g preg n an t femal esexamin ed . In spite of the observation that the youn g fur sealappears less burden some to its mother than the youn g sea otter ,n o eviden ce exi sts to date that a fur seal can successfully raise

twin s to wean in g ag e (Peterson an d Reeder ,

Len gth of S tages of the Rep r oduct i ve Cyc l e

Dr. D . G. Chapman , Cha irman , Biomathematics Group , Laborator y of Statistica l Research , Departmen t of Mathematics, Un iversi ty of Washin gt on , studied the data obta in ed from fema le reproduct ive tracts an d prepared the followin g an alysis:

An a lysis of feta l weight da ta;T he procedure of Huggett an d Widdas ( 1 951 )i s used to estima te the feta l g rowth velocity an d hen ce the len gth of the

growth period . Table 53 shows the data of table 50:fetuses classified byweight classes accord in g to time of collection reduced to a percen tage basis.

T he last r ow i n the table i s obta in ed by ( 1 ) calculatin g an unweightedmean of the mean weights i n the three periods;(2 ) fin din g the cube root ofthis mean .

T he use of percen tages i n the table an d the unweighted mean s i n the

TABLE 53 .— Percen t of fetuses i n each wei g ht c l a ss

[T his table i s derived from data in ta ble 50]T ime of co lleetion after July

Mean time in monthsMean of cube roo t of wei ght“


ca lculation ar e n ecessary to give equa l represen ta tion to a l l times of the year.A regression lin e fitted to the cube root of the weights aga in st th e mean time

i n mon ths give a regression coefficien t ofa = 2.292 p er mon th

or on a da ily basisa= 0.076

This i s an estimate of the specific gr owth velocity of Huggett an d Wi ddasIn View of the very sma ll samples obta in ed over a l l parts of the year

except the Jan uary to April period , it i s subject to con siderable samplin g erroran d it seems reason able to roun d the estimate to Whi le this growthvelocity i s somewhat below the va lue ca lcula ted f or the European river otter ,it i s quite close to va lues ca lculated f or the n orthern fur sea l has beenca lculated by Chapman , un pub l ished manuscri pt ) .

If 1 850 g. i s used as an average feta l size at birth,the estimated period of

feta l developmen t after establishmen t of the fetus i s,52 1 850

.08 W 1 54 daysor approximately 5 mon ths.

It i s also n ecessar y to estimate the len gth of the gestation period durin gwhich the blastocyst i s un implan ted . From table 54we have the numbers an d

percen tage of pregn an t an ima ls with an un implan ted blastocyst and a con

cep tus durin g the four season s.

It might be argued that lesser weight should be given to the two shorterperiods, January to February an d March to April . If the results of these twoperiods ar e averaged, an d this average i s in corporated in to an overa l l unweighted average, the result i s essen tia lly the same. (T he average so com

pa ted would be 61 percen t versus the 60 shown i n tableIt thus appears that the period durin g which the blastocyst i s un implan ted

i s ha lf as lon g aga in as the implan ted period, or about 7 1A;mon ths. T he fullgestation period wi l l also in clude the per iod required f or establishmen t of theembr yo , i .e . , the period before l in ear growth i s established . Huggett an d

Wi ddas ( 1 95 1 ) in dicate a rough procedure to estimate this but it i s n ot

kn own whether their va lues apply to an imals that exhibit delayed implan tation . If about 15 mon th i s a llowed f or this period, it follows that the estimated tota l len gth of the period of gestation i s about 1 3 mon ths.

T he period durin g whi ch the fema le sea otter i s n ot pregn an t ( lactatin gan d restin g period ) can be estimated simi larly from the data from table 47 .

This table shows that the percen t n on pregn an t i n the four periods n oted i s30, 30, 48, an d 73 , respectively. In this case the weight to be given to the twofirst periods does make a differen ce . T he average of the four percen tages i s

TABLE 54.-Fr equen cy of un imp l an ted an d imp l an ted p r eg n an cy, by season

[Data from table 47 ]



so thatA+J JA when ce 1

A_ 1 .3 1

JA

_ O.3 1

Now l et Joz number of juven i les i n their year after depen den cynumber of years i n juven ile stage

Jon

=I

( 1

AlsoJ1

so thatJ 1

A ( .91 5 )n

or from (2 )

( .9 1 5 )n1

( .91 5 )n

(9 1 5 )

When ce n 3 years approxima tely. This i s the estimated len gth of the periodbetween the en d of depen den ce an d maturity for fema les.

SUMMARY AND CONC LUS IONS

1 . It is in dicated that breedin g activity reaches a peak i n fall ,but breedin g activity was observed in al l season s.

2. Un implan ted gestation i s estimated to last for 7 to 8 mon ths.

3 . Implan ted gestation i s estimated to last for 4V2 tomon ths.

4. The total gestation period is estimated to last 1 2 to 1 3mon ths .5 . The period between births, i .e. , total len gth of the r ep r oductive cycle , i s about 2 years .6. T he average an n ual birth rate amon g mature fema les i s

50 percen t.7. Parturition occurs i n a l l mon ths, but a min or ity of births

occur i n fall an d win ter mon ths. Parturition reaches a peak i nsummer , and large fetuses occur with greatest frequen cy i n

summer .8 . Depen den t youn g occur with g r eatest frequen cy i n fall an d

with least frequen cy i n late win ter an d early sprin g. In fall , un implan ted preg nan cy reaches greatest frequen cy.

9 . B irth n ormally occurs on lan d.


1 0. Caudal an d cephal ic presen tation of the fetus occurs withabout equa l frequen cy.

1 1 . Twin n in g is possible but rare, an d if twin s ar e bor n thereis n o eviden ce to show that both survive .1 2. Females accompan ied by youn g or showin g positive evi

dence of par turition do not n ormal ly en ter estrus .1 3 . Low frequen cy of estrous an d p r oestr ous females amon g

n on pregnan t females at a l l season s in dicate that impregnationoccurs soon after the on set of follicular activity.

1 4. Ann ually 1 7 percen t of the pregn an t an imals ar e preg nan tfor the first time an d 83 percen t ar e multiparous .1 5. Pregn an cy occurs with equa l frequen cy i n each uterin e

hor n .

1 6. The an n ual rate of reproduction i n the total population i sestimated to be about 1 4 to 1 5 percen t about 1 6 youn g bornper 1 00 in depen den t an imal s of both sexes an d a l l ages ) .

1 7. It is estimated that the female sea otter reaches sexualmaturity at age 4 years (3 years after becomin g in depen den t) .

Reproduction i n the Ma l e

Observation s of cour tship behavior i n a l l season s an d the occurren ce of n ewborn youn g i n a l l mon ths in dicate that male sea ott ersmay be sexual ly active at any season .

A prel imin ary histological study of testes was made of 40 sea

otters taken i n the Jan uary to April period i n 1 958, 1 959 , an d 1 962.

These specimen s in dicate that spermatozoa ar e produced whenthe testes attain a weight of about 1 3 to 1 4 g. Spermatozoa ar e

probably n ot produced by an ima ls havin g a body weight of lessthan 50 l b . , but most of those weighin g 55 lb . an d a l l of thoseweighin g 60 lb. or over may produce spermatozoa .

Dr. Edward C. Roosen -Run ge , Departmen t of B iological Strueture, Un iversity of Washin g ton Medical School , Seattle , kin dlyexamin ed the hi stological specimen s of sea otter testes an d con

tributed the followin g in formation con cern in g the adultNo quan tita tive eva luation was attempted . Spermatogen esis was eva luated

by the stages of germ cells presen t. T he last stage of spermatogen esis i s thati n which the late spermatids (with den se an d elon gate heads) ar e lin in g thelumen of the tubule. If an appreciable number of tubular section s were foun dcon ta in in g this stage or stages immediately precedin g it , it was assumed thatmany spermato zoa were liberated at this time from this testis. If man y stagesof spermatogen esis were foun d, but few of the very late on es, it was assumedthat there was a slowin g down or a stan dstill somewhere i n the developmen tof germ cells or that some periodicity occurred i n the liberation of sperm .


The materia l examin ed appeared to in dicate quite stron gly that there wassuch a periodicity. All adult an ima ls showed a germin a l ep ithelium i n a

state of active production of germ cells, but n ot a l l showed an appreciablenumber of late stages of

‘

spermatogen esis. No an ima l in dicated as“ol d,”

[an ima ls havin g well-worn teeth were arb itrarily classified i n the field as

ol d] showed any sign s of dimin ished sperm output;i n fact, a l l of these an ima ls( 3 ) showed many late stages of spermatogen esis.

Two cases (62—92 an d 624228) were probably hypotrophic. Both were poorlypreserved (hypotrophic testicles ar e common ly more diff i cult to preservewell ) . It appeared to me that these two cases ar e possibly sig n ifican t. Theymay in dicate either a fa irly high percen tage of ma les with degen erative testi cl es an d con sequen tly l ow fertility, or they may in dicate a periodicity i n thespermatogen ic activity which would appear more pron oun ced when specimen s

taken thr oughout the year ar e investigated . Both hypotrophic testicles showedhypotrophic Leydig cells.

T he Leydig cells of the n orma l , adult sea otter testis appear to be ag

g r eg ated i n huge masses aroun d the rete chan n els an d a lmost form an

“en docrin e organ”i n this location . From there , lon g stran ds of these cellspen etrate in to the septa , usua lly i n very close apposition to thin -wa lled vein s.

T he rete itself i s fortified very stron gly with a coarse n etwork of collagen ousfibers. T he gen era l structure of the semin iferous tubules i s en tirely typicalfor mamma ls.

On e con clusion that appears justified on the basis of the testesexamin ed is that the production of spermatozoa i n the sea otterexhibits a mild or modified periodicity. There is n o in dication

that a distin ct season a l periodicity i n sperm production exists, asi n man y distin ctly season al breeders, or that there is con tin uousproduction of sperm as i n the r at . A comprehen sive study ofreproduction i n the male sea otter rema in s to be don e .



Natural Morta l ity

Data ar e n ot available to in dicate exactly when the regularan n ual occurren ce of con siderable late-win ter, early-sprin g mortal ity amon g sea otters on Amchitka Islan d began . Natives whotr apped foxes there i n 1 938—39 reported that “many”dead sea

otters were foun d on beaches in that win ter. Between 1 0 July 1 939an d 1 5 Jan uary 1 940, however, a careful search revealed on ly sixskeleton s on beaches (Loy, Sea otter warden s J . B . Man ganan d G. Ritter, who were on Amchitka from 1 February to 5 September 1 940, reported salvagin g on ly “two sea otter skin s an d

skeleton s” (Amchitka Islan d Report, September 5, 1 940, U.S .

Fi sh an d Wi ldlife Service fi les, un published ) .

Durin g the years that Amchitka was occupied by mi l itaryforces, 1 941 —47, n o reports of un usua l sea otter mortal ity weremade . V . B . Scheffer an d I visited Amchitka on 1 2 November 1 947

an d recorded (field n otes ) that i n walkin g about 4miles of beachwe foun d the remain s of six sea otters . At the time we attributedthese deaths to mi l itary person n el occupyi n g the islan d, two ofwhom we saw target practicin g alon g the beach . On ly a fractionof the beaches where dead sea otters were foun d i n subsequen tyears was examin ed .

In the l ight of later experien ce on Amchitka , I am in cl in ed tobelieve, on the basis of what I saw on that on e day i n 1 947, thatcon siderable n atural morta l ity occurred i n the win ter-sprin gperiod of 1 946—47 . In the late-win ter , early-sprin g period of 1 948,Elmer H an son , a civil ian employed by the Army on Amchitka ,

estimated that more than 1 00 otters died on Amchitka beaches .Jon es an d H an son recorded 1 24 dead otters on the beaches i n thelate-win ter, early-sprin g period of 1 949 (Jon es, R . D n arrativereport s of 1 Jan uary to 30 April an d 1 July to 30 August 1 949 ,un published ) . Both Jon es an d H an son spen t much time on Amch i tka durin g or after World War II . Neither remembers obser vi n g a sign ifican t n umber of dead otters on beaches before 1 948.

Thus, it appears that an an n ual late-win ter, early-sprin g“die-off”began i n the late l 94o’s. All ava ilable coun ts an d estimates ar eshown i n figure 95 . An an alysis of observed mortal ity from 1 955

to 1 963 at Amchitka is presen ted i n the followin g pages .

S tud i es con ducted 1 955-63

Durin g the 1 955—63 study period , I repeatedly surveyed thesame beaches that were searched for dead otters by previous observers . The majority of moribun d otters haul out above the high


T9SO 20

195 7 3 ]

195 9 84

1 96 2 106

1 963 3 6+

NUMBER O F SEA O TTERS

FIGURE 95 .— T he coun ts ( solid lin e ) an d estimates (broken lin e ) of dead sea

otters on Amchitka beaches in dicate the order of magn itude of an nua lmorta lity. Except f or the coun ts of 1 949 , 1 959 , an d 1 962, the figures ar e

on ly roughly comparable . T he inf ormation was obta in ed from un publishedreports i n F ish an d Wi ldlife Service files:1 937 , C . L . Loy an d O . A . Fr i den;1 939 , C . L . Loy;1 940, J . B . Man gan an d G . Ritter;1 947, V . B . Schefferan d K . W. Ken yon ;1 948, E . C . Han son;1 949 , 1 950, 1 953 , R . D . Jon es;1 956, 1 957, 1 959 , 1 962, K . W. Ken yon;1 963 , J . E . Burdick;an d fromRausch T he season of observation i s in dicated as follows:W:

win ter;s prin g;SUz summer ;an d s a l l . In n o case were a l l beachessearched regularly . Coun ts were obta in ed ma in ly on the southeastern halfof the islan d . This data i s useful on ly i n i l lustratin g the relative magn itudeof morta lity i n diff eren t years.

t i del i n e an d die on shore . Dead sea otters float an d if they die inthe water they usually wash ashore . Thus a high percen tage ofthose that die i n study areas may be foun d if beaches ar e searchedsystematical ly an d frequen tly.

To study an n ua l mortal ity as a factor i n population dyn amics,and to ascertain its magn itude an d un derstan d its causes, I madean effort to gather comparable mortal ity data durin g five trips toAmchitka .

Methods of study

Certain beaches on the eastern half of Amchitka were searchedsystematical ly. Observation s ar e avai lable for each mon th of theyear . Most dead otters were on or n ear favorite haulin g-out


beaches . Other accessible beaches i n the study area were searchedperiodical ly but less in ten sively than the favored haulin g-out areas .

Each dead an ima l was autopsied . Specimen s— in cludin g skin s,skulls, bacula, reproductive tracts , stomachs, an d organ s appearin gpathological— were preserved when practicable . The exten t ofdecomposition determin ed the amoun t of in formation an d specimenmateria l that was obta in ed .

Because it was importan t to determin e the period of greatestmortal ity, it was n ecessary to ascertain the usual progress ofdecomposition , an d to estimate the approximate time of death ofan imals that had been dead for varyin g periods . Up to a po in t ,this procedure was useful . The time of death for skeletal remain s

foun d i n midsummer, however, could be placed on ly to the previouswin ter-sprin g season . Durin g periods of high mortal ity thebeaches were searched weekly. Thus, the week of death was kn ownfor man y an imal s an d the mon th of death for others . Data forotters that had been dead for more than to 2 mon ths were r ecorded, but because of un certain ty most of these records wereexcluded from those aspects of the study which required moreexact data . Each carcass was removed from the beach aftern eeded data were recorded an d specimen s taken from it.Average da ily a i r temperatures i n win ter in frequen tly exceed

36°F. , an d sprin g an d fa l l average daily a i r temperatures above

49°F. ar e un usua l . For this reason , otter carcasses decompose

slowly on Amchitka beaches . The study was compl icated whenscaven gers (Bald Eagles an d rats (Rattus n or veg i cus) ) mutilatedcarcasses, sometimes preven tin g the gatherin g of certa in data .

Resul ts

Between July 1 955 an d April 1 963 , approximately 1 5 mon thswere spen t on Amchitka . Durin g six study periods, a tota l of33 1 dead otters foun d on the beaches were examin ed. Because

data from certain in dividuals were in complete, these ar e el imi

n ated, where appropriate , from the followin g discussion s of differ en t aspects of mortal ity .

T H E T IME OF MORT ALIT YIt would be ideal , in a study of sea otter mor tal ity, if data could

be gathered durin g some period of con secutive mon ths for severa lyears . This could n ot be don e, so the data from various seasonsi n differen t years were used to presen t a composite picture ofthe an n ual cycle of mortal ity. The mortal ity study in cluded parts



APR. MAY JUNE JULY AUG. SEPT. OCT . NOV. DEC .

MONTH OF DEATH O F SEA OTTERS

F IGURE 96.—Obser ved mor tal ity of sea otter s at Amchitka Islan d, 1 955—63.

Each bar represen ts the number of otters that were foun d dead an d wer eestimated to have died i n the in dicated mon th an d year . Otters dead so

lon g that the mon th of death could n ot r eason ably be estimated ar e excluded . Data from 259 dead otters wer e used i n this g r aph . No freshly deadotters were foun d i n Jun e, July, or August of 1 955 , i n July of 1 956 , or i nNovember of 1 957.

divin g, habitua lly beg for an d receive food from the mother . Theresult of thi s behavior is that mothers ar e un able to obtain suf

ficien t food for themselves an d their large offsprin g durin g periodswhen heavy seas ren der food gatherin g difficult. For this reason ,

man y mothers deser t their large youn g at this season of stress.

Deserted juven iles were seen searchin g an d screamin g for theirmothers i n the late-win ter, early-sprin g period .

For example, a mother an d a pup, weighin g about 1 2 lb.

were captured together an d tagged on 1 5 February 1 962.

When released they swam off together . Both appeared thin but i nn orma l health . On 1 8 February, the j uven ile was foun d wan der

255THE SEA OTTER IN THE EASTERN PACIFIC OCEAN

¢N

ma

an

on

um

um

ma

ma

ma

ma

ma

ca

a

N

fig2.N

eav2.

v“an

an

ma

ma

pa

Na

an

ma

ca

ea

ea

”a

«N

ma

ma

Na

ma

ma

ma

av

a»

ca

on

ma

an

mu

a

w

Na

Inoua

fica

a

$3

40

ca

a

s

Lox—30

0oa

lacsw

ave—hon

ao

B

ES

R—O


01 -7 IS -2I 22-28 29-4 S -I I 12 -18 I9-25 26-4 5 - I I 12 -18 I9 ' 2S 26-I 16 -22

JANUARY FEBRUARY MARCH APRI I.

PERIODS OF OBSERVAT ION

F IGURE 97.— Morta l ity of sea otters at Amchitka Islan d durin g weekly i n

ter va l s through periods of high morta lity i n 1 959 an d 1 962.

in g about a lon e, cryin g, very weak, an d n ear death from starvation . The mother was foun d dead on 1 9 March . It might becon cluded that even after desertin g her pup, she was un able toregain the stren gth she sacrificed durin g storms while attemptin gto meet the food deman ds of both herself an d her pup . An otherpup (weighin g about 1 7 l b . , kg. ) was captured, tagged, an dreleased together with its mother on 27 February 1 962. The pupwas foun d dead an d emaciated on 5 March .

FIGURE 98.— A moribun d juven ile sea otter . Durin g the late win ter an d

early sprin g season of stormy weather starvin g juven iles haul out on shorean d di e . En teritis i s usua lly a termin al symptom. This an imal i llustratesthe fin al comatose stage that occurs shortly before death . Amchitka Islan d,26 February 1 962. (KWK 62—1 7—22)


.258 NORTH AMERICAN FAUNA 68

data obtain ed i n summer, fa l l , an d early win ter ar e n ot directlycomparable with data obtain ed i n late win ter an d early sprin g.

Between 1 October an d 1 1 December 1 957, 48 percen t of the r emain s foun d were juven iles . The rema in s of most dead an imals

were judged to have la in on beaches sin ce the previous win tersprin g period . On ly seven were judged to have died i n Septemberor later . There is a greater probabil ity of fin din g rema in s of adultsbecause they ar e more durable than rema in s of immature an imals .T he skeleton s of juven iles,un less in sheltered location s well abovetide l in e, suffer en vironmen ta l attrition more rapidly than theharder bon es of adults . S ix months or more after the mortal ityperiod, remain s of man y juven iles had disin tegrated an d were n ot

amon g the bon es stil l on beaches . This probably explain s whyjuven i les did n ot predomin ate .

In 1 963 , when juven i les composed 94 percen t of the deadan imal s, the study period was 1 0 March to 1 2 April . The datafrom 1 962 in dicate that mortal ity amon g adults may in crease as

the period of high mortal ity advan ces In Jan uary an d

February 1 962, before the height of the mortal ity period, adultscon stituted 1 6 percen t of the an imal s that died . Durin g an d afterthe period when the morta lity reached i ts peak i n March, 39 percen tof an imals that died were adults . Th is might in dicate that adultsar e better able to withstan d en vironmen tal stresses than immaturean imals recen tly separated from mothers . In 1 963 the period ofgreatest adult morta l ity may n ot have been in cluded i n the studyperiod, an d a disproportion ately high mortal ity of juven iles wasin dicated by the avai lable data . The 1 959 data show, however, thatthe mor tal ity amon g adults may, i n some years , be high throughoutthe period of in creased mortal ity (fig.

The 1 959 an d 1 962 study periods ar e the on ly two which span n eden tire periods of greatest an n ual mortal ity (fig. Therefore,the proportion of juven iles 60 an d 75 percen t, respectively) toadults i s probably more represen tative of the usual mortal itypattern .

SEX -SPEC IFIC MO RT ALITYMore males than females were foun d dead on beaches . Amon g

juven i les, the disparity was greater than amon g adults . Rausch( 1 953 ) n oted in his 1 95 1 an d 1 952 in vestigation s that“the heaviestmortal ity occurred i n subadult males .”T he r aw data from theremain s I examin ed, however, ten d to exaggerate this diff eren ce .The accurate determin ation of sex by the examin ation of juven ile skulls or other bon es is perhaps impossible . If a carcass was


JAN .

1962

MONTH OF DEATH

FIGURE 1 00.— Ag e an d sex of sea otters dyi n g i n the wi n ter-sprin g period of

1 961 - 62. A— juven ile ma le;B— juven ile fema le;C— juven i le, sexunkn own;D— adult ma le;E— adult female .

mutilated by scaven gers an d the reproductive organ s removed,the sex of the an ima l was i n question . On partial ly mutilated car

casses, the likel ihood that a male might be iden tified was g reater .

Eagles, for example, usua l ly remove the viscera first . The gen ita l ia

of the females ar e easily taken , but the baculum of the ma le isattached to the ischium by a stron g ligamen t composed of theischio an d bulbo-cavern osus muscles . These parts may remainattached to the skeleton , iden tifyin g it as a male for weeks lon ger


- l O

MAR. APR. TO I7 MAY IMONT H O F DEATH

F IGURE 1 01 .— Ag e an d sex of sea otters dyin g i n the win ter-sprin g period of

1 958—59 . A— juven i le ma le;B— juven ile fema le;C— juven i le , sexunkn own ;D— adult ma le;E— adult fema le;F— adult, sex unkn own .

than a fema le may be iden tified . Because of this situation an d to

avoid a bias i n favor of ma les, on ly the freshly dead beach speci

men s foun d i n 1 959 , 1 962, an d 1 963 ar e l isted to give the bestavai lable in dication of the sex ratio of otters dyin g durin g theperiod of en vironmen ta l stress (tableAmon g 1 1 7 juven i les examin ed on beaches i n the three season s,

58 percen t were males . In 1 963 , the sex ratio was but i n

this year the field study was aban don ed while the high morta l ityperiod was probably stil l i n progress an d the results may n ot be

represen tative .

That males ar e n ot as hardy as females was repeatedly demon

TABLE 56 .— Ag e an d sex of otter s foun d f r esh ly dead on Amchi tka beaches

Juven ile Adul tMales Females Males

Num Per Num Per n um Num Per Num Per n um GrandYear ber cent ber cent ber ber cent ber cent ber to tal



TABLE 57.—A bn orma l con di t i on s foun d i n sea otter s tha t di ed on beaches of

Amchi tka Is l an d,A l aska

Date Condition

30Oct . 1 95726 Jan . 1 959

1 7 June 1 9561 4Mar 1 959

59—49

59—1 00 31 Mar . 1 959

59—1 55 6 May 1 959

59—85 25 Mar . 1 959

59-48 4Ma r . 1 959

1 S ee section on Parasites and Miscellaneous D iseases f or a more deta iled analysis .

TABLE 58 .— S ummar y of obser va ti on s f r om 83 sea otter s foun d dead a t

Amchi tka Is l an d, A l aska , 1 959

Number ofObservation adults

T otal an imals exam inedS ke letal remains only foundF ield necropsy perf ormedDental malocclusion indicated 3Bone damage to jawT ooth damage ( dental attrition ) 4

None to moderateModerate to

Les ions:5H emorrhagic enteritis present.S tomach parasite ( T . deci p i en s ) present.Possible physical injury

Food in stomach1 S k’ul ls only examined .2 In juveni les, malocclus ion occurs while the permanent teeth ar e growing, particularly whendeciduous teeth a r e pushed out of l ine . In o l d adults , p ostcan i n e teeth may be worn to the guml ine or to th e bone .

8 When teeth of ol d an imals ar e severely wor n , infection of the bone and osteolysis may occur.4 S ee Dental Attrition5 S ee Par as ites and Mi scellaneous Diseases .

°All carcasses showed signs of emaciation . Body weights ( particularly f or adults ) were ah

normally l ow ( see Body Measurements ) .

Fractured skull .Bruised head .Bruises , blood clots around headand neck.

Broken neck .Non dr a i n i n g abscess dorsally inneck and head .

2 broken ribs .Extensive body bruises andswel l ings .

Body bruises perforatedintestine .

Internal hemorrhage— quantityof blood in abdominal cavity.

Perforated intes tine and intussusception of small intestine.

Br uises in genital area .

Bruised pen is .

Pen is swo llen and extr uded.Uter ine cyst 1 80X 50mm .

Abscess in jaw, l iver discoloredand with abnormal adhes ions .

1

Liver with abnormal adha i on sand discoloration .

1

H emorrhagic nasal passage .

Cutaneous emphysema .Lungs black, pneumonia?Mal ignant neoplasm of thein testine .

1

Congenital cystic kidney andedema .1


ibi ted a degree of malocclusion caused by the growth of theerman en t p ostcan i n e teeth . In the early stages of eruption of the

erman en t teeth, the deciduous teeth ar e pushed upward, so thati s impa ired . When the deciduous teeth ar e fin a l ly lost,

ar e still below the level of adjacen t teethon ) . Adults havin g poor teeth comprised 78 percen t

foun d dead . The attrition of teeth appears to be an

oi the reduction of soft-bodied in vertebrates . H ard

r g an i sms ar e probably eaten to a greater deg ree by thisAmchitka population than i n less den sely populated areas .

havin g good teeth n ot on ly compose a min ority ( 1 7 per

oi the dead adults on beaches but healthy adults spen d less

on shore (as in dicated by an ima l s captured there ) durin g

ds of storm surf than do emaciated juven i les an d old adults .

r an d sea con di t i on s

e fal l of 1 959, the U.S . Weather Bureau began to record

ather con dition s i n the outer Aleutian Islan ds . Before this time ,such records were available . Thus , durin g the 21 Jan uary to

May 1 959 study period I kept a daily record of weather con

ion s . These data demon strated that the in creased mortal ityn ci ded with the period of greatest storm activity .

lete weather records ar e n ow available for the years after

1 960. These data were recorded at Shemya Islan d , which is 200miles west of Amchitka , but radio reports of weather at Shemya

received while I was on Amchitka in dicated that a few hours afterweather con dition s were reported at Shemya simi lar weatherreached Amchitka . The an n ual cycle of weather con dition s i n the

outer A leutian s is quite un iform.

The average season al morta l ity observed on Amchitka from1 955 through 1 963 an d the mean mon thly win d velocities recorded1 960 through 1 963 ar e shown i n fig ure 1 02 . This graph demonstrates that the period of greatest morta l ity, when 75 percen t of

the an n ual mortal ity occurs , coin cide an n ual ly with the period ofmaximum win d velocities i n the late-win ter, early-sprin g period .

It al so shows that the period of least mortal ity occurs durin g thesummer period of min imum win d velocities . In the fal l , when theseason of storms begin s, a sl ight in crease i n mortal ity occurs .

Most an imal s, however , emerge from the summer, early-fal l periodin good physical con dition an d the mortal ity remain s low un tilafter a period of susta in ed stormy weather reaches a peak i n

March .

The gen eral coin ciden ce of high mortal ity an d stormy weather


JAN . FEB. MAR. APR. MA Y JUNE JULY AUG. SEPT. OC T. NO V. DEC . 25

JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC .

4 8 5 2 3

F IGURE 1 02 — Average season al mortality of 31 1 sea otters foun d dead on

Amch itka beaches 1 955—63 , an d average mon thly win d velocities i n the

outer Aleutian Islan ds measured by th e U . S . Weather Bureau, 1 960

through 1 963 .

or high velocity win d-swas quite eviden t . It was al so eviden t, however, that the W in d, as such, was on ly in directly respon sible forprecipitatin g mortal ity an d that more deta i led in formation con

cern in g en vironmen ta l stresses was n eeded . Therefore i n 1 962,

between 1 9 Jan uary an d 3 1 March (70 days ) , I kept a dai ly recordof surf con dition s an d sea otter mortal ity for both the Berin g Seaan d Pacific Ocean coasts of Amchitka . Five surf con dition s were

recorded:ca lm (n o surf) , l ight surf, moderate surf, heavy surf,an d violen t surf.The vast exten t an d great depth of the Pacific Ocean as com

pared to the relatively sma l l an d sha l low Berin g Sea creates con

di t i on s respon sible for differin g surf con dition s on the coasts exposed respectively to these two bodies of water .

Un der the force of storm win ds , heavy seas may build up i n theBeri n g Sea , but within a few hours after the passin g of a stormthe surf may subside an d relatively ca lm or moderate waves maypreva i l .

In con trast, groun d swells i n the Pacific Ocean may travel to



exceeded on both coasts . Thus , morta l ity occurred i n proportionto the ava ilable habitat an d population size rather than in proportion to the in ten sity of storm wave activity . About two-thirds ofthe available habitat, population , an d morta l ity were foun d on thePacific coast (tableA lthough the period of heavy surf began i n late Jan uary, the

in creasin g rate of sea otter mortal ity did n ot reach a peak un tilthe en d of February (figs . 1 03 an d This is explain ed by thefact that the otters en ter the win ter with reserves of body fat an di n good gen era l physical con dition . Durin g weeks of stormy

weather, those an imals least able to supply their n utrition al n eedsexhaust their physica l reserve . After becomin g emaciated an d

bein g subjected to con tin uin g en vironmen ta l stress , they die .

Autopsies revea l that a lmost a l l an imals foun d dead on beachesshow sign s of starvation i n spite of the fact that their in testin altract often con tain ed the remain s of sea urchin s ( see Food an d

Feedin g Behavior ) .

A n n ua l mo r ta l i ty at Amch i tka est ima ted fr om an ima l s foun d deadon beaches

S in ce many of the haulin g-out areas on the eastern half ofAmchitka were searched carefully an d frequen tly durin g theperiod of high morta l ity, probably most of the dead otters i nthese limited areas were foun d . T he habitual ly used haul in ggroun ds con stitute less than 1 0 percen t of the shorelin e on theeastern half of Amchitka . Other areas could n ot be searched as

carefully as the areas of con cen tration . On several occasion s , dead

otters that had been buried i n kelp by storm waves or carried from

the beach area by eagles were foun d after havin g been missed on a

previous search . A few dead otters were foun d well up on off

shore rocks that we rarely visited . On the basis of these an d otherfield observation s, I have estimated that at least 30 percen t of the

TABLE 59 .— S ea otter mor ta l i ty i n r e l a ti on to p op u l a ti on coun ts an d ava i l abl e

habi ta t , easter n ha l f of Amchi tka

Pacific coast Bering S ea coastNumber Percent Number Percent

Dead dt ter s 1O tter population 2Available habita t

1 Count, 1 9 January to 4 April 1 962 .

9 Aerial count, 1 9 May 1 959 .

3 S quare miles of water 30 fathoms or less in depth , easter n half of Amchitka . Measured fromU .S . Coast and Geodetic Survey Char t 8864.


otters dying a lon g the shores of the eastern ha lf of Amchitka i n theperiod of high morta l ity were n ot foun d . A rough estimate of theann ua l mortal ity i n 1 959 an d 1 962 on Amchitka is presen ted below

Number of dead otters1 959 1 962

Carcasses foun d i n win ter-sprin g period 84 1 06

Estimate of carcasses n ot foun d 25 32

Estimated tota l morta lity this period 1 09 1 38

Estimated morta lity i n rema in der ofthe yearEstimated an nual morta lity on easternhalf of AmchitkaEstimated an n ua l morta lity on westernha lf of Amchitka (otter population 30%of eastern ha lf, data from aeria lsurveys )Tota l estimated an nua l morta lity

The estimated Amchitka otter population i n 1 959 was about

( see Distribution an d Numbers ) . Thus , the an n ual mortal ity

there i n at least two season s was about 9 to 1 1 percen t of the total

estimated population . If, in stead , the direct coun ts of livin g an d

dead otters ar e used for the eastern ha lf of Amchitka , then the84

m e?)1 00 an d m 1 962

about 1 0 percen t 1 00 of the population as observed i n

1 959 .

mortal ity i n 1 959 was about 8 percen t

Mo r ta l i ty est imates de r i ved fr om r ep r oduct i ve tr acts

The data avai lable from other studies ( see Len gth of stages ofreproductive cycle of fema le sea otter, by D . G. Chapman , an d

Field coun ts of sea otters ) makes possible an estimate of themortal ity that occurred i n the tran sition from the depen den t stage

to the juven ile stage . S in ce there ar e 50 youn g/1 00 adult females

per year an d sin ce the sex ratio amon g youn g is this

implies 25 female youn g per 1 00 adult females .

Let the mortal ity that occurs at the en d of the depen den t stagebe T;then

( 1 - T )g—z Jo if females a lon e ar e con sideredAlso

from equation (2 ) ( see Len gth of stages of r e.085 productive cycles of female sea otter ,

”by D . G.

Chapman , p . 243 )


so that.OS5A

.766

( 1

1 I 1 A

( 1222

from ( 1 ) ( see Chapman , as above )When ce1—T = .53

an d

T : .47

An other way of con siderin g the same problem is as follows

Each 25 female youn g must survive to replace the mortal ityoccurrin g amon g the mature females

(25 ) ( 1

or ( l —T )or 1 —T : .44 an d T : .56

A lthough these ar e sl ightly differen t, they suggest that the transi t ion al morta l ity from depen den t to juven ile stage is about 50percen t . Some of this may occur durin g the depen den t period .

Al so, if the morta l ity amon g juven i les is higher than percen t this would mean the tran sition al mortal ity is sl ightly lower .

This could a lso mean that the estimated len g th of the in depen den tjuven i le period is somewhat less than 3 years .

It should be n oted that these estimates of percen t as an

an n ua l morta l ity, 50percen t mortal ity at the en d of the depen den tyoun g stage, an d a juven ile period of 3 years apply to females .The data do n ot provide comparable estimates for males .

MORTA LITY ON T H E SH UMAG IN ISLAN DSThe outer Shumag i n Islan ds provide in terestin g materia l for

comparison with observation s from Amchitka . The outer Shumag i n s, in cludin g Nagai an d a l l i slan ds lyin g east an d west ofit, ar e chosen because ( 1 ) A population of about sea otters

is foun d there, (2 ) it appears to offer idea l sea otter habitat, an d

(3 ) it was accessible for aeria l an d surface observation s .

The outer Shumag i n s ar e surroun ded by n early 700 square milesofwater less than 30 fathoms deep . The islan ds ar e n ear en ough

to each other to a l low sea otters to move easily from on e to an

other an d n ear en ough to other areas alon g the southeast coastof the Alaska Pen insula to a llow population dispersion .



Amchitka was 8 to 1 1 percen t of the population (perhaps higheri n certain season s ) . In the areas of un crowded population , thean n ual morta l ity was much lower . It was n ot calculated becausetoo few dead otters were foun d .

The n atura l forces which con trol the magn itude of the sea

otter population at Amchitka were a l imited food supply an d

climate . From his observation s on Amchitka , Rausch ( 1 953 ) susp ected that much of the an n ua l mortal ity was the result of “Apopulation that exceeded the carryin g capacity of the habitat.”Theappl icable gen era l ization was aptly stated by Lack ( 1 954)climatic factors can exert an importan t modifyin g in fluen ce i n the con trol ofan ima l n umbers. Thus, a lthough on e may speak loosely of morta lity due toclimate, the actua l cause of death i s often starvation

,which can be den sity

depen den t.The data presen ted here an d i n the section s on Food an d Feed

i n g Behavior an d Distribution an d Numbers , I believe, supportLack’s statemen t.The followin g poin ts ar e the eviden ce that lead to the con clusion

stated above:1 . The food habits studies of otters at Amchitka in dicated thathealthy adults, havin g ample body fat i n the late-win ter, earlysprin g period , fed to a large exten t on fish an d octopus . S ea ottersat Amchitka were l imited i n their search for food to a relativelyn arrow belt of water surroun din g the islan d where water depthsdo n ot exceed 30 fathoms ( see D ivin g) . Observation s at Amchitkain dicated that population s of bottom-inhabitin g food species werereduced ( see Food an d Feedin g Behavior ) .

2 . Observation s in dicated that large juven i les when desertedby mothers were un able to obtain a sufficien t quan tity of highcalorie food species . Apparen tly they lacked both the ski l l an dstren g th to capture an d hold most fish an d octopus . This may betrue also of agin g adults .

3 . Both of these age groups were forced to obtain what n ourishmen t they could from depleted population s of seden tary an d oftenhard-shel led an d low-calorie in vertebrates . Because of the hardshell s of these organ i sms the teeth of adult otters i n the Amchitkapopulation showed greater attrition than did those of an imal s

from less crowded population s . The teeth of old adults were oftenworn to the guml in e . Eviden ce of bon e in fection , which oftenresulted when tooth attrition was severe, was foun d in 72 percen t of a sample of dead adults . Juven iles i n the process of r ep l aci n g deciduous teeth were un able to eat a sufficien t quan tity of theavailable hard-shelled organ isms .


the agin g an imals an d j uven i les , forced to util ize poor

ds, were further hin dered i n feedin g activities by sus

periods of rough seas . Agin g adults, an d juven i les desertedther s, after exhaustin g accumulated summer an d fal l r e

of body fat , developed en teritis which is typ ica l of thati n other species of an imals un der con dition s of starvationress ( see Parasites an d Miscellan eous D iseases ) .

5 . Adult otters at Amchitka weighed less than otters from lesscrowded population s ( see Body Measuremen ts ) .

6 . When weaken ed an imal s exhibitin g symptoms of en teriti s(black feces ) were captured an d placed i n a pool of clean water

where they were furn ished adequate food, some of them regain edhealth . After they were in troduced to a diet of fish , a l l of these

captives refused to eat sea urchin s an d most hard-shelled mollusks .The gastroin testin al tract of simi lar an imal s that died on beacheseither were empty, or con tain ed on ly hard-shelled organ isms .

PARA SITES AND MISCELLANEOUS D ISEASESBoth i n the wild an d i n captivity sea otters ar e afflicted by a

variety of pathological con dition s . Systematic, lon g-term studiesof pathology were n ot un dertaken , but an imal s foun d dead or

dying on beaches were examin ed (Rausch an d Locker, 1 95 1 ;Rausch, 1 953 ) an d observation s of captives were recorded (Kirkpatrick, et al . , 1 955;Kenyon , Yun ker , an d Newell , Jell isonan d Nei l an d ( 1 965 , p . 8—9 ) l ist the parasites of sea otters . In the

followin g section s these studies ar e reviewed briefly an d addition al

observation s ar e presen ted .

Most sea otters foun d dead on Amchitka Islan d displayed termin al symptoms of en teritis . Other pathologica l con dition s, suchas n eoplastic an d degen erative chan ges i n the liver , ulceration of

the jaws an d a lveoli of the teeth , an d in fection s of the paws al sooccurred .

In ter n a l (he lm i n th) p ar asi tes

More than 30 sea otters foun d dead or i n moribun d con dition on

Amchitka beaches i n 1 949 , 1 95 1 , an d 1 952 were studied by Rausch(Rausch an d Locker, 1 951 ;Rausch , Th e helmin ths recorded

from these were:(Cestoda ) Pyr ami cocep ha lus p hocar ui n (Fabricius, 1 780) (Trematoda ) Or thosp lan chnus fr ater culus Odhn er ,1 905, Phoci tr ema fusi forme Goto an d Ozaki , 1 930, Pr i cetr ernaza l op hi (Price , Mi cr op ha l lus p i r um (Afan as

’ev,1 941 )

(Nematoda ) T er r an o'

va (Por r ocaecum) deci p i en s (Krabbe, 1 873 )(Acan thocepha la ) Cor yn osoma str umosum (Rudo l ph i ,


R . L . Rausch ( letter, 1 5 Sept. 1 967 ) statesMore recen tly, Cor yn osoma macr osomum Nei l an d, 1 962, has been describedfrom a sea otter from Prin ce William Soun d , an d a sin gle specimen eviden tlyrepresen tin g this species had been col lected earlier from the same host fromS imeon of Islan d (see Nei l an d, Cestodes collected by K . W . Ken yonfrom sea otters from Amchitka Islan d have been iden tified provision a lly as

D i p l og on op or us tetr ap ter us (von S iebold, 1 848 ) (Rausch , this speciesa lso was recorded from a sea otter from Prin ce William Soun d .

In gen eral, these helmin ths probably affect the host l ittle, if atal l (Rausch, H owever, two species, Mi cr op ha l lus p i r um an d

T er r an ova deci p i en s, were con sidered to be pathogen ic . The cuticul ar spin es of the former eviden tly cause mechan ica l in jury tothe in testin a l mucosa , an d, when the trematodes ar e abun dan t,severe en teritis may result. Immature specimen s of T . deci p i ens

frequen tly pen etrate the in testin a l wa l l an d en ter the body cavity,where other organ s may be in vaded . Periton itis followin g suchperforation s may result i n the death of the host.

Durin g the 1 955—63 study period , I made gross examin ation s

of about 50 otters believed to have been i n good health when . ki l led

at Amchitka . Although both T . deci p i en s an dM. p i r um were foun d,there were n o gross lesion s i n the in fested an ima ls . In Novemberof 1 957, Dr . Ken n eth L . Bin kley examin ed seven adult otters atAmchitka, on ly on e of which appeared to be i n “poor con ditionwhen captured . On ly the ill an imal was in fested with an ap p r eci

able n umber of T . deci p i en s ( 65 worms ) an d M. p i r um (man y

worms ) , but there was n o sure in dication that this an imal’s poorcon dition was a result of parasite in festation . Problems en counter ed with T

_. deci p i en s ar e discussed un der “In Captivity .

”

In 1 959 the stomachs of otters foun d dead on beaches were ex

ami n ed when possible . Amon g 27 juven i les, 2 con tain ed T . deci p i ens

an d amon g 1 4 adults, 5 were in fested . In n on e of the an imal s ex

ami n ed were helmin ths foun d i n the coelom an d n o in stan ce ofperforation caused by helmin ths was n oted . The an imals, i n mostcases, had been dead for severa l days before they were examin ed .

Periton itis caused by perforation of the gastroin testin al tractwould probably have been detected . Examin ation of sample areasof the sma l l in testin e revea led moderate to light in festation i n

some an ima l s, but for M. p i r urn diagn osis was con sidered un

satisfactory because of decomposition . In addition , this parasitein habits crypts i n the wa l l of the smal l in testin e an d is n ot easilydetected i n gross examin ation .

K . A . Nei l an d ( letter, 9 July 1 962 ) examin ed the in testin a l tractsof 8 adult sea otters chosen at ran dom from 1 50 an imal s that were

shot in the sprin g of 1 962 at Amchitka . In these he foun d a total



mon parasite of sea otters, you surely would have n oticed it, especia lly i ncaptive an imals.

I have examin edman y sea otters an d foun d n o extern al parasitesother than n asa l mi tes (H alarachn idae ) Although these ar e techn ical ly ectoparasites, they ar e foun d within the n asal passages . Aspoin ted out previously (Ken yon ,

Yunker,an d Newell ,

in festation of the sea ott er with H a l ar achn emi r oun g ae is probably

fortuitous . The on ly massively in fected an ima l (over mites )was acaptive that was held un der abn ormal con dition s i n a freshwater pool . In festation i n the wild appears to be in sign ifican t .

En ter i t i s

The followin g discussion presen ts observation s obtain ed at

Amchitka Islan d an d in formation con tributed by M. C. Keyes,Bureau of Commercia l Fisheries .

En teritis is frequen tly observed as the termin al symptom at

death i n sea otters at Amchitka . It is similar to the en tero toxemiafoun d i n the fur sea l , harbor seal , an d certa in domestic an imals .A Cl ostr i dium organ ism has been isolated an d iden tified from a

fur seal . Keyes ( 1 963 ) uses the n ame n ecr ohemor r hag i c en teritis .T he symptoms observed i n the sea otter ar e quite similar to thoseobserved i n lambs an d other mammal s .

Symptoms exhibited by sea otters foun d on Amchitka beachesar e l isted:1 . The an imal may be un able to stan d or walk .

2 . It may appear semicomatose or very lethargic an d fearless .3 . It often exh ibits hiccup- l ike con vulsion s.4. The vibrissae may be exten ded rigidly forward .

5 . The n ecropsy reveal s in testin al lesion s of variable exten t .Youn g an imals may die whi le lesion s ar e sma ll, affectin g 3 to 4

in ches of the sma ll in testin e . T he in testin e is in flamed , muscleton e i s lost, an d affected areas become blackish or green ish blacki n color . In adult an imals , lon g section s of the smal l in testin e showthis con dition at death . The colon has n ot been specifical ly observed

to show the exten sive lesion s foun d i n the small in testin e .

The smal l in testin e an d colon often con tain the remain s of abouta dozen sma l l sea urchin s . Black tarry feces may or may n ot be

voided before death . In youn g an ima l s particularly, the progressof en teritis to death may be rapid .

6 . Death may occur before the typical black feca l matter isvoided . The black con dition of the feces is called melen a (a com

bin ation of the iron foun d i n hemoglobin and hydrogen sulfide to


gether produce iron sulfide, the putr afact ive chan ges i n the i ntestin e produce the s ) .

7. I have examin ed the stomachs of more than 200 otters thatshowed symptoms of en teritis at death . Non e has con tain ed food .

The stomach may con ta in from 1 0 to 50ml . of l iquid which maybe pinkish, reddish brown , or yel lowish . The mucosa may show

inflammation .

8. Weight loss, probably caused by dehydration an d starvation ,

characteristica l ly accompan ies en teritis . A captive juven ile male( 59 that died showin g symptoms of en teritis , lost 26 per

cen t of its body weight i n 3 days .

It appears probable that a Cl ostr i dium organ ism i s presen t i na l l an imals an d that it becomes active when the an imal is sub

jected to stress, such as starvation or n ervous ten sion . Un sat i s

factory con dition s i n captivity, such as lack of water, may cause

such n ervous ten sion . In captivity, I have observed that an ima lsgiven access to an abun dan t supply of clear water an d abun dan tfood have n ot been subjected to sufficien t stress to develop en teritis .As poin ted out elsewhere

,an imals which show symptoms of

en teritis when captured may recover i n captivity when givenabun dan t food an d water . Stress may be caused i n captivity if thefur becomes dirty an d the an ima l i s chilled . Extreme an xiety ac

compan ies chill in g, a large in take of food may occur but un lessthe fur con dition can be improved the an imal experien ces stress;en teritis usual ly develops, an d is followed i n a few hours by death .

In the wild, lack of n ourishin g food an d accompan yin g rough ,stormy seas appear to cause stress that results i n en teritis an dtermin ates i n death .

Addition al laboratory examin ation of specimen material takenfrom sick or dyin g sea otters is n eeded before we can attain a

proper un derstan din g of the relation ship between en teritis an d

the trematode Mi cr op ha l lus p yr um, an d the bacterium, Gl ostr i

dium, i n the sea otter .

In fect i on an d l i ver degen er at i on

Dr . Dean Jen sen , College of Veterin aryMedicin e , Colorado StateUn iversity, kin dly made a study of pathological tissues obtain edfrom an imals foun d dead or dyin g at Amchitka .

An adult female (D7 havin g well-worn teeth , weighed 56

lb. kg. ) when captured a l ive on 1 December 1 957 . H er

weight at death, 6 December 1 957 , was 47 lb . ( 1 9 This an ima llacked en ergy an d ate sparin gly durin g the period of captivity.


Fur preen in g was a lso in adequate . The an ima l , i n gen eral, ap

p ear ed to be i n poor con dition .

Necr op sy.-The l iver appeared fibrous an d spotted with various

shades of brown an d reddish in flammation . In three places theomen tum adhered abn ormally to the l iver an d there were n umerous

abn ormal adhesion s between the lobes of the liver . Yel lowish scar

tissue surroun ded the areas of adhesion . The spleen appeared ab

n ormal , exhibitin g a somewhat Opaque whitish scum over on e

side . Lin ear in den tation s crisscrossed this surface . Specimen s were

preserved i n AFA solution , then tran sferred to 70 percen t a lcohol .A large abscess surroun ded the root of the lower right can in e

tooth . Con siderable osteolysis of the jaw had occurred aroun d the

root of the tooth formin g a hole in the bon e which measured1 0x8 X 7 mm. Other organ s appeared n ormal to gross examin a

tion .

Dr . Jen sen ’s an alysis

Hemopoietic system:H istopatho logy: Spleen :Paren chyma i s dimin ishedwhile capsule an d trabeculae ar e abun dan t. These chan ges in dicate a trophyfrom unkn own cause . T he periphery of some cen tral a rterio les con ta in a

homogen ous aci di p hi l i c substan ce which may be amyloid [starch-like] .

Liver:Man y lobules show fatty metamorphosis i n cen tra l zon es. This chan gei s n ot un iform.

A lthough Dr . Jen sen gave n o diagn osis i n this case , it was ap

paren t that this an imal was moribun d . It would appear that toxin sfrom the in fected jaw may have caused the fatty degen eration

an d sclerosis of the liver .

The results of a n ecropsy of an other otter was similar but n o

loca l ized in fection was foun d:KWK adult fema le , weight

lb . 1 7 collected 27 March 1 959 , foun d dead well abovehigh-tide lin e i n sleepin g position . The l iver appeared swollen an d

fibrous with con siderable yel lowish discoloration , scar tissue, an dabn orma l adhesion s to the diaphragm an d in testin es . Peripheralblood vessels of the liver an d in testin es were turgid . The otter had

bled from the rectum before death .

Ma l i gn an cy

On 22 October 1 957 , a youn g adult female sea otter (B— 1 2

weighin g 42 1h . ( 1 9 was foun d dead on a rock well above

high—tide lin e at Amchitka . A n ecropsy revealed abn orma l tissue

growth i n the viscera an d a quan tity of dark , apparen tly bloodyfluid i n the coelom. Extern al ly i n other respects the an ima l ap

p ear ed n ormal .

Dr . D . V . Brown , then Associate Professor of Pathology, Un i



B l i n dn ess

Otherwise healthy sea otters blin d i n on e eye were occasion al ly

seen at Amchitka . No wild otter blin d in both eyes was observed .

The corn ea of the left eye of a yearl in g otter (Susie ) was pun cturedn ear the cen ter by a tiny “pinhole”when she was captured at

Amchitka i n 1 955 . Within weeks the eye became cloudy an d

even tua l ly completely blin d . About 2 years before her death i n1 96 1 the right eye also became cloudy (presumably aff ected by theother blin d eye ) an d tota l bl in dn ess resulted . Because she had

learn ed the topography of her en closure well before losin g hersight, she appeared to experien ce n o difficulty i n fin din g her foodan d her way about her quarters .

In tussuscep t i on

B lockin g of the smal l in testin e by the in testin e swallowin g

itself occurred i n three captive otters . These an imal s were held in

un satisfactory cages without sufficien t water for immersion . Thean imals appeared to experien ce emotion a l stress, as eviden ced byfrequen t voca l ization for on e or more days before death occurred .

Predation

No in formation exists to in dicate that predation by an imal s

(other than man ) on the sea otter is an importan t factor i n itspopulation dyn amics . Ava ilable in formation on predation is pre

sen ted below

SH ARKS

It i s beyon d question that some sea otters ar e killed by sharks .Sn ow ( 1 9 1 0, p . 278 ) states

Woun ded otters I have taken on a f ew occasion s, but they had been bitten bysharks, as I kn ow from fin din g severa l of t he sharks’ teeth broken off i n

woun ds.

Orr ( 1 959 ) discovered the broken tooth of a great white shark(Car char adon car char i as) i n the lacerated body of a sea otterfoun d dead at Pebble Beach , Cal if. H e con sidered that on e otherotter he examin ed defin itely died from shark woun ds an d thatseveral others foun d dead an d bearin g laceration s may have diedas a result of shark attacks . That skin divers may have in flictedfata l woun ds with spears , a lthough a possibility

, must be con

si der ed an opin ion to be carefully weighed, sin ce n o proof that this


l e . Limbaugh ( i n Gi lbert, 1 963 ) says that whitesharks may be threaten in g”the smal l sea otter population on thecen tral Ca l iforn ia coast . The deg ree to which man or sharks killsea otters alon g the Cal iforn ia coast sti l l appears to be an un

resolved question . In Alaska n o deaths attributable to sharks ar erecorded .

K ILLER WH ALE O r c i n us or ca

Presumably the killer whale may eat sea otters . I have watchedkiller whales an d otters i n the same area an d have n ot seen a

whale attack an otter . Nik o l aev ( 1 965b , p . however, saw a

killer whale catch on e sea otter .

On 1 March 1 959 , n ear South Bight on the Pacific shore ofAmchitka , I watched from the cl iff top as five ki l ler whales cruisedabout outlyin g reefs . As the whales approached the reefs a harbor

seal left the water an d climbed on to the rocks . The whales cruisedclose to the reefs , then proceeded eastward paral lel to the shorean d in to an area where four sea otters were feedin g. On e otter

was eatin g on the surface when the whales approached an d passedon ly a few feet ben eath it . This otter appeared to sen se the pres

en ce of the whales . It stopped eatin g an d remain ed motion less

while they passed . Otherwise , the otters seemed un disturbed by the

whales an d the whales exhibited n o discern ible in terest i n theotters .On 9 April 1 959 , R . D . Jon es an d I observed killer whales an d

otters i n the same gen era l area off K i r i l of Poin t on the Berin g S eashore of Amchitka . On several occasion s between 1 345 an d 1 645

we spen t n early an hour watchin g two groups of killer whales ,on e of 9 an d the other of 1 8. They moved paral lel to the shore an d

remain ed from a quarter to on e-half mi le from lan d . Several in divi dua l s rai sed the head an d an terior quarter of the body above the

surface as if to search the surface visua lly . Sea otters that were

food diving i n their vicin ity ceased this activity an d l ay stil l on

the surface or moved slowly toward shore on the surface .

‘

We didn ot see any behavior by the whales which in dicated to us that asea ott er was attacked .

A further observation by Jon es ( letter , 9 July 1 96 1 ) i s similar .

At Rat Islan d he saw six kil ler whales which remain ed for sometime

“from 25 to 1 00 yards off”shore an d i n the vicin ity of “a

large pod (over 200) sea otters .

”The sea otters exh ibited n o

alarm an d the whales did n ot attack them .

Although Barabash-Nikiforov ( 1 947 ) gives n o observation of


a ki l ler wha le attack on a sea otter , he lists them as an en emy an d

presumed “that kil ler whales terrorize sea otters .”

BALD EAGLE H a l i aee tus l eucocepha l us

The sea otter population at Amchitka progressed from n ear ex

tin ction at the turn of the cen tury to maximum size i n about 40years . At the same time a large population of eagles occupied

Amchitka .

From man y mon ths of field observation s by a n umber of observers there is on ly on e authen tic observation of an eagle attackin g a l ivin g sea otter . This occurred on 3 Jun e 1 96 1 at Barr H ouse

Cove on Amchitka Islan d . In a letter of 1 7 October 1 961 , R . D .

Jon es reported what he an d Vern on D . Bern s observed

We were on the beach of the cove watchin g the eagles with bin oculars[an eagle] laun ched an d flew to sea losin g a ltitude rapidly an d di sap

pearin g behin d the islan d . T he eagle quickly return ed directly to the islan dcarryin g a large bulky object [which it] carried to the n est an d

upon our approach took win g. It was n ot n ecessary for us to climb the p i nn ac l e to kn ow there was a sea otter p up i n [the n est] f or the screamin g of thep up was a l l too clear . We did climb it, however, an d observed three eaglen estlin gs an d the still livin g pup .

S ea otter rema in s frequen tly occur i n eagle n ests (Krog, 1 953;Kenyon , 1 96 1 , 1 964) where the two species occur together . Thatcertain in dividual eagles may develop a taste for sea otters , whileothers do n ot , is in dicated by the failure of Murie ( 1 959 ) an d

D . C . H opper ( i n Jon es , R . D . ,un published report of 1 Jan uary

to 3 1 August 1 953 ) to fin d sea otter rema in s i n eagle n est s theyin vestigated on i slan ds where sea otters were n umerous . I ob

tai n ed man y observation s at Amchitka of eagles feedin g on car

casses of sea otters that died of n atural causes an d saw themcarry parts of these carcasses away i n their claws . The otter r emain s frequen tly seen i n eagle n ests un doubtedly in clude manythat were obta in ed by scaven gin g rather than predation .

On e observation quoted from my field n otes is typ ical of man ySt. Makar ius Bay, Amchitka Islan d, 2 April 1 959 , 0900. At water’s edge an

adult eagle was fin ishin g the rema in s of a large fish (ca . 30 i n . m . ) lon g,washed ashore dead ) whi le four other eagles (a l l i n subadult plumage )rested on the beach an d bluff. In the midst of this group , a youn g male sea

otter— just awaken ed from the n ight’s sleep— squirmed about on the drygr ass (est:wt .: 25 lb . Obviously the eagles were payin g n o

attention to the sea otter an d the otter was certa in ly n ot a larmed at the

eagles’ presen ce .

In places where on e or more eagles were n ear , I frequen tly saw

helpless youn g sea otters left floating on the surface while the



Various reports of poachin g by foreign n ation als i n the outerAleutian Islan ds ar e n ot con firmed .

The problem of i llegal kill in g of sea otters may be of moreimportan ce i n Ca l iforn ia . Capta in H oward Shelby of the Cal iforn iaDepartmen t of Fish an d Game reported that i n on e period ( late1 957 an d early 1 958 ) i n the Mon terey area a lon e 1 8 dead otters

were foun d .

“Some had a hole clear through them, either spear orbullet woun d . H e sa id further that “it’s my opin ion that therear e people an d there ar e groups of people who do defin itely shootthis an imal . Then there ar e quite a group that target practice atanythin g .

”(Ca l iforn ia Sen ate, 1 963 )

Summary

1 . Few sea otters were foun d dead on Amchitka beaches i nthe period 1 938—40. The first report of sign ifican t n atural mortal itywasmade i n the sprin g of 1 948 when “more than 1 00”otters werefoun d dead on beaches . S in ce the late l 94o’s sign ifican t late-win ter,early-sprin g morta l ity was observed when biologists visitedAmchitka . Durin g five study periods from 1 956 to 1 963 , datawere obta in ed from 3 1 1 otters foun d dead or dyin g on beaches ofthe eastern half of Amchitka Islan d .

2. The greatest n umber of otters usua l ly died i n the mon thof March but con siderable mortal ity also occurred i n February,April, an d May . In this late-win ter, early-sprin g period about

three-quarters of a l l an n ua l mortal ity occurred .

3 . Approximately 70 percen t of the late-win ter, early-sprin g

mortal ity occurred amon g juven iles deserted by mothers . The other30 percen t of dead an ima ls were predomin an tly adults showin gsign s of age.

4. Durin g the period of stress caused by storms , mothersdeserted their large juven i les at an earlier age than they did at

other season s . They appeared to do th is because it was difficult fora mother to obtain sufficien t food to satisfy both herself an d thelarge juven i le . Few very smal l pups were foun d dead even thoughthey were presen t i n the population at a l l season s .

5 . Morta l ity was usual ly greater among males than amon g

females . Amon g j uven i les th is disparity was greater than amon g

adul ts . Ma les i n captivity were foun d to be less hardy than females .

6 . Vigorous adults were able to obtain adequate n ourishmen t

from high-calorie foods , such as fish an d octopus . These organ isms

were seldom obta in ed by juven i les an d aged an ima ls .

7 . A high percen tage of juven i les an d aged an imals foun d


dead on beaches exhibited malocclusion of the p ostcan i n e teeth .

In juven iles this con dition resulted when deciduous teeth werebeing replaced by perman en t teeth . In adults malocclusion resulted

from severe tooth attrition which may have been caused by chew

i ng hard-shelled in vertebrates .

8. Prolon ged storm con dition s precipitated morta l ity but theamoun t of mortal ity was foun d , i n 1 962, to be related to the avail

able feedin g habitat an d population den sity .

9 . The relative in ten sity of storm wave action was greater on

the Pacific Ocean coast than on the Berin g Sea coast, but the mor

tality on each coast was proportion a l to population den sity an d n ot

to relative in ten sity of storm con dition s , in dicatin g that the th r es

hold of con dition s causin g mortality was passed on both coasts .

1 0. The an n ual mortal ity of the Amchitka population was estimated i n 1 959 an d 1 962 to be about 8 to 1 1 percen t . Two methods

of estimatin g mortal ity gave similar results .1 1 . In the Shumag i n an d San ak Islan ds areas , where the sea

otter population was about four an d two otters per square mile of

water less than 30 fathoms deep , respectively, n o eviden ce was

foun d to in dicate un usual mortal ity i n the late-win ter an d early

sprin g storm periods .1 2. The Amchitka population was about 1 9 otters per square

mile of water less than 30 fathoms deep an d had overexploited

cer tain food resources . Because of this fact, the population wasrestricted by relatively high mortal ity which resulted primarilyfrom maln utrition an d was precipitated by en vironmen tal stresses

durin g late-win ter , early-sprin g storms .1 3 . Sea otters ar e in fested by a variety of in tern al parasites

but these rarely appear to be the direct cause of sign ifican t mor

tal ity. Ext ern a l parasites ar e l imited to fortuitous in festation s

of n asal mites . Such in festation i s un usual i n wild otters .1 4. The most frequen tly observed con dition at death was

emaciation accompan ied by hemorrhagic en teritis . Chron ic disease

con dition s an d bodily in juries were observed .

1 5 . Sharks, the Bald Eagle , an d killer whale ar e kn own to killsea otters . Predation , however, i s probably an in sign ifican t sourceofmortal ity.

1 6 . En vironmen ta l pol lution i n areas n ow heavily util ized byman will probably preven t the sea otter from reoccupyin g al l ofits former ran ge .

1 7. No eviden ce is avai lable to in dicate sig n ifican t illegal kil li n g by man of sea otters i n Alaska . In Cal iforn ia ,

however,i l legal

kill in g by man may, today, hin der the in crease of the sea otterpopulation .

IN CAPTIV ITY

The sea otter is highly adaptable to l ife i n captivity. When itsen vironmen tal an d food n eeds ar e met , it is hardy an d appearscon ten ted i n a i r temperatures from about 1 5° to 85 ° F. By n ature

it is placid an d tames quickly. Some in dividua ls accept food from

the han d within a few min utes of capture .

Certain features of the captive en vironmen t ar e, however, extr emel y critica l . The sea otter i n captivity must have free accessto an abun dan t supply of clean water . It al so requires access toclean , dry areas but, i n warm weather , it may spen d en tire days

without leavin g the water . Free a i r circulation i s a lso a requiremen t . Clean l in ess of the fur is essen tia l;if the fur becomes soiled,the a i r blan ket trapped amon g its fibers is destroyed, the skinthen becomes wet, an d death from chill in g soon follows .Its food requiremen t of about 20 to 25 percen t of its body weightper day must be fulfi l led . It readily eats a variety of fish , mollusks ,an d crustacean s but will remain i n good hea lth on a mon oton ous

diet .

If clean water is withdrawn for even a short period, as durin g

travel on ship or a ircraft, death may occur soon after the an imal s

ar e a llowed to en ter cold water . When water is n ot available ,captives ar e emotion al ly upset an d extremely sen sitive to ai r

temperatures . In dry cages, ai r temperature n ear 50° F. has caused

distress, an d an ima ls exposed for a few hours to temperatures

n ear 70° F. died .

The in formation gain ed from holdin g man y captive otters is

reviewed below.

Capture

Most sea otters taken al ive ar e captured i n n ets . The historical

record in dicates that i n early times, a lso, n ets were employed .

Steller ( i n Jordan ,1 898— 1 899, Vol . 3 , p . 2 1 4) states that an chored

n ets were spread on the water’s surface an d that carved wooden

otters were used to attract otters in to them. Of the captives hesays:

When they ar e caught i n the n ets they ar e so fran tic that i n their despair



the ease with which they may be captured on shore as (most

difficult first) :( 1 ) mothers with youn g, (2 ) adult females, (3 )

juven iles, an d (4) adult males . Mothers with youn g were difficultto n et because ( 1 ) they were a lert, slept l ightly, an d retreated to

the water at any hin t of dan ger, an d (2 ) they came ashore i n

places that were least accessible to en emies .Because the sea otter has an acute sen se of smel l, an ima ls of

a l l ag e an d sex classes must be “approached upwin d . Amon g rocks

an d n ear cliff s, eddy curren ts may carry en ough scen t i n an up

win d direction to a larm an d stampede otters before they can be

captured .

Captured otters were removed from the lan din g n et either byplacin g a sma l l carryin g cage at its mouth (fig. or by l iftin g

F IGURE 1 05 .— After a sea otter was n etted, a carryi n g cage was placed

horizon ta lly on the rocks an d the otter was a llowed to move from the n et

in to the cage . After the an ima l en tered, the cage was turn ed upright an dthe lid was fasten ed . T he cage was then strapped to a packboard or

suspen ded from a pole for tran sport to a truck or boat. (KWK 55—8— 1 0)


the an imal by its hin d legs in to a vertical ly placed cage . An otter

held off the groun d by its hin d legs is un able to ben d its body faren ough to bite its captor . The caged otter (fig. 1 06 ) was then

carried to a boat or to the n earest road .

En vironmen ta l Needs o f Captives

From 1 932 to 1 937 Soviet biologists experimen tal ly held captivesea otters (Barabash-Nikiforov , An imal s were even tual ly

held successfully i n cages built at the edge of a bay where tidal

water was used to flush an d clean the en closures (Reshetk i n an d

Shi dl ovskaya , The detail s of this work were unkn own to

us un til 1 962 . Even so , a l l coasta l areas at Amchitka , where our

work was don e , were exposed to storm waves , so we could n ot

use en closures placed directly i n sea water . After con siderable ex

p er imen tati on , a satisfactory field holdin g facil ity was con structedon lan d .

«A .

FIGURE 1 06 — This 65-l b . ma le otter was carried f or over a mile i n this man n er .After an in itia l fran tic struggle when n etted , it settled down an d rodequite ca lmly i n the cage . (KWK 56—3—40)


If sea otters ar e to survive i n captivity, they should, withinabout 2 hours after capture, be placed i n specia l quarters . Thequarters, whether in the field or i n a zoo, must essen tia l ly simulatethe n atura l en vironmen t . If this procedure is n ot followed, deathmay occur within a few hours or weeks, depen din g on which n eedsar e n eglected an d the degree of n eglect . The followin g brief historyof experimen tal attempts to hold otters i n various kin ds of enclosures i llustrates the requiremen ts for exactin g care .

T he first modern U.S . attempt to hold captive sea otters wasmade i n March 1 95 1 . Refuge Man ager Robert D . Jon es of theAleutian Islan ds Nation al Wi ldlife Refuge an d a crew of menwen t to Amchitka Islan d aboard the U.S . Fish an d Wildl ife Servicevessel Br own Bear . A camp was established at Crown Reefer Poin t,an d at least 35 otters were captured on tida l rocks . An attemptto hold these an ima ls i n shal low, mud-bottomed, fresh-water lakeswas un successful . Al l died within a few hours or a few days aftercapture .

In February 1 954, Drs . Don ald Stul l k en an d Charles M. Kirk

patrick, i n compan y with U.S . Fish an d Wi ldl ife Service em

p l oyees, visited Amchitka . In formation about the physiology ofsea otters an d their behavior i n captivity was obta in ed (Stul l kenan d Kirkpatrick, 1 955;K irkpatrick et a l . , Otters were keptexperimen ta lly i n two ways:( 1 ) In a large wooden tan k of seawater an d (2 ) i n an aban don ed house where dry grass was used

as beddin g. Al l an ima l s placed i n the tank soon showed symptoms

of shock an d exposure, an d died within a few hours or a few days .

Of those kept on dry beddin g, three were given con stan t atten tionan d survived . They were brought to Seattle i n Jun e 1 954 by R . D .

Jon es . Subsequen tly, when shipped to the Nation a l Zoolog ical Parki n Washin gton , D C , an d placed i n a smal l in side pool , a l l died

within a week.

In March an d April 1 955, 3 1 otters were captured at Amchitka ,held on beddin g of dry straw i n a buildin g, then placed aboard

ship i n small cages havin g dry beddin g (fig. Forty percen t( 1 2) of the an imal s died before leavin g Amchitka or aboard ship .

The rema in der ar e thought to have died soon after liberation at

the Pr ibilofs ( see Tran splan t Attempts ) . It became obvious thatif the captive sea otters’ fur became soiled, the an imal s could n ot

again clean their fur an d survive after l iberation i n cold water.My sea otter studies began on 26 July 1 955 , when on e A leut

laborer, An ton e Bezezekoff , an d I wen t to Amchitka Islan d an d

remain ed un til 5 October . Our primary purpose was to learn howto ma in ta in captive sea otters i n good hea lth . We held otters ex



which sea water was pumped for 3 to 4 hours each day. Whengiven on ly in termitten t access to water, however, the waterproofcon dition of their fur even tua l ly deteriorated . In addition , an imal s

kept with l imited access to water frequen tly developed in fection sof the paws an d fl ippers which, i n combin ation with even tualwettin g of the un derfur, con tributed to the morta l ity . Althoughsurvival was improved i n the outdoor cage , it was eviden t thatcagin g methods were still in adequate .

In October 1 957, an outdoor, cemen t pool, 1 5 feet m. ) lon g,8 feet m. ) wide, an d 4 feet m . ) deep, was built on

Amchitka . Surroun din g the pool was a wooden platform 7 feetm. ) wide, an d the en tire in stal lation was surroun ded by a

board fen ce 7 feet m. ) high (figs . 1 08 an d The eu

closure was un roofed . A con tin uous flow of water was furn ished bya clear, fresh-water stream. All healthy an imal s placed i n thisen closure rema in ed hea lthy

,an d severa l that were afl‘l i cted with

en teritis an d apparen tly starvin g when captured regain ed health .

The basic reason for the fai lure of early experimen ts withcaptives became obvious . Un der n orma l con dition s in the wild , the

F IGURE 1 08.— This en closure aroun d a cemen t pool satisfactorily preven ted

escape an d furn ished idea l con dition s where otters could be held in defin itely.

Water from a stream was brought to the pool i n the wooden pipe, at left.A ramp was con structed ( f ar right ) on which a dory, used to obta in fish

f or otter food , was beached . Storm waves often destroyed the ramp .

(KWK 57—27—1 2 )


F IGURE 1 09 .— T he cemen t pool i n the en closure shown i n figure 1 08 where

otters were ma in ta in ed i n excellen t hea lth . (KWK 57—29—4)

sea otter exi sts on ly i n clean water an d the fur remain s waterrepellen t . The skin i s n ever wet but is protected by a blanket ofai r trapped i n the fur fibers . Th e waterproof qua l ity of the delicatefur is lost when an ima ls ar e improperly held .

In shal low lakes mud an d detritus became en tan gled i n

fur fibers, admittin g water to the skin . In the large wooden tank

an i n sufl‘icien t flow of water al lowed suspen ded food an d

feca l matter to accumulate an d become imbedded i n the fur . Also ,there was n ot en ough space for the ott ers to get out of the waterto dry themselves . The same results occurred as i n the lake . When

otters were given in termitten t access to water food scrapsan d sl ime became imbedded i n the fur durin g periods when waterwas n ot available . The progress of wettin g was less rapid un derthe latter con dition s because a degree of clean sin g was possible .

In addition , humidity developed with in adequate circulation ofoutdoor a i r an d hin dered the dryin g of fur when otters were heldin a buildin g.

Even i n the large outdoor pool , built i n 1 957, care was n ecessaryto limit the n umber of otters held . If more than five were held

simultan eously, the pool had to be dra in ed an d clean ed dai ly topreven t an accumulation of food scraps an d feces that affectedthe water-repellen t qual ities of the fur . Captive otters were n ot


aff ected adversely by frigid temperatures (fig. 1 1 0) when heldi n proper en closures .No con clusive data ar e ava ilable to demon strate that fresh waterprovides a satisfactory perman en t en vironmen t for captive sea

otters . Although n o record exists to show that sea otters wereever foun d i n fresh water i n n ature, captives held i n clean freshwater at Amchitka showed n o detectable il l effects . On e female,Susie, l ived for 6 years i n a fresh-water pool i n Seattle . An autopsyrevealed, however, that her reproductive tract had n ot on ly failedto mature but had regressed an d was less developed than i n

n orma l juven i le otters . Could this con dition have been related tothe fresh-water en vironmen t ? In addition , severe in festation of

n asal mites (H a l ar achn e mi r oun gae) , a con dition n ever foun d i na wild otter, con tributed to her death (Ken yon , Yun ker, an d

Newel l , I con clude that fresh water may be temporarilysatisfactory for captive an ima ls but that lon g-term studies of

captive otters should be con ducted on an ima ls kept i n sea water .

F IGURE 1 1 0.— Air temperatures down to + 1 5

° F . were withstood with n o

appa ren t detrimen ta l effects by captive otters i n the outdoor pool . Icewhich quickly formed durin g cold spells was removed to provide openwater. T he otter i n the foreg roun d holds up i ts paws i n typica l beggin gposture . (KWK 59—3—1 )



TABLE 60.— Foods offer ed to cap t i ve sea otter s

Food item Acceptabil ity RemarksCr ustacea 1King crab (Par al i thodes )T anner crab (Ch ion oecetes ) A l imited amount (2 to 3 lb. p erShrimp (m isc . sp . ) an imal ) was eaten eagerly. If . how

ever, fish was also available i t waseaten and the remain ing crab wasleft unea ten .

Mo l lusca 9Snails, mussels, l impets Accepted Eaten w

lhen hungr y and nothing else

ava i l a l eClams (S axi domus, Chim e ) Eaten to capacity if sufficient avail able .

Octopus (O ctop us ) H ighly preferred Do .

S quid (Lol i g o ) _ do

Echinodermata 3S tarfish Refused S ample bitten ofi then discarded.Sea urchin (S tr on g yl ocen Accepted Eaten when gravid;refused when n otgravid, and other foods available .

Pisces 4H er r ing (Cl up ea ) Accepted_S almon (On cor hyn chus )Arctic char (S al vel i n us ) do ._

Lan cetfish (A l ep i saur us ) doCod Preferr edH ake (Mer lucci us ) doRockfish H ighly preferr ed .

Green l ing (H exag r ammos )Lingcod (Op hi odon )S cul pin (H emi l ep idotus )Poacher (A g on us )Gl obefish (Cycl op ter i ch thys do . .

H al ibut (H i p p og l ossus ) do

Sole (Lep i dop setta ) PreferredCanned fish ( salmon ,mackerel , sardines ) _ Refused Refused even when very hung ry.

Cooked fresh fish (Greenl ing, Do .

S alted and brined ( codfish ) Small amount eaten r eluctantly.s

Aves:Goose flesh (Ph i l acte ) Eaten r eluctantly when very hungrybut passed through tract undi gested( S tul l k en and Kirkpatrick, 1 955 )

Mammalia:Sea l flesh (Phoca ) -Do .

Mink food Dried commercial mink food was mixedwith fresh fish . No t ea ten even whenhungry.

1 Large pieces of shell discarded but many small pieces swallowed. J . Van ia found that ca ptive otters took l ive Dungeness crabs (Can cer mag is ter ) eagerly and were preferred to the excluis ion of other foods during extended periods .

2 Clam shells discarded but smal l shells of mussel s and snails crushed and swallowed.

3 Many pieces of shell swal lowed .4 V iscera and hard bones of head discarded but other bones and skin usually swallow'

ed .5 Soviet bio logists apparently successfully f ed salted cod and haddock after soaking 8—1 0 daysin winter, 4—5 days in summer" ( Shi dl ovsk aya , Our otters m ight have taken some of the

food items that were refused if they had been al lowed to become sufficiently hungr y.

al ive when removed from n ets were stored un til n eeded. i n cages

suspen ded in sea water from K i r i l of dock .

Most fish taken at Amchitka were heavily in fested :with theroun dworm T er r an ova deci p i en s. This parasite was tolerated i nsmal l n umbers by sea otters but when heavy in festati on s wereaccumulated i n captive an imal s they became lethargic an d ex

h ibi ted mala ise . On autopsy, in testin es of juven i les were foun d tobe perforated by the worms . After 1 956 , a l l fish given to captive

Refused at first but eaten when nothingelse available .

Eaten rel uctantly when nothing el seava ilable .

-Do .

Do .

.Do .

Do .

Eaten regul arly and consistentlymgy feedings.

0 .

Do .

Do .

Eatelr;when nothing else available .

0 .

Do .

Do

THE SEA OTT ER IN THE EASTERN PACIFIC OCEAN 295

were held frozen (at about + 1 0° F. ) for at least 24 hours .en tly al l helmin th parasites were killed by this treatmen t .

A Soviet biologist (Sh idl ovskaya, 1 947 ) states that fresh fishis always better than frozen fish . Our experien ce is n ot i n

accord with this statemen t . Durin g exten ded periods i n captivity,

otters were regularly fed fish that had been frozen an d healthremain ed excellen t .

FOOD QUANT ITY REQUIREDDurin g the period March 1 956 through December 1 957, records

of the food con sumed by Susie, a captive female sea otter , were

kept on 602 days . Keeper Richard D . Clark used a 25-l b . capacity,Chatillon , platform-sprin g scale to weigh a l l food to the n earestlb . (occasion al ly to 14 The otter was fed three times da i ly

(morn in g, n oon , an d late aftern oon ) . Food i n excess of the otter’sdaily con sumption was offered . Before the morn in g feedin g, the

pool was drain ed an d a l l food scraps from the previous day wereremoved an d weighed . From these data the approximate weightof the food con sumed was ca lculated . A screen over the poo l dra inmin imized loss of remn an t food scraps . The data from the dailyfeedin g record ar e summarized i n table 6 1 .

The weight of this fema le ( six weighin gs ) averaged 39 lb .

She con sumed about (dai ly average , 1 year , 1 957 )lb . kg. ) or about 23 percen t of her body weight per day,

approximately 228 g. day/k g . of body weight . The extremes, usin gmon thly averages were 24 percen t ( i n February) an d 20 percen t( i n April ) of body weight con sumed per day.

Th e actua l daily con sumption of food ran ged from a min imum

of about 2 lb . kg. ) to 1 6 lb . The ran ge i n amoun t

TABLE 61 .— Food consump ti on of a 3 9 l b. kg . ) sea o tter (S usi e ) a t the

S ea tt l e Zoo

Ki logr ams of food

Observation food Maxi intake entireperiod consumed mum period

1 March3 1 December 1 956 1 9303

1 Jan ua r y1 5 December 1 957 3

T ota l ( and mean

1 T he average daily in take during each month was computed .3 Except August when n o data were kept.3 A second otter was placed in the enclosur e at the en d of this per iod .


eaten was between lb . kg. ) an d lb. kg. ) 94 percen t of the time an d between lb . kg. ) an d lb . kg. )78 percen t of the time (fig.

Figure 1 1 2 demon strates that i n a win ter mon th (February)more food was con sumed than i n a summer mon th (Aug ust ) . InFebruary the in take i n a 24-hour period ran ged from 6 lb .

kg. ) to lb. kg. ) an d i n August from 5 lb . kg. ) tolb. The average dai ly con sumption i n February waslb . kg. ) an d i n August lb . About an d

2 5 5 6 5 IO .5 II.5 I2 5 I3 .5 I4 S IS . S

POUNDS EAT EN

F IGURE 1 1 1 .- T he amoun t of food con sumed by a captive fema le otter was

recorded on 602 days. Food was ava i lab le i n excess of her da ily requiremen t,an d the amoun t con sumed i n a sin gle day varied from about 2 lb . ( 1 kg. )to lb . Da ily con sumption was between an d lb. on

567 days (94 percen t of the time ) an d between an d lb . on 470

days ( 78 percen t of the time ) .



M A M J J A S O N D

MONT HS | 9 5 7

F IGURE 1 1 3 — Average da ily weight of food con sumed each mon th i n 1 957

by an adult fema le sea otter weighin g about 39 lb . In this period theaverage da ily con sumption was lb . (23 percen t of the body weight ) .

through August, records were kept of their combin ed food in take .The combin ed weights of the two an ima l s was about 1 02 lb . an d

they con sumed ( durin g 21 2 days when records were kept ) an

average of lb. of food da i ly, or percen t of their combin edbody weights . Un less competition for food stimulated Susie’sappetite an d in creased her in take , this would in dicate that therate of con sumption of the ma le exceeded that of the female .

An adult male, Gus, n ow ( 1 967 ) i n the Tacoma Aquarium

about 20 percen t of his body weight, of fish an d squid daily.

weighs 76 lb . kg. ) an d rarely fai l s to con sume 1 5 lb.

H i s food is stored frozen i n 5 lb . kg. ) blocks an d three of thesear e offered da i ly (fil l eted r ockfish morn in g an d even in g an d squidat n oon ) . From 1 September 1 966 through 3 1 August 1 967 hecon sumed lb. kg. ) of food . Durin g the year period,the otter con sumed more than 99 percen t of the food offered. When ,

on several occasion s,more than 1 5 lb . of food was off er ed

'

the

otter either refused it or did n ot con sume the en tire ration at a

subsequen t feedin g. On hi s un iform an d regulated diet this otterappeared to remain i n excellen t con dition .

Some captive otters were temperamen tal about their food . A

food that was eaten en thusiastical ly on e day was ign ored or eatenreluctan tly the n ext. This behavior was especial ly eviden t whenan abun dant supply of food was avai lable . Days of high con

sumption might in dicate that a fresh supply of particularly desirable food was available .


When the food supply was l imited on Amchitka an d severa l

otters were held simultan eously i n a pool, we foun d that largejuven i les , weighin g 20 lb . (9 kg . ) to 30 lb . ( 1 4 ma in ta in ed

health an d vigor when fed a min imum dai ly average of about 6 lb .

(3 kg . ) of food per an ima l an d that adults could subsist on a

min imum average of about 8 lb. (4 kg. ) fed da i ly per an ima l i n

morn in g, n oon , an d even in g feedin gs . Given these quan tities , thean imal s were always hun gry an d ten ded to rob food from eachother . S tul l ken an d Kirkpatrick ( 1 955 ) foun d that when captivesheld i n dry beddin g were given on ly about 1 2 to 1 5 percen t oftheir body weight per day en teritis developed .

The n orthern fur seal which, un l ike the sea otter , has a thickblubber layer i n addition to its fur , was foun d to require on ly

about 7 percen t of its body weight i n food per day (Scheff er,l 95ob) .

C on c l usi on s

When food was off ered daily i n excess , the average dai ly con

sumption by a fema le durin g 602 days was about 23 percen t of thebody weight. The da ily con sumption varied g reatly. Con sumptionper day ran ged from about 5 percen t to 40 percen t of the body

weight . This an imal appeared to be i n excel len t health durin g thestudy period .

When a captive ma le was offered food that was l imited to 20percen t of his body weight each day, he con sisten tly ate theamoun t offered an d rema in ed vigorous an d healthy.

At Amchitka when a sufl‘

ici en t n umber of fish could n ot be

caught, otters were held temporarily i n apparen t good health on

less than the optimum food requiremen t . Food represen tin g 1 5percen t of the body weight per day was n ear the min imum tempo

rary requiremen t.

C OST OF FO OD

In quiries have been received con cern in g the econ omic possibil ityof operatin g a sea otter “fur farm.

”Aside from the high expen seof catching an d tran sportin g the an imal s an d buildin g suitablequar ters for them, the cost of feedin g would be an importan t consideration .

For 1 year a record was kept at the Seatt le Zoo of the cost tofeed an adult fema le sea otter (Susie ) . The in formation was

given to us by Zoo Director Fran k Vin cen zi ( lett er, 8 April 1 963 )an d i s summarized below:


Clams— 20 l b ./week at 20 cen ts/1b. 52 weeksOctopus— 346 1b. at 20 cen ts/lb .

F ish lb . at 1 0 cen ts/lb .

Total cost of food— 1 year$27.75/week or $3 .96/day

The cost of food for Gus i n 1 year, 1 September 1 966 to1 September 1 967, was more than ( squid at 30 cen ts perpoun d an d fil l eted fish varied from 30 cen ts to 35 cen ts per poun d ) .

Poin t Defian ce Aquarium D irector Cecil Brosseau con siders thatthe an n ual food cost is close to or about $5 per day.

FEED ING BEH AVIOR OF CAPT IVESWhen captives were kept i n ample water they ate readily . Cer

tain in dividuals con sumed food eagerly immediately after capture .

Others, i n apparen t good health, refused to eat for 24 hours or

slightly lon ger . O ld an d apparen tly i l l an ima ls sometimes refusedto eat , or ate too l ittle to survive .

Within 1 or 2 days of capture, captives learn ed to beg for

food an d even after storin g a quan tity un der the foreleg would

float on their backs, both forepaws upheld i n a beggin g posture(fig. Food was usual ly tossed to otters in dividually as theyfloated on their backs . Pieces of fish were sometimes caughtbetween the forepaws but more usual ly the food item was al lowedto strike the chest before it was grasped by the paws . Often whenan atten dan t en tered the en closure carryin g a bucket of fish the

more aggressive in dividua ls would rush from the water to takefood from the han d (fig. At such times they n ever attemptedto bite an d would take food lyin g flat on an exten ded han d , avoidin gcon tact between teeth an d fin gers .

Large adults habitual ly robbed smal ler adults an d juven iles, evenwhen the larger on es had a l l they could carry un der the forelegs .The robber would approach the victim from behin d or ben eathan d with on e or both forepaws wren ch the food from the smalleran ima l ’s chest (fig. Certain aggressive adult females growledan d sn apped at a robbin g male , but juven iles an d subordin ate

adults offered n o resistan ce other than to rol l away from the

robber . Frustration , or perhaps an ger, was expressed by thevictim at such times by slappin g the chest with rapid strokes ofboth for ep aws.

Because food reserves were often low, it was difl‘i cul t to assure

that a l l captives received sufficien t food . To reduce pilferage , a

bamboo pole was used to deter food-robbin g an imals . On e adult

fema le, however , became so adept that while divin g an d projecting



F IGURE 1 1 5.— A— A large an d un usua lly light-colored adult fema le ag g r es

sive l y wren ched a food item from a juven ile otter . After graspin g the

food tightly to her chest with the forelegs, the adult rolled away an d

d ived . T he youn g otter was un able to retrieve any food after it had beenstolen . B— T he juven i le attempts to retrieve a fish which the adult femalehad stolen from it. T he adult, after rearin g back, rolled forward an d

d ived, frustratin g the a ttempts of the juven ile to retrieve i ts food.(KWK 59—1 3—3 an d 4)


Wild sea otters habitual ly eat while floatin g on the surface ( seeFood an d Feedin g Behavior ) . When captives were held i n en

closures without sufficien t water to swim i n , they ate poorly. Theyrefused some foods that were readily eaten by captives held i n a

pool . They were n ervous an d distressed . Stul l ken an d Kirkpatrick( 1 955 ) n oted that three successfully main tain ed captives kept i ndry beddin g lost weight, frequen tly appeared listless, an d i n

weaken ed con dition durin g the first 1 0 days i n captivity. D igestion

was apparen tly disturbed when an imal s were kept on dry beddin gwithout a pool . Flatus was observed frequen tly i n otters kept ondry beddin g but n ot i n an imals kept i n a satisfactory pool . Simi larfood was given to both groups of an imals .In dividua l an ima l s i n apparen t good health refused to eat whenheld on dry beddin g without access to a pool . On e adult male

refused to eat for 4 days an d was then released , weaken ed butsti l l apparen tly hea lthy. An adult fema le kept i n similar quartersrefused food for 6 days before release . Juven iles, i n gen eral , were

more adaptable than adults . Sea otters require an abun dan t supplyof clean water i n which they can con sume food an d clean theirpelage while eatin g. On ly while i n tran sit for a brief period shouldthey be held i n cages without bathin g water .

D ai ly Cyc l e of Activity

BEH AVIOR DURING T H E DAY

Two days, on e i n midsummer (29 August 1 957 ) an d the otheri n midwin ter (21 Jan uary 1 960) were spen t by V . B . Scheffer an dme n ear the en closure of an adult female sea otter (Susie ) i n theSeattle Zoo . H er activities as l isted below were timed with a stop

watch an d recorded (table Activities were classified accordin gto four primary categories:

Gr oom i n g

Rubbing the fur with the paws, prin cipally the forepaws . It wasaccomplished whi le sittin g beside the pool or while roll in g overan d over i n the water or lyin g on the surface of the pool .

Rest i n g

When the eyes were shut the otter was presumed to be sleepin g.

If the eyes were open while she l ay quietly, she was recorded as

n appin g.


TABLE 62.— A cti vi ty of a cap ti ve sea otter i n day l i g ht hour s, summer ( 1 957 )

an d wi n ter ( 1 9 60)

[A i r temperatur e:29 Aug . 1 957 at 051 5 , 52° F . ( 1 1° at 1 200, 70° F . at 1 900,

66° F . ( 1 9

°

MinutesIn water On land T ota l

Activity 29 Aug . 21 Jan . 29 Aug . 21 Jan . 29 Aug . 21 Jan . 29 Aug . 21 Jan .

GroomingEnergetic

RestingS leepingNapping.

FeedingExercise

741 369 1 74 1 71

Feed i n g

Food was p laced i n the otter’s pool at about 0900, 1 230, and

again i n late aftern oon if n on e rema in ed . Food rema in in g over

n ight i n the pool was eaten by the otter before her regular feedin gtime . Feedin g activity was most in ten se shortly after fresh foodwas placed i n the pool . At other times, food items were retrievedfrom the bottom an d eaten .

Exer ci se (swimmi n g)

Like many zoo an imals , the sea otter developed an exercise

routin e durin g which she circled her pool . In a certa in place she

would dive, i n an other she rose to the surface an d turn ed, swam

a short distan ce on the surface, then dived to complete the circuit.If a n umber of visitors stood n ear the fen ce by her pool , theexercise routin e might in clude a vertica l rise with on e forepaw

on the pool edge while she glan ced at the visitors . This was a lso

don e before feedin g time, when she glan ced i n the direction fromwhich the keeper would come . Occas ion al ly the otter left the poolto wa lk briefly about her en closure . Such short walks did n ot

follow a set pattern simi lar to the swimmin g routin e . Play wasrecorded when the otter picked up leaves , pean ut shells , or a

scrap“of paper an d with her teeth an d forepaws ban died it about;

a lso when sma ll rocks were retrieved from the bottom of thepool an d poun ded i n an apparen tly a imless way on the edge ofthe pool . This activity apparen tly became an exercise routin e .



0 I I I2 I3 I4 IS I6 I? [ 8

S UNRIS E LOCAL T IME— HOURSEXERC IS E FEEDING GROOMING

F IGURE 1 1 6 .— T he activi ties of a captive fema le sea otter were recorded for

each minute from before sun rise to after sun set on 29 August 1 957. T he

minutes spen t i n five categories of activity ar e summarized above for

each hour of observation .

PLAY E RES T ING

activity, groomin g an d exercisin g combin ed , was simi lar (72

percen t in summer an d 75 percen t in win ter ) . Groomin g activity,however

,con sumed more time i n summer than i n win ter .

D a i l y act i vi ty of wi l d an d cap t i ve otter s

T he daily pattern of activity of the captive female and a wild

female sea otter (further data ar e i n the section on Breedin g

Behavior ) would be expected to show obvious diff eren ces becausea wi ld otter must search for food . Table 64 illustrates thediff eren ces . The data (although recorded in the same man n er)ar e n ot strictly comparable because the captive otter was observedfrom the time of awaken in g i n the morn in g un til retirin g at n ight.T heWi ld otter was observed on ly from 1 052 un til 1 820 ( local time,Amchitka Islan d ) . In gen eral , however , this comparison il lustratesthe fact that a wild otter must spen d more than on e-half of itstime in feedin g wh ile the captive spen t less than 1 0 percen t of her

THE SEA OT TER IN THE EASTERN PACIFIC OCEAN 307

TABLE 64.— Comp ar i son of da i ly activi ti es of wi l d an d cap ti ve fema l e sea

otter s i n summer

Wild otter Captive otter21 August 1 955 1 29 August 1 957

Activity Minutes Percent Minutes Percent

Exercise and play

1 See Breeding Behavior for further data .

time i n thi s activity . The wild otter n early sati sfied her n eed forexercise while divin g for food . The captive satisfied this n eed byswimmin g an d groomin g to a greater degree than the wild otter .

The percen t of time devoted to rest by both an imals diff ered theleast.

BEH AVIOR AT N IGH T

From 1 Jan uary to 9 September 1 958, Mr . Ca l P ierce, n ightwatchman at the Seattle Zoo, recorded observation s of the behaviorof two captive sea otters . The objective was to obta in observation sof the time each an imal spen t i n an d out of the water an d i n theden . For a variety of reason s , some n ights were missed;substitutewatchmen did n ot a lways properly record the data . Usable obser

vat ion s were taken on 1 99 of the 252 n ights . Observation s wereusual ly made at hourly in terva l s from 1 800 to 2200, an d two tofour times between 2200an d 0600. Usually the watchman recorded

on ly whether each an ima l was i n the pool , beside the pool , or i nthe den . Two den s were available , an d both sea otters a lways had

free access to a l l areas within their en closure . Weather con dition swere n ot recorded durin g the observation periods , but on severaloccasion s the watchman n oted that even durin g heavy rain theotters rema in ed i n the open , sleepin g i n or beside their pool .Feeding, groomin g, an d play were n ot recorded systematically,

but were n oted on a n umber of occasion s at various times durin gthe hours of darkn ess up to about 2200. Durin g late n ight an d earlymorn in g hours, however , the an imal s usual ly slept quite soun dly .

Sometimes they awoke with a start i n the light of the watchman ’s

flashl ight. If beside the pool when awaken ed, they immediately

plun ged in to the water;if sleepin g on the water, they would dive .

Observation s made after 9 September ar e n ot used . About thistime the behavior of the male became abn ormal , an d he spen t i n


creasin g amoun ts of time i n the den . H i s health steadily deter iorated an d he died on 22 September .The gen era l behavior pattern for each an imal durin g the n ight

is in dicated i n figures 1 1 7 an d 1 1 8 . Both an ima ls ten ded to remain

in the water more than out of it during the early even in g hours .Durin g late n ight an d earlymorn in g hours, the male spen t a n early

equal time i n an d out of the water while the female ten ded to spen dmore time out of the water than in it . Both an imal s preferred torema in out of doors, whether sleepin g on the pool edge or i n thewater, but the fema le con sisten tly spen t more time i n the denthan did the ma le .

Even durin g win ter mon ths the sea otters seldom sought shelteri n the den (figs . 1 1 9 an d The amoun t of time spen t i n the

water at n ight, however , was greatly reduced i n win ter mon ths .The ma le spen t on ly 20 percen t of the n ight i n the pool durin gJan uary.

Durin g the sprin g an d summer the amoun t of time he

F IGURE 1 1 7.

— Behavior of an adult ma le sea otter durin g a mean or averagen ight . T he mean percen t of observation s of the an ima l i n three location s durin g the n ight ar e shown .



MONTH JAN

NO . OBS. I24

F IGURE 1 1 9 — Season a l behavior of an adult ma le sea otter at n ight . T hemean percen t of observation s of t he an ima l i n three location s durin g9 mon ths i s shown .

F IGURE 1 20— Season al behavior of an adult fema le sea otter at n ight. T hemean percen t of observation s of the an ima l i n three location s durin g9 mon ths i s shown .

“


Admin istered cc. Sparin e . (Based on a dose of 2 mg . Sparin e p er lb. bodyweight, the weight was 43 lb. which resulted i n a tota l dose of 90 mg .

Sparin e comes 50 Dose admin istered approx. 0900 h r s 2 November ,the an ima l died 1 230 h r s 2 November. Lun gs completely hemorrhagic. Tracheaextremely hemorrhagic. Blood dark r ed, tarlike coagulation s. Heart showedcompen satory en largemen t . Liver pa le an d an emic lookin g . Rema in in g organ sn orma l with some postmortem discoloration . Stomach partially filled withfood.Overheatin gwas probably al so an importan t factor i n the deaths

of these an ima ls . Post mor tem examin ation s revealed that threecaptive otters were sufferin g from in tussusception s of the smal lin testin e . This con dition preven ts the n ormal passage of in testin alcon ten ts . The reason that it occurred is n ot kn own but I suspectthat stresses created by un satisfactory holdin g facil ities and duri n g travel were importan t factors .In review, captives died ( 1 ) as a result of chill in g when the fur

became soiled an d its in sulatin g a i r blan ket was destroyed, (2 ) as

a result of heat prostration i n heated compartmen ts when deprivedof bathin g water, (3 ) when in fection s occurred i n the extremities,4) when old an d i l l an ima ls fai led to eat after capture, (5 ) whenparasitic roun dworms ( T er r an ova) in gested with fish flesh pen etr ated the in testin e an d caused periton itis, (6 ) of lun g hemorr hages when

“tran quilized”otters were carried i n smal l cagesaboard a heated, passen ger-carryin g aircraft, (7 of lun g con

gestion caused by a heavy in festation of n asal mites H a l ar achn e

(Ken yon et a l an d (8 ) of in tussusception s of the smal lin testin e. En teritis was a frequen t termin al con dition . Causes ofdeath ar e discussed further i n the section on Parasites an d Mi scell an eous D iseases .

In con clusion , when parasite-free food requiremen ts ar e met

an d the essen tial physical features of the sea ott er’s marin e em

vi r onmen t ar e dupl icated , it adjusts easily to a healthy l ife i ncaptivity.

D rug Use

Certain drugs were foun d useful i n the care of captive otters .If drugs had n ot been used , some captives that survived probablywould have died . No attempt was made to use drugs fired from a

gun to capture sea otters .

N embuta l

Stul l ken an d Kirkpatrick ( 1 955 ) foun d that the n ormal an es

thetic dose for dogs (40 mg . per kg. or 80 mg . per lb. of body


weight ) in jected in traperiton eal ly caused death i n a sea otter i n

less than 30min utes . On e-half the dog dose gave good an esthesiabut thermoregulation was upset. No further experimen ts withNembutal were con ducted .

Pr omaz i n e hydr och l or i de“S p ar i n e (Wye th)

The use of thi s tran quilizer was suggested by K . L . B inkley,D .V.M. It was foun d to be a useful agen t i n speedin g the adjustmen t of n ervous an ima l s to captive con dition s . The dosage of1 mg . of S parin e per kg. (2 mg . per lb . ) of body weight was satisfactory. The in tramuscular in jection took effect within 5 min utes .The an ima ls so treated rema in ed i n a relaxed state for about 24hours . This degree of sedation is, however, usually un n ecessaryan d un der certain con dition -s harmful , sin ce food in take an d pelagecare were substan tial ly reduced durin g the tran quil ized period .

We foun d that about ha lf this dose or less, i .e . , about to 1 mg .

Sparin e per lb . of body weight,in duced adequate tran quility an d

that the otters gave n early n orma l atten tion to their bodily n eeds .

When the eff ects of the drug wore off , the treated an imals i n al l

cases remain ed tame an d well adjusted .

Sparin e was particularly useful when mothers with smal l pups“

were captured . On on e occasion a mother with a n ewborn pup was

placed i n the en closure without receivin g an in jection . The mothergrasped the pup i n her mouth an d swam fran tical ly about thepool seekin g escape (fig. 1 21 ) rather than swimmin g i n the n ormal

man n er on her back with her pup on her chest . She surely wouldhave drown ed the pup if we had n ot recaptured her, taken the pupfrom her, an d given her the min imum in jection . Within 5 min uteswe return ed the pup an d the mother cared for it i n the n ormalway from then on (fig.

Usual ly when a sea otter pup was taken from its mother itcried almost in cessan tly, day an d n ight, an d accepted little foodvolun tarily . We foun d that after a min imum in j ection of Sparin esuch orphan s became calm an d after the effects of the drug haddisappeared the pup appeared to have become “imprin ted”on

the human foster paren t . Treated pups readily accepted food an d

on ly cried when desirin g atten tion . Un fortun ately, time an d facilities were n ot ava ilable to main ta in helpless captives in defin itely .

No,harmful side eff ects from min imum in jection s of Sparin e

were detected i n otters kept i n a satisfactory en closure with a pool .Because it was importan t that sea otters give frequen t atten tionto their pelage an d ma in tain their da ily in take of food , it wasdesirable that use of tran quil izers be kept to a min imum. The



F IGURE 1 22 — T he same fema le an d p up as shown i n figure 1 21 about 1 0minutes after the mother had received an in jection of Sparin e tran quilizer.Although the mother appeared drowsy, she carried the p up on her chest an dgroomed i ts fur , n ot as thoroughly, however, as she n ormally should have .

She a lso ate , an d nursed her pup . After recoverin g from the eff ects of the

tran quilizer, the mother rema in ed tame an d satisfactorily cared for herpup . (KWK 57—29—28 )

n o harmful side effects . I have used the drug on on ly two sea otters.It was my gen era l impression that the an imals did n ot regain

n ormal a lertn ess as soon as those given Sparin e an d gave imadequate atten tion to feedin g an d pelage care .

Pi p er az i n e c i tr ate

This vermifuge was admin istered as a precaution ary measure

to captive sea otters by in j ectin g an aqueous solution in to fishbefore feedin g. Before fish were frozen routin ely prior to feedin g,


captives became heavily in fested with T er r an ova deci p i ens . Theeffectiven ess of the vermifuge was difficult to evaluate but it hadn o i l l effect on the sea otters .

Vi tami n s

Because certa in fish con ta in thiamin ase , an en zyme that in hibitsthe proper util ization of vitamin B (Lee, thiamin e hydr o

chloridewas admin istered as a prophylactic measure . Pi l l s con ta ini n g vitamin B complex imbedded i n the flesh of fish ar e readily

eaten by otters an d a r e admin istered dai ly to otters held perman en tl y i n cap tivi ty .

A n t i bi ot i cs

In fection s i n paws, particularly the fron t paws, occurred whencaptive an imal s apparen tly scratched or cut these members durin gcapture or i n cages . An adult male with a badly in fected fron tp awwas given un its of Ben zathin e pen icill in G

“Bicill in”

(Wyeth ) an d the in fection disappeared after about 4 days . Twoweeks later, however, the p aw aga in began to swell an d an addi

t ion a l dose of un its of Bicillin was admin istered an d the

in fection disappeared perman en tly. The life of this an imal , as wellas those of several addition al otherwise healthy an imal s, were

probably saved through the in jection of either Crystal l in e p otassium pen icil lin G“Pen icil l in”(Wyeth ) or Bicill in .

Pen tobar bi ta l sodi um g r . i n each cc ., i sop r opyl a l coho l

p er cen t , p r opy l o n e g l yco l p e r cen t ,“Letha l”(H aver -Lockhar t)

This drug admin istered in tramuscularly was used to kill ottersthat were captured i n n ets an d for various reason s were n eeded

as specimen s . The man ufacturer recommen ded a dose of 1 cc . for

every 5 lb . of body weight, but the sea otter was easily affected

an d we foun d that a dose of 1 0 cc . would kil l large adults . The

immediate effect is similar to other tran quilizers . Death followedin jection i n about 8 to 1 0min utes .

Tran sportation o f Captives

Durin g tran sit from on e location to an other, the difl‘icul ty of

con troll in g en vironmen tal temperatures an d of furn i shin g suffi

cien t bathin g water causes severe complication s . The lon ger the

period i n tran sit the more critica l these factors become .

Sea otters have been tran sported i n automobiles, aircraft, an d


ships . After man y failures, kn owledge is n ow available to assuresuccessful tran sportation , provided that con trol of critical con dition s is possible .

AUTOMOBILEOtters were tran sported on ly short distan ces by truck or auto

mobile . They were taken from the place of cap tur e'

on Amchitkato field headquarters an d later between holdin g facilities an d shipsor a ircraft . Because the trips were short, the an imals were con

veyed i n smal l carryin g cages an d n o complication s were en coun

ter ed. H owever, they appeared disturbed, an d whin ed or“whistled”en route . The longest automobile ride, 40mi les, was i n 1 965 whenan adult ma le,

“Gus, was taken from a dock i n Seattle to the

Tacoma Aquarium at Poin t Defian ce . This an imal appeared quitecon ten ted throughout the trip .

A IRCRAFTOn several occasion s the on ly a i r tran sportation avai lable was

that of commercial passen ger plan es . H ere , because of passen gern eeds, it was n ot possible to ma in tain temperatures low en oughfor sea otters . Distressed otters whin ed, whistled, an d sometimesscreamed

,an d attempted to escape from their cages by tearin g

at the wire screen cage with their teeth an d forepaws. When avail

able, ice was p laced i n the cages an d cold water from bottles waspoured on the otters . This they drank eagerly an d rubbed in totheir fur . Thi s treatmen t did n ot satisfactorily solve the problem,

but several otters survived trips from Seattle to Wash in g ton , D C.

i n 1 954 an d from Amchitka to Seattle i n 1 955 an d 1 956 . The on lyotters that survived trips on heated, passen ger-carryin g aircraftwere given con stan t atten tion , ice, an d water durin g the trip .

Of 1 9 otters taken at Amchitka an d carried on commercia l , p as

sen ger-carryin g a ircraft, 6 survived to reach Seattle . Of these, on lytwo ultimately recovered from the trip . The time en route was from36 hours to more than 4 days, an d it appeared that few an imal s

could tolerate such prolon ged periods of stress .To avoid self-in jury an d reduce excitemen t durin g a i r tran s

ports, K. L . Bink ley, decided to admin ister a tranquil izerimmediately before shipmen t from Amchitka on 2 November 1 957.

H e wr ote:

This was don e an d the an ima ls shipped . Un fortun ately, fata l complication s developed when the tran qui l an ima ls were exposed to feeta ltitude i n a n on p r essur i zed plan e . Although it i s n ot kn own f or sure , ap

p ar en t l y the drug causes a lowerin g i n metabolism, an d also i n the an ima l ’s



mouths an d sprin kled on their fur,they became quiet. It appeared

that even at the relatively low cabin temperature they suff eredfrom heat distress when their fur was dry . Al l arrived at St . PaulIslan d i n excel len t con dition .

Travel in g cages with fa lse wire bottoms were used durin g al l

experimen ts i n aeria l tran sportation to reduce fur soi lin g to a

min imum. On the short trip from Amchitka to St. Paul thefur remain ed clean because the an imals were n ot fed en route .

On trips of lon ger duration ( 1 5 to 36 hours ) fur soilin g could n otbe avoided. Although body wastes fel l through the false cagebottoms , the an ima ls habitually l ay on their backs to eat (fig. 1 23 )Fish scraps an d sl ime then accumulated i n the fur with resultan tloss of waterproof con dition .

F IGURE 1 23 — Captive otters held on dry beddin g habitua lly l ay on their backor side. F ish scraps an d slime thus fell in to the fur whi le the an ima ls ate.

When the otters gr oomed an d rubbed the f ur with their paws, it becamesatur ated with filth an d particles of beddin g materia l

,an d i ts waterproof

qua l ity was destroyed . When this an ima l was placed i n wa ter it did n ot

float i n the n orma l man n er but san k because the a i r i n i ts fur was lost.In this con dition an ima ls placed i n cold water quickly chill an d di e . (KWK55—5—1 )


SH IPOtters were carried aboard ship i n two ways:( 1 ) i n cages

with beddin g an d n o water for bathin g, an d (2) i n a cage whichin cluded a tan k of con stan tly flowin g sea water . Usin g the firstmethod, when straw beddin g could be chan ged frequen tly an d

con dition s were such that the an ima ls remain ed dr y an d did n ot

chil l , they rema in ed i n satisfactory con dition . The three ottersbrought successfully from Adak to Seattle aboard a large ship i nJun e of 1 954 by R. D . Jon es were well protected from the weather .

The an ima l s, however, required con stan t atten tion an d when placedi n a Seattle zoo pool the fur became wet to the skin , causin g thean imal s to shiver . In an other experimen t (April frigidweather caused chill in g an d high mortal ity amon g the soiled

an imal s resulted .

An experimen t to test the secon d method was con ducted i nNovember-December 1 965 . A young adult male an d an aged female

were captured on 7 November at Amchitka an d placed aboard theMV Comman der . Th eir cage in cluded a tank havin g a flow ofabout 50gal lon s of water per min ute . Between capture an d arrivalat Seatt le on 3 December frequen t storms were en coun tered . Thefemale , probably n ear death when captured , refused to eat an d

died on 1 3 November . The male “Gus”survived the -mile

trip an d arrived i n excellen t con dition .

It was demon strated that:( 1 ) sea otters may be tran sportedwithout food an d i n smal l cages aboard un heated aircraft forseveral hours an d arrive at their destin ation in excellen t con dition .

Delays en route an d overheatin g, however, may result i n highmortal ity. 2 ) Aboard ship is a satisfactorymethod of tran sportin gott ers over g reat distan ces if a pool with an ample flow of cleanwater is avai lable . (3 ) For shor t distan ces (up to 40 miles, at

least ) tran sportation by automobile is satisfactory.

Tran sp l an t Attempts

The idea of tran splan tin g sea otters from areas of abun dan ceto unpopulated parts of their former ran ge, from which they wereextirpated i n the 1 9th cen tury, has lon g been popular . S in ce 1 950,six attempts to tran splan t otters were un dertaken , the first five

by the U.S . Fish an d Wi ldl ife Service an d the sixth by the AlaskaDepartmen t of Fish an d Game . A brief resume of these attemptsis presen ted below. Addition al in formation con cern in g them i s

given un der En vironmen ta l Needs of Captives”an d“Tran sporta

tion of Captives .”


A late-win ter, early-sprin g attempt, 1 95 1 , to tran splan t sea

otters by ship fa iled because of in sufficien t kn owledge of the otters’n eeds i n captivity. The 35 an ima ls that were captured on AmchitkaIslan d a l l died there before any were placed aboard the waitin gship .

Studies of captive otters were con ducted i n the win ter of 1 954on Amchitka an d were reported by Kirkpatrick et a l . ( 1 955 ) an d

Stul l ken an d Kirkpatrick The kn owledge ga in ed throughthese studies was useful but did n ot assure survival of captives

whi le awa itin g tran sfer or while i n tran sit to a n ew location .

Nevertheless, a tran splan t of 3 1 otters captured on Amchitkawas attempted between 28 March an d 4 April 1 955 . These otterswere carried from Amchitka to the Pribilof Islan ds i n cages withbeddin g of straw aboard the chartered fishin g vessel Par ag on .

Durin g the trip their fur became matted with filth , an d when the1 9 survivors were liberated each an ima l left a dirty brown traili n the water . Three of these were recaptured by han d within a

few min utes of release . They were soaked to the skin , rigid with

cold, an d n ear death . Non e of the an imals liberated was subse

quen tly seen at the Pribilofs, an d it is reason ably certain thatn on e survived .

In early sprin g, 1 956, Refuge Man ager R . D . Jon es , with Navyassistan ce, captured five otters at Amchitka an d took them vi a

ship 240miles to Attu i n the Near Islan ds . Jon es told me that thepelage of these an imal s when they were released was i n the usualsoiled con dition of an imal s held i n dry beddin g. No eviden ce is

avai lable to demon strate whether or n ot any of these otterssurvived .

Because these experien ces demon strated the n eed for a short

period of time i n tran sit, the n ext experimen ta l tran splan t wasan attempt to take otters from Amchitka to the Pribi lofs by ai r

1 1 December 1 957 . As described un der “Tran sportation of Captives”n on e of the eight otters taken aboard a commercia l , passen

ger-carryin g a irl in er at Amchitka reached their destin ation .

The n ext experimen tal aeria l tran splan t was un dertaken i n 1 959when an a ircraft could be devoted exclusively to this un dertakin g.

From 6 to 8 May, durin g a severe storm, 1 0 subadult otters werecaptured an d placed i n the pool en closure . Three an imals, i n

weaken ed con dition when captured , soon died . Furthermore, the

Amchitka pool was too smal l for 1 0 otters . Un less the an imal s

were hea lthy when captured, their chan ce of survival was reducedby crowdin g an d competition for food . Therefore, when an imal s

died they were n ot replaced .



l ived an d were r el eased i n what appeared to be excellen t con dition .

In a l l, 23 otters survived to be liberated on the west coast of Chi

chag of Islan d i n Southeastern Alaska . Subsequen t reports ofsightin gs in dicate that at least some of these an imals survived the

win ter of 1 965-66 . Further tran splan ts were con ducted i n 1 966 an d

more ar e plan n ed .

The kn owledge an d techn iques ar e n ow ava ilable to hold captiveotters i n excellen t health an d to tran sport an d l iberate them i n

con dition to survive . Large juven i les weighin g about 24 to 35 lb .

( 1 1 to 1 6 approximately a year or somewhat older, ar e mostadaptable to life i n captivity an d ar e hardy an d more adjustableto stresses of travel than ar e older an imals . A l so, they ar e of acon ven ien t size to han dle . Before bein g tran sported i n smal l

carryin g cages, an imals should be held i n a satisfactory en closure

for an adjustmen t period of a week or more .It i s yet to be shown that tran splan ted otters wil l form colon ies

an d repopulate vacan t habitat . Southeastern Alaska off ers hundreds of mi les of coastlin e suitable for sea otters . Wi l l the tran splan ted otters behave like certain other mammal s an d scatterafter release an d therefore fa i l to form breedin g aggregation s

‘7

Might they a lso behave like other mammal s an d seek to return tothe home territory where they were captured ? These question s canbe an swered on ly by con tin ued experimen tation .

MANAGEMENT

Man agemen t of sea otters depen ds on kn owledge of populationsize an d tren d . This kn owledge may n ot become avai lable un til

a cropping program has been i n operation for severa l years . A

ten tative man agemen t program can , however, be set on the basis

of presen t kn owledge .

In the case of the sea otter, in complete kn owledge of population

dyn ami cs factors dictates that a flexible man agemen t program be

in itiated . This should be closely coordin ated with a con tin uin g

program of studies of reproduction ,mortal ity , maturation ,

agin g;optimum population size , movemen ts , an d habitat status . Quan titat ivel y these factors wil l vary i n differen t habitats an d accordin g

to population den sity, food ava ilabil ity, etc .

If a wildlife resource is to produce a maximum sustain ed

an n ual yield , mortal ity from a l l causes must n ot exceed recruitmen t

at an optimum population level . At the presen t stage of our

kn owledge of sea otter biology , the followin g recommen dation s for

a man agemen t program appear relevan t

1 ) To attain kn owledge of the population level of maximum

susta in able yield , a relatively i solated study population should be

chosen (Amchitka i s a possible choice ) . (2) At the chosen location

a sustain ed an n ua l harvest should be taken without regard to

econ omic yield . (3 ) An n ual population surveys (preferably aerial )should be con ducted where harvests take place . (4) Late win teran d sprin gmortal ity should be mon itored . ( 5 ) Al l female r ep r oduc

tive tracts , with careful ly gathered field data , should be an alyzed .

(6 ) Durin g harvestin g operation s an imal s of a size most desired

by the fur market should be taken without regard to sex (the sexof an otter i n the field i s difficult to recogn ize ) except that a l l

fema les accompan ied by youn g should be spared . (7 If it becomeseviden t that a kill predomin atin g i n ma les is desired, harvestin goperation s should be con cen trated at or n ear kn own male con cen

tr at i on areas .

Wh i le a regular an n ua l crop of otters is bein g taken from the

chosen study population , otters should al so be taken i n other areas

where they ar e n ow kn own to be abun dan t . These areas ar e ( 1 ) theShumag i n Islan ds , (2) the Berin g Sea off Un imak Islan d an d the

tip of the Alaska Pen in sula , (3 ) the San ak Islan d—San dman Reefs


area, (4) the western An dr ean of Islan ds ( in cludin g the Del ar ofs) ,an d 5 ) the western Rat Islan ds .

EST IMATED YIELDIf a harvest is taken from any population an n ually, the kil l

should probably be limited in itial ly to about percen t of thetota l population (both sexes an d a l l ages older than depen den tyoun g) .

The total Alaska fur seal population i s about an imals,in cludin g an an n ua l production of about youn g (Rop p el ,John son , An as, an d Chapman , T he youn g con stitute about30 percen t of the population . In the sea otter it was in dicated ( seeReproduction i n the Fema le ) that 2 years n orma l ly elapse betweenbirths an d that the an n ual mean n umber of youn g i n the p op ul a

tion is about 1 4 percen t, or approximately on e-half that in thefur seal i n which 1 year n orma l ly elapses between births . It hasbeen foun d durin g man y years of croppin g the fur sea l that, on a

sustain ed yield basis , about 5 to 6 percen t of the total populationmay be cropped an n ual ly . Un der this man agemen t system the furseal herd grew from a population of about seal s i n 1 9 1 1

to about on e an d a ha lfmil l ion i n the late 1 940’s (Ken yon , Scheffer ,an d Chapman , 1 954) an d between 1 9 1 1 an d 1 963 yielded

skin s (Rop p el an d Davey,

Thus, un til further experien ce is ga in ed , it may be con cludedthat about to 3 percen t of the tota l sea otter population maybe cropped an n ua l ly on a susta in ed yield bas is .

Further studies of reproduction an d of the eff ect of croppin g

on population s may modify this prelimin ary estimate . In spite ofthe in dication that a fema le sea otter may hear n o more than on e

youn g i n each 2-year in terval , it is possible that because matern al

care is in ten sive an d prolon ged the survival rate of youn g i n a

sea otter population might exceed that i n the fur seal population .

C LOSED AREAS

Man y observation s in dicate that before sea otters move froma populated area to adjacen t vacan t habitat, a large loca l population

i s formed ( see Distribution an d Numbers ) . They apparen tly moveas a result of overuti l ization of food resources by a crowded

population . It fol lows that if vacan t habitat is to be repopulated,large local population s should be a l lowed to form to create the“population pressure”n ecessary to cause sig n ifican t emigration .

Thus, it is my opin ion that the spearhead”of population exp an


REFERENCES

ABEGGLEN , C . E . , A . Y . ROPPEL, an d F . WILKE.1 960. Alaska f ur sea l in vestigation s, Pribilof Islan ds, Alaska . Repor t of

field activities Jun e-October 1 960. U.S . F ish an d Wildlife Service,Marin e Mamma l Biologica l Laboratory, Seattle, Wash . Un published .

ALLAN SON , A .

1 955. S ea otters on S an M iguel . Pacific D iscovery, vol . 8, No . 3,p . 24-25 .

ANT H ONY, A . W.

_1 925. Expedition to Guada lupe Islan d, Mexico , i n 1 922. Proceedin gs Ca liformia Academy of Scien ce, 4th series, vo l . 1 4, NO . 1 3 , p . 277—320.

BAILEY,V .

1 936. T he mamma ls an d life zon es of Oregon . U.S . Bureau of BiologicalSurvey, North American Faun a NO . 55, 41 6 p .

BARABAS H —NIKIFOROV, I . I .1 947 . Ka lan . [T he sea otter , pp. 1 Soviet Mi n i str ov RSFSR . Glavn oeup r avl en i e p o zap ovedn ikam. ( In Russian . ) [Tran slated from Russianby Dr . A. Birrou an d Z . S . Cole . Published f or the Nation a l Scien ceFoun dation by the Israel Program f or Scien tific Tran slation s, Jerusa lem,

1 962. 227 p . , illus. ]BAUER, RIC HARD D . , ANGEL M . JOH NSON , an d VICTOR B . SCH EFFER.

1 964. Eye len s weight an d ag e i n the fur sea l . Journ al of Wi ldlife Man agemen t, vol . 28, No . 2

,p . 374—376, April.

BEALS , F . L .

1 943 . Memoran dum to Regi on al D irector, F ish an d Wildlife Service, Jun eau,

Alaska . Sept. 28, 1 943 . 3 p . 1 map .

BEE, J . W. , an d E . R . HALL.

1 956 . Mamma ls of n orthern Alaska on the arctic slope . Un iversity of

Kan sas, M iscellan eous Publication No. 8 . 309 p .

BELKIN , A . N .

1 966 . On the population abun dan ce of sea otter on the Kuril Islan ds.

Tran saction s Pacific Research In stitute of Marin e F isheries an d Ocean ogr ap hy, vol . 58, p . 3—1 3 .

BENT LEY, W . W.

1 959 . S ea otter a lon g the Ca liforn ia coast. Journ a l of Mammalogy, vol .

40, NO . 1 , p . 1 47.

BOOLOOT IAN , R. A .

1 961 . T he distribution of the Ca liforn ia sea otter . Ca liforn ia F ish an d

Game , vol . 47, No . 3 , p . 287—292.

BURROUGH S , R . D .

1 961 . T he n atural history of the Lewis an d Clark Expedition . M ichiganState Un iversity Press, East Lan sin g. 340 p .


CALIFORN IA SENAT E.1 963 . Eff ect of the sea otter on the aba lon e resource . Sen ate Perman en tFactfin di n g Committee on Natura l Resources, Subcommittee on sea otters,Hearin g, S an Luis Obispo , Nov. 1 9 , 1 963 . 1 48 p . (Processed . )

1 965 . T he sea otter an d i ts effect upon the abalon e resource [Section 1 ,

Chapter 7,pp . 1 29 In Third Progress Report to the Legislature,

1 965 Regular Session . Sen ate Perman en t Factfin di n g Committee on

Natural Resources ( Sacramen to ) . 1 44 p .

CH APS K II , K . K .

1 952. Ag e determin ation of some mamma ls accordin g to bon e microstructure .

( In Russian . ) Journ a l In stitute Natura l Scien ces, Moscow, IzvestiyaEstest iven n on auchn og o In stituta imen i P.S . Lesg a f ta , vo l . 25 , p . 47—66 .

Cocxs, A . H .

1 881 . Notes on the breeding of the otter . Proceedin gs, Zoologica l Society of

Lon don , p . 249—250.

COMMERCIAL F IS H ERIES REVIEW.

1 964a . Sea otter population survey. Vo l . 26 , NO . 4, p . 1 2—1 3 .

1 964b . S ea otter population survey con tinued . Vol . 26 , NO . 5, p . 1 3 .

1 9640. S ea otter population determin ed by cen sus. Vol . 26,No . 8 , p . 1 5 .

COWAN,I . MoT . , an d C . J . GUIGUET .

1 956 . T he mamma ls of British Columbia . British Columbia Provi n cialMuseum, Han dbook No . 1 1 . 41 3 p .

Cox, K . W .

1 962. Ca liforn ia aba lon es, Family Ha liotidae . Resources Agen cy of Ca lif or n i a Departmen t of F ish an d Game, F ish Bulletin No . 1 1 8. 1 33 p .

DALL, W . H .

1 870. Alaska an d i ts resources. Sampson Low, Son , an d Marston ,Lon don .

628 p .

DUKES , H . H .

1 943 . T he physiology of domestic an ima ls. Comstock Publishin g CO . Ithaca ,

N.Y. 5th ed. revised .EBERT

,EARL E .

1 968 . A food habits study Of the southern sea otter , En hydra l utr i s n erei s .

Ca liforn ia F ish an d Game,vo l . 54, NO . 1 , p . 33—42.

ELLIOT T , H . W .

1 875 . A report upon the con dition of affa irs i n the territory of Alaska .

Governmen t Prin tin g Office , Washin gton , D C . 277 p .

ES SAPIAN , F . S .

1 953 . T he b irth an d growth of a porpoise. Natura l H istory, vo l . 62, p . 392.

EVERMANN , B . W.

1 923 . Marin e life of the Pacific . Commonwea lth Club of Ca liforn ia , T r an sac

tion s,vo l . 1 8, No . 3 , p . 1 09 .

EYERDAM, W . J .

1 933 . S ea otters i n the Aleutian Islan ds. Journ a l of Mammalogy, vol . 1 4, No .

1 , p . 70—71 .

FAY, F . H .

1 958. Pacific walrus investigation s on St. Lawren ce Islan d , Alaska . AlaskaCooperative Wildlife Research Un it . 54 p . (Processed . )

F IS CUS , CLIFFORD H . , an d H IROS H I KAJ IMURA .

1 967. Pelagic fur sea l investigation s, 1 965 . U. S . F ish an d Wildlife Service ,Specia l Scien tific Report— F isheries, No . 537. 42 p .


G . BAINES , an d F . WILKE .1 964. Pelagi c fur sea l investigation s. U . S . F ish an d Wildl ife Service,Specia l Scien tific Report— F isheries NO . 475 . 59 p .

F IS H ER, EDNA M .

1 939 . Habits of the southern sea otter. Journ a l of Mamma logy,vol . 20,

No. 1 , p . 21 —36 .

1 940a . Early life of a sea otter pup . Journ a l of Mamma logy, vol . 21 , NO . 2,

p . 1 32—1 37.

l 94ob. T he sea otter past an d presen t . Proceedin gs S ixth Pacific Scien ceCon gress, NO . 3 , p . 223—236 . Un iversity of Ca liforn ia Press, Berkeley.

1 941 a . Prices of sea otter pelts. Ca liforn ia F ish an d Game,vol . 27, No .

4, p . 261—265 , October .l 94l b . Notes on the teeth Of the sea otter . Journ a l of Mamma logy

,vol .

22, NO . 4, p . 428—433 , November .1 942. Osteology an d myology of the Ca liforn ia river otter . Stan fordUn iversity Press. 66 p .

F ISH ER, H . I .1 957 . Footedn ess i n domestic pigeon s. Wilson Bulletin , vol . 69 , p . 1 70—1 77 .

FISLER, G. F .

1 962 . Ingestion of sea water by Per omyscus man i cu l a tus. Journ a l of Mam

ma l og y, vol . 43 , No . 3 , p . 41 6—41 7.

Fox, D . L .

1 953 . An imal Bi och r omes. Cambridge Un iversity Press, p . 1 95. [Footn oteby Dr . E . M . Scott con cern in g the purple p igmen t of sea otter bon es, p .

FRIEDMANN,H . ,

an d M . DAVIS .

1 938.

“Left-han dedn ess”i n parrots. Auk , vo l . 55, p . 478—480.

GENTRY,R. L. , an d R . S . PET ERSON .

1 967. Un derwater vision of the sea otter . Nature, vo l . 21 6, p . 435—436 .

GILBERT , P . W . (Editor ) .

1 963 . Sharks an d surviva l . D .C . Heath, Boston . 578 p .

GOLODOFF, INNOKENTY.

1 966 . T he last days of Attu Village. [As told to Karl W . Ken yon .] AlaskaSpor tsman , vol . 32, No. 1 2, p . 8—9 .

GRIBK OV, P. F .

1 963 . O r asp r ostr an en n mor skoi vydry p o p ober ezh ’yu K amchatsk ogo poluostr ova . [Dispersion of the sea otter a lon g the coa st of the Kamchatkapen in sula .] In Vop r osy g eog r afii K amchatk i . [Problems on the geographyof Kamchatka .] K amchatsk aya Pravda , Petropavlovsk-K amchatsk i i , vol .

1 , p . 68—71 .

GULIN,V.

1 952. Neobychnyzyver ’n a chukotka [Unusua l mamma l i n Chukotka ] .

[Torch] (Moscow ) , vol . 50, p . 31 , i llus.

HALL, E . RAYMOND.

1 945 Chase Littlejohn , 1 854—1 943:Observation s by Littlejohn on hun tin gsea otters. Journ a l of Mamma logy, vol . 26, No . 1 , p . 89—91 .

an d KEIT H R. KELSON .

1 959 . T he mamma ls Of Nor th America , vol . 2, p . 949—950. Ron a ld Press CO . ,

New York.



KENYON , K . W .

1 959 . T he sea otter . Smithson ian Repor t f or 1 958, publication 4364, p .

399—407.

1 961 . Birds of Amchitka Islan d, Alaska . Auk,vol . 78, No. 3 , p . 304—326 .

1 964. Wildlife an d historica l n otes on S imeon of Islan d, Alaska . Murrelet,vol . 45, NO . 1 , p . 1 —8.

l 965a . Food Of harbor sea ls at Amchitka Islan d, Alaska . Journ a l Of Mam

ma l og y, vol . 46, No . 1 , p . 1 03—1 04.

1 965b . Aeria l survey Of sea otters an d other marin e mamma ls, AlaskaPen in sula an d Aleutian Islan ds, 1 9 April to 9 May 1 965 . U. S . BureauOf Sport F isheries an d Wildlife, Seattle , Wash . 52 p . (Processed. )

an d D . L . SPEN CER.

1 960. Sea otter population an d tran splan t studies i n Alaska , 1 959 . U.S .

F ish an d Wildlife Service, Special Scien tific Report— Wildlife, No . 48.

29 p .

an d V. B . SCH EFFER.

1 962. Wildlife surveys alon g the n orthwest coast of Washin gton . Murrelet,vo l . 42, No . 3 , p . 29—37 .

C . E . YUNKER, an d I . M . NEWELL.

1 965 . Nasa l mites (Ha larachn idae ) i n the sea otter . Journ a l of Parasitology,vol . 51

,No . 6 , p . 960.

VICT OR B . SCH EFFER, an d DOUGLAS G . CH APMAN .

1 954. A population study of the Alaska fur -sea l herd . U.S . F ish an d WildlifeService, Specia l Scien tific Report—Wildlife , NO . 1 2 . vi 77 p . (Pr ocessed . )

KEYES , MARK C .

1 963 . Necrotic hemorrhagic en teritis i n a sea l . Sma ll An ima l Clin ician ,vol .

3 , NO . 1 1 , p . 627.

K ING, JUDIT H E .

1 964. Sea ls Of the world . British Museum (Natura l H istory) , Lon don . 1 54 p .

KIRKPATRICK , C . M. , D . E . S TULLK EN , an d R. D . JONES , JR.

1 955 . Notes on captive sea otters. Journ al Arctic In stitute of NorthAmerica , vo l . 8, No. 1

,p . 46—59 .

K LUMOV, S . K .

1 957. [Breedin g places Of the fur sea l (Ca l l or h i n us ur si nus ) an d areasin habited by the sea otter (En hydr a l u tr i s ) i n the Kurils an d a ten tativeestimation of their numbers ] Dok l ady Ak ademy Nauk S S SR, vo l . 1 1 7,

No . 1 —6, p . 1 53—1 56 . Tran slated an d published by American In stitute of

Biologica l Scien ces.

KROG, J .

1 953 . Notes on the birds of Amchitka Islan d, Alaska . Con dor, vol . 55, p .

299—304.

LACK, D .

1 954. T he n atura l regulation of an ima l numbers. Oxford at the C laren donPress. 343 p .

LANE, F . W.

1 946 . Right an d left i n an ima ls. ZOO Life , vol . 1 , p . 30—31 .

LANG, T . G. , an d K . S . NORRIS .

1 965 . Swimmin g speed of a Pacific bottlen ose porpoise . Scien ce , vo l . 1 51 , p.

588—590.


LAUGH LIN , W . S .

1 963 . T he earl iest Aleuts. An thropologica l papers of the Un iversity of

Alaska , vol . 1 0, No . 2, p . 73—1 36 .

LEE, C . F .

1 948 . Thiamin ase i n fishery products:a review. Commercia l F isheries Review,

vol . 1 0, No. 4, p . 7—1 7.

LENS INK,C . J .

1 958 . Report on sea otter surveys 6 May to 28 September 1 957 . UnpublishedReport, 6 1 p . , i n F ish an d Wildlife Service F iles.

1 960. Status an d distribution of sea otters i n Alaska . Journ a l of Mam

ma l og y, vo l . 41 , No . 2, p . 1 72—1 82.

1 962. T he history an d status of sea otters i n Alaska . A thesis submittedto the Faculty of Purdue Un iversity i n partial fulfil lmen t of the requiremen ts f or the degree of Doctor of Philosophy. Un published , copy i n F ishan d Wildlife Service files.

LIERS,E . E .

1 951 . Notes on the river otter (Lutra can aden si s ) . Journ a l of Mammalogy,vol . 32, No. 1 , p . 1 —9 .

LOY, C . L .

1 940. Sea otter report Of Amchitka Islan d , Alaska ,July 1 0, 1 939 to January

1 5, 1 940. Un published report i n F ish an d Wi ldlife Service files.

an d O . A . FEIDEN .

1 937 . S ea otter survey of Amchitka Islan d , Alaska , July 1 1 to September1,1 937 . Un published report i n F ish an d Wildlife Service files.

LUT KE,F .

1 835 . Voyage autour du mon de dan s l es an n ees 1 826 , 1 827 , 1 828, et 1 829 .

Paris, F irmin D idot Freres, 3 vols. an d atlas.

MANGEN , J . B. , an d G . RIT T ER.

1 940. Amchitka Islan d Report. U .S . F ish an d Wildlife Service, un published .

MARAK OV, S . V .

1 963. Relic of n ature or exploitable species?— Fate of the K oman dor sk n

sea otter . Pr i r oda No . 1 1 , p . 79—83 , Moscow. [Tran slated by U.S . De

p a r tmen t Of Commerce, Office of Techn ica l Services, Join t Publica tion sResearch Service , Washin gton , D C ]

1 965 . T he presen t status of the Koman dorski population Of En hydr a l utr i sL . an d prospects f or i ts practica l usage . In Marin e Mamma ls, E . N .

Pavl ovsk i i , B . A . Zenkovi ch , et a l ., (Editors) . [p . 21 2 Tran slated

by Nan cy McRoy, April 1 966 .

MAYNARD, LT . WASH BURN .

1 898 T he sea otter [vo l . 3 , p . 300 In Sea l an d sa lmonfisheries an d gen era l resources Of Alaska . U.S . Treasury Departmen t,4 volumes, published 1 898;Mayn ard’s con tribution dated 1 874. ( 55th

Con gress, l st session ,House Documen t 92, p ts. 1

MCCANN , CH ARLES .

1 955 . Observation s on the polecat (Pu tori us p utorius Lin n . ) i n New Zea lan d .Records of Domin ion Museum,

vol . 2,pt. I I I , p . 1 51 —1 65 .

MCCRACKEN , HAROLD.

1 957. Hun ters of the stormy sea . Doubleday, Garden C ity, N .Y. 3 1 2 p .

MCLAREN , I . A .

1 960. Ar e the Pin n ipedia byp hyl et i cs ? Systematic Zoology, vo l . 9 , NO . 1 ,

March , p . 1 8—28.


MCLAUGH LIN , PAT SY A .

1 963 . Survey Of the ben thic in vertebrate faun a of the eastern Berin g S ea .

U.S . F ish an d Wi ldlife Service, Specia l Scien tific Report —F isheries, NO .

401 . 75 p .MCLEAN

,J . H .

1 962. Sublittora l ecology of kelp beds of the open coast area n ear Carmel,Ca liforn ia . Biologica l Bulletin , vol . 1 22, NO . 1 , p. 95—1 44.

M ILLER, P. , an d L . G . M ILLER.

1 967 . Lost heritage of Alaska:T he adven ture an d ar t of Alaskan coastalIn dian s. World Publishin g CO . , C levelan d, Ohio . 289 p .

M ILLER, G . S . , an d R . KELLOGG.

1 955. List of North American recen t mamma ls. U.S . Na tion a l Museum,

Bulletin 205. 954 p .M IT CH ELL, EDWARD.

1 966 . Northeastern Pacific Pleistocen e sea otters. Journ a l F isheries Research Board Of Can ada

,vol . 23 , NO . 1 2, p . 1 897— 1 91 1 .

MURIE, O . J .

1 940. Notes on the sea otter . Journ a l Of Mamma logy, vol . 21 , No . 2, p .

1 1 9- 1 3 1 .

1 959 . Faun a of the Aleutian Islan ds an d Alaska Pen in sula . U.S . F ish an d

Wildlife Service, North American Faun a , NO . 61 . 406 p .

NEILAND, K . A .

1 962. Alaskan species of acan thocepha lan genus Cor yn osoma Luehe , 1 904.

Journ a l of Parasitology, vol . 48, p . 69—75.

NIKOLAEV, A . M .

1 960. O di n ami ke chi sl en n ost i K a l an ov v S S SR [Chan ge i n the number ofsea otter i n the USSR] . Trudy Sakhalin sk

,K omp l ek sn . Nauchn .

-Issl ed .

In st. 9,1 08—1 21 . Referat . Zur .,

Biol . , 1 962 No . 1 41 256 . [Tran slated ab

stract seen . ]1 961 . O . r asp r ostr an en n chi sl en n ost i i bi ol og u k a l an ov. [T he biology an d

population spread of the sea otter . ] Trudy S oveshchan i i Ikhthi ol .

Kommiss . Akad . Nauk S SSR 1 2, p . 21 4—271 .

1 965a . T he status of the stock Of Kuri le sea otters an d fur sea ls an d

measures Of their reproduction . In Marin e Mamma ls, E . N . Pavl ovsk i i ,

B . A . Zenkovi ch , et a l ., (Editors) . [R 226—230 ] Tran slated by Nan cy

McRoy, Apr i l 1 966 .

1 965b. On the feedin g of the Kurile sea otter an d some aspects of theirbehavior durin g the period of i ce . In Marin e Mamma ls, E . N . Pavl ovsk i i ,

B . A . Zenkovi ch , et a l ., (Editors) . [R 231 Tran slated by Nan cy

McRoy, April, 1 966 .

an d V. A . SK ALK IN .

1 963 . O p i tan i i Kuril’ sk ikh ka l an ov . [T he diet of the Kamchatka sea

Otter i n the Kurile Islan ds ] Tr . Sakha lin sk. K omp l ek snyi Nauchn .-Issl ed.

In st. 1 4,p . 54—78.

NOVIKOV, G . A .

1 956 . Predatory mamma ls of USSR faun a . ( In Russian . ) Moscow, Academyof S cien ces Of USSR. 294 p .

NOZIK OV, N .

Russian voyages aroun d the world . Hutchin son Co . Ltd . Lon don .

1 65 p . [Tran slated from Russian by E . an d M . Lesser . ] NO publicationdate i s given .



ANCEL M . JOH NSON , RAYMOND E . ANAS , an d DOUGLAS G. CH APMAN .

1 966 . Fur sea l in vestigation s, Pribilof Islan ds, Alaska , 1 965. U.S . F ish an d

Wildlife Service,Specia l Scien tific Report— F isheries, No . 536 . 45 p .

SCAMMON , C . M .

1 870. T he sea otters. American Natura list, vol . 4, No . 2,p . 65—74.

SCAPINO, ROBERT P .

1 965 . T he third join t of the can in e jaw. Journ a l of Morphology, vol . 1 1 6,No. 1 , p . 23—50.

SCH EFFER, V . B .

1 940. T he sea otter on the Washin gton coast. Pacific Northwest Quarterly,vol . 3 , p . 370—388 .

l 95oa . Growth layers on the teeth Of Pin n iped ia as an in dication Of ag e .

Scien ce , September 1 5, vol . 1 1 2, No . 2907, p . 309—31 1 .

l 95ob . T he food of the Alaska fur sea l . U .S . F ish an d Wildlife Service,Wildlife Leaflet 329 . 1 5 p .

1 951 . Measuremen ts of sea otters from Western Alaska . Journ al of Mamma l ogy, vol . 32, No . 1 , p . 1 0—1 4.

1 955. Body size with relation to population den sity i n mamma ls. Journ alof Mammalogy, vo l . 36, No . 4, p . 493—5 1 5 .

1 958. Lon g life of a river otter . Journ a l of Mamma logy,vol . 39 , No. 4,

November, p . 591 .

1 960. We ights of organ s an d glan ds i n the n orthern fur sea l . Mamma lia ,vol . 24, No . 3

,p . 476—481 .

1 962. Pelage an d surface topogr aphy of the n orthern fur sea l . U.S . F ishan d Wildlife Servi ce, North American Faun a , NO . 64. 206 p .

1 963 . Book review:“T he n atura l history Of the Lewis an d Clark expedition ,

edited by Raymon d Darwin Burroughs. Pacific Northwest Quarterly, vol .54, NO . 2, p . 80—81 .

1 964. Estimatin g abun dan ce of pelage fibres on fur sea l skin . Proceedin gsZoologica l Society of Lon don

,vol . 1 43 , par t 1 , p . 37—41 .

an d ANCEL M . JOHN SON .

1 963 . Molt i n the n orthern fur seal . U . S . F ish an d Wildlife Servi ce , SpecialScien tific Report— F isheries, No . 450. 34 p .

an d BERTRAM S . KRAUS .

1 964. Den tition of the n orthern fur sea l . F ishery Bulletin , vol . 63 , No. 2, p .293—342.

an d FORD WILKE.1 950. Va lidity Of the subspecies En hydr a l utr is n er eis , the southern sea

otter. Journ a l of the Washin gton Academy of Scien ces, vol . 40, No . 8, p .269—272, August 1 5.

SCH UMACH ER,G . H .

1 96 1 . Funktion elle Morphologie der Kaumuskulatur . Gustav F isher , Jen a .

S H IDLOVSKAYA, N . K .

1 947 . [Direction s f or the feedin g an d care of the ma le sea otter , p . 225

In Ka lan ,by I. I . Barabash-Nikiforov, Soviet Mi n i str ov RSFSR.

Glavn oe up r avl en i e p o zap ovedn ikam , p . 263—266 . [Tran slated fromRussian by Dr. A . Birrou an d Z . S . Cole . Published for Nation a l Scien ceFoun dation by Israel Program f or Scien tific Tran slation s, Jerusa lem,

1 962. 227 p . , illus. ]


S IN HA, A . A .

1 965 . Morphology of the fema le reproductive organ s of sea ottersE n hydra l u tr is Un iversity of M issouri , Ph .D . , 1 965 , Zoology (Unpublished ) .

C . H . CONAWAY, an d K . W. KENYON .

1 966. Reproduction i n the female sea otter . Journ a l of Wildlife Man agemen t, vol . 30, No . 1 , p . 1 21 —1 30.

an d H . W. MOS SMAN .

1 966 . Placen tation of the sea otter . American Journ al Of An atomy , vol .

1 1 9 , No . 3 , p . 521 —554.

an d C . H . CONAWAY.

1 968 . T he ovary of the sea otter . An atomica l Record , vo l . 1 60, p . 795—806 .

SLIJPER, E . J .

1 956 . Some remarks on gestation an d birth i n cetacea an d other aquaticmamma ls. H va l radets Sk r i f ter , vo l . 41 , p . 1 —62.

1 962. Wha les. Basic Books Publishin g Co . 475 p . En glish tran slation of

Wa l vi ssen , D . B . Cen ten’s, Ui tg ever smaatschap p ij, Amsterdam.

SNOW , H . J .

1 91 0. In forbidden seas. Edward Arn old , Lon don . 303 p .

S T EJNEGER, L .

1 936 . Georg Wilhelm Steller . Harvard Un iversity Press. 623 p .

ST ELLER, G . W .

1 751 . De Bestn s marin is. Novi Comm . Acad . S ci . Pet r op ol i tan ae , vo l . 2, p .

289—3 98, 3 p l s. [En glish tran slation by Wa lter M iller an d Jen n ie Emerson Miller (part 3 , p . 1 79 In T he f ur sea ls an d fur sea l islan ds

see Jordan an d Clark , 1 898—1 899 , U. S . Treasury Departmen t, Documen t

ST ILES , W. B .

1 953 . T he sea otter (En hydra mari n a ) . Un published manuscript, F ish an d

Wi ldlife Service files, Washin gton , D C. 1 9 p .

S TULLK EN , DONALD E . , an d C . M . KIRKPATRICK .

1 955 . Physiological investigation of captivi ty morta lity i n the sea otter(En hydra l utr is ) . Tran saction s 2oth North American Wildlife Con feren ce, p . 476—494.

SVERDRUP, H . U M . W . JOH NSON ,an d R . H . FLEMING.

1 942. T he ocean s. Pren tice-Ha ll , En glewood C liff s, N .J 1 087 p .

SWICEGOOD, Lcdr . S . P .

1 936 . Amchitka sea otter survey expedition . Un published memo fromComman din g Officer, U.S . Coast Guard Cutter Che l an .

, 3 1 August 1 936 .

5 p . U.S . F ish an d Wildlife Service files.

TAYLOR, WALT ER P.

1 9 1 4. T he problem Of aquatic adaptation i n the Carn ivora , as illustratedi n the osteology an d evolution of the sea-otter . Un iversity Ca l iforn iaPublication , Bulletin Departmen t of Geology, vol . 7, p . 465—495 , 1 5 textfigures. (p . 468— drawin g of skeleton i n stan ding attitude . )

T H EN IUS, E . , an d H . HOFER .

1 960. Stammesgeschichte der S aug et i er e . Sprin ger , Berlin . 322 p .

U . S . BOARD ON GEOGRAPH IC NAMES .

1 963 . Decision s on geographic n ames i n the Un ited States. Decision list No .

6302. 81 p .


U . S . BUREAU OF F ISH ERIES .

1 906—1 1 . T he commercia l fisheries of Alaska i n 1 905 (An nua lreports. )

1 91 2—42. Alaska fisheries an d fur -sea l in dustries i n 1 91 1

(An nua l reports. )1 929 . Laws an d regulation s for the protection Of fur sea ls an d sea otters.

Departmen t of Commerce Circular 285, 2d ed . Alaska F isheries Service .

1 0 p .

VORONOV,V . G.

1 960. Opyt ot l ova k a l an ov (En hydr a lutr i s L . ) n a Kuril sk ikh ostr ovakh .

[Experimen ta l trapp in g of sea otters (En hydr a l u tr i s L . ) i n the KurileIslan ds ] Trudy Sakha lin sk. K omp l ek sn . Nauchn .

—Issl ed. In st . 9 , p . 1 22

1 29 . 1 960 Referat . Zhur.,Biol . 1 962, NO . 1 4 1 222. (Abstract Of tran slation

on ly seen . )1 965 . Presen t problems i n the study an d in dustria l use of the Kurile sea

otter. In Marin e Mamma ls, E . N . Pavl ovsk i i , B . A . Zen kov i ch , et a l .

(Editors ) . [p . 221 —225 ] Tran slated by Nan cy McRoy, April , 1 966 .

1 967 . T he effect of tsun ami on sea otter population s. Pr i r oda (Nature ) , No.

8, p . 70—72 .

WARREN , J . M .

1 953 . Han dedn ess i n the Rhesus monkey. Scien ce,vol . 1 1 8, p . 622—623 .

WILDMAN , A . B .

1 954. T he microscopy of an ima l textile fibres,in cludin g methods f or the

complete an a lysis of fibre blen ds. Wool In dustries Research Association ,

T or r i don , Headin gley, Leeds. 209 p .

WILKE,F .

1 957 . Food of sea otters an d harbor sea ls at Amchitka Islan d . Journ a l ofWildlife Man agemen t, vo l . 21 , NO . 2, p . 241 —242.

WILLIAMS , C . S .

1 937 . Notes of the distribution an d food habits of the American sea otter,1 936 . Un published man uscript

,F ish an d Wi ldlife Service files.

1 938. Notes on food of the sea otter . Journ a l Of Mamma logy, vol . 1 9 , No . 1 ,

p . 1 05—1 07.



26 Ju ly to 5 October . Aleutian Islan ds. At Amchitka Islan d observe sea

otters;experimen ts with methods of holdin g otters i n captivity an d Oh

ta in in g a food supply f or them. (Ken yon . )1 0 October . Seattle, Wash . Place two sea otters i n Woodlan d Park ZOO .

1 956

5 May to 26 Ju ly . Aleutian Islan ds. At Amchitka Islan d , field studies Of seaotters an d further experimen ts with feedin g an d ho ldin g i n captivity.

(Ken yon an d Len si n k . )30 Ju ly. Seattle, Wash . P lace two sea otters i n Woodlan d Park ZOO .

1 957

6‘ May to 28 S ep tember . Alaska survey. From Kodiak Islan d to Adak Islan d,field studies of population size an d distribution of sea otters were con ductedusin g boats an d a ircraft. (C . J . Len si n k rema in ed i n the field durin g theen tire period . R . D . Jon es, R . Lopp, D . L . Spen cer, W . Troyer, an d W ilkeparticipated with h im i n diff eren t areas. )

1 October to 1 1 D ecember . Aleutian Islan ds. Amchitka Islan d , field studies Ofotters an d further experimen ts i n captive care an d feedin g of otters. (K . L .

Binkley, Ken yon , an d H . R . K r ear . )1 4 D ecember . Seattle, Wash . P lace two sea otters i n Woodlan d Park Zoo .

1 958

1 0—2 1 Mar ch . Ca liforn ia . Search f or sea otters i n coasta l areas an d at San taRosa an d San M iguel Islan ds of the Chan n e l Islan ds group aboard theM/V T r i n i ty. (W . J . Barmore an d Ken yon . )

1 959

1 4—21 Januar y. Aleutian Islan ds. Adak Islan d . Con duct two experimen ta laeria l surveys of sea otters usin g U.S . Navy UF—l a ircraft. F light time

hours. (Ken yon . )21 Jan ua r y to 20 May . Aleutian Islan ds. At Amchitka Islan d , field stud ies

of sea otters an d experimen ts with otters i n captivity were con ducted.(Ken yon . )

1 9 May . Aleutian Islan ds. Aeria l survey of sea otters from Attu to AmchitkaIslan d usin g DC—3 a ircraft. F light time: hours. (Ken yon , T . Smith , D . L .

Spen cer, an d J . Tilford . )20May. Pribi lof Islan ds tran splan t. F ly seven sea otters to St. Paul Islan di n a DC—3 a ircraft an d liberate them there . F light time: hours.

21 May. St. Paul Islan d . Observation s of l iberated otters.

21 —28 May. Aleutian Islan ds. Aeria l survey Of sea otters from Semi sop ochn oi

Islan d eastward to Herbert Islan d i n th e Islan ds of Four Moun ta in s, i nelusive, usin g a DC—3 a ircraft . F light time: 1 9 hours. Tota l flight timeen tire Operation : hours . (Ken yon , Smith , Spen cer, an d Tilford. )

1 3 Ju ly . Washin gton State . Aeria l recon n aissan ce Of coasta l waters a lon gouter coast of the O lympic Pen in sula usin g a U.S . Coast Guard UF—2 a i r

craft . F light time:3 hours. (G . Eddy, Ken yon , F . Richardson ,an d V . B .

Scheff er. )1 4—1 8 Ju ly. Washin gton State . Boat survey of rocks an d islets Off the outer

coast of the Olymp ic Pen in sula . (Eddy, Ken yon , R ichardson , an d Scheffer . )


1 960

2—5 March . Aleutian Islan ds . Aerial surveys of sea otters from the Islan dsof Four Moun ta in s to the San dman Reefs in clusive, usin g a DC—3 a ircraft.Tota l flight time: hours. (Kenyon , D . W . Rice, Smith , an d Spen cer . )

30May to 1 3 Ju ly. Islan d surveys (surface on ly ) i n Alaska . F ield studies of

sea otters at S imeon of , Little K on i uJI , Heren deen , an d Naga i i n the Shuma

g i n Islan ds;at Caton an d San ak Islan ds;a t T i g a l da Islan d an d i n the

waters Off Un imak Islan d i n the Aleutian Islan ds, an d a t Amak Islan d;tran sportation between islan ds was furn ished by the M/V Wi n dwar d . (C . H .

F iscus, Ken yon , an d the late T . O’Br i en . )

1 961

3 Ju ly to 1 August . Comman der Islan ds. F ield Observa tion s of sea otters a t

the Soviet con trolled islan ds of Medny an d Berin g;tran sportation aboardthe USSR ships Ore l an d S ter egush ti an d the U. S . FWS vesse l Pen gui n I I .

(Kenyon , K . Ni g g o l , A . Y . Rop p e l , an d Wilke . )2 1 October to 5 November. Aleutian Islan ds. An a ttempt to harvest an d study

sea otters i n the outer Aleutian s was n egated when a U.S . Navy UF—2 a i r

craft carryin g the field party crashed on 27 October at Adak Islan d durin gan aerial survey. (L . W . Croxton an d Ken yon , an d D . C isn ey, kil led i ncrash . )

1 962

1 4 Jan ua r y to 4 Ap ri l . Aleutian Islan ds. At Amchitka Islan d con duct fieldobservation s Of sea otters an d co llect specimen s from State of Alaska kill Of1 50 sea otters. (Croxton , Jon es, an d Ken yon . )

29 March an d 5— 1 0 Ap ri l . Aeria l surveys i n Alaska . Aeria l survey of sea

otters i n the Aleutian Islan ds from Kiska Islan d to Amak Islan d;the San akIslan ds;San dman Reefs;Shumag i n Islan ds;an d a reas a lon g the south coa stof the Alaska Pen in sula to Ku l i ak Poin t. Total flight time: hours . (J .

J . Burn s, Ken yon , J . S . Kobza , Smith , an d Spen cer . )8—1 1 S ep tember . Washin gton State . In vestigate reports of possib le sea ottersightings a lon g the outer coast of the O lympic Pen in sula . (Ken yon . )

26—29 October . Alaska State biologists ki ll 24 sea otters on Amchitka . (Cr ox

ton an d E . K l i n khar t . )2 7—28 October. Washin gton State. Investigate repor ts Of possible sea otter

sightings i n the S an Juan Islan ds of Puget Soun d aboard the M/V T r i n i ty .

(Ken yon , Rice, an d Scheffer . )

1 963

4March to 1 3 Ap ri l . Aleutian Islan ds. At Amchitka Islan d col lect specimen s

from 303 sea otters taken by State of Alaska biologists. (J . E . Burdick ,E . K l i n khar t , an d J . Van ia . )

1 - 22 Ju ly. Aleutian Islan ds. F ield observation s of sea otters at Adak Islan da n d Bul di r Islan d i n the outer Aleutian Islan ds. Tran sporta tion from Adakto Bul di r aboard USCGC C l over, return on USCGC K l ama th . (V . D . Bern s,E . L . Boeker, Jon es, Ken yon , A . E . Peden , an d M . Zhan . )

3 1 Ju ly to 3 August. Aleutian Islan ds. At Amchitka Islan d 20 sea otterswere taken by State of Alaska b io logists an d specimen s furn ished to the

Bureau of Sport Fisheries an d Wi ldlife (E . K l i n khar t an d J . Van ia ) .


1 964

In Seattle workin g on 1 963 Specimen s an d an a lyzin g accumulated field data .

1 965

23 Jan uar y to 1 0 Febr uar y. F ie ld Observation s Of coasta l an d islan d areas OfBaja Ca liforn ia , Mexico to examin e sea otter hab itat an d search f or possiblesurvivin g an ima ls. (D . W . Rice, D . Ll uch B. , an d Ken yon . )

1 8 Ap r i l to 9 May . Aeria l survey Of sea otters i n the Aleutian Islan ds, ColdBay to Attu Islan d . (E . K l i n khar t , D . L . Spen cer, T . A . Smith , J . Kin g, an dKen yon . )

23 October to 9 November . At Amchitka Islan d . Mon itor effects of AECDOD Lon g Shot n uclear b last. Aeria l surveys an d surface Observation s.

(E . K l i n kha r t , D . L . Spen cer, T . A . Smith , R . Tremb lay, an d Ken yon . )9 November to 3 D ecember . Tran sport ma le sea otter (Gus ) aboard M /VComman der from Amchitka to Seattle . (Ken yon , Capt. C liff An dersen . )

1 966

Work i n Seattle on specimen s an d accumulated data .


INDEX

Man y geographic location s ( islan ds, poin ts, passes, etc. ) men tion ed i n the

text a r e omitted from the in dex . T hey may be foun d i n the text un der theislan d groups (An dr ean of Islan ds, Fox Islan ds, etc. ) or adjacen t geographicareas ( such as Alaska Pen in sula ) , which ar e in cluded i n the in dex . In gen era l ,scien tific n ames of organ isms ar e omitted from the in dex but ar e in cludedin the text. An attempt was made to avoid repea tin g i n the in dex what may

be foun d i n the table of con ten ts.

aba lon e (H a l i otis ) , 1 08, 1 29 , 1 86.

aba lon e fishermen , 1 30.

Abeg g l en , C . E . , 26 1 , 326 .

Adak Islan d , Alaska , 1 65—1 66.

adaptability, 303 .

AEC (Atomic En ergy Commission ) ,340.

aeria l photography, 1 45 .

aeria l survey (see survey ) .Ag at tu Islan d , Alaska , 1 47 .

agin g, premature, teeth , 248.

a ircraft tran sport , 3 1 6—3 1 7 .

Akutan Village, Alaska , 1 71 .

A l a ria (see a lso kelp ) , 57 .

Alaska Departmen t of Fish an d Game,iv, 39 , 1 57.

Alaska :Pen in sula , 1 77—1 78 .

population s Of sea otters, 1 37— 1 83 .

southeastern , 1 83 .

Statehood Act , 2.

Aleutian Islan ds, Alaska , 5 , 1 33 , 1 47

1 75 , 337—340.

Alexan der Archipelago , Alaska , 57,

1 83 .

a lgae (see a lso kelp )corallin e, 1 09.

r ed an d brown , 1 1 1 .

Alizarin r ed S dye, 53 .

Allan son ,A . , 1 86 , 326 .

Alles, J . J . , ii i .Amak Islan d , Alaska , 1 72—1 75.

Amch itka Islan d , Alaska , 1 5 1 —1 57 , 337 ,

338 .

Amlia Islan d , Alaska , 1 67—1 68.

An acapa Islan d , Calif. 1 86 .

An as, R 324, 334.

An dersen , C. , 340.

An derson , H . , 1 30.

An dr ean of Islan ds, Alaska , 1 60—1 68.

Afi o Nuevo Islan d , Ca lif. , 1 87.

An thon y, A . W. , 1 87, 326 .

an tib iotics, 31 5.

Aquarium, Tacoma , Wash . (Poin t Defian ce ) , iv, 39 , 1 05 , 300, 3 1 6 .

Ar g obucci num , 1 1 8.

A r sen i ev , V . A . , 1 87 .

Ashbrook , F . G. , 41 .

Asia , 4.

At i g ar u Poin t, Alaska , 1 33 .

Atka Islan d , Alaska , 1 66—1 67.

Atka mackerel , 1 02.

Atka Vi llage , Alaska , 1 66 , 1 67.

Attu Islan d (Near Islan ds ) , Alaska ,

1 47—1 49 , 320.

auction , public, 3 .

Augustin e Islan d , Alaska , 1 79.

automobi le tran sport, 3 1 6 .

Ba iley , V. , 1 85 , 326 .

Ba in es, G. , i i i , 1 46 , 243 , 328.

Ban fie l d, A . W . F. , iii , 1 83 .

Barabash-Nikiforov, I . I 5 , 66 , 70,

1 09 , 1 1 1 , 1 32, 1 33 , 1 35 , 1 87 , 1 88, 21 8,

22 1 , 235 , 238, 239 , 242, 279 , 285, 287,

326 .

Barmore, W . J . , 338.

Bauer , R . D . , 52, 326 .

Bea ls , F . L. , 1 48, 1 52, 1 56 , 1 57 , 326 .

beddin g, dry , 303.

Bee , J . W . , 1 33 , 326 .


behavioradoption , 1 01 .

beggin g, 300.

dayt ime, 303 .

depen den ce of youn g, 87—89 .

divin g of youn g, 98.

exercise of captive, 304.

family ties, 223- 224.

feedin g, 300, 304.

food gatherin g by youn g, 98.

frustration , 82—85.

gregariousn ess, 224.

groomin g, 39, 73 , 74—76, 1 00, 303304.

i n ter sp ecific strife, 1 02.

juven i les vs. adults, 221 —222.

ki llin g fish , 1 08.

matern a l:mother-youn g bon d , 91—94.

movin g youn g, 95.

segregation of mothers, 21 3 .

solicitude, 89—94.

n ighttime, 307 .

nursin g, 96.

play, 1 01 , 224.

poun dingchest, 82—86 , 300.

rock, 304—305 .

techn ique, 1 09 .

protective, 221 .

restin g, 99 , 303—305.

run n in g, 70.

season a l, 305 .

sleeping, 59.

stea lin g, 21 6, 220, 299 , 300—301 .

swimmin g of youn g, 98.

tamen ess, 300, 3 1 2.

wa lkin g, 70, 1 1 2.

washin g, 1 1 2.

Belkin , A . N. , 1 87, 1 89 , 326 .

Ben tley, W . W 1 87, 326.

Berin g Islan d , 1 , 1 88.

Berin g, V . , 1 35, 1 88.

Bern s, V. D . , i ii, 280, 339 .

Bezezekoff , A . , i ii , 1 71 , 288, 337.

Bezezek off , F. , iii , 1 71 , 337.

Binkley, K . L. , ii i , 272, 309, 31 6 , 31 7338.

Biologica l Structure, Departmen t of ,

Un iversity of Washin gton , 247.

Bixby Creek, Calif. , 1 86.

blin dn ess, 1 06 , 278.

2

blood quan tity, 30.

blubber, 6, 39, 1 05.

body (g en er a l description ) , 6 .

Boeker, E . L . , iii , 339.

Bon d , R. M. , 1 86.

bon esdamage, 51 .

fossi l , 4.

purp le, 1 1 1 .

wh ite, 1 1 1 .

Boo l oot i an , R . A . , mi , 1 86, 326.

Bristol Bay, Alaska , 1 73.

British Columbia , Can ada , 1 83—1 84.

Brooks, J . W. , i ii .Brosseau, C. , i ii, 39, 300.

Brown , D . V . , iii , 276, 277.

Bryan , W . F. , 73 .

Bucci n um, 1 1 8 .

Bul di r Islan d, Alaska , 1 50.

Bul di r Reef, Alaska , 67, 69 .

Burdick , J . E . , 1 1 1 , 339 .

Burn s, J . J . , 1 1 1 , 339 .

Burroughs, R. D . , 1 85, 326.

Buterin , M. , 321 .

cagin g, dry, 293 .

ca lculus, den ta l, 52.

Ca liforn ia Departmen t Of F ish an d

Game, 1 30.

Ca liforn ia,killin g sea otters, 282.

Ca liforn ia sea otter popula tion , 1 85

1 87.

Ca l iforn ia Sen ate, 1 30, 1 86 , 327.

Can ada , Nation a l Museum Of, 1 83 .

Can adian hun ters, 1 36 .

Can ton (see a l so Ch in a ) , 1 .

Cape Halkett, Alaska , 1 33 .

Cape Sagak , Alaska , 1 70.

Carlisle, J . G. , i ii , 1 86.

Carlson , C . E . , i ii .Carmel Cove, Ca lif. , 1 29 .

Carn ivora , 4.

Caton Islan d , Alaska (see San ak Islan ds ) .

cataracts, 261 .

Cedros Islan d , Mexico, 1 33 , 1 87.

cetacean , 4.

Chan n el Islan ds, Ca lif. , 1 86.

Chapman , D . G. , ii i , 225 , 241 , 243 , 261 ,267, 324, 330.

Chap sk i i , K . K . , 52, 327 .

Cher n abur a Islan d, Alaska , 1 76.



food— Con t.species listed, 1 1 6—1 1 7.

storage capacity, 1 1 2.

Food Scien ce P ion eer Researchoratory, 1 27 .

For z i at i , A . F. , 53 .

fossi l bon es (see bon es) .Fox, D . L. , 1 1 1 , 328.

Fox Islan ds, Alaska , 1 69—1 75 .

Friedman , H . , 82, 328.

Fr i den , O . A 1 52, 1 56 .

fulmar , 1 3 1 .

fur (see a lso pelt )color, 8, 9.

farm, 299.

31

22323331

:6 ’ 293 .

crushes sea otters, 1 81 .

wettin g Of, 29 1 .

in fluen ce on distribution , 1 33—1 35

tran sport, 1 82.

gastrolith 1 1 1 . Ichihara , T . , 52, 329.

Gen try, R. L. , 55, 59, 328. In dia , 4.

Gi lbert, P. W. , 279 , 328. in lan d watersGilmore, R . M. , ii i . Puget Soun d , 57, 1 84, 1 85, 339 .

Glaser , F 1 35. Southeastern Alaska , 1 83 .

Gol odoff , I . ,i ii, 1 47, 328, 337. Stra it Of Juan de Fuca , 5, 281 .

goose, Emperor, 1 03 , 1 3 1 . Islan ds of the Four Moun ta in s, Alaska ,Green go , R . E . , 1 84—1 85. 1 68—1 69, 339 .

green lin g, frin ged, 293 . in sulation (see fur ) .

Gr ibk ov, P . F 1 35 , 328 . in testin egroomin g (see behavior ) . perforated, 294.

growth: len g th , 26 .

adolescen t, 229—230. Izembek Bay, Alaska , 1 72, 1 73 .

pren ata l , 237.

Guada lupe Islan d, Mexico , 1 33 .

Gui guet , C . J . , iii , 1 84, 327 .

Gulin , V. , 1 35.

gull , glaucous-win ged, 63 , 1 03 .

Gun ther , E . , i ii , 1 84.

Gus ( captive otter ) , 39 , 298, 300,31 9, 340.

habitat, 6, 1 46—1 47.

H a l ar achn e, 1 03 , 292.

Ha ll, E . R. , 4, 66, 1 33 , 326 , 328.

Ha ll , K. R . L . , 83 , 85 , 1 08, 329 .

Hamilton , W. J Jr . , ii i , 237, 238,Han n a , G . D . , i ii , 1 22, 1 81 .

Han sen, H . P. , 1 1 0.

Han son , E . , 2 , 250.

Harbo , S . J . , iii .Harris, C . J . , 3 , 329 .

Hartt, A . C . , iii , 66 , 67, 68.K ag a l ask a Islan d , Alaska , 1 66 .

harvest, 2, 324. K a i ek ov, 1 81 .

hearin g, 56 .

heart, 27—28 .

helmin th parasites (see a l so par asites) , 271—273 .

Hertlein , L . G. , iii .H exag r ammos, 293 .

H ildebran d , M. , 48, 329 .

Hokka ido, Japan , 1 33 .

Hooper, C . L. , 66, 1 1 2, 329 .

Hooper, D . C . , 2, 1 63, 1 64, 280, 337.

Howell, A . B. , 60, 329 .

Hubbs, C . L. , i ii .Huggett, A . St. G. , 237, 238, 243 , 329 .

Hutchin son , H . B. , 1 47, 1 52, 329.

Japan ese, 1 47, 1 76 .

jaw-muscles an d join ts, 42—43 .

Jellison , W . L. , 271 , 329.

Jen sen , A . , i ii , 28, 29 , 238, 329 .

Jen sen , D . , 275 .

John son ,A . M. , 1 1 1 , 37, 52, 1 71 , 324, 326 .

John son , E . J i ii .John son , M . L. , i ii .John son , M. W. , 29 .

Jon es, B . F. , 66, 68, 1 48 .

Jon es, R . D . ,Jr . ,iii

,2,1 23, 1 28, 1 31 ,

1 48, 1 49, 1 50, 1 63 , 1 64, 1 65 , 1 66, 1 70,

1 73 , 250, 279, 280, 288, 31 9 , 320, 329

330, 337, 338, 339 .

Jordan , D . S 284, 329 .

Joyn t, G. T . , 67, 68, 1 52, 1 59, 1 64, 329 .

juven i le stage, 245 .

T H E SEA OTTER IN THE EASTERN PACIFIC OCEAN

K ajimur a , H 1 7 1 , 230.

Kamchatka , 41 , 1 33, 1 89 .

Kan aga Islan d , Alaska , 1 64—1 65 .

K ar r i ck , N . L. , ii i , 1 27.

K ava l g a Islan d , Alaska , 1 59 .

Kayak Islan d , Alaska , 1 79—1 81 .

Kellogg, R. , 4, 332.

kelp (see a l so a lgae )beds, 57 , 67drifting, 67, 69 .

Kelson , K . R. , 4, 328.

Ken a i Pen in sula , Alaska , 1 79—1 81 .

Keyes, M . C. , i ii , 274, 277, 330.

kidn ey, 27—28 .

killin g , acciden tal , 281 .

kill of sea otters, 1 39 , 339 .

Kin g, J . , 340.

Kin g, J . E 27, 330.

K in g, J . G. , i ii .K irkpatrick , C . M. , iii , 2, 1 9 , 43, 1 1 1 ,1 3 1 , 271 , 288, 293 , 299 , 301 . 303

309 , 3 1 1 , 330, 335 , 337 .

Kiska Islan d , Alaska , 1 50.

K i sma l i uk Bay,Alaska , 1 71 .

Klein , D . R. , i ii .Klin gbei l , J . A . , 1 83 .

K l i nkha r t , E . G. , ii i , 321 , 339 , 340.

K l umov, S . K . , 1 89, 330.

Kobza , J . S . , 339.

Kodiak Islan d , Alaska , 1 79.

Kraus , B . S . , 44, 334.

K r ea r , H . R. , iii , 338.

K r en i tz i n Islan ds, Alaska , 1 71 — 1 72.

Krog , J . , 280, 330.

K udi akof Islan d , Alaska , 1 73 .

K uju l ik Bay, Alaska , 1 78.

Kuril Islan ds, 3 , 1 33 , 1 89 .

Laboratory of Sta tistica l Research ,Un iversity Of Washin gton , 243 .

Lack , D . ,270, 330.

Ladr eau, F 1 86 .

Lan e, F . W. , 82, 330.

Lan g, T . G. , 63 , 330.

Larsen , H . , 28 1 .

Larson , C . , iv.La rus g l aucescen s (see gull ) .Laughlin , W . S . , ii i , 1 79 , 33 1 .

Lavren tiya , U . S . S . R. , 1 35 .

Lee , C . F. , 3 1 5.

Leedy, D . L. , iii .

347

Macr ocyst i s (see a lso kelp an d algae ) ,57.

Macy, P . T . , ii i .Magee, E . G. , i i i .Man gan , J . B. , 250, 33 1 .

Manville , R . H . , iv.Mar ak ov, S . V . , 69 , 1 88, 208, 293 , 33 1 .

Margolis, L. , i ii .Marin e Mamma l Biologica l Laboratory, 39.

markin g, 200—204.

Martin -Rice, Ltd. , 40.

Martin , V. F. , i ii , 1 85.

Massey Un iversity, 35 .

Mattison , J . A . , 1 05 .

Mayn ard , W. , 37 , 33 1 .

McAtee , W . L. , 1 35 , 1 8 1 , 333 .

McCan n , C . , 39 , 33 1 .

Mccracken , H . , 1 75, 33 1 .

McLa r en , I . A . , 4, 33 1 .

McLaugh l i n , P . A . , i ii , 1 74, 332.

McLean , J . H . , 1 29 , 332 .

McRoy, C . P. , 1 73 .

Len si n k , C . J 1 1 1 , 2, 1 35, 1 36, 1 39 , 1 40,

1 46 , 1 56, 1 64, 1 65, 1 71 , 1 73 , 1 75,

1 76, 1 77, 1 79 , 1 80, 1 82, 1 83 , 331 ,

337, 338.

Letho l , 3 1 5 .

Lewi s an d C lark, 1 85.

l ice, 76 .

Liers, E . E . , 237, 33 1 .

Limbaugh , C. , 279.

Lin g, J . K . , i ii , 32, 35 .

Littlejohn , C. , 66, 328 .

liver, 27—28.

Ll uch B. , D . , 340.

Locker, B. , 271 , 333 .

Lon don , En glan d , 40, 41 .

lon gevity, 53 .

Lon g Shot, 340.

Lopp , R. , 1 79, 338.

Lower (Baja ) Ca liforn ia , Mexico, 5,1 33 , 1 87, 340.

Loy, C . L. , 1 52, 1 56, 250, 33 1 .

Luk an n on , 1 81 .

Lutke, F. , 1 81 , 33 1 .

Lu tra , 42.

Lutr a can aden sis (see otter, Americanriver ) .

Lutra lutra (see otter , Europeanriver ) .

Lutr a r eevei , 4.


measuremen ts, iv.body weight, adult, 20.

in testin e len g th, 26 .

len gth (see Body Measuremen ts)1 9.

miscellan eous, 26 .

organ weights, 27.

skin len gth (compared with bodylen gth ) 26 .

weight loss at death , 25 .

weight, pregn an t fema le, 230.

we ight (see Body Measuremen ts)1 9.

Medny Islan d , 1 88.

Mexico , 5, 1 87.

midden , 1 29, 1 79, 1 84, 1 85.

M iddle Reef, Alaska , 69.

migration , 6 .

mi le, n autica l an d statute , iv.mi litary, at Amchitka , 250.

Miller, G . S . , 4, 332.

M i ller , P . an d L . G. , 1 , 332.

mink, 43 .

M itchell, E . D . , i ii , 4, 332.

mite, n asa l , 1 03 , 274, 292.

mollusks, 1 1 0.

molt, 37—39 .

mon ia , pearly (see oyster , rock ) .Mon terey, Ca lif. , 1 30.

Morro Hermoso , Baja Ca liforn ia ,

Mexico , 1 33 , 1 87 .

morta lityag e-sp ecific, 253 , 258.

body f at , 261 .

body weight, 271 .

defective teeth, 50, 26 1 , 263 .

durin g fl ight, 3 1 7 .

emaciation , 261 .

en teritis, 26 1 , 271 .

estima ted , Amch itka , 266 , 268.

factors, 261 .

food depletion , 270.

juven iles, desertion Of, 270.

peak period , 266 .

rate, 245.

San ak Islan d, 269 .

sex-Sp ecific, 258.

Sh i imag i n Islan ds, 268.

starvation , 261 , 271 .

storm waves, 264, 266 .

studies, 1 955—63 , 250, 251 .

study methods, 251 , 252.

morta lity— Con t.time of , 252, 253 .

tooth attrition , 27

weather related, 263 .

Mossman, H . W. , i ii , 232, 335.

Murie , O . J . , 1 , 1 23 , 1 50, 1 57, 1 59, 1 65,

1 75, 21 8, 221 , 238, 280,

musclemasseter, 42.

masticatory, 42.

tempora l, 42.

musculature of jaw, 42—43 .

Muscu lus, 1 1 8.

mussels, blue, 52, 83, 1 06 .

Mustelidae, 4.

Nakn ek River, Alaska , 1 75.

Natividad Islan d , Mexico, 1 87.

Nazan Bay, Alaska , 1 66.

Near Islan ds, Alaska , 1 47—1 49 , 1 88.

Nei l an d, K . A . , i ii, 271 , 272, 329, 332.

Nelson , U. C. , 1 1 1 .

n embuta l, 31 1 .

Ner eocyst i s (see a lso kelp ) , 57.

Nesterov, G. A . , 1 88.

n ettin g, 284—286 .

Nevzor off , J . , 1 29, 337.

Newell, I . M. , ii i , 27 1 , 292, 330.

Ni g g ol , K . , 339.

Nikolaev, A . M. , 65 , 1 05 , 1 35, 1 49, 1 89,

204, 279 , 321 , 332.

Nikolski Vi llage, Alaska , 1 46, 1 70, 1 71 .

Norris, K . S . , 63 330.

Novikov, G. A 39 , 332.

Noz ik ov, N. , 1 81 , 332.

O’Br i en , T . P. , 1 1 1 , 339.

octopus, 1 02, 1 1 8.

Ogden , A . , 1 , 1 33 , 1 87, 28 1 , 333 .

Ogla la Pass, Alaska , 1 54.

Og l iug a Islan d , Alaska , 1 59.

Oregon , 1 85 .

orphan , 243 .

Orr,R . T . , 1 1 1 , 1 87, 278, 333.

Osmeridae (smelt ) , 83 .

otterAmerican river , 4, 9—1 3 , 43 , 55,1 84, 236 .

European river , 39 , 236, 238.

oyster , rock (pearly mon ia ) , 43 , 1 09,1 1 8 .

oystercatcher, b lack, 1 03 .



reproduction— Con t.spermatogen esis, 247—248.

sexua l maturityag e of , 229—230.

fema le, 245—246.

ma le, 247.

summary of fin din gs, 246- 247.

terms, defin ition Of, 229 .

tracts fema le, 225—228.

twin n i n g, 242.

un implan ted period, 245.

research , bio logica l, 3 .

Reshetk i n , V . V. , 287, 293 , 333.

Rice, D . W. , iv, 339, 340.

Richardson , F ii i, 338.

Ritter, G. , 250, 33 1 .

Roosen -Runge, E . C. , i ii, 247—248 .

Rop p el , A . Y. , ii i, 26 1 , 324, 326 , 339 .

run n in g (see behavior ) .Sagen , L . V . , i ii .Sakha lin , 1 33 .

Sama l g a Islan d, Alaska , 1 70- 1 71 .

San ak Islan d , Alaska , 1 74—1 76 .

S an Ben ito Islan ds, Mexico, 1 87 .

San dman Reefs, Alaska , 1 74—1 76 .

San d Poin t, Alaska , 1 76 .

San Fran cisco Bay, Ca lif . , 281 .

S an Juan Islan ds, Wash , 1 84.

San Luis Obispo , Ca l if. , 1 30.

San M iguel Islan d, Ca lif. , 1 86—1 87.

S an S imeon , Ca lif. , 1 29 .

San ta Barbara Islan d, Ca lif. , 1 86 .

S aa i domos (see clam) .

Scammon , C . M. , 1 33 , 1 87 , 334.

Scap in o , R . P. , i ii , 42, 43 , 334.

scen t glan ds, 4.

Scha ller , G. B. ,1 08, 329 .

Scheff er , V. B. , i ii , iv, 2, 5, 21 , 24,29, 3 1 , 35, 37, 39 , 44, 52, 53 , 55, 1 57,

1 84, 238, 250, 299 , 324, 326, 334, 338

339 .

S chi zothaer us (see clam) .Schn eider , K . , iv, 3 , 53 .

Schumacher, G . H . , 42, 334.

Sczuck , E . , ii i .Scott, D . B. , i ii , 50.

Scott, E . M. , 1 1 1 .

sea cow, Ste ller’s, 239 .

sea cucumber, 1 21 .

sea l ion , Steller, 1 03 .

sea urchin , 52, 1 28—1 29 , 1 88.

a starvation diet, 1 32.

method of in gestion , 1 1 9, 1 21 .

sea l, fur , 34, 37, 39, 1 36, 324.

morta lity, 26 1 .

pregn an cy, 230.

twin n in g, 243 .

sea l, harbor, 1 02, 1 85 .

Seattle Fur Exchan ge, 41 .

Seguam, Islan d, Alaska , 1 68.

Semi di Islan ds, Alaska , 1 82 .

Semi sop ochn oi Islan d , Alaska , 1 57

1 58 .

S er r i p es (see clam ) .sex, iden tification of , 1 4—1 9 .

sex ratio , 241 .

Seymour , A . H . , 1 1 1 .

shark predation , 278.

shearwater, 1 3 1 .

sheddin g (see molt ) .sheep ran ch, 1 70.

Shelby, H . , 1 86 , 282.

Shemya Islan d , Alaska , 1 47 .

Shi d l ovsk aya ,N . K . , 1 1 9, 1 21 , 287 , 293 ,

295 , 334.

Shelter Cove, Ca lif. , 1 30.

sh'ip tran sport, 31 9 .

Shumag i n Islan ds, Alaska , 1 76—1 77,

337, 339.

S iberia , 1 .

sight, 55.

i n food fin din g, 1 07 .

S imeon of Islan d , Alaska , 1 77.

S in ha ,A . A . , i ii , 225, 228, 229, 232,

236 , 335.

siren ian , 4.

S itka , Alaska , 1 83 .

Ska l k i n ,V . A 65, 1 05, 204, 332.

skinpreparation , 42.

storage, 42.

Skripn ikov, E . P. , 1 88.

skull, study of , 42S later , D . W. , iv.sleep (see behavior ) .S l ijp er , E . J . , 29 , 239 , 240,

smell , 55.

sen se of , 286 .

Smith , A . G. , i ii .Smith , T . A . , 1 1 1 , 273 , 338,

smokin g (of fur ) , 40—41 .


Sn ow, H . J . , 66 , 69, 89 , 9 1 , 1 1 0, 242 ,

273 , 278, 335.

Southeastern Alaska , 57.

Soviet Un ion , 3 .

sea otter population s, 1 87— 1 89 .

Sparin e, 3 1 1 — 3 1 2.

speed (see swimmin g an d run n in g) .

Spen cer, D . L. , iv, 68 , 1 46 , 1 61 , 1 72,1 78 , 1 78, 338, 339 , 340.

spleen , 27, 29 .

squid , 1 1 9 .

Stager , K . E . , 1 86 .

starfish , 1 1 9 .

S tejn eg er , L. , 239 , 335 .

Steller , G . W . , 1 , 79 , 284, 285 , 335 .

Stiles, W . B . , 335 .

Stillwater Cove, Ca lif. , 1 29 .

ston es, stomach , 1 1 1 .

storage of food , 1 1 1 .

Stout , J . , 1 85 , 333 .

Stoves, J . L. , 40.

St . Paul Islan d , Alaska , tran splan t to ,3 1 7.

stress, 30.

causes of , 275.

S tr on g y l ocen tr o tus (see sea urchin ) .

S tu l l k en , D . E . 2, 1 9, 288, 299 , 303

309 , 3 1 1 , 330, 335 , 337 .

subspecies 5 .

Sumn er, L . 1 86 .

surveyaeria l 1 40—1 45 , 321 , 338 , 339 , 340surface, 1 46 , 338, 339 .

surviva l factor , 239Susie (captive otter ) , 1 06 , 1 09 , 289,292, 298 , 299 .

ag e, 53 .

Sutwi k Islan d , Alaska , 1 78.

Sverdrup , H . U. , 29, 335.

Swicegood , S . P. , Lcdr . , 1 52, 1 56 , 335 .

swimmin g , 60—64.

methods of , 60—62.

speed an d agility, 62—64.

Of youn g, 98 .

tactile sen se , i n feedin g, 1 06 .

taggin g (markin g ) , 200—204.

Tahoma Reef, Alaska , 69 .

ta il , 6 .

T an ag a Islan d , Alaska , 1 63— 1 64.

taste , 56 .

taxon omy, 4.

35 1

Taylor, W . P. , 4, 60, 335 .

teeth (see den tition ) .temperamen t, 285 , 298.

temperaturebody, 29- 30.

environmen ta l, 305 .

frigid , 292.

T err an ova deci p i en s (see parasites) .T hen i us, E 4, 335 .

Thomas, R. , iv, 1 46 , 1 72.

three-mi le limit, 66 .

Tiderip Po in t, Alaska , 1 71 .

T i g a l da Islan d , Alaska , 1 72.

Tilford , J . , 338 .

Todd , E . I . , iv.

toppin g, of pelt, 40—41 .

touch , 56 .

tran quilizers, 3 1 2, 3 1 4.

tran splan t, 2, 1 82, 1 83 , 338.

T r anvet , 3 1 3 , 321 .

Treaty Of 1 9 1 1 , 1 35 .

Tremblay , R. , 340.

Troyer , W. , 1 79, 338.

tsun ami , 1 81 .

tun icates , 1 1 0, 1 21 .

Ulak Islan d , Alaska , 1 60.

Umn ak Islan d , Alaska , 1 72—1 75 .

Un alaska Islan d , Alaska , 1 71 .

Un ga Vi llage , Alaska , 1 76 .

Un imak Islan d , Alaska , 1 72— 1 75 .

Un iversity of I llin ois, 42.

Un iversity of Washin gton , 1 85 .

Un ited StatesBoard on Geographic Names , 1 58,

1 68, 335 .

Bureau of F isheries, 1 , 1 35, 1 36 ,1 39 , 1 52, 1 75 , 1 79, 336 .

Coast an d Geodetic Survey, iv ,1 67 .

Coast Guard , 1 , 1 72.

Departmen t of th e In terior , 1 52.

Fish an d Wildlife Service , 337.

Geologica l Survey, 1 81 .

Nation a l Bureau of Stan dards, 53 .

Nation a l In stitute Of Den ta l Research , 50.

Nation a l Park Service, 1 86 .

Navy, 1 65 , 338 .

Navy Departmen t Survey, 1 932,1 47.

Public Hea lth Service , 337 .


Van couver Islan d , Can ada , 1 , 5.

Van der sl uys, C. , 1 84.

Van ia , J . S . , iv, 3 , 39, 285 , 3 1 3 ,339 .

Vasi l i ef Bay, Alaska , 1 66 .

vesselsChe l an , 1 52.

Br own Bear , 288.

C l over , 339.

Comman der , 3 1 9 , 340.

H akyuo Ma ru , 1 52.

K l ama th , 339 .

Or e l , 339.

Par ag on , 320, 337.

Pen gui n II , 339 .

S an Pa tr i ck , 1 60.

S ter egushti , 339 .

T r i n i ty, 1 87, 339 .

Wi n dwar d, 1 73 , 339 .

Ven i ami n ov, I . , 1 81 . Yadon , V. L. , iv.vertebrates, 1 1 0. youn g, n ewborn , 20.

vibrissae, 37, 1 07 . Yunker, C . E . , iv, 271 , 292, 330

Vin cen zi , F. , iv, 299 .

vitamin s, 3 1 5 .

Vo l se l l a , 1 1 8 .

von Bl oeker , J . C. , 1 86 .

Voron ov, V . G. , 1 81 , 285 , 336 .

U . S . GO VERNMENT PR I NT I NG O FFIC E:1 9 7 0 0— 8 5 5 -6 47

wa lkin g (see behavior ) .

Warren , J . M. , 82, 336 .

Wash in gton State, 1 84, 281 , 339 .

water, fresh an d sea , 292.

We lan der, A . D . , iv.wha le, killer, 279 .

whiskers (see vibrissae ) .

Wi ddas, W . F. , 237, 238, 243 , 329 .

Wildman , A . B. , 33 , 336.

Wi l imovsky, N . J iv.Wilke, F. , iv, 2, 5, 1 1 3 , 243 , 261 , 328,336 , 337 , 338, 339 .

Wi lliams, C . S . , 1 23 , 1 50, 1 63 , 1 65, 1 75,

336 .

Wi lliams, L. , iv.Wilson , Woodrow, 1 35 .

Woolford, R. , 281 .

World War I I , 1 , 1 47, 1 52, 1 76 .

worms, an n elid (see a l so parasites) ,1 1 0.

Zaochn i , D . , 337 .

Zhan , M. , iv, 339.

ZOO , Seattle (Woodlan d Park ) , iv, 1 05,299 , 307, 337, 338.

Zoological Park , Nation a l , 288.

Documents

ge - Forgotten Books