"" CARD 81 EVOLUTION OF MAMMALS

Mammals were once on insignificant group of vertebrates. But after the decline and extinction of dinosaurs about 6S million years ago,

mammals came to dominate the animal kingdom in some ways.

KEY FACTS

THE RISE OF MAMMALS

Scientists disagree about what

brought an end to the Age of

Dinosaurs some 65 million years

ago. But whatever the cause, di­

nosaurs had totally disappeared

within a million years. Mammals

then expanded rapidly in forms

and sizes, filling vacant spots in

the planet'S ecology.

About 80 million years before

the dinosaurs disappeared, the

mammals split into two main

reproductive groupings: marsu­

pials and placental mammals. A

marsupial gives birth after a very

short gestation period, when its

offspring is barely formed. The

infant then spends a number of

months feeding on its mother's

milk, usually within her pouch.

A placental mammal has a more

efficient initial method of devel-

WHAT IS A MAMMAL?

All mammals feed their young

with milk that is produced by

the mother's body. No other

class of animals does this.

Several mammalian features

are found in other vertebrates.

Most mammals give birth to live

young, but so do some fish and

amphibians. On the other hand,

monotreme mammals (the platy­

pus and echidnas) lay eggs.

opment for its young in which

the offspring remains inside the

womb for a longer time than a

marsupial does. It is nourished

by the mother's blood via the

placenta, an organ attached to

the womb lining.

Right: Kangaroos and other mar­supials spend a long time develop­ing in their mothers' pouches.

Right: All but three species of mammal give birth to live off­spring. But this characteristic appears in oth­er classes of an­imals as well.

Most mammals are hairy and

warm-blooded with fairly steady

Left: A female mammal's pro­duction of milk for her offspring is called lacta­tion. This pro­cess is unique to all mammal species.

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l eft: Young wan­dering shrews and all other placental mammals spend longer develop­ing in the womb than young mar­supials do. As a result, newborn placental mam­mals need less help than new­born marsupials.

body temperatures, but some,

including humans, are almost

hairless. Others may vary their

body heat, especially if they hi­

bernate. While most mammals

are active, consuming lots of en­

ergy, tree sloths are sluggish.

Mammals have a few unique

skeletal features, such as a lower

jaw that is formed from a single

bone on each side.

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The earliest mammals were small, shrewlike creatures. ~ THE FIRST MAMMALS ~ EVOLUTION & EXTINCTION The tremendous diversity of modern mammal species

evolved from these ancient animals. Today mammals

range in size from the featherweight pygmy shrew

to the 130-ton blue whale. They have adapted to

all of the Earth's environments. One group of

mamma/~the bat~has even learned to fly.

~ FROM REPTILES TO MAMMALS Mammals evolved very gradual­ly from reptiles. Approximately 300 million years ago, the first true reptiles, known as diapsids and synapsids, appeared. Diap­sids were the ancestors of dino­saurs and today's birds, lizards, snakes, and crocodiles. Synap­sids were the ancestors of vari­ous reptiles, including the ones that evolved into mammals.

legs. They also had flexible ver­tebrae, possibly enabling them to curl up. They may even have suckled their young.

Probably, later mammal-like reptiles had hair, more constant body temperatures, and sweat glands that were modified to give milk for the young. Like to­day's monotremes (egg-laying mammals), the first true mam­mals probably laid eggs.

By 225 million years ago, there were some mammal ancestors that seemed closer to mammals than reptiles. One example is the shrewlike Megazostrodon.

Yet for 150 million years, dino­saurs dominated the world. Fos­sils indicate that all the earliest true mammals were small. Only after the sudden decline of di­nosaurs, approximately 65 mil­lion years ago, did mammals begin to develop the great va­riety of forms and sizes that we know today.

During the years of dinosaur supremacy, mammals consoli­dated their efficient basic de­sign. They evolved a powerful four-chambered heart as well as a diaphragm to help them inhale and exhale and to sup­ply the lungs with oxygen. A "false" palate in the roof of the

By the middle Triassic period, 230 million years ago, some reptiles had become mammal­like. The reptile's multi boned lower jaw began changing in­to the mammal's single-boned jaw. In addition, unspecialized reptilian teeth began to evolve into specialized mammalian teeth with incisors in front, fol­lowed by large canines, pre­molars, and molars.

Megazostrodon

A group known as cynodonts were equipped with fairly large, doglike skulls and mammal-like legs rather than squat reptilian

Thrinaxodon

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Haramiya

Kuehneotherium

MID-TRIASSIC PERIOD 225 million years ago

mouth enabled them to eat and breathe at the same time. Hair­covered skin containing sweat glands helped the animals re­main warm or cool according to need. Perhaps most signifi­cant, the skull became larger to hold an increasingly large and capable brain.

Front cover: Big cats such as the mountain lion are usually the top predators in their range.

Front insets: Mammals such as the greater horseshoe bat (left) and the killer whale (right) have evolved to conquer the skies and oceans.

Below: Thrinaxodon was a small, swift flesh eater that could regulate its own body heat. Its descendants split into three main groups. Two of these survived and evolved into today's mammals, from the duck­billed platypus to chimpanzees and humans.

There were three main groups of early mammals. They can be distinguished from one another by their teeth. Megazostrodon

was the ancestor of the insect­eating mammals. Its cheek teeth -premolars and molars--€ach had three cusps (raised points) arranged in a line, helping the animal slice the hard shells and wing cases of its insect prey. To­day, the only surviving descen­dants of Megazostrodon are the egg-laying mammals.

Living about 230 million years ago, Haramiya was the ancestor of rodents. It had large, gnaw­ing incisors and cheek teeth that had several cusps to grind plant matter. This line of early mam­mals became extinct about 60 million years ago because it was not able to compete successful­ly with the descendants of the

Taeniolabis

EARLY CRETACEOUS PERIOD 140 million yeors ogo

third and most adaptable early mammal-Kuehneotherium.

Kuehneotherium had cusps on its premolars and molars that enabled it to crush and slice. Its descendants-the pantotheres -adapted to a wide variety of diets and became the ancestors of all of today's mammal species except the monotremes.

Fossilized skeletons of an early pantothere called Crusafontia in­dicate that it was a small, tree­dwelling insect eater. Its body length was approximately eight inches. It had a long tail, which probably helped it to balance and may also have been prehen­

sile (capable of gripping twigs and branches). This squirrel-like animal is believed to be the an­cestor of whales, kangaroos, el­ephants, bats, and most other mammals, including humans.

Duck-billed platypus

Chimpanzee

LATE QUATERNARY PERIOD Present day

EVOLUTION OF FISH

~--~- - --~~---- - - - --- - - ~

Fish were the first vertebrates to appear on earth, nearly S 00 million years ago. Since that time they have evolved into one

of the most diverse and successful of all animal groups.

KEY FACTS

FISH DIVERSITY

Some fish have developed ex­

traordinary adaptations. Many that live in the ocean depths are

illuminated by rows of fluores­

cent lights. These lights protect

the fish by imitating light from

the surface and disguising their

silhouettes. However, few pro­

tective measures are effective

against a shark. It can detect

tiny electric impulses flickering

through a victim's nervous sys­

tem, so it can find prey even in

dimly lit water.

The variety of shapes and col-

ors of fish is amazing. Some,

like clownfish, advertise their

identities with bright colors.

Others are well camouflaged.

The upright seahorse swims

Left: The elec­tric eel of the Amazon basin has organs in its tail that can discharge up to 550 volts of electricity-en­abling it to stun prey such as an­other fish or a frog.

FROM FISH TO LAND CREATURES

The fins of most fish consist of

flexible rays that are connected

to bones inside their bodies. In

bony fish the rays may be visi­

ble. In others they are covered

yvith thick skin. In some fish, like

the lungfish and the coelacanth,

each fin has an internal bone

structure like that of an arm.

The bones support fin rays.

Such "lobe-finned" fish were

common in the Devonian peri­

od, 400 million years ago. Fossils

suggest that they crawled out

of the water on limblike fins and

became the first vertebrates on

land. Eventually, their descen­

dants lost their fin rays and ac­

quired lungs, developing into

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Left: The flash­light fish lives in the ocean's dimly lit depths. Using a chemi­cal process, its light-emitting organs produce a glow that con­fuses predators.

unnoticed among underwater

plants, and the gray-mottled,

flat flounder blends into the

ocean floor.

Many fish display remarkable

powers of navigation. In order

to spawn, a salmon can find

its way from the ocean back to

the freshwater stream where it

was born. It may detect chemi­

cal changes in the water.

Some fish, such as the mud­

skipper, are able to absorb oxy­

gen from both air and water.

This amphibious lifestyle en­

ables them to exploit extra

food sources.

creatures resembling newts.

These gave rise to reptiles and

ultimately birds and mammals.

Left: The five­foot-long coel­acanth is the closest living relative, of the first land verte­brates. Discov­eredin 1938, this "living fos­sil" is almost identical to fos­sils that are as old as 140 mil­lion years.

01602009 11 PACKET 91

Although all fish are superbly adapted water-dwelling

vertebrates, there are many differences among them.

In fact the word fish encompasses a huge variety of

animals. To a biologist, a lamprey, a shark, and a perch

are no more alike than a snake, an eagle, and a gorilla.

~ FISH EVOLUTION The most primitive fish today are the 32 species of hagfish: wormlike scavengers with no jawbone and no true backbone, ribs, or skull. In place of jaws, a hagfish has a rasping tongue. A flexible rod of gristle called the notochord acts as a backbone.

Similar in appearance to hag­fish are the 40 parasitic lamprey species, which suck body fluids from living fish. Lampreys do not have jawbones, but they have rudimentary skeletons made of cartilage.

Although hagfish and lam­preys are grouped together as "jaw less fish," they are very dif­ferent and are placed in sepa­rate classes. According to fossil remains, the first fish, such as Arandapsis, were also jawless

but had broad bodies armored with bony plates, which proba­bly kept them on the seabed.

Fish with proper skeletons and jaws appeared much later. They evolved along two distinct lines represented by the other two classes of modern fish: sharks and rays in one class and bony fish in the other.

Sharks and rays have skeletons of cartilage, but bony fish have skeletons of true bone. The two types split apart some 400 mil­lion years ago and have been evolving ever since, with vary­ing success. Bony fish have di­versified into more than 20,750 species, compared to about 710 species of sharks and rays. These two classes account for over half the vertebrate species on earth.

~ WHAT IS A FISH? Fish come in many shapes and sizes and vary greatly in their habits. However, they all rely on water to supply them with needed oxygen, which they ab­sorb through gills. They also de­pend on water to maintain a steady body temperature.

Another feature that all fish have in common is that they are vertebrates. A vertebrate is an animal with a backbone, a structure that evolved for the first time among fish about 480 million years ago. All the other vertebrates-amphibians, rep­tiles, birds, and mammals­trace their ancestry to those primeval fish.

Other vertebrates gradually found ways of living on land. But fish, with very few excep­tions, have stayed in the water.

Front cover: The diverse wo:rl:d:O;f~~II~~~~E~iiill~~~~ fish includes fast-moving killers such as the great white shark, camou­flaged ambushers like the toad fish (inset left), and primitive sucking parasites like lampreys (inset right).

Arandapsis

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DEVONIAN PERIOD 400 million years ago

Hemicyclaspis

~ LIVING IN WATER The main difference between living in water and living in air is that water is much denser, re­quiring more energy to move through it. The bodies of many aquatic animals such as jellyfish have much the same density as water, so they float. They do not need skeletons or muscles since the water holds them up.

Fish are supported in a similar way, but they are heavier, so they tend to sink slowly. Sharks and other fast-moving fish over­come this by swimming with their winglike fins angled up­ward. The related rays spend their adult lives on the seabed. Many bony fish have swim blad­ders (gas-filled buoyancy cham­bers) that they are able to fill or

empty in order to rise or sink. The density of water has two

further consequences. First, a fast-moving fish must be stream­lined to pass through water eas­ily. The torpedo-shaped bodies of marlins and sharks are good examples: Second, because wa­ter is so dense, fish can generate a lot of thrust if their fins are con­nected to strong muscles, even though the fins themselves are relatively small compared with a bird's wings.

The fins' muscles need a firm foundation, which is the main function of the backbone. The vertebrate skeleton evolved to enhance the swimming ability of fish. It developed into a sup­porting frame only after their

HOLOCENE PERIOD Today

descendants emerged from the water to live on land.

Living in water, fish must deal with the problem of becoming waterlogged or sometimes de­hydrated. Water continuously passes into the body of a fresh­water fish by a process called osmosis. Since the fish's body fluids are more concentrated than the surrounding water, the water seeps in to dilute them. In order to avoid becoming fa­tally bloated, the fish must con­stantly pump out water. For a marine fish, the problem is re­versed. Its body fluids are less concentrated than the salt wa­ter around it, so water seeps out of its body. It must constantly drink water and expel the salt.

Cartilaginous fish: Sharks,

chimaeras, skates, and rays. Their skeletons,

made of car­Wage, are

lightweight.

Bony fish: The last group to evolve, it in­cludes more

than 20,750 living species.

These fish have skeletons made

of true bone.

Jawless fish: These include

the most primi­tive living fish

species: hagfish and lampreys. They lack jaws

and have a pli-able notochord as a backbone.

THE FALCON FAMILY

There are about 60 falcon species throughout the world, ranging from the tiny, sparrow-size falconets of Southeast Asia to the great white gyrfalcon of Arctic North America and Eurasia.

KEY FACTS

HUNTING CHARACTERISTICS

Falcons in the genus Falco usual­

ly have pointed wings and are

impressive fliers. The largest­

such as the gyrfalcon and the

peregrine, lanner, saker, lugger,

and prairie falcons-are strong

predators, killing birds in midair.

Hobbies have long wings and

are very fast fliers. They feed pri­

marily on large insects such as

dragonflies but can also catch

swifts, swallows, and bats.

Eleonora's falcon of the Medi­

terranean and the sooty falcon

of North Africa seize small mi-

FALCON CONSERVATION

People have both admired and

persecuted falcons for centuries.

Falconry-a sport using trained

birds to hunt wild game-be­

gan in the Far East about 4,000

DID YOU KNOW? • The rarest falcon is the Mau­

ritius kestrel. Only 10 or so are

left on the island of Mauritius.

• In species like the peregrine

falcon, Barbary falcon, or gyr-

grating birds. The red-headed

falcon of Africa and India and

the merlin of northern Eurasia

and North America are fast little

falcons that hunt small birds in

open country.

South America's forest falcons

have short, rounded wings and

long tails, giving maneuverabili­

ty. They twist and turn through

trees in pursuit of prey, which

they seize with their long legs.

Right: When it hunts, a kestrel hov­ers and scans the ground below for small mammals.

years ago. In medieval societies,

each noble rank was allotted a

particular falcon species. These

"noble hawks" were highly val­

ued, and any peasants caught

harming them or stealing their

eggs were severely punished.

But attitudes toward falcons

changed in the 17th century.

Landowners and gamekeepers

destroyed them as pests, along

with other birds of prey. In addi­

tion, collectors killed and stuffed

birds. Falcon eggs were prized

for their scarcity and the chal­

lenge of taking them from cliff­

ledge nest sites.

left: In Great Britain, the lanner falcon was traditionally used only by squires.

falcon, the female weighs near­

ly twice as much as the male.

• The gyrfalcon is the only day­

active bird of prey that is able to

survive the Arctic winter.

PRINT Fn IN I I S A

Since World War II, sympathy

for falcons has grown, and there

has also been a revival of falcon­

ry. Falcons are now protected in

many countries, and conserva­

tion projects are trying to save

rare species such as the Mauri­

tius kestrel.

But threats to falcons remain .

Because they are predators at

the top of the food chain, fal­

cons may suffer severely from

pesticide pollution. Toxins build

up in their bodies when they eat

poisoned prey. The decline of

the peregrine falcon during the

1950s and 1960s as a result of

DDT alerted conservationists to

the destructive effects pesticides

can have on wildlife.

• The crested caracara is Mex­

ico's national bird. Nicknamed

the "Mexican eagle," it is big,

w ith broad wings and slow

wing beats.

0160200991 PA KE

Although the falcon family includes the carrion-eating ~ DIFFERENT TYPES OF FALCON caracaras, all the other falcon species feed on a wide variety

of live prey. 50me of the smaller birds capture insects, voles,

and even snakes. Other members of the falcon family catch

birds the size of ducks and owls. Big species, such as the

peregrine falcon and the magnificent gyrfalcon, at

The falcons (Fa/conidae) are the

second biggest family of day­

active birds of prey, after eagles,

vultures, and hawks. They live in

diverse habitats on every conti­

nent except Antarctica. Some,

such as kestrels and peregrines,

may nest in city centers, while

others live in remote areas. times prey on mammals that are as large as hares. There are four subgroups: the

laughing and forest falcons; the

falconets and pygmy falcons;

the caracaras; and the true fal­

cons (genus Fa/co).

~ ORIGINS It is thought that falcons initially

evolved in South America. The

caracaras, forest falcons, and

laughing falcon that now live

in South America may be direct

descendants of the first falcons.

Over time changes in

global climate resulted

in fewer forest areas and

more grasslands as well

European kestrel: This very adaptable bird lives in a vari­ety of habitats. It generally hunts by hovering for some time on fast-beating wings and then swooping to the ground to snatch its prey in its feet.

laughing falcon: Named for its shrill call , which sounds like hysterical laughter. This bird specializes in catching snakes. After scanning the ground from a tree , it drops like a stone onto its victim.

as other kinds of open habitats.

Falcons then developed special

adaptations that exploited the

new habitats. The first birds re­

sembling today's typical falcons

were probably kestrel-like

predators that hunted a

variety of prey using

several different

techniques.

The true falcons are the larg­

est subgroup, with 38 species.

These aggressive birds include

the peregrine falcon, the gyrfal­

con, and the hobbies, merlins,

and kestrels. Most are solitary

and defend their own hunting

and breeding territories. Some

Crested caracara: Inhabits open country in addition to mountains and forests. It is not a powerful hunter, feeding on sick or wounded animals as well as fish , frogs , and any carrion it finds. In contrast to other falcons ' sharp, curved talons, it has flat , blunt claws that are adapted for walking and scratching in soil or vege­tation for insects.

Merlin: One of the smallest typical fal­

cons , it hunts by fly­ing fast and low over its moorland habitat, following each turn

of its bird prey.

tropical species live in pairs, de­

fending a territory and hunting

together. Others, such as the

lesser kestrel and the red-footed

falcon, live in groups.

The falconets and pygmy fal­

cons inhabit the tropics of Africa,

India, and Southeast Asia. They

are the smallest day-active birds

of prey. The laughing and forest

falcons are a little-known group

of seven primitive species in Cen­

tral and South American forests.

There are nine caracara spe­

cies. These primitive falcons live

only in the Americas. In contrast

to other falcons, they are bulky,

broad-winged birds with long

legs. They are sluggish, spend­

ing much of their time perching

or walking around, searching

for food.

~ BREEDING Typical falcons remain with the

same mate for many years. The

courtship displays may involve

spectacular aerobatics with the

birds chasing each other and the

male diving, swooping, and roil­

ing over on his back. At times he

circles with prey in his talons and

then drops it to the female be­

low, who turns on her back to

catch it. During the display, the

birds give shrill chattering, cack­

ling, and wailing calls. Later, they

frequently perform bowing cer­

emonies at the nest site.

Instead of building nests, most

falcons lay their eggs on a rock

ledge, often using the same site

year after year. Kestrels may use

ledges on buildings. Some spe­

cies nest in tree holes, using oth­

er birds' abandoned nest holes.

Gyrfalcon: The largest " and most powerful fal­con , it inhabits cliffs and uplands. It chases its mammal and bird

prey relentlessly, fly­ing low over the ground ,

often for long distances.

African pygmy falcon: A bold pred-ator for its size, it kills large in­

sects and small birds. It has large ear openings that help

it pinpoint the source of even the faintest rus­

tle of its prey.

Caracaras, however, do create

untidy, bulky structures of sticks

and twigs in trees or cacti, on

cliffs, or on the ground.

In most species, both parents

incubate the eggs, although the

female spends more time on the

nest. The male usually feeds the

female during the egg-laying as

well as incubation periods.

The newly hatched chicks are

covered with thick white down

and then grow a longer, denser

coat of grayish down after 10 to

12 days. Small species remain in

the nest for four to five weeks

and larger species, six to seven

weeks. After they fledge, the

young are dependent on their

parents another two to three

weeks in smaller falcons and up

to eight weeks in large species.

Front cover: Like most typical fal­cons, the saker is a powerful hunter and prefers open country.

Front insets: The crested caraeara (left) is a primitive falcon. The pere­

grine falcon (right) has been used by falconers for centuries.

HOW ANIMALS STAY CLEAN

Like humans, animals also try to keep themselves clean. But unlike us, they do not restrict themselves to baths and

showers or even to washing with water.

KEY FACTS

SOCIAL GROOMING

Mutual grooming often plays

a vital role in primate societies

and is part of the daily routine.

Unable to reach the fur on its

back, an individual must often

PREENING

Feathers are complex structures

that need a lot of care. In order

to fly well, a bird must keep its

plumage in good condition.

Most birds have preen glands

that produce an oil, which they

spread over their feathers with

their bills. This gland is largest in

water birds like ducks, geese,

petrels, and pelicans. Ducks and

geese preen up to 17 times daily

so that water rolls off their feath­

ers, leaving them light and dry.

rely on another to keep the area

free of dirt and parasites.

Primates of all sizes-from go­

rillas to chimpanzees--engage

in mutual grooming. This activi-

Left: The bar­bary ape lives in a highly or­ganized com­munity. Parents and older, non­related group members help groom the young.

Some birds expose their preen

gland to the sun to stimulate

the release of the oil.

Grooming movements can

serve as social signals among

birds. Courting birds may en­

gage in ritualized mutual preen­

ing. By turning its head away to

preen its feathers, a bird may in­

dicate submission to its partner.

Right: Birds spend much of their time preening and always preen after a bath.

© MCMXCII IMP BV/ IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A.

ty usually takes place among rel­

atives, strengthening the bond

between a paired male and fe­

male or between a mother and

her young . But grooming unre­

lated group members also has

its rewards. Vervet monkeys, for

example, live in big groups with

much rivalry and bickering. Sci­

entists have observed a female

vervet helping an unrelated fe­

male who groomed her earlier.

Thus, keeping clean not only

contributes to personal well ­

being, but it is also the founda­

tion of social alliances.

Left: The an­hinga can sub­merge silently in water due to its water­permeable plumage. To keep its feath­ers in good condition, it spreads its wings to dry after fishing for food.

0160200881 PACKET 88

An animal cannot survive if its body is not adequately

shielded from the elements. It therefore needs some kind of

protective covering such as fur, feathers, scales, or thick skin. /"

This covering must be maintained in prime condition at all

times-by preening, bathing, or other cleaning methods.

~ FU R, FEATHERS &: SCALES Fur keeps an animal warm, but a bird's volume without contrib-it must be kept "open" to be ef- uting much to its weight. They fective. Fur insulates by trapping also form a waterproof outer lay-warm air between its fibers. If it er, enabling a bird to take off is caked with dirt, the fur cannot without being dragged down trap air. by the weight of the water.

Feathers provide better insula- The risk of infection from par-tion. Penguins have a thick layer asites or wounds is a problem of insulating fat under their skin. for all animals. If fleas and ticks But their dense down and stiff are not removed regularly from feathers playa key role in keep- a mammal's coat, infected sores ing them warm by maintaining develop. Bats lick their wings ev-a layer of warm air between the ery day to heal tiny nicks. Even skin and the Antarctic cold. snakes, with seemingly spotless

The oily feathers of water birds scales, must rub against rocks to provide buoyancy by adding to get rid of mites.

Front cover: Like many birds that eat carrion (dead animal flesh), the king vulture has no neck plumage to get soiled.

Front inset left: The Cape buffalo takes mud baths to soothe its skin and protect it from parasites.

Front inset right: A clean­er fish is able to obtain food by grooming larg­er fish such as angelfish.

Many animals have cleaning equipment right on their bod­ies. A bird such as a heron, bit­tern, or tinamou has a patch of down that grows continually on its breast and belly. The tips of these feathers constantly dis­integrate to form a fine, water­resistant powder. As the bird preens itself or fluffs its breast feathers, the powder spreads over its body, helping to re­move excess oil and grease that would impede flight.

Some mammals also have built-in cleaning equipment. The slow loris combs its fur with its long lower incisors,

Left: A lion must lick a wound almost constantly to prevent it from becoming infected.

Left: Ground­dwelling birds such as the jun­gle fowl like to take dust baths to remove any excess oil from their plumage.

while the aye-aye lemur uses a thin claw on its index finger to untangle its fur and pick off parasites. The echidna has a special long claw on the sec­ond toe of its hind foot with which it scrapes off parasites from between its long spines.

Some animals actually pro­vide a cleaning service for oth­er species. Small, colorful fish that are called cleaner wrasse nibble dead skin, fish lice, and fungus off the scales of larger fish. The oxpecker, a small bird, provides a similar service by picking ticks and fleas off large grazing mammals.

Right: Water birds such as herons preen often in order to keep their feathers waterproof.

~ BATHING Wallowing in mud can serve a cleansing purpose. A mud bath helps remove ticks from a hip­po's body and soothes the irri­tated skin. The mud also dries on the animal to form a thin crust that keeps parasites from getting to the skin.

Elephants also take mud baths and spend a great deal of time caring for their inch-thick skin. If possible, an elephant bathes in water daily, using its trunk to spray water over its own back or a companion's. After bathing, it rolls in dust or sprays dust on its back with its trunk to cover its skin with a thin film that pro­tects against parasites.

Many birds, from house spar­rows to eagles, also take dust baths. Desert birds and game

Left: Using its trunk, an elephant can spray its entire body with mud and water.

birds vigorously fluff up their feathers to create dust clouds, which help remove excess oils that might mat their feathers.

Some birds "bathe" in smoke, fumigating parasites from their feathers by flying right through smoke rising from a chimney.

A crow or jay may clean itself by spreading its wings, ruffling its plumage, and then sitting on an ants' nest, so that the insects can crawl through its feathers. It is not clear how this activity aids cleanliness, but the formic acid that the ants excrete may repel parasites, relieve itching, or de­stroy feather mites. The pango­lin, an African mammal that has armorlike scales, also engages in "anting." It raises its scales to al­low the insects to crawl under­neath, then flattens the scales to crush the ants, creating an abra­sive effect.

With more than 3,000 species, lizards outnumber all other reptiles. Extremely varied in shape and size, they have successfully colonized almost every habitat on earth.

KEY FACTS ~------<~~ ----------------------------~--------------------~

LIZARD FEATURES

Scales: Lizard scales are made of keratin-the substance that forms human fingernails. New scales constantly grow beneath the old ones, which the reptile sheds in patches. Lizard scales take many forms. The Gila mon­ster and beaded lizard found in the southwestern United States have hard, knobby scales that repel predators, sand, and heat. The thorny devil's spikes, the crests of some male iguanas, and the "horns" of some cha­meleons are all modified scales. Limbs: Most lizards have very muscular legs with clawed feet for digging, running, or climb-

LIZARD DEFENSES Lizards have many different de­

fenses against predators. Best known is their ability to shed their tails when attacked.

Some lizards rely on a quick

• The giant mosasaur lizards of 100 million years ago devel­oped nostrils on their heads and paddlelike limbs similar to those of whales.

• Marine iguanas often dive to depths of 65 feet to forage for seaweed. These lizards have

ing-whatever the habitat de­mands. However, burrowing liz­ards like the so-called slowworm of Europe and the glass lizard of the United States have no legs at all. They move like snakes in sand or soft soil. Teeth: The teeth of lizards vary

escape. Fast-moving sand liz­ards like the fringe-toed lizard dive into the sand and "swim" away under the surface. In con­trast, the chuckwalla from the

Left: A lizard's cast-off tail wriggles, dis­tracting the predator while the lizard es­capes. It will grow another tail later.

special glands for ridding their bodies of salt.

• When threatened, a horned lizard can squirt a drop of blood out of its eye in order to startle an enemy.

• Some lizards possess a "third eye," called a parietal eye, near

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A.

Left: A chame­leon has mus­cular legs and a gripping tail, so it can hold onto branches tightly while stretching out acrobatically to reach an insect.

according to their diet. Insect eaters have sharp teeth for seiz­ing and holding prey. Plant eat­ers, such as iguanas, have teeth with serrated edges for ripping vegetation. The caiman lizard, which eats shellfish, has blunt teeth for crunching hard shells.

Southwest's deserts relies on staying put. It wedges its body into a crevice and keeps gulp­ing air until it swells up like a balloon, making itself impossi­ble to dislodge.

The Australian frilled lizard frightens away enemies by ex­tending its huge throat frill and opening its mouth wide. To de­ter attackers, the African arma­dillo lizard holds its tail in its mouth, turning itself into an unapproachable spiny ball.

the back of the head. Covered in translucent skin, it acts as a light meter to help control the reptile's sun-basking hours.

• Most small lizards live a few years at most. But one captive slowworm reached the age of 54 years.

0160200881 PACKET 88

Lizards are found all over the world, from equatorial

deserts to cold regions inside the Arctic Circle. These reptiles

range in size from tiny geckos to massive monitors, and

they display an amazing variety of survival adaptations.

Some species are capable of gliding through the air. Other

lizards are able to move underneath sand dunes. Still

others can even patter across water on their hind legs.

~ ORIGINS Lizards share a reptile ancestor

with dinosaurs and crocodiles.

By the time the dinosaurs began

roaming the earth, lizards were

already evolving along a sepa­

rate path.

The oldest known true lizard

fossils are from the late Triassic

period, 150 to 200 million years

ago. But many scientists believe

that there were earlier true liz­

ards, which have not yet been

discovered in fossilized form.

One extinct group of lizards,

Front cover: Although Aus­tralia's thorny devil looks in­timidating, it preys only on tiny ants.

Front inset left: The frilled lizard scares off its enemies by spreading its neck frill to make itself look bigger.

Front inset right: The ko­modo dragon is the heaviest liz­ard. It is a very fierce, powerful flesh eater.

the mosasaurs, lived in the sea.

At over 20 feet long, they were

much larger than modern liz­

ards. No lizards live entirely in

the sea today, but marine igua­

nas in the Galapagos Islands do

dive off rocks to find seaweed.

By the Oligocene epoch, 26

to 38 million years ago, many

lizards almost identical to mod­

ern forms had appeared.

Right: A chameleon is able to grip branches firmly because it has op­posable digits on its feet.

~ BREEDING Most lizards lay eggs, which are

placed in a scraped-out hollow.

Small lizards often lay only one

or two eggs, but larger species

like iguanas lay up to 50. The

egg usually has a leathery skin

and gets bigger as the embryo

grows. Gecko eggs are an ex­

ception, with shells that harden

and then remain the same size.

Many lizards are extremely fast

runners. The fastest are those

that run on their hind legs, us­

ing their long tails for balance.

The racerunner lizard of North

America can run 15 miles per

hour, and the tropical American

basilisk lizard can dash across

the surface of water. In contrast

to these species, chameleons

move slowly.

Many lizards are well adapted

for life in the desert. The Aus­

tralian thorny devil as well as

the American horned "toad"

have short, flat bodies covered

with fierce-looking spikes. Their

Left: The basilisk lizard is sometimes called the Jesus lizard because it can run across water.

Some lizards, including many

in cold climates, produce live

young. Outside the body of the

mother, the eggs would perish

in low temperatures. Some spe­

cies, like the whip-tailed lizard,

reproduce without mating. They

are all-female species whose off­

spring are genetically identical

to their mothers.

coloring and body texture cam­

ouflage them in their arid, rocky

habitats. The spikes also have a

cooling function. By increasing

the body surface area, they aid

heat loss and provide surfaces

and channels on which mois­

ture from the air can condense.

Other desert lizards cope well

in sandy conditions. The fringe­

toed lizard has scaly fringes on

its feet, so it moves easily over

sand. It can also bury itself when

threatened and "swim" under

the sand. Another species that

uses the same tactic is the Ara­

bian toad-headed agamid.

Right: The feet of Australia's leaf­tailed gecko are adapted for grip­ping smooth surfaces.

~ DIVERSITY Lizards come in many sizes and

shapes. This diversity is the se­

cret of their success as an order.

The smallest lizards are geck­

os, some of which weigh a frac­

tion of an ounce. Geckos have

tiny hairs on their feet, so they

can cling to slight irregularities

on a surface. These "sticky" feet

and a gecko's light weight en­

able the lizard to climb appar­

ently smooth surfaces and walk

upside down on a ceiling.

At the other end of the scale

Left: The whip­tailed lizard is an all-female species of the southwestern United States and Mexico. The offspring hatch from un­fertilized eggs and are exact clones of their mothers.

is the jungle-dwelling komodo

dragon of Indonesia. It reaches

a length of 10 feet and a weight

of over 330 pounds. This pow­

erful, fast-moving predator can

kill wild pigs and deer.

Chameleons are tree dwellers

that can change color to blend

in with their surroundings. Their

toes, which are separated into

opposed groups, give them a

firm hold on branches. Their

prehensile (gripping) tails pro­

vide extra security.

FLIGHTLESS BIRDS

... , ,, 1 • '.. .. ' .. _~ : "'. . " ~ '.' . . . _ .... . • .. _

A bird that cannot fly may seem a contradiction in terms. Yet some birds are better able to exploit their habitats

by keeping their feet on the ground than by flying.

KEY FACTS --------------------------------------------------~

EVOLUTION OF RATITES AND PENGUINS

Ratites appeared 80 million years ago. Different types evolved on each continent when the land­masses separated. The surviving ratite groups are classified in dis­tinct orders, indicating that each group is highly differentiated.

Below: A full-grown rhea can run

I faster than a horse over the pam­pas of South America.

CONSERVATION

Flightless birds on islands with­out mammal predators were threatened when settlers intro­duced livestock, pets, and pests. The birds lacked defenses, and

I their ground nests were vulner­able. One victim was New Zea­land's kakapo, and now only about 40 birds remain.

All ratites must have evolved from ancestors that could fly, since they share many charac­teristics with flying birds. Along with biochemical evidence, the similar bone structures of ratites and weak-flying tinamous from Central and South America sug­gests that the ancestors of these birds may have been related.

Kiwis have declined since the first Europeans arrived in New Zealand over 150 years ago. Al­though the brown kiwi and the great spotted kiwi are still wide­spread on South Island, land clearance poses a threat to the brown kiwi on North Island. To protect the endangered little

© MCMXCII IMP BV/ IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A.

Penguins developed about 70 million years ago and evolved underwater "flight" 45 million years ago. Since then, they have changed little, spending up to three-fourths of their life in icy southern waters.

Below: Using its razor-sharp claws, a cassowary can disembowel an en­emy with a well-aimed kick.

spotted kiwi, its population was moved to Kapiti Island in Cook Strait. While its numbers have increased, it is still at risk.

Rheas are hunted for food and for their plumage, which is used for feather dusters. They are also killed because they supposedly damage crops.

The ostrich is not threatened, but many populations have de­clined because of habitat loss. Cassowaries are at risk due to destruction of tropical forests. Humans have actually helped the emu, which has colonized dry areas in Australia's interior where watering points were set up for cattle and sheep.

Left: The little spotted kiwi has no defenses against mammals that settlers brought to New Zealand.

0160200921 PACKET 92

Some birds became flightless because they lived on

predator-free islands and, as a result, had no need to take

to the air. Others, like penguins, exchanged their wings for

paddlelike structures that helped them "fly" underwater.

Still other birds, such as the ostrich, developed long,

powerful legs on which they could outrun their enemies.

~ WHY FLIGHTLESS BIRDS DEVELOPED The 50 or so flightless bird spe­cies alive today all evolved from flying ancestors. Although flight has advantages, it also imposes restrictions. It limits a bird's size and weight, reducing the bird's efficiency in exploiting certain food supplies. In addition, a bird must develop special muscles to fly and keep its plumage in per­fect condition. So when there was little benefit from flying, as on islands that had no mammal predators, birds such as the ka­kapo and many rail species be­came flightless .

Front cover: The brown kiwi has an excellent sense of smell. It searches for beetles as well as earthworms in soft soil with its long, curved bill.

Front inset left: On land, the appropri­ately named rockhopper penguin hops with both feet.

Front inset right: The ka­kapo uses its bill and sharp claws to climb trees.

In the vast, open South Amer­ican pampas and African savan­nas, the ostrich and the rheas abandoned flight for greater size. Their long necks and legs let them spot predators at a dis­tance and sprint to safety.

Penguins' wings evolved into "paddles," propelling them un­derwater. Growing larger and heavier, these birds acquired an insulating layer of fat and con­quered the icy Antarctic waters.

Right: Although the emperor pen­guin is clumsy on land or ice floes, it moves well in the water.

~ FOOD &: FEEDING Flightless birds must generally feed on the ground, but they are good at exploiting the avail­able food supplies. Rheas eat weeds that most other animals avoid, while the ostrich selects the most nutritious plants on the dry plains. Both birds have long digestive tracts that help

~ BREEDING New Zealand once had no land­based predators, so the kakapo could safely nest on the ground . But settlers introduced rats and cats, which stole its eggs.

Many penguins do not use a nest at all. They incubate their eggs between their warm feet and a warm fold of their bellies.

Up to 12 females mate with a dominant male rhea, laying a total of about 60 eggs in his nest. The male then incubates the clutch, and he cares for the chicks for up to six months.

Cassowaries, emus, and kiwis form pairs, but a female casso­Left: Since a cassowary has a short­er neck and legs than an ostrich, it can forge through dense thickets.

deal with their vegetarian diets. The emu prefers seeds, fruits,

flowers, and young shoots. With its large fat reserves, it can trav­el hundreds of miles if there is a food shortage.

Penguins feed on prey in the water, diving for several minutes to find their food.

wary may mate with one or two other males after laying her first clutch. The male incubates the eggs and rears the chicks.

A male ostrich loosely bonds with a dominant, "major" hen but mates with up to five other hens. Unlike other ratites, both the male and major hen incu­bate the eggs. Although these eggs are the largest bird eggs, they are the smallest in relation to the female's size-at about 1.5 percent of her body weight. After hatching, ostrich broods often join up and are guarded by one or two adults. Right: A male ostrich may help in­cubate dozens of eggs from several females in one nest.

Ratites are large, flightless birds that have lost the large keel on their sternum, or breastbone. In flying birds this bone anchors the powerful flight muscles.

People exterminated two rat­ite orders: New Zealand's moas and Africa's and Madagascar's elephant birds. The surviving orders contain the ostrich, cas­sowaries, rheas, emu, and kiwis.

The ostrich, the largest bird in the world, is the only species that has just two toes per foot. It can run over 40 miles per hour and over 60 in short bursts.

Left: When it is in the wild, the flightless kaka­po feeds mainly on shrub ber­ries, roots, and grasses. Birds in captivity favor sweet foods as well as fruit.

The two rhea species live in grassland and scrub from Brazil to South America's southern tip. Like the ostrich, they have prom­inent wings and flap these dra­matically when courting.

In Australia the emu lives in open areas, while the three cas­sowary species dwell in the jun­gles. Cassowaries possess only remnants of wings.

All four kiwi species are squat, essentially wingless birds that forage in the forests and scrub of New Zealand. Their feathers resemble a mammal's hair.

FROGS AND TOADS

There are nearly 2,700 frog and toad species, making up the bulk of the world IS amphibian species. Most of these creatures go through a larval stage and spend part of their lives in water.

KEY FACTS

CAMOUFLAGE AND SELF-PROTECTION

~ro9S face many predators, and

their thin-skinned bodies offer

little protection against sharp

I claws, teeth, and beaks. To sur­

:,ive, frogs use ca~ouflage and, In some cases, pOisonous secre­

tions in their skin.

One North American treefrog

is patterned and colored so as

to blend in with rough bark and

patchy lichens. Rainforest frogs,

such as Hyla granosa from Ecua­

dor, are frequently bright green,

matching the lush foliage.

The Asian horned frog mimics

the colors and textures of dead

leaves on the forest floor. It even

TOADS

Toads belong to the family Bu­

fonidae, one of the 20 frog fami­

lies. Compared to frogs, toads

are squat and often seem clum­

sy. They are usually warty, with

drier skin than frogs' skin. Many

have short hind legs, which are

better for walking than hopping.

Most toads are dull in color, but

there are exceptions, such as the

European green toad, which has

green and orange markings.

Right: The male midwife toad car­ries the eggs on his back until they I are ready to hatch.

Left: A poison­arrow frog pro­duces a dead­ly toxin. Some tribes in South American for­ests smear this poison on the tips of their ar­rows and blow darts.

Most toads are active mainly

at night. In the breeding season

large numbers gather at ponds

.9 MCMXCII IM P BV/IMP INC WILDLIFE FACT FILE TM PR INTED IN U.S.A

Left: The Asian horned frog has flaps of skin, or "horns," that camouflage it among leaves on the forest floor. Horned frogs do not move much, preferring to wait and am­bush snakes, lizards, mice, and the oth-er vertebrates that form their staple diet.

has a dead leaf's shape, with flat

points over its eyes and snout.

Frogs that produce dangerous

toxins often advertise this with

brilliant skin colors. Phyllobates terribilis from Colombia is one of

the most lethal, making enough

toxin to kill12 or more people.

Its warning color is bright yel­

low or orange.

or other breeding sites. Individ­

uals often return to the same

pond year after year.

0160200931 PACKET 93

Frogs and toads can be found in a variety of habitats

throughout the world. They live in swamps, in trees, on

the ground, and even in arid deserts, where they bury

themselves between the infrequent downpours. These

amphibians range in size from a tiny South American

treefrog only a few inches long to the huge goliath frog

of the West African rainforests, weighing over six pounds.

~ EVOlUTION Amphibians-the class between fish and reptiles- were the first vertebrates to move from water to land. Frogs and toads form the largest order of amphibians.

The earliest froglike fossil was found in Madagascar and is 220 to 230 million years old. Called Triadobatrachus, this animal was about four inches long, with a wide, flat skull, elongated hind legs, and a short tail.

The first true frog fossils, called

Front cover: The European treefrog often spends the day perched near water while it soaks up sun.

Front inset left: Like most treefrogs, the South Ameri­can brown and gold treefrog has adhesive pads at the tips of its fingers to grip branches.

Front inset right: A com­mon frog has reached the adult stage when its tail is fully absorbed.

the" ancient frogs" (Archaeoba­trachia) lived some 150 million years ago. The next group, re­ferred to as "middle frogs," ap­peared 100 to 135 million years ago. The "new frogs," forming the suborder Neobatrachia, date back 50 million years. All mod­ern frog families originated in these three ancient suborders.

Right: Frogs use their strong legs to make a series of springy leaps, while toads crawl.

~ HABITAT Most frogs live near water rath-er than entirely in it. A frog that spends most of its life in water usually has powerful, webbed rear limbs. Its eyes and nostrils are set high on its head, so it can see and breathe with most of its body submerged.

Central and South American treefrogs form one of the larg­est groups. They are excellent climbers with large, adhesive toe pads that enable them to cling to smooth leaves as well as branches. Rhacophorus nigro­

palmatus is a species that can glide from tree to tree. As it

Left: Treefrogs can climb relatively smooth surfaces using their suction­like toe pads.

Left: Frogs go through a two­stage develop­ment from the egg to the final adult form. The larval stage, or tadpole, devel­ops in water and feeds on plants.

leaps, this frog spreads out its webbed hands and feet to form a gliding surface.

Spadefoot toads are named for the leathery projections on their hind limbs that they use to burrow backward into the ground. The American spade­foot lives in desert regions and escapes the long months of dry weather by burrowing under the ground. Once the rains be­gin, the spadefoot comes out of its burrow to spawn. All the developmental stages are then sped up, so the cycle is finished in three weeks.

Right: Frogs do not have clearly defined necks, so their heads seem directly attached to their bodies.

~ lIFECYClE Frogs' eggs lack shells but are protected by a jellylike material. Many frogs lay their eggs in clus­ters, while some toads lay their eggs in long double strings. In some places frogs make foam nests to protect their eggs. For­est frogs may lay their eggs on leaves overhanging water, so emerging tadpoles fall from the leaves into the pond or stream. Other frogs lay their eggs in spe­cially created mud basins or in small pools. They leave a mud­dy passage to help the tadpoles reach larger bodies of water, or they carry the tadpoles there.

The egg is fertilized in most species as it emerges from the female. The single cell begins to divide, and the embryo length­ens into the larval stage called a tadpole. The speed of growth depends on the species as well as the climate. When the em­bryo has developed a mouth,

eyes, and external fishlike gills, it usually hatches from its jellylike casing and continues to devel­op as a free-swimming tadpole.

Most tadpoles feed on small plant organisms. Some filter wa­ter through an internal particle trap. Others are equipped with a horny mouth lining that they use to file organic material from leaves and rocks. Most of a tad­pole's body consists of the long, coiled intestine that it needs to digest plant food.

Eventually the hind legs begin to grow out from the body. The tadpole's forelimbs appear from under a flap of skin, and its tail is reabsorbed by the body. Its soft bones harden, while its mouth widens. Increasingly, the tad­pole begins to look like a frog. When the tail has disappeared, metamorphosis is complete, although the new frog contin­ues to grow.

HOW MAMMALS SWIM

- -- -- - - - - - - - . - ~--- -

A surprising number of mammals are able to swim. Those that spend all or most of their time in the water have special adaptations that

allow them to swim fast or dive deep for long periods.

KEY FACTS

AQUATIC MAMMALS

Most mammals can swim, but only two groups spend all their time in water. They are the ce­taceans (whales, dolphins, and porpoises) and sirenians (the du­gong and manatees).

While the pinnipeds are most­ly aquatic, they come ashore to breed. This group contains true

I seals, eared seals (fur seals and sea lions, which have small ex­ternal earflaps), and the walrus.

There are also four-legged, of­ten furred mammal species that

TAIL POWER

Seals swim by moving their rear flippers sideways, but cetaceans and sirenians lack external hind limbs. Instead, they have flat, horizontal tails. Manatees have spade-shaped tails, while other species have fishlike tails.

The animal is propelled by its tail as well as the rear third of its

I DID YOU KNOW? • Blubber is not a soft or jelly-like substance. It is hard like a slab of bacon. • An adult male sperm whale was recorded making a dive of oVer an hour and a half.

are at home on land but spend some of their time in the water, cooling off, grazing, or hunting prey. They range in size from the

body. Its tail and body move up and down, not sideways. Large muscles above the midline impel the upstroke. Smaller muscles, below the midline, pull the tail down. The flukes (two halves of the tail) flex up but not down,

left: The Florida manatee's broad, rounded tail both propels and sta­bilizes its huge bulk.

• A bull elephant seal has 124 gallons of blood, while a per­son has less than 5 quarts. • The hippopotamus at times submerges to walk along the riverbed. It sinks or rises to the

© MCMXCI I IMP BV/IMP INC WILDLIFE FACT FILETM PRINTED IN U.SA

left: Like oth­er sirenians, a manatee is to­tally aquatic. But it must rise to breathe every few minutes. It is also limited to warm tropi­calor subtropi­cal waters.

polar bear and hippopotamus, through medium-size beavers and otters, to the small Pyrene­an desman and water shrews.

Left: The flukes of its tail propel the humpback at speeds of up to 17 miles per hour. At times the whale slaps the water, per­haps to stun its prey.

so on the upstroke the tail is ful­ly spread for maximum power.

To lessen resistance, the ani­mal has a streamlined body. Its smooth, firm skin reduces drag. Cetaceans may lubricate their skin to minimize friction .

The front flippers aid steering and balance. Some species have dorsal fins to improve balance.

surface by contracting or ex­panding its lungs. • The sperm whale has been recorded at a depth of close to 3,760 feet, and it may dive to 9,840 feet.

016020097 1 PACKET 97

Only the fully aquatic mammals have completely conquered

the problems of moving, feeding, and staying warm in water.

However, the ability to swim gives a land-based mammal

certain advantages, including the possibilities of expanding

its range, broadening its diet, and avoiding enemies.

~ ROWING & PADDLING Fur seals, sea lions, and the wal­

rus propel themselves with row­

ing strokes of their front flippers.

For maximum speed, they also

use their flexible hind flippers

and rear end.

A four-legged, partly aquatic

mammal often does a kind of

"dog paddle." A long tail may

be used as a rudder. However,

the giant otter shrew keeps its

legs close to its body and undu­

lates its long, flattened tail.

Limbs and tails are frequently

adapted to maximize their area

in the water. A water shrew has

hairy fringes on its feet and its

Right: Thick skin plus a layer of blubber up to six inches thick keep the walrus warm in Arctic seas.

Front cover: With its flexible neck, the belu­ga whale can turn sharply.

Front inset left: The South American sea lion swims with a speed and a grace that few other mammals can match.

Front inset right: The hip­popotamus en­ters a river to take the weight off its legs.

tail's underside. The Pyrenean

desman has a long, flattened tail

and stiff bristles on its webbed

feet and partly webbed fingers.

The larger Russian desman can

use its flexible snout as a snorkel.

All beavers paddle with their

webbed hind feet, using their

broad, flat tails as rudders. But

the polar bear-which spends

much of its life in Arctic waters­

does not have such adaptations.

~ ECHOLOCATION Underwater visibility is generally

poor, and below 650 feet there

is little light. Like bats, dolphins,

porpoises, toothed whales, and

seals use echolocation to survey

their surroundings, communi­

cate, and hunt prey.

~ STAYING WARM Mammals have two adaptations

to keep out the chill of icy water.

Many furred mammals, such as

mink, otters, and muskrats, pos­

sess two layers of hair. The long,

water-repellent guard hairs cov­

er a dense, fluffy undercoat. The

guard hairs mat together when

wet to form a waterproof "skin"

that traps an insulating layer of

air in the undercoat. Water nev­

er reaches the skin. After a few

shakes on land, the animal is dry.

A water shrew does not have

Left: A water shrew traps an insu­lating layer of warm air in its fine fur when it dives.

The animal emits sound clicks,

each shorter than a millisecond.

If these bounce off an object, the

animal picks up the echo, which

tells it the distance, shape, and

size of the object. It can focus its

clicks on a small fish to pursue it.

long guard hairs but traps air in

its velvety fur. Water eventually

reaches the skin, so when the

shrew lands it runs through a

tight tunnel to wring itself dry.

Truly aquatic mammals lack

fur but have insulating blubber (oil-filled cells) below their skin.

Some whales' blubber is a foot

thick. To regulate its tempera­

ture, a whale can open or close

blood vessels in its blubber, let­

ting blood flow near its skin if it

needs to cool off.

Right: The common seal's stream­lined body enables it to swim and dive rapidly.

~ DIVING Whales must breathe air but can

stay underwater for more than

an hour, and some dive over a

half-mile. While a seal exhales

before it dives, a whale inhales,

diving with a lungful of air.

Pressure at depths below 325

feet causes lungs to collapse, so

the whale stores oxygen in its

blood and muscles. It has a large

Left: The polar bear uses its forelegs to pull itself through the water.

Left: The sleek­skinned com­mon dolphin is the fastest of all small dol­phins, but it must still sur­face to breathe.

volume of blood, rich in hemo­

globin-a protein carrying dis­

solved oxygen. The whale drops

its heartbeat, slowing the flow

of blood, and it can reserve ox­

ygenated blood for its brain . It

can tolerate relatively high lev­

els of carbon dioxide dissolved

in the bloodstream.

If they surface too quickly, hu­

man divers get the "bends," a

condition where dissolved nitro­

gen bubbles out into the blood.

To avoid this problem, a whale

has oily foam in its air passages

to absorb the nitrogen. This is

expelled when the whale sur­

faces and blows.

Left: The European otter is equally at home in water or on land.

HOW MAMMALS HUNT

Many mammals actively hunt for prey, rather than simply foraging for food. The most specialized hunters are members of the true

carnivore families, which feed almost exclusively on flesh.

KEY FACTS --------~~------- -----~--~----------------~--------------------------~

WHAT MAKES A GOOD HUNTER?

To detect prey, hunting mam­mals need keen sight, smell, or hearing. They must also be able to move fast, judge distances, seize prey, and quickly kill it. The carnivores, including the dog, cat, bear, weasel, civet, and hy­ena families, possess many of these hunting characteristics.

Cats are muscular and lithe with quick reflexes. Their long, flexible bodies and strong limbs are suited to bursts of action, rather than long chases. Most cats have sharp, retractile claws. While stalking prey, a cat keeps its claws sheathed, but when it leaps it unleashes them, using them to hold the prey while it attacks with its jaws and teeth.

With short bodies, large rib cages, narrow hips, and long, slender legs, many dog family members are adapted to long

chases, using their stamina to wear down prey. They run on the tips of their toes, aided by blunt, nonretractile claws.

Many weasel family members have long, sinuous bodies and short legs, so they can pursue mice, rabbits, and other prey into their underground tunnels.

A hunting mammal general­ly has fairly close-set eyes at the front of its skull, giving it binocu­/ar(overlapping) vision. This en­ables it to judge distances and hit its prey when it leaps. In con­trast, most prey animals have eyes at the sides of their heads, giving them all-around vision to look out for predators.

Cats have some color vision and keen night vision, with re­flective tissue in each eye that maximizes image detection. Their touch-sensitive whiskers

Left: Lionesses are more effi­cient hunters than lions. But both sexes have long canines set in short jaws, giving them tremen­dous biting power.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A.

Above: Before pouncing, the serval listens intently to pinpoint the loea­tion of its prey.

help in the dark, and they can hear high-frequency sounds, such as small rodents' squeaks.

Dog family members depend mostly on smell to follow prey, often hunting with their muz­zles close to the ground. Some foxes and jackals have superb hearing. With its huge ears, the bat-eared fox can hear dung beetle grubs gnawing under­ground. Other foxes listen for rodents burrowing in snow.

Left: An otter swims as well as the fish it preys upon andean travel 7,300 feet underwater be­fore surfacing. Matted guard hairs covering its coat help keep it warm.

0160200941 PACKET 94

Hunting mammals have evolved specialized techniques

to ensure their survival. Some stalk their prey at night,

while others catch their victims during the day. Some work

in teams, while others hunt alone. Most have sharp teeth

that can cut through flesh strong claws, acute senses, and

muscular bodies capable of sudden bursts of activity.

~ ORIGINS Some of the earliest mammals

ate insects. Instead of actively

hunting, they probably foraged

for prey, scurrying through the

undergrowth and devouring in­

sects as they came upon them.

For many millions of years, al l

mammals were foragers, eating

insects, plant material, or both .

The ancestors of today's car­

nivores evolved in the Eocene

epoch, 54 to 38 million years

ago. They developed carnassial teeth, which could cut through

animal flesh. All modern carni­

vores possess carnassials.

Front cover: The Alaskan brown bear learns by trial and error to seize leaping salmon in its jaws or claws.

Front inset left: The leop­ard is a wary hunter, looking out for the lions and tigers that will attack it if they can.

Front inset right: Like foxes and jackals, the coyote pounces from a height onto prey.

t -

Left: African wild dogs seize a wildebeest by the upper lip, which seems to tranquilize it. Meanwhile, fel­low pack mem­bers grab its tail and rear limbs to bring it down.

~ SOLITARY HUNTERS The polar bear is camouflaged

by its white fur, whether it stalks

seals on the ice or crouches by a

hole in the ice, waiting for seals

to rise for air. Many bears, such

as the American black bear and

grizzly, catch fish in the shallows.

They hook prey with their claws

or grab fish with their jaws.

Cats are superb stalkers. They

crouch low and creep slowly,

pause stock-still for minutes if

necessary, and then explode

into a charge or leap. The chee­

tah is one of the few cats that

chases its prey. With its long,

Left: The cheetah 5 sinuous, lithe body is suitable for a high-speed chase rather than an ambush.

flexible spine, it can sprint over

60 miles per hour, although it

lacks the stamina for a lengthy

chase. To kill prey, the cheetah

bites it on the throat and holds

on until it suffocates. Specially

adapted nasal passages let the

cat breathe while biting .

Members of the weasel family,

such as otters and mink, can be

ferocious. The weasel, the small­

est in the family, can kill a hare

10 times its weight. It mesmer­

izes birds by doing spins and

somersaults, then lunges into

the air to seize a victim.

Right: Camouflaged and warmed by its coat, the polar bear waits for seals to surface.

~ TEAMWORK ON THE HUNT The gray wolf hunts in packs. In

forests where deer are the main

food, up to eight wolves hunt

together over a territory of 40

square miles. In the Asian and

North American tundra, gray

wolves hunt for caribou in packs

of up to 20 animals, roaming up

to 400 square miles.

A hunting pack, often in sin­

gle file, travels through its terri­

tory until it flushes out a lone

quarry or encounters a grazing

herd. The wolves usually corner

single animals. With a herd of

large prey such as musk oxen or

caribou, they harass the group

until panic disrupts its defensive

formation. The wolves then iso­

late a vulnerable animal, such as

an old adult or a calf.

The African wild dog is an ex­

pert in hunting cooperatively.

Packs of 6 to 30 dogs cover up

Left: In a team effort, some lions hide downwind, while others herd prey into the ambush.

to 30 miles per day, searching

for prey. The dominant breed­

ing pair leads the hunt, usually

at dawn or dusk. After selecting

a victim, such as a gazelle, and

separating it from the herd, the

wild dogs wear it down by their

speed and stamina . They can

keep up the chase for 3 miles at

a speed of almost 40 miles per

hour. The wild dogs attack the

tired animal from both ends,

bringing it to the ground and

quickly disemboweling it.

Lions hunt as a team. When

they move in on a herd of prey,

they may spread out in a line to

intercept strays. Often the males

roar, so the herd panics, splitting

and fleeing in all directions.

Chimpanzees may also work

in teams to capture a monkey.

They chase their prey through

the branches and force it to take

risks until it is cornered or falls to

the ground, where other chim­

panzees trap it.

Marsupials range from tiny shrewlike animals to kangaroos. Barely developed at birth, the young live on their mother's milk for up to a

year and a half and are often protected in a special pouch.

KEY FACTS

AMERICAN MARSUPIALS

1 0 large marsupials remain in the Americas. The surviving spe­cies are mainly in the opossum family. Most are good climbers, with well-developed digits and a thumblike big toe. They usual­ly have prehensile tails, which they curl around branches when climbing. Some, such as the Pat­agonian opossum and several mouse opossums, can store fat in their tails if food is scarce.

The Virginia opossum of Cen­tral and North America eats any-

I thing from fruit to city garbage. The largest American opossum, it can be over three feet long . In contrast, the Formosan mouse

opossum of Argentina measures about five inches.

The water opossum, the only truly aquatic marsupial, uses its webbed hind feet to swim. The entrance of the female's pouch closes to keep water out when

SMALL MARSUPIALS OF AUSTRALIA AND NEW GUINEA

The most numerous marsupials in Australia and New Guinea are probably the dasyures, a family of primarily small flesh eaters. A number of them resemble mice or shrews, with pointed snouts for digging up insects and small but sharp teeth .

The fierce, carrion-eating Tas-

man ian devil is the biggest das­yure. The spotted-tailed native cat is almost as large. It prefers live prey such as wallabies and some reptiles .

Bandicoots, phalangers, and gliders also live in this area. Ban­dicoots have thickset bodies and dig up worms and grubs with

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A

Left: The lutrine water opossum nests in reeds at the riverside. It is a strong swim­mer, lashing its tail like a whip from side to side and paddling with its hind feet.

she submerges to find fish, crus­taceans, and frogs.

Shrew or rat opossums live in the Andes. Usually less than 31 inches long, they are most active at night, foraging on the ground for insects or small vertebrates.

their three-toed forefeet. The brindled bandicoot may have the shortest gestation of any mammal (12~ days).

Phalangers have big eyes and gripping tails . Most are night­active tree dwellers . New Guin­ea's cuscuses possess tiny ears and dense fur. Brush-tailed pos­sums in Australia and New Zea­land have larger ears.

The sugar glider and its rela­tives live in forests and eat fruit, leaves, gums, pollen, sap, and nectar. Using skin membranes between their limbs, they glide from tree to tree.

The marsupial mole has a cy­lindrical body, blunt snout, short but strong legs, and sleek, pale brown fur. It uses its sturdy claws to burrow and eats insect larvae.

Left: A tough plate on the marsupi­al mole's nose protects it as it digs.

0160200981 PACKET 98

Marsupials are found mainly in Australia, New Guinea,

and the Americas. They include grazing species, such as

kangaroos; fruit and nectar eaters, like woolly opossums;

and flesh eaters, such as the spotted-tail native cat and

Tasmanian devil. Marsupials are adapted to a variety of

different environments, with opossums climbing in trees

and the marsupial mole burrowing in the ground.

~ ORIGINS Some 100 million years ago, the marsupial and placental mam­mals diverged . Placentals devel­oped a system of nurturing their young inside the female's body, while marsupials gave birth to embryonic offspring and then nursed them outside of the fe­male's body, usually in a pouch.

The oldest fossils of marsupials come from 75-million-year-old rocks in North America. Those animals spread into what is now South America. Then the land­masses separated. Marsupials in North America, unable to com-

Front cover: The koala is a peace­able tree dweller.

Front inset left: The sugar glider "flies" between trees.

Front inset right: Most newborn marsupials suckle for some time in their mother's pouch.

pete with placenta Is, died out. Isolated from placentals, mar­

supials in South America evolved freely for 60 million years. Two to five million years ago, a land bridge reunited the two Ameri­cas. Placental mammals moved south, and the big marsupials became extinct. Smaller marsu­pials survived, and some even went north. Today the Virginia opossum is the most common North American marsupial.

The earliest marsupials in Aus­tralia date back some 32 million years. They probably reached there via Antarctica, which con­nected Australia to the Americas. In time Australia split away and drifted north, remaining isolated from other landmasses. Its mar­supials evolved without compe­tition into a range of creatures.

Numbat: Lives in the wood­lands of southwestern Aus­

tralia . It employs its claws to dig out termite colonies, ex­tract ing the insects with its

tongue. Since the female lacks a pouch , she keeps

her litter in a burrow.

~ THE LARGE MARSUPIALS The best-known Australian mar­supials are the koala, wombats, kangaroos, and wallabies. The koala and wombats have some similarities, but the koala lives only in trees, while wombats live in burrows. The koala finds all its food in the trees, eating the leaves of about 20 species of eucalyptus. The female bears one offspring every two years. It lives in her pouch for 7 months and then travels on her back, fi­nally leaving her at 11 months.

Wombats are squat and pow­erful, using their long claws to dig burrows as long as 100 feet. They rest underground to avoid the daytime heat and emerge to feed on grasses after dark.

Kangaroos and wallabies are, respectively, big and small mem­bers of the .same family. While they are related to kangaroos, rat kangaroos are much smaller and belong to a separate family.

Some prehistoric kangaroos were huge-1 0 feet high. The largest marsupial today is the red, or plains, kangaroo. Some males are over 5 feet tall and weigh about 200 pounds. The red kangaroo is widespread in Australia's dry flatlands. Prefer­ring to travel in groups, it can leap 5 feet with a slow hop and over 13 feet in a hurry. Males can move 40 miles per hour.

Other kangaroos include gray kangaroos, which inhabit forest

~ BREEDING Marsupials get their name from the Latin marsupium, meaning "pouch." Most have some sort of pouch in which their young develop. In some, such as a kan­garoo, it opens forward . In oth­ers, such as the koala, it opens to the rear.

Compared to placental mam­mals, marsupials have a very

Western gray kangaroo: One of the largest marsupials. After leaving the pouch, the joey (young) returns for milk, suckling at a "personal " teat that yields the correct milk composition .

Tasmanian devil: Weighs up to 18 pounds and reaches three feet in length .

and scrubland. They sleep in the shade during the day and come out at dusk to graze.

The whiptail wallaby lives on grassy hillsides, where it grazes in groups of about 50 animals. The swamp wallaby is at home in marshy country on the east­ern coast, while the brush-tailed rock wallaby hops among rocks and cliffs in the mountains of New South Wales, employing its long, slender tail for balance.

One of the smallest true kan­garoos is the quokka. About the size of a hare, it has a squat body with short ears. It inhabits the swamps and thickets of Austra­lia's southwest coast and one or two small islands.

short gestation. Opossums are born in only 12 to 14 days, pha­langers in 16 to 17 days, koalas in 34 to 36 days, and kangaroos in 36 days at most.

The newborn is hairless, blind, and embryolike with only crude limbs. As it makes its way to the pouch, it sometimes follows a track of fur licked down by its mother. After it is inside, it sucks on a nipple that swells to fill its mouth and remains securely at­tached for several months. The pouch protects the offspring, so

It eats mainly dead flesh , using its pow­erful jaws and large teeth to rip carcasses apart and crunch up bones. It has been known to steal poul­try and lambs from ·farms.

Mouse opossum: The 47 species vary greatly in their diets, climbing abilities, and habitats. The young cling to their mother, since she lacks a pouch .

it can reach a well-developed stage before facing the dangers of the outside world .

In some kangaroo species, the mother mates shortly after giv­ing birth. But the fertilized egg remains in her body and only develops after the first offspring has left her pouch . The young kangaroo goes out for brief peri­ods at first, leaving the pouch for good at 5 to 11 months old. It may stay with its mother for another 2 to 6 months, suckling from outside the pouch .