Geographic variation in caribou on the Canadian arctic islands

Geographic variation in caribou on the Canadian arctic islands

D. C. THOMAS AND P. EVERSON Canadian Wildlife Service, No. 1000, 9942 - 108 Street, Edmonton, Alta., Canada T5K 2J5

Received January 30, 198 1

THOMAS, D. C., and P. EVERSON. 1982. Geographic variation in caribou on the Canadian arctic islands. Can. J. Zool. 60: 2442-2454.

Analyses of body, leg bone, skull, and pelage data indicated a cline in the characters of caribou (Rangifer tarandus) from central Boothia Peninsula to the western Queen Elizabeth Islands. The main difference between the skulls of barren-ground caribou (R. t. groenlandicus) on central Boothia Peninsula and the more northerly Peary caribou (R. t. pearyi) was a shorter muzzle in the latter. Pelage tone was markedly lighter in Peary caribou and they were smaller in most body measurements, most notably in the length of long bones. Two major populations of Peary caribou were identified: one on the western Queen Elizabeth Islands (Parry Islands), the other on Somerset and Prince of Wales islands. Differences in skull size and form suggest that each population was composed of two or more subpopulations. The larger and darker R. t. groenlandicus occurred on north-central Boothia Peninsula and the two subspecies and apparent intergrades were present in winter on northern regions of the peninsula. The morphological similarity of Peary caribou on Somerset and Prince of Wales islands is explained by interisland movements resulting in genetic mixing. The same is true for caribou on the western Queen Elizabeth Islands and that population apparently has little genetic interchange with the other.

THOMAS, D. C., et P. EVERSON. 1982. Geographic variation in caribou on the Canadian arctic islands. Can. J. Zool. 60: 2442-2454.

L'analyse des donnCes sur le corps, 1'0s de la patte, le crine et le pelage du caribou (Rangifer tarandus) a rCvClC l'existence d'un gradient entre le centre de la PCninsule de Boothia et l'ouest des Iles de la Reine Elizabeth. Les caribous de Peary (R. t. pearyi), plus borCaux, ont le museau plus court que celui des caribous de la toundra (R. t. groenlandicus) de la PCninsule de Boothia, et c'est 18 la principale diffkrence entre les crines. La coloration du pelage est considCrablement plus pile chez le caribou de Peary et toutes les structures de ce caribou sont en gCnCral plus petites, particulikrement les os longs. Deux populations principales du caribou de Peary ont pu 6tre distingukes: l'une dans l'ouest des Iles de la Reine Elizabeth (Parry Islands), I'autre dans les iles Somerset et Prince de Galles. Les diffkrences de taille et de forme du crine laissent croire que chacune de ces populations est constituCe de deux sous-populations ou plus. Rangifer tarandus groenlandicus, plus gros et plus foncC, habite le centre nord de la PCninsule de Boothia et les deux sous-es@ces, de m6me que ces spCcimens d'intergradation, sont prCsents en hiver dans les rCgions du nord de la pdninsule. La similarit6 morphologique des caribous de Peary dans les iles Somerset et Prince de Galles s'explique par les diplacements entre les iles, dkplacements qui favorisent le mixage gCnCtique. Cela est vrai aussi des caribous des iles de l'ouest des lles de la Reine Elizabeth et cette population semble avoir peu d'Cchanges gCnCtiques avec l'autre population.

[Traduit par le journal]

Introduction Peary caribou (Rangifer tarandus pearyi) occur on

most of the Canadian arctic islands except for Baffin Island. Barren-ground caribou (R . t. groenlandicus) occur on the adjacent mainland between Hudson Bay and the Mackenzie River. The taxonomic status of caribou is uncertain in intermediate regions where overlap has or may have occurred; namely, on Banks, Victoria, Prince of Wales, and Somerset islands and on the Boothia Peninsula. The objective of this study was to explore geographic variation in the morphology of caribou on the Boothia Peninsula and some of the Canadian arctic islands in order to help clarify their taxonomic status and the interrelationships of subpopulations of Peary caribou.

Manning (1960) concluded that the caribou on Banks and Victoria islands were intergrades, the result of interbreeding of groenlandicus and pearyi after ice

barriers melted between them. The caribou on Banks Island were judged to be pearyi > groenlandicus; those on northern and southern Victoria Island were believed to be intermediate and groenlandicus > pearyi, respectively (Manning 1960). The caribou of southern Victoria Island may be remnants of the Dolphin and Union herd, comprised of intermediate-sized individuals (groenlandicus > pearyi) that migrated between the mainland and Victoria Island up until the 1920s (Manning 1960). Banfield (1961) classified the caribou on Banks Island and northern Victoria Island as pearyi and was uncertain about the status of caribou on southern Victoria Island.

Manning and Macpherson (1 961) presented evidence for and against intergrades on Prince of Wales Island and concluded that skull shape provided over- whelming evidence against it. They concluded that the caribou of Prince of Wales Island were ultra pearyi,

0008-4301 /82/102442-13$01 .OO/O 01982 National Research Council of Canada/Conseil national de recherches du Canada

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THOMAS AND EVERSON 2443

further removed from groenlandicus than were High Arctic (north of Parry Channel) caribou. They and Macpherson (1965) suggested that reproductive isola- tion between separate species may have broken down on Banks and Victoria islands but not on Somerset and Prince of Wales islands because of later contact there.

Caribou obtained on Boothia Peninsula in 1977 were significantly larger than their counterparts on the islands in body size and length of leg bones (Thomas and Broughton 1978). They were groenlandicus, as suggested by Banfield ( 196 I ) , groenlandicus-pearyi intergrades, or a mixture of both. The smallest adults obtained on northern Boothia Peninsula were, however, no larger than pearyi on Somerset and Prince of Wales islands and their pelage was typical of pearyi.

Manning ( 1960) and Banfield ( 1961) recognized that geographic variation occurred in Peary caribou but they had insufficient samples to examine it. Analyses of body and leg-bone measurements obtained annually from 1975 to 1977, indicated some significant differences among samples of Peary caribou from several islands (Thomas et al. 1976; Thomas et al. 1977; Thomas and Broughton 1978). In general, the largest caribou occurred on Somerset and Prince of Wales islands and the smallest on Prince Patrick Island, with significant differences between those groups in length and girth measurements. Thomas et al. (1977) concluded, after a preliminary analysis of the morphometric data and the pelage characteristics, that two populations of Peary caribou occurred on the islands from which samples were obtained and another population of uncertain taxonomy occurred on Boothia Peninsula.

In the light of the observed variation in Peary caribou, of the known interisland movements of Peary caribou on the western Parry Islands (Miller et al. 1977), the complex movements among Somerset Island, Prince of Wales Island, and the Boothia Peninsula (Miller and Gunn 1978; Miller and Kiliaan 1980), and the ques- tionable relationships of caribou on Boothia Peninsula, it was opportune to collate and examine all the morphometric and pelage data collected from caribou in those areas since 1974, and to add the results of an analysis of skull measurements.

Materials and methods From 1974 to 1977, 190 Peary caribou were collected in

March and April from Somerset (SOM), Prince of Wales (PW), Bathurst (BATH), Byam Martin, Melville (MEL), Eglinton (EGL), and Prince Patrick (PP) islands (Fig. I ) . An additional 22 caribou of uncertain taxonomic status were collected from Boothia Peninsula (BP) in March and April of 1976 and 1977, and 5 adult males from PW in August 1978. The Peary caribou on BATH, MEL, EGL, and PP were termed the Pany population after the name of the islands they inhabited. Peary caribou on PW, SOM, and adjacent islands

were named the Peel population after the channel that separates most of those islands.

The age of each animal >2 years old was ascertained by counting the number of rest lines in stained sections of the first incisor and the first molar. Ages of younger caribou were evident from the wear and eruption patterns of their teeth. Age was expressed to the nearest year, i.e., 22 (March sample) became 3 years.

Weights of entire caribou were measured on a circular spring scale. Body measurements were taken to the nearest 0.5 cm with a steel tape. Body length was the distance from the base of the tail to the tip of the nose along the medial contour. Girth was measured just posterior to the forelegs with about a 2-kg pull on a steel tape. Shoulder height was measured from the dorsal tip of the spinal vertebrae to the tip of the right front hoof wi th the foreleg in a natural, extended position. Hind foot length was the distance from the tip of the calcaneous to the tip of the extended right hoof, the tape passing from posterior to anterior surfaces. Leg bones were measured with vernier calipers to the nearest 1.0 mm.

Body and long-bone mesurements of individuals older than 2 or 3 years, depending on the growth form of the body component, were compared using a 'one-way analysis of variance (ANOVA) and Scheffe's multiple contrasts (SMC).

With vernier and outside calipers, we measured 17 characters on each skull, as described by Banfield (1961) (Fig. 2). Dimensions of skulls aged <5 years were corrected to 5 years for each island or peninsula by multiplying by the expected remaining growth factor:

where do = measured dimension at age a; a = age of skull i~ years; m = slope of regression of log dimension on log age; d5 = predicted dimension at age 5 years.

The adjustments were necessary to increase the sample sizes for the multivariate analysis of variance (MANOVA) of the data. That program accepted only full data sets for each individual and consequently the sample sizes were reduced because of missing values among the 17 characters. The data gaps resulted from missing or damaged parts of skulls. Only 7 of 22 and 42 of 98 caribou obtained from the BP and Peel (excluding the 1978 sample) populations were 25 years old. In contrast, 83 of 90 caribou collected from the Pany population were 2 5 years old. Hereafter, age-corrected data will be referred to as "adjusted data."

Multivariate analysis permitted us to consider all 17 characters simultaneously, an approach more appropriate than the analysis of individual characters (Gould and Johnson 1972). Our null hypothesis, i.e., that there was no difference in the size of caribou from the various geographical regions, was tested first with a MANOVA and then pairwise comparisons were performed using Mahalanobis generalized distance (D*), which considers the differences in means, variances, and covariances among groups (Gould and Johnson 1972). The measure D~ indicates relative phenotypic similarity.

We also used univariate ANOVA and SMC to compare the means of individual skull characteristics among all locations based on (I) the adjusted data and (2) unadjusted data for caribou >45 months old. Growth in skull characters after that

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CAN. J . ZOOL. VOL. 60, 1982

FIG. 1. The Canadian arctic islands and the Boothia Peninsula on which caribou were collected for this study and their geographic relationship to Cornwallis, Devon, Victoria, and Banks islands.

age was not significant. We then compared the means for the three populations using only the unadjusted values. The univariate analyses were performed as a check on the multivariate results and as a means of increasing the sample sizes because they avoided the problem of excluding data for an individual because one or more measurements were missing.

The pelage tone of the backs, legs, and heads in photographs of caribou collected in 1977 each was rated on a scale of 1 to 5 (1 is predominantly white . . . 5 is predominantly brown). This was done independently by two people using photographs of representative class types for comparisons. The ratings for the three body areas were averaged, and the results of the two observers were averaged to produce a composite scale of 0 to 5. Analysis was by ANOVA and SMC; the significance level was 0.95.

Results Body and skeletal measurements of adult females

Plots of individual measurements against age for each population indicated that shoulder height increased

throughout life, body length and girth increased until about age 5 years, and growth of the leg bones and hind foot virtually ceased by age 2 years. There was no significant difference after age 2 years in any of the measurements but the sample sizes were small. Never- theless, those 3 years old (n = 15) were excluded from the analyses for body length, shoulder height, and hind foot length (Table I), because of their slightly smaller average size. For example, in the sample from SOM, five 3-year-old females averaged 144.4cm in body length versus 150.6 cm for 12 older females (NS , P > 0.05). This conservative approach was taken because differences in the age structures of the various groups could have an influence on the mean values for body length, shoulder height, and girth, where some growth occurred beyond age 3 years. The mean ages of all caribou collected in 1977 were 3.9 years (BP), 4.0 years (SOM-PW), and 9.9 years (Parry Islands) (Thomas and

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FIG. 2. The 17 measurements of caribou skulls and mandibles used in this study: A , basal length; B, orbital width; C, nasal length; D, post nares; E, maxillary tooth row; F, maxillary diastema; G, occipital height; H, nasal width; I, canine width; J, incisive foramen; K, mastoid width; L, rostra1 height; M, zygomatic width; N, mandibular length; 0, mandibular height; P, mandibular tooth row, and Q, mandibular diastema.

Broughton 1978). Therefore, the differences in height, length, and girth between the Parry group and the other two would have been even greater had the age structures been similar.

Coefficients of variation on data for females older than 2 years were 4-7% for shoulder height, girth, and body length, and 2-4% for leg bone measurements. Measuring error was judged to be excessive for shoulder height and therefore that variable was not used in most

comparisons. In contrast, measuring error was essentially nil for the long bones.

Analysis of statistics for body length, girth, and lengths of femurs, tibias, and metatarsi of females older than 2 or 3 years (as appropriate) from BP, PW, SOM, BATH, MEL, EGL, and PP islands (Table 1) produced significant F values in all ANOVAs. The SMC tests indicated the following significant differences: (1) in girth: BP > SOM, SOM < PW and BATH, and PP < all the others except SOM; (2) in femur length: PW > MEL and PP; (3) in femur, tarsus, and metatarsus lengths: BP > all the others. The large girth (mean 112.6 cm) of caribou in the EGL sample was an anomalous statistic and was not explainable on the basis of differences in subcutaneous fat because their fat reserves were negligi- ble (Thomas et al. 1977). Differences in body weight among the groups reflected differences in fat reserves and pregnancy rates and therefore they were excluded from the size analyses, except between groups with similar fat reserves and pregnancy rates. The statistics for the six size measurements (Table 1) included all specimens >2 or 3 years old, as appropriate, whereas the SMC analysis was conducted on complete sets of data; that is, if one of the measurements for an individual was missing, that individual was removed from the sample.

Female Peary caribou in the Peel and Parry populations (rows 8 and 9, Table 1) differed significantly only in body weight, body length, and femur lengths. The weight differences probably reflect fat and pregnancy rate differences to a greater extent than size variations.

The observation that all but one of the caribou obtained on northern BP appeared to be predominantly R. t. pearyi, and those obtained from central BP appeared to be more like R. t. groenlandicus, led to a comparison of adult females in the two samples (Table 2). The adult females collected on central BP were larger in all eight characters and differences were significant for weight, femur length, and tibia length. However, each of the long bones in the sample from northern BP was significantly longer than those from any of the islands (Tables 1 and 2). Those data tended to confirm the existence of two types of caribou on BP in the winter, both different from the forms found in winter on SOM and PW islands.

Body and skeletal measurements of adult males We included only males older than 3 years in the

analyses of body length and girth statistics because the 3-year-olds differed significantly from older males in the only adequate sample, that from SOM. Significant differences among the samples obtained in winter where n > 5 were the following: (1) body length: PW > MEL and PP; SOM > MEL; (2) girth: SOM > MEL and PP, PW > PP; (3) femur length: Me1 < PW and SOM; and (4) tibia: SOM > MEL and PP. The Peel population

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TA

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TABLE 2. Comparative statistics (f + SE in centimetres) for standard body measurements and long bone lengths of female caribou collected on central and northern Boothia Peninsula

Age group Central Northern Parameter (years) (n = 4) (n = 5, 6)b Pa

Body weight Body length Girth Shoulder height Hind foot length Femur length Tibia length Metatarsus length

"If significant. bn = 6 for Rind foot and leg bones.

differed significantly from the Parry population in all the characters (Table 3).

The five bulls collected on PW in August 1978 significantly exceeded those from the Parry group in body length and leg bone measurements. They were also significantly larger in body length than the males collected on SOM. Their much larger mean girth (1 29.8 cm) was not compared statistically with the others because it could be influenced by subcutaneous fat deposits. Their long bones were similar in length to those in the March-April samples from SOM and PW (Table a), but their bones averaged 0.5 (femur) to 1.6 (metatarsus) cm shorter than those of the three young males (ages 3, 3, and 4 years) collected on northern (2) and central BP. The five bulls weighed 177-21 1 kg and their average weight (203 kg) was greater than that of any collection of barren-ground caribou in Canada.

Skull measurements Plots of individual measurements against age indi-

cated that growth continues throughout life for some of the 17 characters (e .g . , basal length, mandibular length, mandibular height, and mandibular diastema); others are essentially static after age 5 years (e.g., orbital width, nasal length, mastoid width, rostra1 height, and zygomatic width), whereas the length of the molarifom tooth row decreases slightly after age 3 years. Growth was not significant after age 4 years for any of the characters.

Univariate AI'dOVA and SMC of adjusted data for the skulls of females revealed the following significant ( P < 0.05) differences: (1) BP skulls generally were larger than all the others in all the length and width characters but not in the depth characters (Fig. 2); (2) there were no differences between PW and SOM skulls except in nasal length and tooth row lengths; (3) there were few differences among skulls in the Parry group and only one difference between MELV and PP skulls; i.e., the differences involved skulls from BATH and EGL; and

(4) PW and SOM skulls were larger than BATW, MEL, EGL, md PP skulls in 37 of 136 of the character comparisons.

Values of Mahalanobis D' for the 17 characters in females indicated significant differences in skull size among all samples except within the MEL, EGL, and PP group and between BATW and EGL (Table 4). The small sample sizes for males resulted in fewer significant differences but similar trends. The significant differences between the sample from BATH and those from MELV and PP is remarkable, as is the significant difference between samples from SOM and PW.

Univariate ANOVA and SMC of unadjusted data for the seven characters in Table 6 revealed the following significant differences (P < 0.05) among BP (n = 7-43), SOM (n = 8-12), PW (n = 19-24), BATH (n = 5-6), MEL (n = 19-24), EGL (n = 3-9, and PP (n = 17-21) for females >3 years old: BP > SOM for character J; BP > PW for characters A, C , F, J , M, and Q; BP > BATW for characters A, C, F , J, M, N, and Q; BP > EGL for characters C and J ; BP > PP for characters A, B , C, E, F , J , M, N, 0 , and Q; SOM > BATH for characters C and N, SOM > PP for characters E, F, N, and Q; PW > BATH for J; PW > MEL for character J; PW > PP for characters E, F , J , 0 , and Q; MEL > SOM and PP for character G; EGL > PP for character F; EGL > BP, SOM, PW, and PP for character G; and BATW > BP, SOM, and PP for character G.

The unadjusted data for the skull measurements of adult males (>3 years old) on SOM (n = 4-7), MEL (n = 3-6), and PP (n = 12-14) revealed that the sample from SOM was significantly larger than the other two for all characters except G, E, K, and L. There were no differences between the MEL and PP samples except for characters G, K, and L.

The SMC for the 17 skull characters in adult females suggested there was no difference between PW and SOM and generally no difference among skulls from the

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TA

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tistic

s (i k S

E i

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irth

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(n =

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THOMAS AND EVERSON

Parry group. Therefore, we grouped the data and compared females in the three populations and found significant differences among them except for characters 0 and P. Differences between the Boothia and Peel ,A

populations were significant for all characters except for - O)

D, E, G, 0, and P. Differences between Peel and Parry 2 * groups were significant for A, E, F, J, M, N, and Q. J=

2.5 Differences between Peel (n = 7-9) and Parry (n = - h

= ' 2 6-21) males (unadjusted data) were significant for all

73 g characters except D, G, H, and L. Z 2

Coefficients of variation (CV) calculated for data 0 from females and males over 3 years of age (Table 5)

s 8 indicated combined inherent variation plus measuring - g .z

errors. We arbitrarily selected, for some of the compari- -gz sons, characters with CV values less than 4.0 in the sex with the larger sample size (females). The seven ! $ z5 ,a

characters were also the least variable for both sexes s 8 0 C

combined (Table 5). Data (unadjusted) for the seven a 2 characters with the lowest CV values (Table 6) revealed 3 g that in general the skulls from caribou on BP were - a 3 largest, those from PW, SOM, and EGL were inter- @ mediate in size, and the BATH, MEL, and PP islands -0 o

group were smallest. 5 v h

.$ 9 Among-population ratios of means for the 17 charac- a- ters in females indicated that the skulls of caribou from Cu o 5 u BP, compared with those of the Peel group, were much 0) 5

2 c larger in length of the incisive foramen (15.3%), nasal 2 .g length (1 1.7%), mandibular diastema length (1 1.4%), 2 2 nasal width (10.2%), and rostra1 height (9.4%), but they cc - rA were smaller in the length of the mandibular tooth row 3 a 0) 2 (2.1%) and in occipital height (1.3%). The skulls of E S

2 caribou from BP, relative to those of caribou on the % g Pany Islands, were much larger in lengths of the incisive z .s & foramen (26.4%), nasal bones (1 5.6%), mandibular a, diastema (15.1 %), and maxillary diastema (10.3%), but 3 5 they were 7.3% smaller in occipital height. Skulls of 2 .$ female caribou from the Peel group were larger than those of caribou on the Parry islands in length of nasals 5% (3.5%), length of the mandibular diastema (3.3%), ~5 mandibular length (3.0%), and canine width (2.7%). 9"

$ 2 Occipital and rostra1 heights were smaller by 6.1 % and O 1 "

2.0%, respectively. ,d 2 g The major difference in the skulls of the BP, Peel, and 3 - 5

Pany groups was in muzzle length. Ratios (percent) of .z 3 5 .$ average incisive foramen lengths to average lengths of 5-0 the mandibular tooth row, the character most uniform a 2 among the groups, clearly show that difference: BP, 2 4

E .5; 46.7; Peel, 39.6; and Parry, 37.0. The same trend was 4 5 indicated by the ratios of mean lengths of mandibular w

cl diastema to mean lengths of mandibular tooth row: BP, a a 91.4; Peel, 80.4; and Parry 79.5. The relationships b

among the mean values for the 17 skull characteristics in our three groups, the Peary caribou of Banks Island, and R. t . groenlandicus (Banfield 196 l ) , in which the Parry

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TABLE 5. Coefficients of variation for 17 skull characters in samples of female and male Peary caribou older than 3 years

Coefficients of variation

Unweighted Skull character and code Femalesa ales meanC

M Zygomatic width A Basal length N Mandibular length B Orbital width F Maxillary diastema K Mastoid width E Maxillary tooth row length P Mandibular tooth row length I Canine width Q Mandibular diastema L Rostra1 height 0 Mandibular height J Incisive foramen D Post nares G Occipital height C Nasal length H Nasal width

"Unweighted mean for samples from Prince of Wales ( n = 7-8), Somerset ( n = 9- 12), Bathurst ( n = 5-6). Melville ( n = 17-24), Eglinton ( n = 5), and Prince Patrick ( n = 17-21) islands.

bunweighted mean for samples from the Peel group ( n = 6-9) and the Parry islands ( n = 17-21). 'Unweighted mean for all eight samples.

group forms the standard, demonstrated the following (Fig. 3): (1) the increasingly longer muzzle in the sequence Parry, Peel-Banks, BP, and R. t. groenlandicus, as exemplified by the characters nasal length, diastema, and incisive foramen; (2) the similar skull depths of the three groups that we measured and the much larger values for the Banks and groenlandicus groups; (3) the progressive increase in overall skull length and width in the series Parry, Peel-Banks, BP, and groenlandicus as exemplified by nasal length, mastoid width, and zygomatic width; (4) the closeness of the Peel and the Banks groups; and (5) the general intermediate position, between the Peel and groenlandicus groups, of the five bulls taken on PW in August 1978.

Morphological characters least affected by nutritional differences provide the best clues to possible genetic differences. According to Klein ( 1964), the skull has the highest priority for growth, followed by other skeletal extremities, and progressively to the central vertebral column. Therefore, skull size and shape are expected to be the most reliable indicators of possible genetic differences followed in turn by metatarsal length, tibia length, femur length, girth, body length, and body weight. Body weight comparisons are valid only between groups with similar fat reserves.

Pelage tone The caribou in the sample from BP were significantly

darker than any of the samples from the islands (Table 7). Calves were excluded from the analysis because they were lighter in tone. The tone of five calves averaged 2.4 compared with 3.2 for 12 older caribou in the sample from BP. Pelage tone may be independent of nutritional history but no data are available.

Discussion Peary caribou in our collections appear to fall into two

large groups, one on the Parry Islands and one on SOM-PW. The caribou on BATH, MEL, EGL, and PP constitute a fairly homogenous population. Genetic mixing among subpopulation components is likely because of the considerable interchange of caribou among MEL, EGL, and PP (Miller et al. 1977). There is a distinct possibility, however, that the caribou collected on EGL were visitors from south of Parry Channel, perhaps from Banks or Victoria islands. The five females collected there were significantly (P < 0.05) heavier and of greater girth than females on PP, although their fat reserves were lower (Thomas et al. 1976). The seven caribou in the sample were the only ones seen on EGL in late winter 1975, except for one other, which adds support to the argument that they may have strayed

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TA

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Reg

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2452 CAN. J . ZOOL. VOL. 60. 1982

a-(n =46-55) 30- FEMALES 6-(n.28-36)

301 MALES a-(n.16-21) b-(n.6-9)

- 3 l l l l l l l l l l l l l l l l l l

A B C D E F G H I J K L M N O P Q Skul l Character

FIG. 3 . Percent deviations from the Parry population (a) of skull measurements of adults 3 years old from the Peel population (b ) , the Boothia Peninsula (c), the five males collected on Prince of Wales Island in August (see text) (d) , Banks Island (e), and R . t. groenlandicus (f) (date for e and f in Banfield 1961) for basal length (A), orbital width (B), nasal length (C), post nares (D), maxillary tooth row (E), maxillary diastema (F) , occipital height ( G ) , nasal width (H) , canine width (I), incisive foramen (J), mastoid width (K), rostra1 height (L), zygomatic width (M), mandibular length (N), mandibular height (0), mandibular tooth row (P), and mandibular diastema ( Q ) .

TABLE 7 . Pelage tone (i k SD, n in parentheses) of caribou > I year old collected at five locations in March-April 1977. Higher numbers of the 0 to 5 scale indicate darker pelage (see

text for methodology)

Location Adult females All samples

Boothia Peninsula 3 . 2 k 0 . 9 (7) 3 .2k0 .7 (12) Somerset Island 1.7 (1) 2 .0k0 .4 (3) Prince of Wales Island 1.7 k 0 . 3 (6) 1 . 6 k 0 . 2 (7) Melville Island 1 .5k0 .3 (10) 1 .5k0 .3 (10) Prince Patrick Island 1 .7k0 .2 (7) 1 . 7 2 0 . 2 (10)

from their normal range. The caribou collected on BATH were similar to those on islands to the west. Gene flow in the past, when numbers were much larger, probably was greater between BATH and MEL than between BATH and PW.

There appear to be several subpopulations in the SOM-PW-BP region, some with characteristic interisland movements. Some movements are traditional (Miller and Gunn 1978; Miller and Kiliaan 1980; F. L. Miller, personal communication), but there appears to

be considerable annual variability in the proportion of the total population that migrates. In March-April 1977, for example, the majority of caribou in the subpopulation that usually winters on SOM were on PW.

Caribou collected on SOM and PW in winter were intermediate in size, although they were closer in size to the Parry population than to the groups on BP. Peary caribou in the Peel population were slightly smaller than the caribou on Banks Island, based on a comparison of our data on skull size to those in Manning (1960) and Banfield (1961) and unpublished data on weights and body measurements. The significantly larger size of some characters of Peary caribou south of Parry Channel could be caused by nutritional differences during growth, by long-term adaptation to the different en- vironments, or by interbreeding with larger caribou that occur on the mainland. The third explanation is probably the most important factor. The abrupt change in size of caribou from central BP to SOM and PW, and the intergrades on northern BP, suggest a merging of the two subspecies.

The skulls of the female caribou that we sampled on central BP, presumably the resident population, were similar in size to Banfield's (1961) sample of groenlandicus. The mixture of pearyi, groenlandicus, and intergrades sampled on northern BP probably was largely from the segment that migrates to PW in the spring and returns in the autumn.

Data on the relative sizes of the various subpopulations are meagre. About 5000 caribou occur on SOM and PW in the summer (Fischer and Duncan 1976; A. Gunn, personal communication). Thompson and Fischer (1980) estimated there were 1739 caribou on Boothia Peninsula in June 1975, including about 550 caribou that migrated to Boothia Peninsula, presumably from PW, between early August 1974 and mid-March 1975. A migration from BP to the islands may have occurred after their surveys on 5- 12 June 1975. Assum- ing that their estimate of 1739 caribou was high because of low coverage and the chance inclusion of many large calving groups, their data are consistent with a migration of 500-600 caribou to PW after 12 June 1975 and their return after early August. If that interpretation is correct, an equal number remained on BP during that summer.

The fetuses of the three females collected on northern BP on 5 April (1976) were about 14 days further advanced in size and development than fetuses in females collected 2 days earlier on PW (Thomas et al. 1977). This difference suggests that timing of conceptions in the three females, one typical pearyi and two intergrades, were synchronized more closely with groenlandicus on BP rather than with pearyi on the islands. Recent information on calving dates on PW

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(F. L. Miller, personal communication) suggests that the peak of calving is after 20 June. The data from the fetuses suggest the timing of calving on BP probably is similar to that of barren-ground caribou on the Canadian mainland, i.e. 80% of conceptions occur between 19 and 29 October (Dauphin6 and McClure 1974) and the peak of calving occurs 8- 14 June (Parker 1972; Kelsall 1968).

The relationships of caribou in Northern Canada would be more comprehensible if we knew the origins of the present subspecies and intergrades. The genus was traced back to about 440000 B.C. in Eurasia and its existence in North America may be equally long (Banfield 196 1). The concensus among Canadian tax- onomists was that woodland caribou (R. t . caribou) evolved south of the Wisconsin ice sheet, barren-ground caribou in the Beringia refugium in Alaska-Yukon and Peary caribou in a Queen Elizabeth Islands refugium (Banfield 1961) or a Pearyland refugium in northern Greenland (Manning 1960; Manning and Macpherson 1961; Macpherson 1965). Those authors did not dis- count the possibility that the present forms evolved through natural selection after retreat of the last ice sheet. There is doubt now that a Pearyland refugium existed, but most of Banks Island and part of Prince Patrick Island remained ice-free.

Manning (1960) documented a cline in several characters from typical barren-ground caribou on the Cana- dian mainland through the series: the Dolphin and Union herd (now extinct), the Victoria Island group, and the Banks Island group, to the typical Peary caribou of the Queen Elizabeth Islands. Our results, contrary to those of Manning and Macpherson (1961), clearly show that a similar cline exists to the east with intermediate forms present on northern BP, SOM, and PW. Manning and Macpherson ( 196 1) concluded, largely from skull ratios, that the caribou on PW were ultra pearyi and not intergrades. They almost certainly sampled caribou that were summer visitors to PW, probably from the same segment from which we obtained five bulls in August 1978. They purposely collected the largest caribou and their series of seven males was about the same size as our sample of five bulls, based on skull length (their mean for condylobasal length reduced 20-25 mm to approxi- mate basal length).

The five bulls in our August sample do not fit in any of the other groups because of their great weight and relatively short legs. It is unlikely that males over 3 years of age (n = 11) that averaged 86 kg (range, 69- 106 kg) in March-April on SOM and PW could attain an average weight of 203 kg by 7 August. The males taken in August undoubtedly would have gained more weight before the arrival of snow. The lengths of the leg bones and the skull dimensions suggest that the five bulls did

not come from the subpopulations that we sampled on BP. There remain two possibilities. Either they were pearyi-groenlandicus intergrades from some other subpopulation (possibly from Victoria Island) or they were larger-than-average males from SOM and PW islands that were able to almost double their weight during the summer. By comparison, all of the 398 male groenlandicus taken from the Kaminuriak population weighed less than 175 km (Dauphine 1976) and the heaviest male recorded by Kelsall (1968) was 153 kg.

Gene flow may be slow and sporadic between the various subpopulations because of different movement patterns. Considerable interchange of caribou between regions could occur without any gene flow if there was no contact during the rut. The possible 2-week disparity in the timing of breeding between caribou that winter on the Boothia Peninsula and those wintering on SOM and PW would also tend to reduce gene flow, or the establishment of groenlandicus on the islands, assum- ing that the mortality of young would be greater if they were born outside the optimum period for that environ- ment. Migrations of groenlandicus from the mainland to BP had ceased or at least dwindled several years before the settlement of Spence Bay was established in 1947 (A. H. Macpherson 1959, unpublished report Canadian Wildlife Service). In our view, the remnant group that resides year-round on BP is best described as groenlandicus, although it may cany some genes of pearyi. In time it may become intermediate in form between those subspecies by infusion of pearyi genes and little or no contact with groenlandicus.

The genetic composition of intermediate forms is probably changing constantly as they receive genes disproportionately from time to time from either subspecies and as the climate changes and selection favors one form. We envisage that intermediate forms would be extinguished periodically and geographic variation would proceed on the small populations until overlap occurred once again. Periodic near extinction of pearyi in certain regions, as documented on the western Queen Elizabeth Islands since 1961, would result in strong selection of the fittest individuals. Genetic drift may also become a factor because only a few individuals may survive major die-offs.

In conclusion, we believe that the present boundaries between groenlandicus and pearyi, as shown by Banfield (1961), are valid. Caribou north of Parry Channel are relatively pure pearyi stock; the most isolated groups are located on Axel Heiberg and Ellesmere islands. The caribou that winter on PW and SOM are predominantly pearyi and comparable to the pearyi on Banks Island. The resident caribou of BP are predominantly groenlandicus. Intergrades occur on norhtern BP in the winter and on PW and SOM in the

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2454 CAN. J. ZOOL. VOL. 60, 1982

summer. The taxonomic status of the caribou on Victoria Island remains unresolved.

Acknowledgements We thank numerous colleagues and the Resolute Bay

Hunters and Trappers Association, notably G . Eckalook and A. Eckalook, for help in obtaining the caribou specimens. E . Arnett and C . Maloney prepared many of the skulls and measured some of them. M. Kingsley provided statistical advice and A. Gunn, F. Miller, A. Macpherson, W. Stevens, and G . Scotter improved the manuscript. Logistical support was provided by the Polar Continental Shelf Project and financial support by the Northwest Territories Wildlife Service and the Canadian Wildlife Service.

BANFIELD, A. W. F. 1961. A revision of the reindeer and caribou, genus Rangifer. Bull. Natl. Mus. Can., Biol. Ser. No. 66.

DAUPHIN^, T. C., JR. 1976. Biology of the Kaminuriak population of barren-ground caribou. Part 4. Growth, reproduction, and energy reserves. Can. Wildl. Serv. Rep. Ser. No. 38.

DAUPHIN& T. C., JR., and R. L. MCCLURE. 1974. Synchron- ous mating in Canadian barren-ground caribou. J. Wildl. Manage. 38: 54-66.

FISCHER, C. A., and E. A. DUNCAN. 1975. Ecological studies of caribou and muskoxen in the Arctic Archipelago and northern Keewatin. Report to the Polar Gas Environmental Program by Renewable Resources and Consulting Services Ltd., Edmonton.

GOULD, S. J., and R. F. JOHNSON. 1972. Geographic variation. Annu. Rev. Ecol. Syst. 3: 457-498.

KELSALL, J. P. 1968. The migratory barren-ground caribou of Canada. Can. Wildl. Sew. Monogr. No. 3.

KLEIN, D. R. 1964. Range-related differences in growth of deer reflected in skeletal ratios. J. Mammal. 45: 226-235.

MACPHERSON, A. H. 1965. The origin of diversity in mammals of the Canadian Arctic tundra. Syst. Zool. 14: 153-173.

MANNING, T. H. 1960. The relationship of the Peary and barren-ground caribou. Tech. Pap. - Arct. Inst. North Am. No. 4.

MANNING, T. H., and A. H. MACPHERSON. 196 1. A biologi- cal investigation of Prince of Wales Island, N.W.T. Trans. R. Can. Inst. 33: 116-239.

MILLER, F. L., and A. GUNN. 1978. Inter-island movements of Peary caribou south of Viscount Melville Sound, North- west Territories. Can. Field-Nat. 92: 327-333.

MILLER, F. L., and H. KILIAAN. 1980. Inter-island movements of Peary caribou in the Prince of Wales Island - Somerset Island - Boothia Peninsula complex, Northwest Territories, May-July 1979. Can. Wildl. Sew. Prog. Notes, No. 107.

MILLER, F. L., R. H. RUSSELL, and A. GUNN. 1977. Interisland movements of Peary caribou (Rangifer tarandus pearyi) on western Queen Elizabeth Islands, Arctic Canada. Can. J. Zool. 55: 1029- 1037.

PARKER, G. R. 1972. Biology of the Kaminuriak population of barren-ground caribou. Part 1. Total numbers, mortality, recruitment, and seasonal distribution. Can. Wildl. Sew. Rep. Ser. No. 20.

THOMAS, D. C., and E. BROUGHTON. 1978. Status of three Canadian caribou populations north of 70" in winter, 1977. Can. Wildl. Sew. Prog. Notes, No. 85.

THOMAS, D. C., R. H. RUSSELL, E. BROUGHTON, E. J. EDMONDS, and A. GUNN. 1977. Further studies of two populations of Peary caribou in the Canadian Arctic. Can. Wildl. Serv. Prog. Notes, No. 80.

THOMAS, D. C., R. H. RUSSELL, E. BROUGHTON, and P. L. MADORE. 1976. Investigations of Peary caribou populations on some Canadian Arctic Islands, March 1975. Can. Wildl. Sew. Prog. Notes, No. 64.

THOMPSON, D. C., and C. A. FISCHER. 1980. Numbers and distribution of caribou on the Boothia Peninsula, Northwest Territories. Can. Field-Nat . 94: 17 1 - 174.

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Documents

Geographic variation in caribou on the Canadian arctic islands