MAMMALS

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MAMMALSMAMMALS

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Mammals

Contents

Origin andEvolutionPage 6

What TheyAre LikePage 18

Behavior andLife CyclePage 32

Relationshipwith PeoplePage 80

Page 60

Diversity

hunters and gatherers to a society based onagriculture. At that time, humans began tobenefit from the meat and milk products ofsmall mammals and to use large animals forlabor. The first animals to be domesticatedwere sheep (about 9000 BC) in the MiddleEast. Pigs, cows, goats, and dogs followed.However, the great majority of mammalspecies continue, even today, to live in thewild.

There are 5,416 known mammal speciesdistributed over different land andaquatic environments. Despite the

characteristics that make them part of thesame class, their diversity is such that thesmallest of them, the shrew, may weigh onlyone tenth of an ounce (3 g), and the largest,the blue whale, can reach 160 tons. But theirdiversity is also evident in their adaptation todifferent environments. There are mammalsthat run and others that glide—some fly, andothers jump, swim, or crawl. Most aquaticmammals have suppressed the developmentof hair or fur, replacing it with thick layers offat. The rigors of low temperatures havemade some animals—such as polar bears,dormice, and certain bats—exceptions to thevital law of homeothermy, as they spend thewinter sunk in deep sleep to save energy.

WALESLand of green meadowsand gentle hills, Walesis famous the worldover for the quality ofits wool production.

Seals, dolphins, bats, and chimpanzees allhave upper limbs with similar bones, but theenvironmental niche they occupy has madeseals develop flippers, dolphins fins, batswings, and chimpanzees arms. Thus from thepolar tundra to the dense tropical jungle,through the deep oceans and high mountainlakes, the whole Earth has been populatedby thousands of mammal species.

But this marvelous animal world hasbeen disturbed by its most numerousspecies—humankind. Indiscriminate

hunting, illegal trade, deforestation,urbanization, massive tourism, and pollutionhave left more than a thousand species(many of them mammals) endangered orvulnerable. However, science allows us tounderstand nature's many wonders, and itcan help us respect the world's ecologicalbalance. In this book, which includesdazzling photographs and illustrations, weinvite you to discover many details ofmammals' lives: their life cycles, their sociallives, their special features, and theircharacteristics, from those of the greatestfriend of them all, the dog, to the mysteriousand solitary platypus.

Mammals began to dominate theEarth about 65 million years ago.Without a doubt, modern humans

are the most successful mammals—theyoccupy all the Earth's habitats! Theirdomestic coexistence with other speciesbegan barely 10,000 years BC, when humanculture transitioned from a world of nomadic

Unique andDifferent

Origin and Evolution

Polar bears are all-aroundathletes, as agile in the water asthey are on land. Excellentswimmers, they move at a speedof 6 miles per hour (10 km/h)

using a very rapid stroke. They can restand even sleep in the water. Like allmammals, they have the ability tomaintain a constant temperature. Thisallows them to tolerate the extreme cold

of the Arctic ice. Here we will tell youmany more things about the particularproperties that distinguish mammals fromthe rest of the animals. Did you know thatmammals appeared on Earth at almost

the same time as dinosaurs? Since theywere unable to compete with the largereptiles of the time, at first they were verysmall, similar to mice. Turn the page andyou will discover many more things.

MILLIONS OF YEARS AGO . . . 8-9

NAMES AND GROUPS 10-13

WHAT IS A MAMMAL? 14-15

CONSTANT HEAT 16-17

POLAR BEARSAlso called the white bear,they are without a doubt“Lords of the Arctic.”Nevertheless, they are onthe road to extinction.

Morganucodon

The origin of mammals lies in the Triassic Period a little more than 220 million yearsago when, in the course of terrestrial evolution, new groups of animals appeared.Their history can be reconstructed in broad outline through the study of fossils.

Among them is the morganucodon, an animal of which we have found numerous remains.

Millions of Years Ago . . .

Clade

Group

Subgroup

Family

Genus

Weight1 to 1.8 ounces(30-50 g)

6 inches (15 cm)

Millionsof Years

KEY

EAR

Mandible Squamosal Angular Subangular Malleus Incus Stapes (Hammer) (Anvil) (Stirrup)

Mammaliaformes

MonotremesMultituberculates Marsupials Placental Mammals

PrimitiveTherians

0

100

200

Period

EXTINCTFAMILIES

TRIA

SSI

C

JURA

SSI

C

CR

ETA

CEO

US

TERT

IARY

Mammaliaformes

Synapsids

Triconodonts

Cynodont

Morganucodon

PRIMITIVEREPTILESResembled mammalsin the bones of theirback, neck, and hips,which allowed themto stand moreupright. Theyreplaced their teethonly once and had amuch larger brainthan today's reptiles.

MAMMALSThe cranium is larger, themandible is formed by asingle bone, the ear isarticulated, and the teeth areof different shapes and sizes.

HUMERUSis bigger, allowinggreater mobilityof the forelimbs.

INTERIOR FOSSAThe transformation of themandibular bones intothose of the modern mammalis not yet complete.

COATAlthough mammals arewarm-blooded and cankeep their bodytemperature constant,their fur coats protectthem from the cold.

EPICONDYLEarticulates with thehumerus and connectsto the forelimbs.

PATELLAis the knee,which connectsthe femur withthe tibia and thefibula.

TROCHANTERis the part of thefemur wheremuscles thatassist locomotionare inserted.

ACETABULUMconnects to thelumbar vertebraeand pelvis.

TAILis shorter thanthat of today'srodents andpointed.

LUMBARVERTEBRAEdo not have ribsand withstand thebody's twisting.

POSTUREThe bones of the back,neck, and hip allowed itto stand more upright.

SCAPULAconnects the legs withthe lumbar vertebrae.

MONOTREMESSTEROPODON GALMANI

Reptile Mammal

MARSUPIALSDIPROTODON AUSTRALIS

PLACENTAL MAMMALSZALAMBDALESTES

MAMMALIAFORMESHad differentiateddentition, with incisor,canine, and molarteeth. They alsodeveloped an extensivesecondary palate, an`dthe mandible wasformed by the dentarybone. The posteriorbones, whicharticulated with thecranium, had becomesmaller.

8 ORIGIN AND EVOLUTION

FROM REPTILE TO MAMMAL

Incus(Anvil)

Stapes(Stirrup) Inner Ear

Malleus(Hammer)

Incisors

Like mammals, theyhad a single dentarybone (mandible).

SingleDentary Bone

(Mandible)

Mandibleformed byvarious bones

EAR Large and articular,it approximatesthose of mammals.

EAR Inner ear

Three tiny bones

Stapes (Stirrup)

Incus (Anvil)

Malleus (Hammer)

HANDS

8 carpal bones

5 metacarpals

5 proximalphalanges

5 medialphalanges

4 distalphalanges

FEET

7 tarsal bones

5 metatarsals

5 phalanges

5 medialphalanges

4 distalphalanges

MOLAR TEETHTriangular inshape, the priorformation ofincisors isreversed, and theyincrease to four.

CaninesPremolars Molars

MultituberculatesThese Mesozoic mammals hadfeatures similar to those of living

rodents. They had incisors in the mandibleas well as in the cranium that grewcontinuously. There were both arborealand digging multituberculates, and theirfossil remains have been found on everycontinent except Australia and Antarctica.

The mammals class is divided into two subclasses:Prototheria, which lay eggs (like other classes suchas birds), and Theria. The Theria, in turn, are

divided into two infraclasses—Metatheria (marsupials),which grow to viability within a marsupium, or pouch,and Eutheria (placental mammals), whose offspringare born completely developed and who todayrepresent the great majority of living mammalspecies, including humans.

PrototheriaOrder MonotremataOviparous mammals (Monotremata) are theoldest of all known groups. It is believed that theirorigin could be independent from that of othermammals and that they descend directly from theSynapsid reptiles of the Triassic Period (more than200 million years ago).Monotremes are the only mammals that lay eggs.However, the shape of their craniums, thepresence of hair, and, of course, mammary glandsshow that they belong to the mammal group. Themammary glands lack nipples, so the young haveto lick milk from a tuft of hair.The only living representatives of this order areechidnas and the platypus. The platypus is aunique species that, because of its similarity tobirds, was impossible to classify zoologicallyfor a long time.

TheriaInfraclass MetatheriaThe principal characteristic of metatherias, ormarsupials, is the way they reproduce and develop. Theyhave a very short gestation period compared to othermammals (the longest is that of the giant gray kangaroo,only 38 days), which means that their newborn are notvery developed but have bare skin and eyes and earsthat are still in the formative stage—although they havea sense of smell, a mouth, and digestive and respiratorysystems adequate for survival. When they are born, theycrawl across their mother's abdomen in search of hermammary glands. Kangaroo offspring climb to the edgeof the mother's pouch (marsupium). They then crawl inand affix themselves to one of the mammary glands,from which they feed until they complete developmentand leave the pouch.

ECHIDNAFamily TachyglossidaeAlso known as the “spinyanteater” because it feedson ants and termites that itcatches with its tongue. Itsskin has hair and spines.

AUSTRALIA

TASMANIAN DEVILFamily Dasyuridae The largest of the carnivorousmarsupials became extinct inAustralia 600 years ago, but itsurvives on the island of Tasmania. Itis a predator the size of a small dog.

ALMOST PATRIMONYUnlike the rest of the world,almost no placental mammals livein Australia and its neighboringislands. The island continentpossesses 83 percent of the unique(endemic) species of mammals.

OPOSSUMSFamily DidelphidaeThey spend most oftheir lives perched intrees and are very timid.

MAMMALS 11

4SPECIES KNOWN

CURRENTLY

300SPECIES EXIST.

OVER

AUSTRALIA SOUTHAMERICA

Mammals Colonizing the World HORNY BEAKis used torummage inriverbeds and mudin search of food.

FINSPlatypuses usetheir limbs toswim.

PLATYPUSFamily OrnithorhynchidaeA monotreme with semiaquatichabits. Its feet and tail possessmembranes that make it palmate,which is useful for swimming. It feedsoff any living thing it finds at thebottom of Australia's rivers or lakesby rummaging with its horny beak.

GEOGRAPHICALLY CONFINEDPlatypuses and echidnas are found onlyin Oceania—the platypus only onAustralia and the echidna (of whichthere are four species) also on theislands of Tasmania and New Guinea.

The first fossils of marsupials andplacental mammals were found in

rocks dating from the late Jurassic andthe earliest part of the Cretaceousperiods. At that time, America, Africa, andAustralia were united in a single continent(Gondwana) and were beginning to

separate. But the placental mammalsevolved further, and at the beginning ofthe Eocene Period (56 million years ago),opossums were the only representativesin America of marsupials, which otherwiseprospered only in Australia's particularclimate and geographic isolation.

Names and Groups


Ord

er D

asyu

rom

orph

ia

Ord

er D

idel

phim

orph

ia

Ord

er D

ipro

todo

ntia

Ord

er M

icro

biot

heri

a

Ord

er N

otor

ycte

mor

phia

Infr

acla

ss M

etat

heri

a

Ord

er M

onot

rem

ata

Ord

er P

auci

tube

rcul

ata

Ord

er P

eram

elem

orph

ia

SubclassPrototheria

MAMMALS 13

GIRAFFEOrder ArtyodactilaeThese are the tallest of living landanimals—they can be over 18 feettall (5.5 m). They are herbivores.Their blood pressure is almost twicethat of other large mammals, andtheir tongues are over 18 inches(0.5 m) long. They live in Africa.

MANDRILLOrder PrimatesWeighing up to 120 pounds (55 kg),these are the largest monkeys in theworld. The males are much largerthan the females, and they have abrilliantly colored face, with deepgrooves running down both sidesof their snout. Mandrills live inAfrica's tropical zones. Theyare omnivores, eatinganything from grasses tosmall mammals.

SEALSOrder CarnivoraAlong with elephant seals, they makeup the Pinnipedia suborder. Theymove very clumsily on land, but theyare very good swimmers. Theyfeed on fish and crustaceansand prefer to inhabitmarine waters nearthe poles, althoughthey reproduce ondry land.

Infraclass Eutheria Commonly called placental mammals, they are the typicalmammals. They probably began diversifying during the CretaceousPeriod (65-150 million years ago) from a different line of themetatherians. They are characterized by the fact that theirembryos are implanted in the uterine cavity and develop an outerlayer of cells in close union with the maternal body, the placenta.They receive nutrients directly from the placenta during theirdevelopment until they are born with their vital organs (except forthose responsible for reproduction) fully formed.

RACCOONOrder CarnivoraLive in forests near rivers.These carnivorous huntersand climbers live in NorthAmerica.

SKINA fur coat andsubcutaneous fatprotect the animalfrom extreme cold.

NECKallows them toreach thehighest leaves.

Jurassic BeaverScientists thought that mammals were able toconquer the Earth only after dinosaurs becameextinct. But the recent find of a fossil of thisbeaver in China suggested that, by the JurassicPeriod, when the giant reptiles were at theirpeak, mammals had already diversified andadapted to water ecosystems 100 million years

earlier than had been believed. TheCastorocauda lufrasimilis lived 140

million years ago.

ANTARTICA AFRICA

EUROPEAMERICA ASIA

OCEANIA

THROUGHOUT THE WORLDThe eutherians, or placental mammals, arethe most important group of mammalsbecause of the number of living species theyrepresent. Their geographic distributioncovers almost the entire planet, including onand beneath bodies of water and polar areas.These animals cover a wide range ofecosystems and forms of life and make up 19orders of viviparous placental mammals.

SPECIES OFEUTHERIANS.

4,000THERE ARE OVER

Ord

er A

rtio

dact

yla

Ord

er C

arni

vora

Ord

er C

etac

ea

Ord

er C

hiro

pter

a

Ord

er D

erm

opte

ra

Ord

er H

yrac

oide

a

Ord

er I

nsec

tivo

ra

Ord

er L

agom

orph

a

Ord

er M

acro

scel

idea

Ord

er P

eris

soda

ctyl

a

Ord

er P

holid

ota

Ord

er P

rim

ates

Ord

er P

robo

scid

ea

Ord

er R

oden

tia

Ord

er S

cand

enti

a

Ord

er S

iren

ia

Ord

er T

ubul

iden

tata

Sup

eror

der

Xen

arth

ra

Infr

acla

ss E

uthe

ria

Subclass Theria


Aquatic TemperateForests

Desert Meadow orPastureland

TropicalSavanna

Humans have adapted toalmost all habitats throughtheir ability to modifycertain elements of theirhabitat to their advantage.

AN UNCOMMON PRIMATE

TropicalRainforest

Taiga Tundra

Take Habitat into AccountBetween every mammal and its natural habitat there is arelationship that exists and is expressed in the animal'sphysical characteristics. Just as the flippers of theelephant seal are used to swim and hunt fish, mimicry andrunning are vital for deer. Physiology is a specialinstrument of adaptation to the environment, as in thecase of the camel.

They often create tools tohelp them adapt to theirenvironment. In this way,they do not need to relyon natural evolution alone.

Close RelativesHumans belong to the primate group. Hominids (orangutans,gorillas, and chimpanzees) are the largest of these, weighingbetween 105 and 595 pounds (48-270 kg). In general, malesare larger than females, with robust bodies and well-developed arms. Their vertical carriage differentiates theirskeletons from those of other primates. Gorillas inhabit only

the equatorial jungles of western Africa. They supportthemselves on their forelimbs while walking. Normally

their height varies between 4 and 6 feet (1.2-1.8 m),but, if they raise their forelimbs and stand erect,they can be over 6.5 feet tall (2 m).

What Is a Mammal?


Mammals share a series of characteristics that distinguish their class: abody covered by hair, the birth of live young, and the feeding ofnewborns on milk produced by the females' mammary glands. All

breathe through lungs, and all possess a closed, double circulatory systemand the most developed nervous systems in the animal kingdom. The abilityto maintain a constant body temperature has allowed them to spread outand conquer every corner of the Earth, from the coldest climates to hotdeserts and from the mountains to oceans.

MAMMALS 15

MAMMARY GLANDSSecrete the milk withwhich the females feedtheir young during theirfirst months of life.These glands give theclass its name.

ALWAYS 98º F (37º C) The ability tomaintain a constantbody temperature isnot a characteristicunique to mammals;birds also have thatability.

LOWER JAWFormed by a single bone,called the dentary, andteeth specialized for eachfunction. The entirecranium has a verysimplified bone structure.

LimbsMammals have four limbs that are adapted formoving about on land. Their forelimbs have certainother abilities (swimming, manipulation, attack anddefense, protection). The exceptions are thecetaceans, so adapted to marine life that they onlyhave two fingerless limbs, and seals (Phocidae).

ELEPHANT SEALSFamily Phocidae

HomeothermyThe ability to keep body temperaturerelatively constant, independent ofthe ambient temperature.Hibernating species are theexception; they must lowertheir body temperature toenter into this state of reducedmetabolic activity. Contrary topopular belief, bears do nottruly hibernate but ratherenter into a period of deepsleep during winter.

GRIZZLY BEAR(BROWN BEAR)Ursus arctos

AN EAR OF BONESThe tiny bones of theear form a system forsensing andtransmitting sound.

A Body for Every EnvironmentSkin covered with hair and sweat glands helps create and maintain aconstant body temperature. At the same time, with eyes placed on each side

of the head (monocular vision, with the sole exception of the primates, whichhave binocular vision), they are afforded important angles of sight. Limbs areeither of the foot or chiridium type, with slight variations depending on thepart of the foot used for walking. In aquatic mammals, the limbs haveevolved into fins; in bats, into wings. Hunters have powerful claws,and unguligrades (such as horses) have strong hooves that supportthe whole body when running.

A THICK SKINFormed by an outer layer(epidermis), anotherdeeper layer (dermis),and a fatty substratumthat contributes tohomeothermy.

GORILLAGorilla gorilla

CRANIUMRelatively largecompared to the size ofthe body. And the brainis more developed andmore complex than thatof any other animal.

HairBody hair is unique to mammals andabsent in other classes of animals.Sirenians, with little hair, and cetaceansare exceptions; in both cases, the absenceof hair is a result of the mammal'sadaptation to an aquatic environment.

CHIPMUNKFamily Sciuridae

BOTTLENOSEDOLPHINTursiops truncatus

DentitionThe majority of mammals change

dentition in their passage to adulthood.Teeth are specialized for eachfunction: molars for chewing, caninesfor tearing, and incisors for gnawing.

In rodents such as chipmunks,the teeth are renewed by

continuous growth.

THE NUMBER OF MAMMALSPECIES ESTIMATED TO

EXIST ON EARTH

5,416

MAMMALS 17

A Perfect System Polar bears, like all mammals, keep theirinternal temperature constant. These

bears tolerate the extreme cold of the Arcticice because they have developed asophisticated system to increase their ability toisolate and capture sunlight. Their transparenthair receives a large part of it and thereforeappears to be white. The hair transmits thislight inward, where there is a thick layer ofblack skin, an efficient solar collector. Their furis made up of hollow hairs, approximately 6inches (15 cm) long, which insulate the bear inlow temperatures and keep the skin fromgetting wet when in the water.

AND FINALLY . . . THE FLOATING SLABWhen they tire of swimming,they rest, floating. They manageto cross distances of over 37miles (60 km) in this manner.

TO GET OUT:ANTISLIP PALMSTheir palms have surfaceswith small papillae thatcreate friction with ice,keeping them from slipping.

Hind Legsfunction asa rudder.

Forelimbsfunction asa motor.

RESPIRATORYPATHWAYSThe bears havemembranes in theirsnouts that warm andhumidify the air beforeit reaches the lungs.

SHELTERED CUBSThe cubs are born inwinter, and the skin ofthe mother generatesheat that protects thecubs from theextreme cold.

UNDER THE ICEFemales dig a tunnel in thespring; when they becomepregnant, they hibernatewithout eating and can lose45 percent of their weight.

CHAMBEROR REFUGE

MAINACCESSTUNNEL

ENTRANCE

SECONDARYACCESSTUNNEL

PRINCIPAL FATRESERVESThighs, haunches,and abdomen

HYDRODYNAMICANATOMY

LAYERS

HAIR

SLOW AND STEADY SWIMMING

GUARD HAIRSOuter

UNDERFURInner

FAT4-6 inches (10-15 cm) thick

Animpermeable,translucentsurface

Hollow chamberwith air

Mammals are homeothermic—which means they are capable of maintaining astable internal body temperature despite environmental conditions. This abilityhas allowed them to establish themselves in every region of the

planet. Homeostasis is achieved by a series of processes that tendto keep water levels and concentrations of minerals andglucose in the blood in equilibrium as well asprevent an accumulation of wasteproducts—among other things.

Constant Heat


GreatSwimmers

Polar bears swim with ease in openwaters and reach a speed of 6 miles an

hour (10 km/h). They propel themselveswith their great front paws and use their

back feet as rudders. The bear's hair is hollowand filled with air, which helps with buoyancy.

When the bear dives, its eyes remain open.

Curling UpMany cold-climate mammals curl up into

balls, covering their extremities andbending their tails over their bodies as akind of blanket. In this way, the surface

area subjected to heat loss will beminimal. Hot-climate animals stretch out

their bodies to dissipate heat.

MetabolismThe layer of fat is between 4 and 6 inches (10-15 cm) thickand provides not only thermal insulation but also an energyreserve. When the temperature reaches critical levels—atthe Pole it can drop to between -60° and -75° F (-50° to -60° C)—the animal's metabolism increases and begins torapidly burn energy from fat and food. In this way, thepolar bear maintains its body temperature.

MigrationWHEN SPRING BEGINS, THESE BEARSTRAVEL SOUTH, ESCAPING THE BREAKUPOF THE ARCTIC ICE.

6 miles (10 km)

over

PER HOUR IS THE AVERAGE SPEED ATWHICH POLAR BEARS SWIM.

POLAR BEARUrsus maritimus

DEVELOPED SENSES 28-29

SOFT CONTACT 30-31What They Are Like

All mammals havestereoscopic vision, whichgives them depth perception.Moreover, in the case ofhunters such as tigers, their

night vision is six times keener thanthat of humans. There are many speciesthat have a very keen sense of smell,and the sense of taste is closely linkedto that of smell. Hair, too, performs

various functions in these animals'lives—conserving body heat, providingprotection, and serving as camouflage.Those that have almost no hair and livein environments where the

temperature is very low, such as whales,have developed a layer of fat under theirskins.

GRACE AND MOVEMENT 20-21

EXTREMITIES 22-23

WHAT DOESN'T RUN, FLIES 24-25

LOOKS THAT KILL 26-27

BENGAL TIGERPanthera tigris tigris is the largestmember of the feline family, easilyrecognized by its orange fur withblack stripes and white spots.

50 MPH(80KMH)

Horses, one of the odd-toed, hoofed, ungulate mammals, are considered symbols of grace andfreedom. They have great vigor and can run swiftly because their spine bends very little,preventing unnecessary expenditure of energy during the rising and falling of their body mass.

They are equipped with strong, light, and flexible bones, and their muscles work by contraction,arranged in pairs or groups that pull in opposing directions.

Grace and Movement

Power to RunHorses are one of the most powerful mammals and achievegreat speeds relative to their body mass. The natural purpose

of their musculature is to allow them to flee their enemies. Thisability has allowed the species to survive for millions of years. Theirgreat energy is generated by contracting muscles.

Skeleton

GALLOPING LEGSThe hind legs generate the impetus and the leap,and the front legs bear the weight upon landing. Tosave energy, the spine hardly arches when running.In felines, however, which are lighter, it does.

VERTEBRAE7 CERVICAL

TENDONSare lengths of connective tissuethat secure one end of a muscle(striated muscle tissue) to a bone(bone tissue). Ligaments connectbones to one another.

FROM 17 TO 19DORSALNormally there are18, but the numberis often higher or

lower.

Ischium

Ilium

Tip ofthe Tarsus

5 OR 6 LUMBAR

PELVIS

FIBULA

TIBIA

PATELLA

METATARSUS

PHALANGES

RIBS

RADIUS

HUMERUS

ULNA

KNEE

METACARPUS

PASTERN

FEMUR

7 SACRAL

STERNUMis the bone thatjoins the ribs inthe front of thechest, formingthe thoracic cageand providingvisceral support.

18 COCCYGEALThe tail can be madeup of a variablenumber of verymobile vertebrae.The medullary canalnarrows.

ATLASFirst cervical vertebrais articulated, allowing the nape tobend up and down.

AXISSecond cervical vertebraallows lateral movement—necessaryfor the horse to turn.

Atlas

Correct position ofan equestrian

BUCCALCAVITY

14TEETH

in each maxillarybone, including:

3 molars3 premolars6 incisors2 canines

HOOFBecause theyhave this kind of“nail,” horses arecalled ungulates,as are tapirs andrhinoceroses.

Muscle fascicle

Muscle fiber (cell)

Perimysium

Blood Vessel

Epimysium

SCAPULARCARTILAGE

SCAPULA

EQUINE FOOT

Metacarpus

Third Phalanx

Second Phalanx

Navicular Bone

First Phalanx

SesamoidBone

Plantar Pad

HeelBar

Frog

Sole

Horseshoe

BRACHIALIS

TRICEPS

CAUDAL DEEP PECTORALMUSCLE

KNEE

Lateral DigitalExtensor

Twins

Lateral Band

CollateralLigament

THE HORSE IN ACTION

THE SPEED REACHEDBY A RUNNING HORSE

EXTENSOR CARPIRADIALIS

COMMON DIGITALEXTENSOR

DEEPDIGITALFLEXOR

ORBITALCAVITY

NASALCAVITY

ANNULARLIGAMENTS

DEEP DIGITALFLEXOR TENDON

PECTORALS

DELTOIDS

CLEIDOMASTOIDS

STERNOCEPHALICUS

Endomysium(between fibers)

Bone

20 WHAT THEY ARE LIKE

34BONES IN THE CRANIUM

210IS THE NUMBEROF BONES INTHE SKELETONOF A HORSE(excluding thetailbones)

Axis

MAMMALS 21

ión b

MMAMMALS 2322 WHAT THEY ARE LIKE

ExtremitiesM

ammals' extremities are basically either of the foot or chiridium type but modifiedaccording to the way in which each species moves about. Thus, for example, they becomefins for swimming in aquatic mammals and membranous wings in bats. In land mammals,

these variations depend on the way the animal bears its weight in walking: those that use thewhole foot are called plantigrades; those that place their weight on their digits, digitigrades; andthose that only touch the ground with the tips of their phalanges, ungulates.

UNGULIGRADE IHORSESIf you observe theirfootprints, you will seethat only their hoovesleave marks. Horses'hooves are made up ofonly one toe.

LYING FOOTPRINTSOther species of unguligrades (or simply ungulates)can have more toes that make up their hooves, butthey do not place weight on more than two of them.

HIPPOPOTAMUS PIG CHEVROTAIN DEER CAMEL

UNGULIGRADE IIGOATSThe majority of ungulates,such as goats, have aneven number of toes. Theyare called artiodactyls asopposed to perissodactyls,which have an oddnumber of toes.

KEYTibia/FibulaTarsiMetatarsiPhalanges

BIG TOE

NAIL

DISTAL PHALANX

MEDIALPHALANX

PHALANX

METATARSAL

CUBOID BONES

SCAPHOID BONES

ASTRAGALUS

CALCANEUS

TARSI

SECONDTOE

THIRD TOE

FOURTH TOE

FIFTH TOE

TALUS

NAIL

DIGITAL PAD

PLANTAR PAD

TOE

SPUR

PAD

METATARSAL

PAD

SOLE

CUNEIFORM BONES

MediumLarge

DIGITIGRADEDOGThese mammals placethe full surface oftheir toes (or some ofthem) on the groundwhen walking. Theyusually leave the markof their front toes anda small part of theforefoot as a footprint.Dogs and cats are thebest-known examples.

RETRACTABLE NAIL

WALK OR CLIMBThere is a fundamental differencebetween the human foot and thatof a monkey. The monkey has along, prehensile digit in its footsimilar to that in its hand. Monkeysuse their feet to grab branches asthey move through the trees.

ELASTIC LIGAMENTWhen the tendon contracts,this ligament retracts, andthen the nail does, too.

EVOLUTIONIt is thought thatwhales descendfrom ancientmarine ungulates,whose spinesundulated up anddown.

SCAPULA

HUMERUS

ULNA

RADIUS

CARPI

METACARPI

PHALANGES

FIRSTFINGER

SECONDFINGER

THIRDFINGER

FOURTHFINGER

PATAGIUM

FIFTHFINGER

ULNA

HUMERUS

FEMUR

CalcareousSpur

TIBIA FOOT

TAIL

Phalanx

MedialPhalanx

TENDON NAIL

DistalPhalanx

Chimpanzee Human

PLANTIGRADEHUMANPrimates, and of coursehumans, bear theirweight on their toes andmuch of the sole of thefoot when walking,particularly on themetatarsus. Rats,weasels, bears, rabbits,skunks, raccoons, mice,and hedgehogs are alsoplantigrades.

Functionally AdaptedAnother criterion for classifying mammals by their legs, in additionto their morphology, is the function the legs perform. Cats, dogs,and horses have four limbs for locomotion. Primates havedifferentiated forelimbs, and they also use legs to capture food orbring it to their mouth. Others use legs to swim or fly.

FelinesThe function of their paws is tosupport their agile and elasticbodies, allowing them to moveabout. The front paws also helpin hunting to catch and hold prey.

ChiropteraFrom the Greek, meaning“winged hand,” this is how batsare designated because theirforelimbs are modified, thefingers thinning andlengthening to be able tosupport a membrane thatfunctions as a wing. The hindlimbs did not change similarly:they have claws.

CetaceansWhales adapted so well to the seathat they seem to be fish. But insidetheir fins —modified front legs—there is a bony structure similar to thatof a hand with fingers. They have nohind limbs: the tail, placed horizontallyand used to move in the water, has noconnection to those limbs.

LEFT FOOT OFCHIMPANZEEPan troglodytesLife-size photo

5 toesTHE NORMAL NUMBERFOR MAMMALS:RUNNING SPECIESHAVE FEWER.

TailHORIZONTAL IN

MAMMALS THATSWIM, AS DISTINCT

FROM FISHSmall

Order

Family

Species

Carnivora

Felidae

Acinonyx jubatus (Africa)Acinonyxvenaticus (Asia)

NOSTRILSVery wide, they allowit to receive moreoxygen as it runs.

SECOND POINTOF CONTACTExtending its fourlegs again, it picks upmore momentum,supporting itself onlyon one back leg.

FIRST POINT OF CONTACTAs it runs, only one legtouches the ground at atime, but during thecervical contraction, theentire body lifts from theground.

70 MPH (115 KM/H) CHEETAHIt only takes 2 seconds to reach aspeed of 45 miles per hour (72 km/h).

18 MPH (29 KM/H)SIX-LINED RACERUNNERCnemidophorussexlineatus

23 MPH (37 KM/H) HUMAN BEINGTrack record: Asafa Powell (Jamaica),110 yards (100 m) in 9.77 seconds

42 MPH (67 KM/H)GREYHOUNDA dog with a light skeletonand aerodynamic anatomy

50 MPH (80 KM/H) HORSEAn anatomy designed forrunning, powerful musculature

BIPEDS VERSUSQUADRUPEDS

ZIGZAGGINGAT HIGHSPEED

TAILLarge compared tothe rest of the body,it acts as a pivotused to suddenlychange direction.

TAKEOFF From the top ofa tree, it jumpstoward anothershorter tree.

IN THE AIRThe flying squirrel does not actually fly—itglides. Between its front and back limbs isa membrane of skin that, like a delta wing,stretches out the moment the animaljumps and stretches its legs. Thanks tothat it can glide from the top of one treeto the trunk of another.

TTailacts likea rudder.

TTOESUpon landing, it grabsonto the surface withits toes.

PPatagium

LANDINGWhile gliding, the squirrelcan change its landing angle.Just before landing, it lowersits tail and raises its frontlegs, using the membranelike an air brake. It landsvery gently on all four paws.

SHOULDERThe extensiveflexion of theshoulder allowsit to take verylong leaps.

LIMBSLong and agile. Ithas a powerful,flexible skeletonand musculature.

PAWSDIGITS5 in the hands4 in the feet

NAILSUnlike otherfelines, theirnails are notretractable,allowing themto grip theground better.

HEADSmall andaerodynamic,with low airresistance.

They are meteors of flesh, bone, and hot blood. Cheetahs are the fastest ofthe land animals and unique members of the Felidae family, which huntusing their keen vision and great speed. They can reach over 70 miles per

hour (115 km/h) in short runs and reach 45 miles per hour (72 km/h) in anaverage of only 2 seconds. They can get above 60 miles per hour (100 km/h),but they can sustain that speed for only a few seconds. They look like leopards,although their physical characteristics are different: they are longer andthinner, and their heads are smaller and rounded.

What Doesn't Run, Flies


CheetahsWhereas tigers prefer to lie in wait forprey and then jump on it, the cheetahuses explosive speed of over 60 miles perhour (100 km/h) to run its prey down.

SiberianFlying

SquirrelFlying squirrels (Pteromys volans)belong to the same rodent family

as common squirrels, to whichthey are similar in both

appearance and way of life. Theylive in the mixed forests of

northern Europe, across Siberia,and into East Asia.

1 STARTThe cheetahbegins runningby lengtheningits stride andextending itsfour legs.

2 SPINALCONTRACTIONThen it gathers its legsunder its body, contractingits cervical spine to themaximum.

3 EXTENDINGTHE SPINEIn a counterthrust opposingthe contraction, the spineextends, creating forwardmomentum. The cheetahcan cover 26 feet (8 m) in asingle stride.

70(115 km/h)MAXIMUM SPEED, BUT CANBE MAINTAINED FOR ONLY550 YARDS (500 M)

milesper hour

SlothThese animals are notable for theirextremely slow metabolism. Theytake half a minute to move alimb! They are also somewhatmyopic, their hearing ismediocre, and their senseof smell barely serves todistinguish the plantson which they feed.They are at the extremeopposite of cheetahs.However, since theypractically live perched intrees, they do not need tomove or see or hear precisely.They are perfectly adapted totheir way of life.

THREE-TOED SLOTHNative to the Amazon River basin

These movementsare possiblebecause its nails arenot retractable, sothat cheetahsfirmly grip theground.

2

Cheetahs canmake sharp turnswhile running athigh speed.

1

MAMMALS 25

Field of Vision

FIELD OF VISION 50 times

Seeing Even in the DarkHunting animals depend on the keenness of their senses to detect their prey.Felines can dilate their pupils up to three times more than humans, and they

see best when light is dim and their prey's movements are very subtle. A systemof 15 layers of cells forms a sort of mirror (tapetum lucidum) located behind theretina or back of the eye. This mirror amplifies the light that enters and is also thereason that the animal's eyes shine in the dark. At the same time, their eyes aresix times more sensitive to light than those of people. Tigers' nocturnal vision alsoincreases because of the great adaptability of their circular pupils when they arecompletely open.

BINOCULARVISIONPart of the fieldof vision of oneeye overlaps thatof the other eye,which makesthree-dimensionalvision possible.Hunters' skillsdepend onbinocular vision,because it allowsthem to judge thedistance and sizeof their prey.

PUPILS They regulate the passage of lightto the retina by contracting inbright light and dilating in the dark.In each species of mammal, thepupils have a distinctive shape.

HUMAN DOG WITH LONGSNOUT

HARESHORT-SNOUTED DOG

LIGHTS OR COLORS

The retina'ssensitivity to lightdepends on rod-shaped cells, andforms and colorsdepend on othercells, which arecone-shaped. Intigers, the formerpredominate.

RETINA OF ANOCTURNALANIMALRods, super-sensitive to light,predominate.

RETINA OF ADIURNAL ANIMALCones, whichdistinguish colorsand details, alongwith light,predominate.

ROD CONE

Tigers have a 255°angle of vision, ofwhich 120° isbinocular, whereashumans have 210° with120° of it binocular.

FOCUS 2

FOCUS 1

THE LIGHT AMPLIFICATIONCAPABILITY OF THE RETINA

OF FELINES

LeftField

RightField ofVision

TIGER CAT GOAT

BinocularField

Tigers are the largest of the world's felines. Predators parexcellence, they have physical skills and highly developed sensesthat they use to hunt for prey. Their daytime vision is as good as

that of humans, except for a difficulty in seeing details. However, atnight, when tigers usually hunt, their vision is six times keener than thatof a human being, because tigers' eyes have larger anterior chambersand lenses and wider pupils.

Looks That Kill


CONJUNCTIVA

CORNEA

LENS

IRIS

PUPILVITREOUS

HUMOR

OPTICNERVE

RETINA

HearingThe auditory ability of dogs is four times greater than that ofhuman beings, and it is highly developed. Their ability dependson the shape and orientation of their ears, which allow them tolocate and pay closer attention to sounds, although this variesby breed. They can hear sharper tones and much softer sounds,and they can directly locate the spatial reference point wherea noise was produced. Dogs hear sounds of up to 40 kilohertz,whereas the upper limit for human hearing is 18 kilohertz.

Sense of SmellTheir most developed sense; they have220 million olfactory cells in their nasalcavities. Mucous tissue, located in thenasal conchae of the snout, warms andmoistens the air that they inhale.

TasteDogs perceive the chemical substances thatfoods are made of by means of receptor cellsfound in the taste buds located at the back ofthe tongue and in the soft part of the palate.

LABYRINTH

SEMICIRCULARCANALS

AUDITORYOSSICLES

INCUS (ANVIL)MALLEUS (HAMMER)STAPES (STIRRUP)

INSIDE THE COCHLEA

INTERNALSTRUCTURE OFTHE BULLA The dome divertssounds toward thebulla, which sendselectric signals tothe brain.

TURBINATE BONES

The epithelium thatcovers these bones isresponsible forsecreting mucus thattraps inhaled particles.

THE TONGUEAND TASTESSweet tastes areexperienced in thefront part of thetongue, sour onesin the center, andsalty ones in theback. On eitherside salty andsweet are mixed.

TASTERECEPTORSIndividual receptorcells passinformation to theolfactory centers ofthe brain.

AUDITORY LEVELS

TASTE BUDSDispersed throughoutthe tongue. Complexinteractions amongthem determine taste bymeans of nerve endings.

FragrantMaterial

Dendrites MucousLayer

ReceptorCell

NerveFiber

Dogs have inherited from wolves great hearing and an excellent sense of smell. Both performan essential role in their relationship to their surroundings and many of their socialactivities. However, they are very dependent on the keenness of their senses depending on

the habitat in which they develop. Whereas humans often remember other people as images,dogs do so with their sense of smell, their most important sense. They have 44 times moreolfactory cells than people do, and they can perceive smells in an area covering some 24square inches (150 sq cm). Dogs can discern one molecule out of a million other ones,and they can hear sounds so low that they are imperceptible to people.

Developed Senses


Reissner'sMembrane

Organ of Corti

ScalaTympani

Dome

Crest

CiliaryCells

PeopleFoxesMiceBatsFrogsElephantsBirds

0 hertz 1 10 100 1,000 10,000 20,000 40,000

ScalaVestibuli

AUDITORYNERVE

AUDITORY CANALTYMPANIC MEMBRANE

COCHLEARNERVE

AURICULARCARTILAGE

AUDITORYCANAL

COCHLEA

MIDDLE EAR

SALTY

SOUR

SWEET

OVALWINDOW

EUSTACHIANTUBE

COCHLEA

1,000over

timesTHE CAPABILITY OF A DOG'S SENSEOF SMELL COMPARED TO THAT OFA HUMAN

SA

LTY/

SW

EET

SALT

Y/S

WEE

T

MMAMMALS 29

FUR SERVES TO PROTECTTHE SKIN FROMEXCESSIVE UV RAYS.UV

30,000THE NUMBER OF QUILLS THATCOVER A PORCUPINE (148 PERSQUARE INCH [23 PER SQ CM])

1

Soft Contact

EPIDERMISOuter layerformed byresistant, flatcells

HAIRSTRUCTURE

DERMIS Layer with bloodvessels, glands,and nerve endings.It is a layer ofsebaceous glandsthat secrete anoily substance,sebum, on thesurface of the skin.

STRATUMCORNEUM

FATTY TISSUEThis is a specializedconjunctive tissuemade up primarily ofconnective cells calledadipocytes, whichstore energy in theform of triglycerides.

SWEAT GLANDSWhen the body is hot, the glandssecrete sweat, which passesthrough the sweat ducts to thesurface of the skin.

Fur and MimicryMammals from cold regions, such aspolar bears, have white fur to camouflagethemselves in snow. Others, such as polar,or Arctic, foxes and the American hare,change their fur color with the seasons,because they live in areas that are snow-covered in winter, where their brownsummer fur would make them easy prey.Lions' beige color helps them avoid beingdiscovered while they stalk their prey.

Diverse HairsThe majority of mammals' fur ismade up of more than one type ofhair, and its different colors are dueto a group of proteins calledmelanins. Each coat has differentlayers. Guard hairs are the first layer,providing protection. Underneaththat, there is a fine layer calledunderfur, formed by constantlygrowing short hairs that renewthe coat.

InsulatingSkinInsulation is one of the functionsof animals' skins and hair. It notonly helps to conserve bodywarmth but also, as in the caseof camels, protects them fromexcessive heat. Its color oftenblends in with its surroundings,serving as camouflage.

The Skin

SUMMER The fur coat of theArctic fox (Alopexlagopus) in summer ishalf as thick as that ofwinter, with less thanhalf the underfur. Insummer, “white” phaseanimals turn a gray-brown to grayish color,and those that have a“blue” phase arebrowner and darker.

WINTERArctic foxes have twokinds of color phases.White phase foxes arealmost pure white inthe winter, whichallows them tocamouflage themselvesin the snow and ice.

GREY WOLF HARE CHINCHILLA MACAQUEMONKEY

COATI SEA LION(JUVENILE)

PORCUPINE


SWEAT PORE

Microfibrils

Macrofibrils

Cortex

Medulla

Scaly Cuticle

RUFFINI'SCORPUSCLE

ARRECTOR PILIMUSCLE

FOLLICLE

VEIN

ARTERY

HAIRSHAFT

DERMAL PAPILLAattaches thedermis to theepidermis.

BAT HAIREach strand of hairhas an outercuticle formed bysuperposed scales.

ENLARGEDWOOL

This is themost complex

natural textilefiber in existence.

It absorbs moisturebut repels water.

Mini-quillsSharp scales

PORCUPINE QUILLSCalled guard hairs, they arelocated outside the fur. In the caseof the porcupine, they have beenmodified to form defensive quills.

WOOL FIBER

Protofibril

Microfibril

Macrofibril

Cortex 90%

Cuticle 10%

POLAR BEAR HAIR

Each one of itshairs is hollow andfilled with air. This

heightens theinsulating capability

of the inner layer.

MERKEL'S DISKA sense receptorunder the skin'ssurface thatresponds to light,continuous touchand pressure

SEBACEOUSGLANDsecretes a waxysubstance, orsebum, whichmoistens the skin,making itwaterproof.

PACINIANCORPUSCLESense receptorsunder the dermis.The Pacini receptorslie under the layerof deep fat anddetect vibration andpressure.

ERECTIONMECHANISM

When the quilltouches a strangesurface, it exerts alight downwardpressure on theepidermis.

The fine tissuethat covers theroot of the quillbreaks.

The erector pilimuscle receivesthe contact signaland contracts.

Root

ConnectiveTissue

Retinaculum

Epidermis

Base ofthe QuillOUTER

FUR

UNDERFUR

LAYER OF FAT

2

3

MAMMALS 31

Admired, adored, and coveted by humans, a mammal's fur coat is much more thana skin covering. It acts as a protective layer against mechanical injuries, preventsinvasion by germs, and regulates the loss of body heat and moisture. In many

species, such as the Arctic fox, it provides camouflage by changing color and texturefrom winter to summer.

HERBIVORES 52-53

THE GREAT CHAIN 54-55

ONE FOR ALL 56-57

WOLVES IN SOCIETY 58-59

THE FIRST DAYS 44-45

TRADEMARK 46-47

DEVELOPMENT AND GROWTH 48-49

OF FLESH THOU ART 50-51

Behavior and Life Cycle

Mammalian reproduction issexual and by internalfertilization, whichinvolves copulationbetween the male and the

female. Mammals are also characterizedby the offspring's dependence on itsparents. In any case, there is a group ofmammals called monotremes that isoviparous; that is, its members

reproduce by laying eggs. Mammalianbehavior consists of a mixture ofinherited components and componentsthat can be shaped by learning. Part ofthis process is accomplished through

play, since the young use suchencounters to practice jumping, biting,hunting, and other survival skills. Youwill discover this and much more whenyou turn the page.

LIFE CYCLE 34-35

BEAUTY AND HEIGHT 36-37

OVIPAROUS MAMMALS 38-39

EFFICIENT NURSERY 40-41

MIRACULOUS PLACENTA 42-43

EAT TO LIVEAn hour after birth, thegiraffe gets up and with its 8feet (2.5 m) of height beginsto take its first steps insearch of its mother's teat.

17

MarsupialsVery short gestation period, afterwhich they develop in a sort of partiallyopen pouch (the marsupium), which thefemale carries on her belly. The majorityof the roughly 300 known species ofmarsupials are solitary, except in matingperiods. In general, they are promiscuousanimals, although some, such as wallabies(small kangaroos), tend to mate with thesame female all their life.

MonotremesMammals whose females lay eggs are generallysolitary species for most of the year. Platypusesare seen as couples only when they mate.Although they have a period of courtship forone to three months, the males have norelationship with the females aftercopulation or with the offspring. Short-beaked echidna females practicepolyandry, copulating with variousmales in various seasons.

Birth, maturity, reproduction, and death: this life cycle hascertain particularities among mammals. As a general rule,the larger a mammal, the longer the members of its

species tend to live but the fewer offspring are born to a singlefemale per litter or reproductive season. Most mammals,including humans, are placental mammals; their vital functionsare fully developed inside the body of the mother.

EASTERNCOTTONTAILRABBITSylvilagusfloridanus

SHORT-BEAKEDECHIDNATachyglossus aculeatus

KOALAPhascolarctoscinereus

AT BIRTHThe young weighsome 1.5 to 1.8ounces (40-50 g).They do not opentheir eyes until the10th day.

BANISHEDOFFSPRING Dominant males keepthe offspring and otheryoung males apart.

NUMBER OF OFFSPRINGIn general, it is inverselyproportional to the species' size.

LONGEVITY

GESTATION PERIODS

COMPARISONOF EGG SIZE

Lactation25 TO 30 DAYSfed upon milk, althoughthey can digest solid foodafter 20 days. The youngabandon the burrow after35 or 40 days and remainin the area where theywere raised (philopatry).

Weaning35 TO 40 DAYSYoung rabbits remain with theirmother even after nursing endsfor protection and the inculcationof species-specific behavior.

SexualMaturity5 TO 7 MONTHSThe better rabbits are fed,the more quickly they becomecapable of reproducing. Theyare considered adults at 8 or9 months, when they weigh

some 2 pounds (900 g).

Lactation22 WEEKSA muscle inside the pouchprevents the infant fromfalling out. At 22 weeks,it opens its eyes, and atype of pap produced byits mother is added to itsdiet, which will prepare itfor an herbivorous diet.

Gestation35 DAYSWith its extremities andfunctional organs barelydeveloped at birth, thenewborn must crawl by itselffrom the cloaca to the pouchto continue its development.

Incubation12 DAYSEggs gestate for a monthbefore hatching. Theyincubate within a pouchfor about 10 days toremain at the propertemperature until theyoung are born.

Leaving the Pouch1 YEARThe offspring reaches a size that allows itto fend for itself. It has alreadyincorporated herbivorous food into itsdiet. The mother can become pregnantagain, but its young will remain nearby.

SexualMaturity3 TO 4 YEARSAt two years, koalasalready have developedsexual organs (femalesearlier than males). Butthey do not startmating until one or twoyears later.

Longevity4 to 10 years

Longevity15 to 20 years

Gestation28 TO 33 DAYSThey spend it in a collectiveburrow (warren) dug in theground and covered withvegetation and fur. Thefemale will abandon it assoon as lactation ends.

Cow

Goat

Dog

Rat

1 OFFSPRING

2-3OFFSPRING

5-7OFFSPRING

6-12OFFSPRING

3 to 9Young

PER LITTER, ANDFROM 5 TO 7

LITTERS PER YEAR

1 to 3EGGS AT A TIME

People

Elephants

Horses

Giraffes

Cats

Dogs

Hamsters

Giraffes

Gibbons

Lions

Dogs

Elephants23

9

7

2

ANIMAL MONTHS

70 years

70

40

20

15

15

3

Life Cycle

34 BEHAVIOR AND LIFE CYCLE

Placental MammalsThis is the largest group of mammals, the one that hasmultiplied most on the planet, although its form ofgestation and lactation produces great wear and tearon the females, making them less prolific. They aregenerally polygenetic: a few males (the mostcompetitive) fertilize many females, and othermales, none. Only 3 percent of mammals aremonogamous in each season. In thesecases, males participate in rearing theoffspring, as they also do when resourcesare scarce. If resources are abundant,the females take care of the young alone,and the males mate with other females.

90 YearsA WHALE'S AVERAGE LIFE SPAN—THEGREATEST OF ANY LIVING MAMMAL

They are bornwithout fur, withsemitranslucentskin.

They havefour to fivepairs ofbreasts.

They makeuse of naturalcaves or digunderground.

Femalerabbits canmate atany time.

By the end oflactation, furcovers thewhole body.

NewbornOffspring

Underground cave ora cave among rocks

UndevelopedLimbs

The fur isalready spiny.

Shell

Dominantmales matewith all thefemales.

Some femalesleave to look forstrong males.

The young animal fastens itself toits mother and is carried aroundby her, clinging to her shoulders.

1 offspring1 BIRTH PER YEAR

0.8 inch(2 cm)

In the Pouch2 TO 3 MONTHSAfter breaking the shell, theyoung are suckled while theyremain in a kind of pouch ofthe female.

0.5 inch(15 mm)

Weaning4 TO 6 MONTHSAfter three months,the offspring can leavethe burrow or remainin it alone for up to aday and a half beforefinally separating fromthe mother.

Longevity50 years

MAMMALS 35

The shell is softand facilitates theoffspring's birth.Unlike birds, theydo not have beaks.

Chicken

Echidna

4 inches(10 cm).

Red DeerThese are svelte, robust, well-formed animals with a majestic

and haughty carriage. They are verytimid and fearful, and it is thought thatthe species is 400,000 years old. Theyare active at daybreak and evening,and males usually live alone. Femalesand younger deer group in herds.

Order

Family

Species

Diet

Weight(male)

Artiodactyla

Cervidae

Cervus elaphus

Herbivorous

400 pounds(180 kg)

Finding a female with whom to mate is the greateffort of the male's life, a competition with othermales of his own species. Each animal has its

particular nuances. For stags, antlers play a fundamentalrole in winning the heart of their chosen one. Whicheverstag has the most beautiful, longest, and sharpest hornswill be the winner. Thus, he will be able to defend histerritory, court the female, and reproduce.

Beauty and Height


FightsWhen two males fight over a harem,each will display his antlers tofrighten his rival. The horns can alsobe used to defend against predators.

MoltHorns are shed every

year. Animals betweenthe ages of 6 and 10

display the finestantlers.

Antlers

BellowsSonorous and discordant, they beginto be heard when spring arrives,announcing the beginning of rut, or matingseason. They not only attempt to keepcompetitors away with their call but theyalso use the sound to attract unattachedfemales to join the male's herd.

NEWNear the end ofsummer, stags displaytheir new antlers,which will be largerand heavier than theprevious ones.

4

DEVELOPMENTStags rub their antlersagainst trees and bushesto get rid of themembrane that coversthem.

3

GROWTHNew antlers are coveredwith a fine membrane,called velvet, that willstay on the horns untilthey are fully developed.

2FALLING OFFAt the onset ofautumn, stags beginto lose their antlers,which will bereplaced by new ones.

1

24 inches(60 cm)

43 inches(110 cm) 31 inches

(80 cm)

MALE FEMALE

ANTLER LAYERS

FORK PALM POINT

CROWN

PEDICLE

BEAM

EpidermisDermis

PeriosteumFibrous tissuethat protectsthe bone

Horns and AntlersHorns are outgrowths of the cranium,covered by a tegument that forms a sheath.They appear in bovids of both sexes and aregenerally permanent. Antlers are alsoextensions of the cranium; they are limitedto the deer family, are present only in males,and are replaced annually.

MMAMMALS 37

MAMMALS 3938 BEHAVIOR AND LIFE CYCLE

The egg is the size of agrape and stays at thebottom of the female'sincubating pouch. Ittakes 11 days to hatch.

A

When born, it isone half inch long.The front feethold on to themother's pouch,where it crawls insearch of food.

B

Seventy dayslater it will leavethe mother'spouch, and themother will placeit in a burrow,where she willfeed it for threemore months.

C

The Cycle

HOW LONG THE BURROW OFA PLATYPUS CAN BE

100 feet(30 m)

Oviparous MammalsF

or a mammal to lay eggs seems improbable, but the surprisingmonotreme females, instead of giving birth to young, are oviparous.They are warm-blooded, have hair, and feed their newborn through

mammary glands despite having no nipples. Platypuses seem like acocktail of nature, inasmuch as parts of their bodies resemble those ofother types of animal. The other monotremes, echidnas, are coveredwith spines, and their young grow in the mother's pouch.

PlatypusCombining the skin of a mole, the tail of a beaver, the feetof a frog, and the beak of a duck, platypuses are

semiaquatic mammals endemic to the eastern part of Australiaand to the island of Tasmania. They construct burrows inriverbanks consisting of a long passageway.

EchidnaLives in Australia, New Guinea, and Tasmania. Ithas an elongated snout in the form of a beak, no

teeth, and a long, retractable tongue. It is a notabledigger and hibernates underground. Echidnas can live upto 50 years, and their hair varies according to the species.

BILL has sensitiveelectroreceptors thatcan perceive the electricfield generated by themuscles of their prey.

RETRACTABLETONGUEA sticky substanceon the long andslender tongueallows it to catchtermites and ants.

EYESare kept closedunderwater.

HAIRThe sharp spinesoriginate within the fur.

SNOUTis used tosearch for andcatch food.

LIMBShave claws at the tipsof their feet, which helpin digging rapidly.

Ornithorhynchidae

Ornithorhynchusanatinus

Herbivorous

5.5 pounds (2.5 kg)

Diet

Weight

Family

Species

Tachyglossidae

Tachyglossus aculeatus

Family

Species

AdultSize

16 TO 24 INCHES(40-60 CM)

12 TO 35 INCHES(30 TO 90 CM)

ReproductiveCycle

The platypus has three reproductive cycles annuallyand spends most of the year in solitude. Platypuses

are seen as couples only when they mate. They have aperiod of courtship before copulation, which isperformed by a juxtaposition of cloacae. Their

reproductive rate is low since they lay only one tothree eggs. The female platypus digs a burrow

before laying her eggs, whereas echidnas have apouch in which they incubate their young.

Unlike the hair on the other parts of itsbody, the hair in the echidna's

pouch is soft.

1/3 inch(9 mm)

ConceptionFor reproduction, the femalemakes a deep burrow, where ithides. It lays the eggs when itfinishes digging the burrow.

1

IncubationThe eggs are covered by a soft shell, and incubationlasts two weeks.

2

BirthWhen the egg breaks, theupright position of themother allows the offspringto find the mammary areas.

3

LactationThe mother has no nipples,but milk comes out throughpores in her abdomen, fromwhich the offspring suck.

4WeaningAfter 16 weeks, the youngbegin to feed on ants andother small insects.

5

Femalesare halfthis size.

MMAMMALS 4140 BEHAVIOR AND LIFE CYCLE

Efficient NurseryM

arsupial females carry their newborn offspring in their marsupium, a pouchattached to their belly. The offspring are not very well developed when they comeinto the world after a gestation period that varies from two to five weeks. Upon

emerging, the offspring must immediately climb with their front paws to the marsupiumto survive. Once inside, they will be protected. They are continually supplied with milkthrough their mother's four teats, helping them complete their growth before leaving thepouch for the outside world.

Entering theMarsupium

THE SIZE OF AN OFFSPRING WHENIT ENTERS THE MARSUPIUM

0.8 inch(20 mm)

After some eightmonths, thekangaroo can leavethe marsupium.But it returns to besuckled andprotected.

A

However, it barelyfits. It entershead first withthe aid of its frontpaws and turnsaround onceinside the pouch.

B

When it is alreadyalternating milkwith grass fromoutside, the youngkangaroo sticks itshead out to eatgrass withoutleaving the pouch.

C

Smoothing the WayWhen preparing for the birth of anoffspring, the female kangaroo licks its coatto form a kind of path some 5.5 inches (14cm) long, which the offspring will follow toreach the entrance to the pouch locatedhigher up on the belly.

1

2

3

REPRODUCTIVE CYCLE

A MarathonSmall kangaroos are born after afew weeks of gestation in an earlystage of their development,weighing less than 0.2 ounce (5 g).They cannot see or hear. They onlymove their front paws, with whichthey drag themselves, followingtheir mother's trail of saliva andguided by their sense of smell.

MOVING OUT OFTHE MARSUPIUMAt eight months, theoffspring leaves the pouchand begins to add grass toits diet, but it willcontinue to be suckleduntil it is 18 months old.

LactationUpon reaching the marsupium, the babyfastens its mouth upon one of the four teatsinside. At this point, the baby is red andlooks very fragile. However, it will growcontinuously over the next four months,during which it will not leave the pouch.

Macropodidae

Macropus rufus

Family

Species

Red KangaroosKangaroos are a family comprising several groups, includinggreat wallabies and tree-dwelling kangaroos. Kangaroos, the

prototypical marsupial, live in Australia and in Papua New Guinea,never more than 9 miles (15 km) from water. They have large, muscularhind legs that they use to take great consecutive leaps, reaching speedsof 15 to 20 miles per hour (24-32 km/h). They are able to maintaintheir balance standing only on their hind legs. Their heel bone(calcaneus) is long and acts as a lever.

The female cangive birth to anoffspring whileanother one is inthe marsupium.

0 daysBIRTH OF THEKANGAROO

2 daysRUT AND NEW

CONCEPTION

236 daysTHE OFFSPRINGBECOMESINDEPENDENT

238 daysRUT AND NEWCONCEPTION

237 daysA NEW KANGAROOIS BORN

The baby kangaroo mustget to the pouch withinthree minutes or it willnot survive.

4.5 feet(1.4 m)

5 feet (1.6 m)

4 feet (1.3 m)

TWOUTERUSES The marsupialfemale has twouteruses.

TEATgrows intandem with theoffspring andcan reach 4inches (10 cm)long. Then itcontracts again.

MAMMALS 4342 BEHAVIOR AND LIFE CYCLE

Miraculous PlacentaT

he largest reproductive group is formed by placentalmammals, in which the unborn offspring develop in thefemale's uterus. During gestation, food and oxygen pass

from the mother to the fetus through an organ known as theplacenta, which allows the exchange of substancesthrough the blood. At birth, the offspring oftenhave no hair, are deaf and blind, and feed onmilk secreted by the female's mammaryglands, which become active after birth.

0.4 inch(10 mm)

0.6 to 0.8 inch (16 to 20 mm)

LEGSExtremities arein the process offormation.

BRAINThe brain isforming; it appearstransparent.

EYE begins todevelop andcan now beobserved.

PLACENTAThe fetus is attachedto the placenta.

SPINECervical and lowerlumbar vertebraebegin to develop.

ORGANSInternal organsbegin to form andbecome visible.

TOESToes on the frontlimbs can also bedistinguished.

EYELIDS They grow veryrapidly, and by day18 the eyes arealready covered.

SPINEThe spine can bedistinguished andis ready to supportthe little rat.

1 to 2 DaysRat embryo at the two-cellstage. By the second day, itwill have four cells, and onthe third day, it will enterthe uterus.

1

4 to 5 DaysAt this point, the embryo iscomposed of four cells andis covered with a thin layerof glycoprotein. It implantsitself in the uterus.

2

6 to 8 Days The blastocyst has nowimplanted and establisheditself in the uterus. The fetusbegins to form, and theblastocyst becomes a yolk sac.

3

11.5 DaysThe embryo has nowfastened itself to theembryonic sac (a sort ofballoon that covers thefetus) and to the placenta.The brain, eyes, and legsbegin to form.

4

17.5 DaysThe eyelids grow veryrapidly, and within a fewhours the eyes will becompletely covered. Thepalate has alreadycompleted its development,and the umbilical cordretracts.

619.5 DaysOnly a few days are leftbefore the female willgive birth to a new litterof little rats. At birth,they are helpless despitethe fact that all theirorgans are developed.

7

14.5 DaysEyes and extremities are

now visible, and theinternal organs begin to

develop. A pre-cartilaginousmaxillary and the outer ear

begin to form.

5

UterusIS BICORNUATE AND HAS

TWO CERVICES.

ORGANSThe organs are nowalmost completeand ready to go outinto the world.

Gestation of RatsGestation lasts between 22 and24 days. Whereas the placenta

is discoid and hemochorial, theovaries are essential formaintaining gestation. If anovariectomy is performed at anystage of gestation, it will alwaysbring about a miscarriage or thereabsorption of the fetuses sincethe placenta does not producesufficient progesterone to maintaingestation. The growth of the uterinehorns becomes visible on the thirteenthday of gestation.

PlacentaFrom whales to shrews, placental mammals arecharacterized by gestating their young inside the motherand giving birth when they are well developed. To do so,they have a special organ, the placenta. This is a spongytissue that completely surrounds the embryo, allowingthe exchange of substances through the blood. In thisway, the mother can transfer nutrients and oxygen tothe embryo, at the same time that she absorbs themetabolic waste of her future offspring. After birth, theplacenta is immediately devoured by the mother, whouses her teeth to help the young leave the structure.

YOLKImplantedblastocyst, withtrophoblastic coneand inner cell mass

MAMMALS 45

Mammals whose offspring develop within the uterus devote a lot of attention to their youngcompared to other animals, because their pups are unable to live on their own at birth. Thatis why they are cleaned, fed, and warmed. Dogs have various developmental stages. First is

the neonatal stage, which lasts from the opening of the pups' eyes untilthey begin to hear. Then comes the socialization stage, whichruns from days 21 to 70, and, finally, the juvenile stage,from 70 days on.


The First Days

The PupsAt birth, pups do not innatelyrecognize members of their species;they do not seem to know that theyare dogs. They must learn this, andthe mother and the rest of the litterare in charge of teaching them this.

From Day 21 to Day 70Natural weaning involves offering pupspredigested food as a replacement for milk. Whenthe mother comes back from hunting, its mouthhas an odor, and the pups, stimulated by the odor,smell her, lick her snout, rub it, and nibble herjaws and face, which stimulates the regurgitationof food. At this stage, in which the pups have milkteeth, they can begin to eat these foods.

BirthLike humans, dogs develop slowlyafter birth, because they are not fullydeveloped when they come into thisworld and are incapable of living ontheir own. They need a structuredenvironment in which they are cared for bytheir parents and other members of the pack.

Up to 20 DaysThis period, in which pups depend totally on themother, lasts from birth to 15 or 20 days, whenthe pups open their eyes. But until then, they arecompletely dependent on their mother, seekcontact with the mammary glands, and whimperif they are alone. They have little ability to keep

themselves warm, and they even need thestimulation of their mother to pass

body wastes.

BLIND EYESStill closed

SKINShort andsoft hair

EYESremain shutuntil thesecond orthird week.

WET HAIROnce dry, pups seeka teat from which tosuck colostrum,which consists of,among other things,immunologicalsubstances.

MEMBRANEPlacenta, whichcovers the pup

STRENGTHThe pups arenow able to beon their own.

Lost Pup

Den

The mothermoves thepups withouthurting them.

STANDING UPThe mother no longerneeds to lie down andis free to move away.

TACTILE REFLEX They push withtheir snout untilthey are hidden.THE DEN

The mother builds aden in a warm placeaway from noise.

SURPRISEREFLEXAt 20 days, pupsstart to hear andreact to sound.

MAMMARYGLANDS

THE MOTHER'SPOSITIONThe mother liesdown to make iteasier for the pupsto reach her.

BirthThe first pup is bornbetween 1 and 2hours aftercontractions begin.

THE MOTHERThe relationships of pups totheir mother and siblings areessential to dogs' laterdevelopment, because,although their socialstructures and relationshipsare largely innate, they mustbe shaped, tested, andpracticed to develop properly.

Lactation PeriodThis period is essential in the reproductive processof mammals. The young of most placentalmammals are totally dependent in the first stagesof their life on mammary milk secretion.

The mother knows each newborn andrealizes if any pup is taken away from her.

Litter3 to 8 Offspring

To move her weak pups, which cannot yetwalk, the mother picks them up by the skin onthe napes of their necks and places them inthe den. Fifteen days after birth, mother dogsexperience what is called the bondingphenomenon: they become aware of thelitter's existence, see them as a group, andnotice if any puppy is missing.

TRANSPORT

0

YEARS

Dog

Lion

Asi

anel

epha

nt

Dol

phin

Gor

illa

3–4years

18months

18months

7–10 months

7weeks

4

3

2

1

EXTENSOR REFLEXAt 12 days, pupsextend their hind legswhen picked up.

UdderCows and mares have twomammary glands thattogether form an udder. Itbegins to function afterbirth and stops when theoffspring stop nursing. Itis regulated by pituitary,thyroid, placental, andadrenocortical hormones.

AlveolusThe functional unitof milk production

AVERAGE LENGTH OF AN ALVEOLUS

0.008 inch(0.2 mm)

4GALLONS (15 L) OF MILK CAN BESTORED IN THEBOVINE UDDER.

COMPOSITION OF MILK (%)

ARTERIALBLOOD

VENOUS BLOOD

MYOEPITHELIALCELLS

BLOODCAPILLARIES

MILK DUCT

MILK-SECRETINGCELL

Milk secretionis stored here.

INTERNALCAVITY(LUMEN)

OuterConnectiveTissue

GLANDULAR LOBULEA group of 10 to 100 alveoli that drain into a common duct

When the ductscontract in response tothe oxytocin hormone(the ejection, or let-down, reflex), milk flowsthrough the lactiferousducts to the mammarygland's cistern.

MILK EJECTION

NORMAL STATE

14 PIG 12 DOG

2 SHEEP 2 HORSE

NUMBER OF MAMMARYGLANDS IN FEMALE MAMMALS

Bone Structure(posterior view)

SuspensoryLigaments

AbdominalWall Muscle

MammaryLymph Node

SECONDARYGLANDULARDUCTS

LACTIFEROUSDUCTMilk circulatesthrough this ductfrom the lobulesto the teat cistern.

TEAT CISTERN

GLANDCISTERN

PRIMARYGLAND DUCTS

SUPPORT LAMINA

SPHINCTERMUSCLE

TEAT DUCT

MammaryParenchyma

Human

Horse

CowBuffalo

Goat

Sheep

PROTEINS CASEIN FAT RESIDUESCARBOHY-DRATES

1.2

2.2

3.54.0

3.6

5.8

0.5

1.3

2.83.5

2.7

4.9

3.8

1.7

3.77.5

4.1

7.9

7.0

6.2

4.84.8

4.7

4.5

0.2

0.5

0.70.7

0.8

0.8

RIGHTFRONTQUARTER

CONNECTIVETISSUE

LEFT REARQUARTER

Brain

Heart

InguinalNerve

Udder

The exclusive characteristic of mammals, the one that immediately identifies them, is thepresence of milk-producing glands with which the females of all mammalian species feedtheir offspring after they are born. The number and arrangement of mammary glands

vary by species. Teats are arranged in pairs and are present in both sexes, although only femalespossess functional mammary glands—and that only while lactation lasts.

Trademark


First impulse:With suction, theneurohormonal

reflex related to lactationgenerates a nerve impulse.

1 This impulse istransmitted bythe inguinal nerve

to the spinal cord andfrom there to the brain.

2 The brain givesoff oxytocin,sending a signal to

the heart through a branchof the jugular vein.

3

The hormone isdistributed tothe entire body

through the arterialsystem. This is how itreaches the heart andthen the udder.

4Milk ejection inthe udder isproduced by the

contraction ofmyoepithelial cells,which constrict thealveoli.

5

How a Cow Gives Milk


Development and Growth

Use of ToolsThe use of tools is not common in mammals. However,chimpanzees are capable of using objects as tools, a skillthey acquire by observing adults. They can use sticks toeat termites or use leaves as spoons to drink water.

Social RelationsPlay also helps encourage apes to identifywith their species. It provides a basis forlearning to communicate through the useof sounds and body posture to express,for example, submission or domination.

A LIFE OF HANGINGA great entertainment for apesis hanging from trees. Thisexercise improves theircoordination and arm strength.

PERCEPTIONThey have sensoryabilities very similar tothose of people, andthey distinguish smellsbetter. Because oftheir large brains, theyare very intelligentand can communicatewith people by signs.

THEY CAN LEARN ANDEXPRESS WORDS USINGSIGN LANGUAGE.

words

SurvivalPlay also functions as a methodof learning to survive in a wildhabitat. It trains carnivores inhunting techniques andherbivores in detecting, andfleeing from, danger.

OpposableThumb

LongDigits

GamesWhat we humans call play appears to belimited only to mammals, because they havewell-developed senses, intelligence, and theability to learn. It is through play thatmammals carry out their learning.

ExtremitiesChimpanzees are characterized by their long arms,which are endowed with great strength, and bytheir opposable thumbs. The digits of their handsand feet are large, allowing them to climb withgreat ease. They can hold onto a branch with theirfoot while they pluck its fruit with their hand.

When they move aroundon all fours, they beartheir weight on the solesof the feet and theknuckles of their hands.

A chimpanzeepokes a stumpin search oftermites, using astick as a tool.

This expressioncommunicatesterror.

This expressiontransmitssubmission.

This gestureindicatesworry.

IDENTIFICATIONOnly 15 minutes of playwith peers per day willmoderate the effects ofsocial isolation.

CommunicationSome mammals, especially chimpanzees, communicatethrough facial expressions. This ability is well developedin the young primates, which express fear, submission,and worry, among other feelings.

15are emitted by chimpanzees,including its pant-hoot: screamsand grunts that can be heard amile and a quarter (2 km) away.Pant-hoots are unique to theindividual and can help to identifyeach member of the group.

TYPES OFCALLS

over

MAMMALS 49

Play is much more than entertainment for young mammals. This activity, which may appearto have no specific purpose, is the way in which they learn to be part of their species in theearly stages of their lives, simultaneously acquiring the basic means of survival. In their

games, chimpanzees perform primary instinctive activities that, with time and improvement, willbecome perfected instinctive activities. These include using tools, balancing in trees, and formingcommunication. Young chimpanzees express themselves by means of sounds, facial gestures, andbody postures they imitate from adults. Play also allows them to develop their muscle strengthand achieve good motor coordination.

Family

Species

Weight

Size(female)

Felidae

Panthera leo

265-410 pounds(120-185 kg)

Lionsare characterized by a strong, muscularphysique. A male requires 15.5 pounds of meat

(7 kg) a day, whereas a female needs 11 pounds (5kg). They have a short digestive tract, which rapidlyabsorbs nutrients from the ingested meat.

SIGHTTheir vision is six timesbetter than that ofhumans. They also havebinocular vision, essentialfor locating prey.

UPPERPREMOLARS

UPPERCANINE

UPPERINCISORS

LOWERINCISORS

LOWERCANINE

ANTERIORPREMOLARS

3 feet(1 m)

9 feet(2.7 m)

COATShort, with a uniformbrown color. Theyhave an off-white tuftof hair on the chin.

CARNASSIALMOLARThey are very large, and thedental crowns are two longblades arranged as shearsthat fit into each other.Together they slice and cutflesh to perfection.

THE TAILMeasures some 35 inches(90 cm) in length and allowsthem to keep their balancewhile running. They also useit to shoo away flies.

BUFFALO ZEBRA GIRAFFE

GNU GAZELLE ANTELOPE

The carnivore group is composed of specieswhose diet is based on hunting otheranimals. The kind of teeth they have help

them efficiently cut and tear the flesh of theircaptured prey. Lions, the most sociable of thefelines, have good vision and sharp hearing;they live in packs, and when they gohunting, they do so as a group.

Of Flesh Thou Art


The bulk of their dietconsists of large mammals,although they also catchsmall mammals, birds, orreptiles when theopportunity arises. They arenot scavengers. Theygenerally eat only freshmeat, something they havekilled or succeeded in takingaway from another predator.

(18 kg)40 poundsOF MEAT CAN BE EATEN BYA LION IN A SINGLE MEAL.

LYING INAMBUSHHidden in the grass, thelioness silently approachesthe prey. Other females waitin hiding.

1ACCELERATIONWhen only a few yards away, itstarts running to catch thezebra. It exceeds 30 miles perhour (50 km/h), and the otherlionesses cooperate in the hunt.

2LEAPThe lioness hurls the weight of herbody on the zebra's neck, tryingto knock it down; if she succeeds,the hunt will be successful.

3LETHAL BITEThe prey falls, and thelioness sinks her fangs intothe neck until she kills it.The other females approach.

4

Main Prey

Teeth

The Hunt

MAMMALS 51

Cows wraptheir tonguesaround the food.

Then they chewit with lateralmovements.

helps ruminants reduce the size of theingested food particles. It is part of the

process that allows them to obtain energyfrom plant cell walls, also called fiber.

RUMEN BACTERIAThe rumen creates an

environment appropriate forthe growth and reproduction of

microbes. The absence ofoxygen inside it favors the

growth of bacteria that candigest plant cell walls to produce

simple sugars (glucose). Microbesferment glucose and provide energy

to grow and produce volatile fattyacids as the final product of fermentation.

INSIDE THE OMASUM

RETICULUM

ABOMASUM

OMASUM

RUMEN

SMALLINTESTINE

LARGEINTESTINE

Cows lightly chew grass andingest it into their first twostomachs: the rumen and thereticulum. Food passes continuallyfrom the rumen to the reticulum(nearly once every minute). Therevarious bacteria colonies beginfermenting the food.

INGESTION ANDFERMENTATION

RUMINATION

REABSORPTIONOF NUTRIENTS

KEY

ACID DIGESTION

DIGESTION ANDABSORPTION

FERMENTATIONAND DIGESTION

ENAMEL

CEMENT

DENTINE

PULP

REGURGITATION REMASTICATION REINSALIVATION REINGESTION

INCISORS

MOLARS PREMOLARS

ROOT

Ruminants, such as cows, sheep, or deer,have stomachs made of four chambers withwhich they carry out a unique kind of digestion.

Because these animals need to eat large quantities ofgrass in very short times—or else be easy targets forpredators!—they have developed a digestive system thatallows them to swallow food, store it, and then return itto the mouth to chew calmly. When animals carry outthis activity, they are said to ruminate.

Herbivores


TeethHerbivorous animals such as horses and bovidshave molars with a large flat surface that reducesfood to pulp, as well as incisors for cutting grass.Grinding is also done by the molars. 30%

OF THE ENERGYFROM CONSUMEDFOOD IS USEDFOR DIGESTION.

OF SALIVA ARE PRODUCEDDAILY IN THE PROCESS.

40gallons

1

Only small particles reachthe omasum, the thirdstomach. Many are recycledand absorbed as nutrients.

3

As they grow, microbes in therumen produce amino acids, thebuilding blocks of proteins.Bacteria can make use ofammonia or urea as sources ofnitrogen to produce amino acids.Without bacterial transformation,ammonia and urea would be of nouse to cows.

5

MAMMALS 53

The abomasum secretes strongacids and digestive enzymes thatfinish breaking down the foodbolus (the mass of chewed food).

4

Filter inside theomasum

After the main process ofdigestion and absorptionof nutrients, what remainscontinues through thesmall and large intestines.There the remainingdigestive productsferment, and wastes, orfeces, are formed.

6

When cows feel satiated,they regurgitate balls offood from the rumen andchew them again in themouth. This is calledrumination; it stimulatessalivation, and, as digestion is avery slow process, cows makeuse of rumination to improvetheir own digestion togetherwith the intervention ofanaerobic microorganisms suchas protozoa, bacteria, and fungi.

2

8 HOURS OFRUMINATIONDAILY

THE RUMINATION PROCESS

(150 l)


Equilibrium of the SystemThere is a very efficient natural equilibrium in the food chains of aterrestrial ecosystem, of which mammals form various parts. For

this balance to be maintained, there can never be more herbivores thanplant food or enough carnivores to overwhelm the herbivores. If therewere more herbivores than plant food, they would eat all the vegetationand then suffer a drastic population reduction. A similar situation wouldoccur if there were enough carnivores to overwhelm the herbivores.

ZEBRA

Level 4Large carnivores are atthe top of the foodchain—there are no otherpredatory species thatregulate their population.

Level 3Small carnivores feed on small,herbivorous mammals or on birds,fish, or invertebrates. At the sametime, they must be on guardagainst other, larger species. Kings of the Jungle

Lions are great carnivores (one of thelargest in size) and strong, with little or nocompetition. Cheetahs will rapidly fleefrom lions if the latter arrive to challengethem for their food. Only when a lion isalone might a pack of hyenas, for example,confront it to steal its meal.

Maintaining ecological balance requires the existence ofprey and predators. Predatorial species bring about asustained reduction in the number of individuals of the

prey species. If predators did not exist, their prey would probablyproliferate until the ecosystem collapsed, because there wouldnot be enough food for them all. Disappearance of predators isthe cause of many imbalances created in certain habitats bypeople, whose predatory ability exceeds that of any other livingspecies. Like all other animal species, mammals do not makeup a food chain in themselves, instead depending at alltimes on the participation of plants and other animals.

The Great Chain

Scavengerseat meat from animals thatare already dead. Somecarnivores become scavengersunder conditions of scarcity.

Trophic PyramidEnergy is transferred from one level to another in an ecosystem. Ateach level, a small amount of energy is lost. What is retained at onelevel is the potential energy that will be used by the next. Biomass isthe total mass of living matter; it can apply to a specific level of thetrophic pyramid, a population of individuals of the same species, or acommunity of different species.

Level 2Primary consumers devourautotrophic organisms (plants oralgae), because they depend onthem for subsistence. And othermammals feed on them.

CompetitionWithin the same level, differentherbivorous rodents (such asrats and prairie dogs) competewith each other for food.

Super-adaptedBecause of their highlyvaried plant diet, theserodents usually have noproblem surviving.

Small OmnivoresFerrets feed on birds andamphibians, as well as on othermammals, such as rats, mice,and moles. They also eat fruit.

SMALL-SPOTTED GENETLike many highly predatorylarge felines and dogs, it is indanger of extinction as aresult of human activity.

Not Only MammalsFerrets are important incontrolling rodents, butthey must simultaneouslyguard against birds of prey.

WOLFeats prey that it catchesbut can also competewith scavenger birds.

GEOFFROY'S CATlikes to hunt largeranimals (such as deer).

Varied DietsThere are species that have anotherspecies as their sole food; but, ingeneral, the chain branches out.

IS GREATER AS ONE GOESDOWN THE PYRAMID.

Population

Level 1Because of photosynthesis, only plantsand algae can transform inorganicmatter into organic matter. They formthe beginning of the food chain.

CHEETAH GAZELLE

LION CAPEBUFFALO

A FOOD CHAIN CANREACH SEVEN LEVELS.

PrimaryProducers—Plants

PrimaryConsumers

SecondaryConsumers

TertiaryConsumers Energy

Consumed

HYENA


One for AllMEERKATS ALSO USEVOCALIZATIONS TOCOMMUNICATE.

FEMALESmust dedicate all theirenergy to the processof reproducing andfeeding and raisingyoung.

MALESdefend their territoryand stand watch. Thedominant male is thereproducer.

BLACK-BACKED JACKALThe meerkats' largestpredator. To detect onebefore it is seen is of primeimportance for the colony.

MARTIAL EAGLESThe most dangerousenemy they have and theone that kills the greatestnumber of meerkats

OFFSPRINGWhen the father ormother standing watchgives the cry of danger, allrun to hide in the burrow.

TRIPOD TAILMeerkats use itto balancethemselves whenthey are in anupright position.

FRONT PAWSThey havestrong claws,which they usefor digging orto defendthemselves.

HIND FEETThey supportthemselves ontheir hind feetwhen theyremain standing,keeping watch.

SIGHTBinocular and incolor, it allowsthem to locatetheir greatestpredators, birdsof prey.

HEADis keptpermanentlyerect, observingthe burrow'ssurroundings.

TerritoryThe area defended provides the foodnecessary for the group's subsistence.Males devote themselves to defense,and when resources run out the groupmigrates to another area.

Defense

LookoutWhen a predator is detected, the lookout warns its groupso that all of them can take cover in a nearby hole. Thisrole rotates among different members of the group, andthe warning is given by a very wide repertoire of sounds,each of which has a distinct meaning.

MEERKATSuricatasuricatta

Family

Habitat

Offspring

Herpestidae

Africa

2 to 7

12inches

(30 cm)

Meerkats are small mammals that live in undergroundcolonies, posting guards while the mothers takecare of their young. During the day they go

above ground to feed, and at night they go into theburrow to take refuge from the cold. In this large family,made up of dozens of members, each one fulfills afunction. When faced with danger, they employ varioustactics to defend themselves. One of these is the squealthat lookouts emit in the face of even slight dangers.

It is common to seethem in the highestplaces of theirterritory on rocks ortree branches.

Weight2 pounds

(1 kg)

Social StructureThe social structure is extensive and well defined,ensuring that everyone has a role to fulfill. The

lookouts (which may be female or male) take turns tosound the alarm over the arrival of strangers; one that isbetter fed replaces another that needs to eat. Theseanimals are carnivorous. They eat small mammals, aswell as insects and spiders.

IS THE NUMBER OFINDIVIDUALS AGROUP CAN HAVE.

ABOUT

30

VIGILANCEFROM ABOVE

1SURROUNDING THE ENEMYThey emit a type ofsqueal. They rock backand forth. They try toappear larger and moreferocious than they are.

2ON THEIR BACKSIf this tactic fails, theythrow themselves downon their backs to protecttheir necks, showingtheir fangs and claws.

3PROTECTIONWhen it is an aerialpredator, they run tohide. If taken bysurprise, adultsprotect the young.

BURROWSThey dig them withtheir sharp clawsand leave them onlyduring the day.

MAMMALS 57

GRAN ATLAS DE LA CIENCIA AAVES 59

CENTRALAREAis inhabited bythe highest-ranking animals.

Social units and mutual aid are common inmammals' lives, except for a few species that live aloneor in small families. Wolves are social animals that live closely

attached to a group—the pack—that forms the basis of their socialstructure. Behavior in a pack is highly regulated and hierarchical.

Wolves in Society


DOMINANT

SUBDOMINANT

OFFSPRING

The FamilyWolves live in packs madeup of two to three pairs ofadults and their variousgenerations of offspring.They cooperate inhunting, killing animalsseveral times larger thanthemselves. Althoughthey share food, wolveshave a hierarchicalorder that obliges theyoung to make wayfor larger and olderfamily members.

6 to 20 individuals

IS THE SIZE OFTHE PACK

DEPENDING ONTHE AVAILABILITY

OF FOOD.

Recognition ofPositionFights and confrontations within the pack arerituals by means of which relations of power andhierarchical status are established and delimited.

DOMINANTPAIR

Low-rankingHigh-ranking

Encounter The low-ranking wolf advanceswith submissive posture: ears laidback and its tail between its legs.

1

VOCALCOMMUNICATIONplays an important role,allowing wolves tolocate packmembers.

INTERMEDIATEREGIONis inhabitedindiscriminatelyby all the wolves.

PERIPHERY, ORTERRITORYis inhabited bywolves of lowersocial rank.

TERRITORYThe highest-ranking adults live inthe central area or home. Theterritory proper lies in the peripheryand is inhabited by subadults andmembers of lower social rank.Between these two areas is that ofvital domain, an intermediate areainhabited by all members. Theterritory can extend over 100square miles (300 square km).

LEGS IN THE AIRThis posture impliessubmission andnonaggression.

DOMINATORSMade up of the breeding pair,which is dominant, and theirdescendants. Only the breedingpair, however, are permanentlydominant. A relationship ofdominance-submissionbetween sexes is alsoestablished. The alpha femaleexercises clear dominanceover the subdominant males.

HierarchyThere are two hierarchies in the pack: oneof males and another of females. At the topof each are the alpha (or dominant) maleand female. Underneath this pair is a groupof subdominant wolves among whom theremay be little or no difference in rank.Among females, a strong dominant-submissive relationship is observedbetween beta and gamma wolves, as wellas of the alpha female over those two.

ExaminationIt crouches in front of the snout ofthe dominant and gives it rapidlicks, submitting to the hierarchy.

2 RecognitionThen it lies down and urinates whilethe dominant smells its genitals toidentify it.

3

GAMESAlthough it looks like the

wolves are playing in thispicture, they are

actually carryingout a game

involvingpower and

hierarchy.

MAMMALS 59

There is great variety amongmammals, and in this chapterwe try to show you somerepresentatives of the mostoutstanding differences among

them. For example, here you willdiscover that there are species, such asbats, that are expert fliers, while others,such as dormice, enter into a deepwinter sleep that allows them to save

energy during times when food is scarce.Here we will also show you how thebodies of some mammals (whales anddolphins) are adapted to aquatic life. Inaddition, we will also consider the ability

of certain mammals to adapt to the hotand dry conditions of the desert. Camels,in particular, are very adept when itcomes to retaining and efficiently usingliquids.

DEEP SLEEP 62-63

RATIONED WATER 64-65

RECORD BREATH-HOLDERS 66-67

AERIAL ACROBATICS 68-69

NATURAL BUILDERS 70-71

Diversity NOCTURNAL FLIGHT 72-73

PLAYING HIDE AND SEEK 74-75

THE LANGUAGE OF WATER 76-77

LIVELY TUNNELS 78-79

DISTINCTIVE STRIPESZebras' stripes extenddown to the underbelly.They confuse predators.

How many times have you heard the expression “deadas a dormouse”? The comparison is no accident,although it should be understood that dormice

do not die: they merely hibernate. In the cold season,low temperatures and scarcity of food lead manymammals to enter into lethargic states. Bodytemperatures drop, heart rates and respirationslow down, and they lose consciousness.

62 DIVERSITY

Deep Sleep

When ActiveThe energy they consume during hibernation isobtained from the subcutaneous fat layer built upduring the autumn. Their nutrition comes fromleaves, bark, nuts, and other (mainly plant) foods.Before the arrival of winter, they stock up ondried fruits to increase their energy, allowingthem to easily climb trees and walls. Beforehibernating, they spend alltheir time eating,accumulatingreserves forwinter.

HibernationDuring this period, dormice enter into a deepsleep. Body temperature drops to 34º F (1º C),appreciably decreasing the heart rate. In fact,up to 50 minutes can transpire between breaths.Throughout these months, they slowly use uptheir reserves, losing up to 50 percent of theirbody weight. Their endocrine system is almosttotally at rest: the thyroid ceases functioning, asdoes the interstitial tissue of the testicles.

Building the NestDormice build their nests out of twigs, moss, and

leaves, although they can also hibernate intrees, stone walls, or old buildings, creating

a nest from fur, feathers, and leaves. Theythen settle into the nest, forming a ball.When they cannot find a natural refuge,dormice may settle into birds' nests withtotal impunity.

They remain in astate of hibernation.

4 monthsThey are consciousand active.

8 months

is what they can weighafter accumulating fatreserves beforehibernating.

Weight loss afterconsuming alltheir reserves

50%

CHESTNUTIts caloriccontributionincreasestheir energyreserves.

ENERGYThey obtain it from thesubcutaneous fat reservesthey accumulated in the fall.

HEARTHeartbeatsdecreaseconsiderably.

NUTSAlthough theyconsume snailsand insects,dormice begin tofeed on nuts priorto hibernation.

ACORNSThe nuts of oaktrees (genusQuercus) are afavorite food ofdormice.

LEAVES OF THEOAK TREESDormice are veryfond of oak trees.

(1°C)THEIR BODY

TEMPERATUREDURING

HIBERNATION

34°FHAZELDORMOUSEMuscardinusavellanarius

Gestation

Habitat

Habits Hibernate 4 monthsof the year

22 to 28 days

Almost all Europe

1RAW MATERIALSTo build their nests,dormice collecttwigs, leaves, moss,feathers, and hair.

2BALLDormice begin toform a ball out ofthese materials, inimitation of theposture they willadopt duringhibernation.

3HOLLOW BALLLike an ovenbirdnest, the ballmust be hollowso it can shelterthe dormouse.

4FINISHED NESTWith an entrance infront, the hollow ballhas been transformedinto a nest.

TEMPERATURE

OTHER PLACES FOR HIBERNATION

BIORHYTHM OF A DORMOUSE WHILE HIBERNATING

WEIGHT

RESPIRATION

Prior Feeding

Their tails are very long. Theycan measure up to 5 inches (13.5 cm) long.

TAILThey coverpart of thebody with it.

Deep Hibernation

BriefActivity

DeepHibernation

AfterHibernation

Weight2 ounces

(51 g)4 to 7 inches (10-17 cm)

POSITION OF THE BODY

FEETremain flexedduring thesemonths.

BIRD'S NESTIf they do notfind a place tobuild their nest,they may takeover a bird's nest.

HOLE IN A TREEcan also serveas a burrow forhibernation.

HEADThey hide itbehind theirlong tail.

RESPIRATIONFifty minutescan passbetween breaths.

March

February

Dec

emb

er

Nov

emb

er

THEIR NORMAL BODYTEMPERATURE.

(35°C)95°F

(300 g)11 ounces

64 DIVERSITY

Rationed Water

HUMPS CAN WEIGH THIS MUCH.

(14 kg)

THE AMOUNT OF WATERDROMEDARIES CANCONSUME IN 10 MINUTES

34 (130 l)gallonsThe Hump as a Reserve

Formed by the accumulation of fat during periods of abundantfood, the hump is an energy reserve that dromedaries use in the

absence of plant foods. This chemical reaction provides camels with asmall but invaluable amount of metabolic water. The breakdown of thefat produces hydrogen, which combines with inhaled oxygen toproduce water. By combining metabolic and cellular water, interstitiallymph, and plasma, they can go without food and water for longperiods of time.

LOOP OF HENLErecovers part ofthe water. Becausethe loop is longerin dromedariesthan in any othermammal, watercirculates for avery long time.

NormalErythrocyte

HUMPFat accumulates and preventsthe excretion of water fromthe whole body. This allowscamels to use a minimum ofwater.

KNEEShave calluses socamels can kneelwithout gettingburned.

KIDNEYSconcentrateurine toretain water.

Kidneysgreatly distill the urine, preventingunnecessary water loss. The urine mayget as thick as syrup and containdouble the salt of seawater. In thisway, camels eliminate impuritiesand filter the blood, losing as littlewater as possible.

ERYTHROCYTES

of consumed fat

2 pounds(1 kg)

of metabolicwater

2 quarts(2 l)

=

The percentage by whichan erythrocyte can swell,increasing its ability totransport water.

240%

Camels have developed a sophisticated physiology in order to face life in hot climates. Theirkidneys are capable of greatly distilling their urine to prevent water loss. When sandstormsworsen, camels curl up on the ground and close their eyes and nasal openings to protect

themselves. When water and food are scarce, they are able to endure by consuming the reservesthey have accumulated and stored in the hump and internal sacs.They also have oval-shaped red blood cells, which can easily movethroughout the body even when the blood has becomethickened from dehydration.

SwollenErythrocyte

RESISTANCE TO THIRST AND HUNGER

Dromedaries cango without foodand water foreight days at atemperature of122º F (50º C).

If all the hump'swater is used up,it hangs off to oneside of the body.

40% The maximumpercentage of bodyweight camels canlose without dying

12% The maximumpercentage of body weight aperson can lose without dying

Weight1,300pounds(600 kg)

10 feet (3 m)

CharacteristicsNOSETheir mucus structure is 100times more complex than thatof humans and retains 66percent of the air's moisture.

BODYTEMPERATUREDuring the day,their bodies act asheat retainers, andduring the night,the excesstemperaturedissipates byconduction.

DROMEDARY, ORARABIAN, CAMELCamelusdromedarius

Habitat

Food

Average life span

Arabia and Africa

Herbivorous

50 years

HAIRis so thick that it preventsheat from reaching the skin.When cold is intense, the hairkeeps the camel warm withits own body heat.

MAMMALS 65

31pounds

Record Breath-HoldersS

perm whales are unique animals whose species is remarkable for many reasons. On theone hand, they have the ability to dive to a maximum depth of 9,800 feet (3,000 m)and remain underwater without oxygen for up to two hours. They are able to do this by

means of a complex physiological mechanism that, for example, can decrease their heart rate,store and use air in the muscles, and prioritize the delivery of oxygen to certain vital organssuch as the heart and lungs. They are the largest whales with teeth, which are found only onthe lower mandible.

SPERM WHALEPhysetercatodon

11 elephants of 8 tons apiece

COMPOSITION

BRADYCARDIADuring a dive, the heartrate drops (a conditionknown as bradycardia),which lowers oxygenconsumption.

3

1

2

IS THE LENGTH OF TIME THEY CAN SPENDUNDERWATER WITHOUT BREATHING.

Adaptation in RespirationWhen they dive to great depths, sperm whales activatean entire physiological mechanism that makes maximum

use of their oxygen reserves. This produces what is called athoracic and pulmonary collapse, causing air to pass from thelungs to the trachea, reducing the absorption of the toxinnitrogen. They also rapidly transmit nitrogen from the blood tothe lungs at the end of the dive, thus reducing the circulation ofblood to the muscles. Sperm whales' muscles contain a largeamount of myoglobin, a protein that stores oxygen, allowing thewhales to stay underwater much longer.

DiveTrue diving champions, sperm whales can dive todepths of 9,800 feet (3,000 m), descending up to

10 feet (3 m) per second in search of squid. As ageneral rule, their dives last about 50 minutes, but theycan remain underwater up to two hours. Beforebeginning a deep dive, they lift their caudal fincompletely out of the water. They do not have a dorsalfin, but they do have a few triangular humps on theposterior part of their body.

Making Useof OxygenSperm whales can dive deeperand stay submerged longer thanany other mammal, becausethey have various ways of savingoxygen: an ability to store it intheir muscles, a metabolism thatcan function anaerobically, andthe inducement of bradycardiaduring a dive.

Spermaceti OrganSperm whales' ability to dive to great depths could be due in part totheir spermaceti organ, located in their heads. It consists of a largemass of waxy oil that helps them both float and take deep dives. Itsdensity changes with temperature and pressure change. It, like themelon of a dolphin, directs sound, focusing clicks, since its eyes are oflittle use when far from light.

TAILis large andhorizontal and isthe whale'smain means ofpropulsion.

RETIA MIRABILIAThe retia is a network ofblood vessels (mirabilia)that filter the bloodentering the brain.

MOUTHBecause of the placementof the nostrils, spermwhales can swim with theirmouth open and captureprey. They feed on squid.

ON THE SURFACEBlowhole remainsopen, allowing thewhales to breathe asmuch oxygen as theycan before diving.

WHEN THEY DIVEpowerful musclestightly close theopening of theblowhole, keepingwater from entering.

AMOUNT OF AIRREPLACED IN ONE

BREATH

85%AMOUNT OF AIR

REPLACED IN ONEBREATH

15%

Muscle

MandibularBone

TeethThey have 18 to 20conical teeth, weighing upto 2 pounds (1 kg) apiece,in each lower mandible.

BLOWHOLEUpon submerging, it fillswith water, which coolsthe spermaceti oil andmakes it denser.

HEARTThe heart rate slowsdown during thedive, limiting oxygenconsumption.

LUNGSabsorboxygen veryefficiently.

BLOODAn ample blood flow,rich in hemoglobin,transports elevatedlevels of oxygen to thebody and brain.

Nostril

REPRIORITIZING OXYGENSperm whales can allocateoxygen to certain vital organs,such as the lungs and heart,directing it away from thedigestive system.

SPIRACLEThe sperm whale breathesoxygen into its bodythrough spiracles locatedon the top of its head.

0 FEET (0 M)ON THE SURFACEThey inhale oxygenthrough the blowholelocated at the top ofthe head.

+ 3,300 FEET(1,000 M)90 MINUTESThey store 90 percentof their oxygen intheir muscles, so theycan be submerged fora long time.

0 FEET (0 M)ON THE SURFACEThey exhale all theair from their lungs;this is calledspouting, or blowing.

MAMMALS 6766 DIVERSITY

Spermaceti

Habitat

Status

Sexual Maturity

Deep waters

Vulnerable

18 years

Weight

Up to 60 feet (18 m)

90% Spermaceti Oil It is made up of esters andtriglycerides.

20 to 90 tons

By Comparison

Up to120minutes

11%

TIME IT TAKES TO ROTATE ANDLAND ON ITS FEET 1/2 SECOND LATER

Cats have a surprising ability toland upright. The secret lies intheir skeleton, which is more

flexible and has more bones than thatof any other mammal. Cats' reflexesallow them to twist using thephysical principle of the conservationof angular momentum. The principle,first formulated by Isaac Newton,states that all bodies in circularmovement tend to a constant amountof energy. Thus, the more the animalextends its legs to its axis ofrotation, the slower it rotates,redistributing the totalenergy of the system. If theanimal tucks in its legs, itrotates more rapidly.

AerialAcrobatics

68 DIVERSITY MAMMALS 69

ELONGATIONCAPACITY

Name

Family

Species

Adult Weight

Longevity

Dimensions

Domestic cat

Felidae

Felis catus

4 to 15 pounds (2-7 kg)

15 years

It extends itsfront legs at rightangles to the axis.

Front HalfThe extended legsreduce the speedof rotation of thispart. It rotates180°.

Cross section ofa semicircular

canal

BullaIt holds thecilia, whichareequilibriumreceptors.

During a rotation,endolymph movesthe cilia in thedirection oppositethe body's motion.

Cochlea

INNER EAR

The “Accelerator”The cat folds its front

legs in to its axis toincrease the speed ofrotation of this part.

It rotates 180°.

AXIS

FORCE OFGRAVITY

The “Brake”It extends its hindlegs perpendicular tothe axis and reducesthe speed of rotationof this part.

FrontHalf

Radius

Axis

StrongRotation

SlightRotation

BackHalf

AXIS

It draws its hindlegs in to the axisof the body.

Back HalfNow the foldedlegs increase thespeed of rotationof this part.

Extreme FlexibilityCats do not have a clavicle, andthe articulations of theirvertebrae are more flexiblethan those of most mammals.They can travel five times thelength of their body in one leap.

The tailstabilizes theweight of thebody during thedescent.

It extends thehind legs tothe height ofthe front legs.

At the momentof landing, thecat slightlyflexes its feet tocushion the blow.

To reducerotationopens arms toincrease theradius of rotation.

To increaserotationcloses arms toreduce the radiusof the rotation.

4 inches(10 cm)

12 inches(30 cm)

10 inches(25 cm)

STARTS UPSIDEDOWNThe cat begins to fall upsidedown and will turn 180ºupon its axis (in two stages),landing upright.

1

FIRST TWISTIn this maneuver, the catrotates the front half of itsbody 180º on its body's axis.The other half rotates onlyslightly as a result.

2

WITHINDEPENDENCELike a skater who extends orfolds the arms to control thespeed of rotation, the catmoves its hind legs—butindependently of each other.

LIKE A SKATER

3

SECOND TWISTThe cat lowers its hind legsand completes a full rotationon its axis. It again carriesout two more rotations, onetighter than the other:

4

FOUR FEET PLACEDUNDER THE BODYWith four feet positionedunder the body, the cat bendsits spine like a parachute andthen merely corrects itsposture for landing.

5

LANDINGIts front legs make the firstcontact with the ground.Then it lands on its hind legs,and, finally, it relaxes its tail.

QUICK AND PRECISE SHAKEDuring the rotation, endolymphcan splash into the semicircularcanals. To return the liquid to itsplace, the cat gives a quickshake of its head.

6

FrontHalf

StrongRotation

SlightRotation

BackHalf

AXIS

1/8 of a second

EquilibriumThe inner ear in the temporal boneis divided into the cochlea, the

vestibule, and three semicircular canals.Inside there is a system of cilia (sensereceptors) and a viscous substance(endolymph) that generates thesense of balance when the twocome in contact with each other.

Time of the FallA fall from a short distance usually causesmore harm than one from a considerable

height, because the cat adopts a defensiveposture only when it senses acceleration in thefall. Upon reaching terminal velocity, it canaccelerate no faster, and the cat relaxes,stretches out, and offers resistance to the fall.

RelaxationTerminalvelocity

Defensiveposture

Firsttwist

HA

RM

HEIGHT

Dam

Lodge

Dry Area

WaterLevel

UnderwaterEntrance

They have no bricks or cement, but beavers, semiaquatic rodents,skillfully manage to build lodges of great architecturalbeauty. They do not work alone, and it is usual for them

to act in family groups. Everyone collaborates in building thehome, which is generally located next to a river or lakesurrounded by forested areas and which can be enteredonly through aquatic tunnels. The task is difficult, andbeavers work their whole lives enlarging, repairing,and improving their dwelling.

Natural Builders

70 DIVERSITY MAMMALS 71

DamBeavers continually repair the dam and add materialsto it. Floating material carried along by the water isretained in the dam, along with the roots ofvegetation that grows upon it, strengthening theentire structure.

The LodgeThese are unique structures, of whichthere are several types, which vary byarea. They are made of interwoven sticks,branches, grasses, and moss, and theyhave a central chamber accessiblefrom underwater. This chamber hasits floor above the water line, hastwo entrances, and can measuremore than 7 feet (2 m) wideand 3 feet (1 m) high.

THE DAMhas two purposes—first, to raise thewater level; and second, to enlargethe flooded area around the den.Dams are built out of sticks and treetrunks.

AMERICANBEAVER Castor canadensis

Habitat

Family

Food

Temperate forests in theUnited States and Canada

Castoridae

Herbivorous

IS HOW LONG A BEAVER CAN STAYUNDERWATER WHEN THREATENED.

15 minutesENTRANCEHere is wherethey enter; it isa straight pathat an incline.

UNDERWATERTUNNELThey move secretlythrough underwatertunnels, generallyremaining underwater

for five minutes.

ROOFMade of trunks, branches,stones, and mud. In thisway they form a small lakewhere they build their hut.

EXITBeavers havewebbed feet thatthey use to diveand for otherquick movements.

BRANCHESThe material most usedin constructing thelodge. They are used tomake the ceiling and tokeep the inside dry.

ROCKSmaintain the structureof the dam, holding thetree trunks in place.

OFFSPRINGlive with their parentsand are independentafter three years.

CHANGESTheir introduction intonew environments maychange the ecological

balance so much thatthey become a pest.

DRY AREACovered withtree bark, grass,and little piecesof wood

Up to 28inches

(70 cm)

THE STRENGTH OF THEIR INCISORTEETH (USED FOR CHEWING) IN

COMPARISON WITH HUMANS

2 times

THEFOUNDATIONIn winter, they storefresh branches inthe pond to serve asa food reserve.

TECHNIQUESBeavers frequently work in groups to gnaw down a trunkand carry it away. One of them cuts the tree with itsteeth while the others stand guard. This work takesabout 15 minutes, and then the tree falls.

Their mandiblesand teeth arestrong, and theyuse their frontfeet as hands.

UNDERWATERENTRANCE

ENVIRONMENTAL IMPACTBeavers can have positive andnegative effects. They create wetlandsfor other species and prevent erosionin some cases. However, their dams

can also cause floods and createstagnant water, thus

destroying other habitats.

TEETHTheir powerful

incisors growthroughout their lives

but are kept at manageablelength by wear and tear from theconstant work of cutting down trees.

Incisors

EyeSocket

Weight66 pounds

(30 kg)12 inches (30 cm)


Nocturnal FlightB

ats are the only mammals that can fly. Scientists call them Chiroptera, a termderived from Greek words meaning “winged hands.” Their forelimbs have beentransformed into hands with very long fingers joined together by a membrane

(called the patagium) that forms the surface of the wing. These mammals' senses areso sensitive that they can move and hunt quickly and accurately in the dark.

THE SPEED SOME BATSMAY REACH DURING FLIGHT

60 miles per hour(97 km)

HUMERUS THUMBRADIUS

SECOND FINGER

FOURTHFINGER

PATAGIUM

1 The animal emits an acousticalvibration imperceptible to thehuman ear because of its highfrequency (about 18 kHz). Thesignal strikes the objectsaround it.

2HAND OR WINGThe first finger, orthumb, has nomembrane and isused as a claw.Powerful musclesmove the entire wing.

1

2

3

4

5

ELASTIC FIBERSThe texture of the wing issoft and flexible. It islined with blood vessels.UROPATAGIUM

HibernationThese bats spend the winter in a lethargicstate hanging by their feet, faces down, incaves and other dark places. Bats are warm-blooded animals while they are active andbecome similar to cold-blooded creatureswhen they are asleep. They enter into a stateof hibernation more rapidly and easily thanany other mammal, and they can survive incold temperatures for many months—eveninside refrigerators—without needing to feed.

Flexible WingsThe patagium is formed by themembranes between the digits. Insome species, the wings are alsoextended by an additional membrane(uropatagium), which joins the hindlimbs to the tail. Their wings are notonly used for flying (pushing the air asif they were oars in water) but alsohelp to maintain a constant bodytemperature and to trap insects, uponwhich bats feed.

When the signals bounce back,the bat perceives theirintensity and phasedifference—the faster andmore intense the return signal,the nearer the object or prey.

Expert PilotsMoved by their chest and back muscles,bats' wings push downward and backward,generating both thrust and lift. Then thewings spread sideways and upward. Finallythey move forward until the tips almostrub the bat's head. Many of these flyingmammals can drift through the air, glidingwithout flapping and maneuvering byfolding their wings.

Their RadarMost of the time bats fly at night innear-total darkness. Instead of light,they use a natural system similar tosonar or radar to guide themselves.This system makes use of acousticalsignals the bats themselves emit whileflying. This system allows them torecognize the location of any object infront of them or of prey, along with itsdirection, size, or speed. It is as if theywere seeing without light.

THIRDFINGER

FRUIT BAT(FRANQUET'SEPAULETTED BAT)Epomops franqueti

Habitat

Family

Length of wingspan

Forests of Ghana and Congo

Pteropodae

14 inches (36 cm)


Playing Hide and SeekJ

ust like other species of the animal kingdom, some mammals that live in the wild rely ontheir bodies' colorations or appearances to disguise their presence. Some mammals imitateobjects in their environment, and others take on the appearances of other animals. Zebras'

stripes, for example, give these animals a very showy appearance—but when moving in theirnatural environment, zebras are camouflaged. Some differentiate between mimicry and crypsis,which is the natural ability to go unnoticed without requiring any associated behavior. In othercases, however, the forms and colors of camouflage would be useless if they were notaccompanied by some kind of imitative behavior. An animal cannot improve its camouflage, butit can improve its mimicry.

In MotionThe patterns of tigers' coats areuseful in concealing their contours,especially when they are movingamong the shrubs and bushes of theplains where they hunt. Elk horns,however, can be concealed amongthe vegetation they resemble only solong as they keep still.

The body's contours are blurredwhen some spots of color are

much darker or lighter than therest of the coat.

DisruptiveColoration

Evolutionary Adaptations

Part of the HideawayChipmunks (Tamias species) live in coniferous or deciduousforests, where they feed on nuts, insects, eggs, seeds, andother plant foods. The colors of their coats are essential,because—although they are very skillful at moving in theupper branches—their small size and short legs make themvery vulnerable when they are on the ground.

PROTECTIVESURROUNDINGSMany have a coat thatchanges color dependingon the surroundings.

FURShades and differencesof color in the coat aresimilar to those of treetrunks and dry leaves.

Different PatternsThe pattern of a zebra's coat does notexactly copy the shapes and colors ofobjects in the wild environmentsurrounding it. Nevertheless, it does havepatterns that allow it, with the help ofcertain behaviors and motions, to disguiseits appearance in more than one setting ofthe zebra's natural habitat. In the case ofArctic animals, it is the uniform whitecolor of the winter environment thatdetermines the way in which speciescamouflage themselves.

SPOTSallow giraffes toconceal themselvesamong the highleaves they reachwith their long neck.

PATTERNSare irregular formsbetween stripes thatallow tigers to lie inambush for their preyamong thickets.

Mimicry is defined as the ability of some living beings toimitate the appearance of another living being or an

inanimate object in the environment. Protective mimicry is thecamouflage used by animals incapable of defending themselvesin any other way. Aggressive mimicry, on the other hand,allows organisms to surprise and attack their prey. This occurs,for example, with wild felines (mountain lions, ocelots, lynxes),which take advantage of their skin colors and the patterns oftheir fur to go unnoticed in their ecosystems. Zebras travel inherds as a natural form of self-protection. The disruptive

coloration of their coats makes it difficult for predators thatrely on speed and sharp senses to distinguish one individualprey from another. Kicking and biting, zebras collectivelydefend themselves from attacks by feline predators. Thesefelines also make use of camouflage strategies to make theirattacks one on one. Many animals make use of elements fromtheir surroundings or even of other living organisms tocamouflage themselves. Sloths are another example; being theslowest of the mammals, they have no choice but to coverthemselves in algae to avoid notice.

STRIPESThe coloration oftheir coat changeswith the incidenceand intensity ofsunlight.

HAVING FUNPlay for dolphins,

as with othermammals, fulfills

an essential role inthe formation of

social strata.

MMAMMALS 7776 DIVERSITY

The Language of WaterT

he ways in which cetaceans communicate with others of theirkind are among the most sophisticated in the animal kingdom.Dolphins, for example, click with their mandibles when in trouble

and whistle repeatedly when afraid or excited. During courtship andmating, they touch and caress. They also communicate through visualsignals—such as leaping—to show that food is close by. They have a widevariety of ways to transmit important information.

Bottlenose dolphin

Delphinidae

Tursiops truncatus

330 to 1,400 pounds(150 to 650 kg)

30 to 40 years

Common Name

Family

Species

Adult Weight

Longevity

3 pounds(1.4 kg)HUMAN BRAIN

SOUND WAVES TRAVEL4.5 TIMES FASTER INWATER THAN IN AIR.

(1.5 km/s)1 mile per

second

4 pounds(1.7 kg)DOLPHIN BRAIN

EmissionSounds are generated by airpassing through the respiratorychambers. But it is in the melonthat resonance is generated andamplified. Greater frequenciesand intensities are achieved inthis way.

Echolocation

1

MessageLow-frequency signals are usedfor communication with otherdolphins, and high-frequencysignals are used as sonar.

2

Reception andInterpretationThe middle ear sends the message tothe brain. Dolphins hear frequenciesfrom 100 Hz up to 150 kHz (thehuman ear can hear only up to 15kHz). Low-frequency signals(whistles, snores, grunts, clinking)are key in the social life of dolphins,cetaceans that cannot live alone.

3

DORSAL FINallows dolphinsto maintaintheir equilibriumin the water.

MORE NEURONSA dolphin's brain,which processes thesignals, has at leastdouble theconvolutions of thoseof humans, as well asnearly 50 percentmore neurons.

MELONis an organ filled with low-density lipids that concentrateand direct the pulses emitted,sending waves forward. Theshape of the melon can be variedto better focus the sounds.

HOW THESOUND ISPRODUCED

MANDIBLEThe lower mandible playsa very important role inthe transmission ofsounds to the inner ear.

MIDDLEEAR

CAUDAL FIN has a horizontalaxis (unlike thatof fish), whichserves to propeldolphins forward.

PECTORALFIN

NASALAIR SAC

SPIRACLE LIP

LARYNX

INHALATIONThe spiracle opens sooxygen can enter.

SIGNALWITH ECHO

1

The dolphin emits aseries of clicking soundsfrom the nasal cavity.

A The melon concentratesthe clicks and projectsthem forward.

B These waves bounceoff objects theyencounter in their way.

C

Part of the signalbounces back andreturns to the dolphinin the form of an echo.

DThe intensity, pitch, andreturn time of the echoindicate the size, position,and direction of the obstacle.

EEXHALATIONAir resonates inthe nasal sacs andis emitted underpressure throughthe spiracle.

Click Click

0 s 6 s 12 s 18 s

Echo Echo

3

The nasal airsacs begin toinflate.

2

The nasalair sacsdeflate

They can go 12minutes withouttaking in oxygen.

Sound

Spiracle

Brain

Air inthe lungs

Air tothe lungs

They reach 22 mph(35 km/h)

7 to 13 feet (2-4 m)

Melon4


Lively Tunnels

HINDFOOT

Normal FootprintDanger Print

Rabbits thatreceive thewarning willremain in place,motionless.

ENTRANCETO THEWARREN6 inches(15 cm)

MOUNDS

FOODDEPOSIT

NEST

RABBIT FOOTPRINTSTheir footprints areunmistakable, the result oftheir peculiar way ofwalking and jumping.

1 Front FeetWhen it jumps, it first lands on itsfront feet, which are bunchedtogether.

2 Hind FeetThen it lets its hindfeet land in front ofits front feet.

3 New HopIt begins the cycleagain by pushing offwith the hind feet.

Both feet leave almosta single footprint,small and not verydistinct.

SONIC ALERTWhen they thump,rabbits produce a soundthat all the rabbits in thecolony hear. If a rabbit istrapped, it will emit asharp squeal that can beheard throughout thearea.

DIETThey feed on herbaceous andgrassy plants, roots, and bulbs.Some of their excrement is soft,covered with mucus, and is re-ingested, the equivalent ofbovine rumination.

PROTECTED INTERIORInterior tunnels are linedwith vegetation andrabbit fur to keep themfrom deteriorating and toprotect them frommoisture.

5 to 8 inches (12-20 cm)FOOD CELLARS

3 to 10 feet (1 to 3 m)LIVING AREAS

Secondary corridorsare often smaller and not interconnected.The offspring of the younger females livethere.Warren

This is the main part of the burrow,where the adult rabbits live. It ismade up of a complex network ofinterconnected corridors and chambers.

When the mother leavesher offspring she sealsthe entrance with dirt toprotect them fromdanger.

The secondary corridorhas only one exit, whichis not connected to thewarren or other areas.

The young rabbit willgrow in safety thereuntil it is capable offending for itself.

SECONDARYENTRANCE

Walking Rabbit Jumping Rabbit

RABBIT FOOTPRINT PATTERNSThey always follow this Y pattern.

This gives rabbitfootprints theirpeculiar Y-shapedappearance.

FrontFeet Hind

Feet

IS THE FARTHEST ARABBIT WILL WILLINGLYGO FROM ITS BURROW.

200 feet(60 m)

IS HOW LONG A BURROWTUNNEL CAN BE.

130 feet(40 m)

DANGER SIGNALIn the presence ofstrangers or in othercases of danger, rabbitsthump the groundwith the back part oftheir hind feet,warning theothers not toleave theburrow.

PREFERRED PLACESThe area around the burrowneeds two things before therabbits will feelcomfortable—grass andcover. Generally rabbitsbuild warrens in meadowsnear thickets or rocks.

Rabbits are gregarious animals that live in colonies in a series of burrows called warrens.The burrows are dug underground and are inhabited by females of high social rank.Rabbits are principally nocturnal and spend most of the day hidden in the burrow, leaving

to eat when night falls.

Relationship with People

The history of cats goes back 12million years to the time whenfelines began to populate theEarth. However, theirdomestication began 4,000

years ago. The Egyptians decided toincorporate them into their home life,thus keeping rats away. Then thePhoenicians took them to Italy and therest of Europe. One of the subjects

discussed in this chapter has to do withthe things that threaten the existence ofmany animal species, including the lossof natural habitats, poaching, pollution,and illegal pet trafficking. Within the

next 30 years, almost one fourth of theEarth's mammals could disappear.

MYTHS AND LEGENDS 82-83

EACH IN ITS PLACE 84-85

RAISING HOGS 86-87

MILK PRODUCTION 88-89

THE HUMAN THREAT 90-91

LIKABLE AND PLAYFULCats are excellent companionanimals and are known fortheir great independence andcleanliness.

MMAMMALS 8382 RELATIONSHIP WITH PEOPLE

UNICORNThis stone sealdepicting a unicornis found in theNational Museum ofPakistan in Karachiand dates from theyear 2300 BC.

MINOTAURIn Greek mythology, thiswas a creature bornwith the body of a manand the head of a bullthat ate human flesh. Itwas born on the islandof Crete of a forcedsexual relationshipbetween Pasiphae, wifeof King Minos, and awhite bull that Poseidongave the king to use asa sacrifice.

LION The Manjusri Buddha,seated on themythical lion who isthe guardian ofBuddhist doctrine

PEGASUSWinged horse, sonof Medusa, whoflew to Olympusand was receivedby Zeus.Thereafter, hetransportedthunderbolts forthe king of thegods, who placed

his figure in thenight sky.

Myths and Legends

WestIn Western culture, theGreeks and Romans havebeen the great producers ofmyths and legends relatinganimals to humans. Humanbodies with the heads of bullsor the limbs of horses aresome of many examples.

TROJAN HORSEUnable to capture the city of Troy during asiege that lasted 10 years, the Greeks builta hollow wooden horse, concealed warriorsinside it, and left it on the beach. TheTrojans, thinking it a gift from Poseidon,brought it into the city. At night, thewarriors left their hiding place and openedthe city's gates to the remainder of theGreek army, burning and seizing the city.

ROMULUS AND REMUSThese two brothers wereabandoned on the shores of theTiber, but they were found by afemale wolf, Luperca, whosuckled and raised them. Later, asadults, they returned to the placewhere they had been abandonedand there founded Rome.

Human history has always been intimately linked with the variousmammals—after all, people are mammals, too! Numerous myths andlegends have arisen from this relationship, such as that of the wolf

goddess Luperca, who saved Romulus and Remus from death—or the storyof the birth of the Minotaur, in which a queen was caused to fall hopelesslyin love with a bull and give birth to a monster with a bull's head and man'sbody. The origin of each myth springs from a particular tradition and meanssomething different in each culture.

CERBERUSThis was the monstrous,three-headed hound ofHades, or hellhound,which guarded thekingdom of the dead,preventing the deadfrom leaving and theliving from entering.

EastIn Eastern culture, animals, especially mammals,have played a leading role in myths and legends.Sometimes one animal has various meanings invarious cultures. To Egyptians, cats representharmony and happiness, but the Buddhist worlddisapproves of cats because they, along withsnakes, were the only ones who did not cry atBuddha's death.

THEIR ORIGIN STEMS FROM THEOBSERVATION OF NATURE.

Myths

CATBastet, the Egyptiangoddess whowatched over thehome. She symbolizesthe joy of living andwas represented as awoman with a cat'shead, because hersacred animal wasthe cat.

84 RELATIONSHIP WITH PEOPLE

Each in Its PlaceN

ature takes care of maintaining its equilibrium, providing each animal its own rolewithin the food chain. When one of the roles is removed, equilibrium in the regionis lost. In Australia, dingoes were a big problem for sheep farmers, who built a

great fence to protect their flocks. This barrier left the wild dogs without prey and otherspecies able to move about more freely in search of food. Dingoes are classified as pestsboth for farm animals as well as for rabies control.

MMAMMALS 85

The Great Fencewas designed to keep dingoes out of the southeasternpart of Australia, protecting flocks of sheep. It ran for

thousands of miles and was largely successful in itsobjective. The number of dingoes in the area declined,and, although the loss of sheep to predators wasreduced, this decline led to an ecological imbalanceby increasing the competition for pasturelandamong rabbits and kangaroos.

The Introduction of the DingoIt is thought that dingoes were domesticated animalsof the Australian Aborigines who lived in the region.

These mammals originated in Asia and were brought toAustralia by humans. They are medium-sized wild dogs withthick tails and are notable for having a very distinctive howlinstead of a bark. When European pioneers arrived inAustralia, dingoes were accepted, but this rapidly changedwhen sheep became an important part of the economy.Dingoes were soon trapped, hunted, and poisoned. PERIMETER

Its shape changes accordingto its upkeep. The Australiangovernment subsidizes theundertaking, but sheepfarmers are the ones whomaintain it.

CHAINBecause of the building of thebarrier, herbivorous animalshave more space to graze, safefrom the presence of dingoes.

CURRENT COURSE

DINGOThe leading predatorsof sheep, dingoes wereisolated from the area.

SHEEPTheir populationincreased with theabsence of the dingo.

PASTURELANDSbecame scarce, makingit difficult for herbivoressuch as kangaroos andsheep to find food.

KANGAROOThey found greaterfreedom to move aboutin search of food.

THE LENGTH OF THE GREAT FENCE.

3,300 miles(5,320 km)

Wool IndustryAustralia is second in the world in woolproduction. It has 110 million sheep within itsborders, constituting 10 percent of worldwool production. In 1989, when part of thefamous fence collapsed, about 20,000 sheepwere lost to dingoes.

ORIGINAL COURSE

AREA FREE OF DINGOES

DINGOCanis dingo

SYDNEY

MELBOURNE

AUSTRALIA

MAMMALS 8786 RELATIONSHIP WITH PEOPLE

Hog farming is one of the oldest forms of livestock production.In fact, the biggest hog producers, the Chinese, began raisinghogs more than 7,000 years ago. But raising hogs has become

more and more complex. Today, to produce largelitters and high-quality pork as quickly aspossible, pigs are crossbred.

Raising Hogs

Pork ProductionThe use of genetics in a pig nursery is complexand important because breeds of pigs are veryspecific. Here are the most notable differencesamong various breeds.

The CutsThe animal can be sold as adressed carcass or in piecesand taken to supermarkets.Its meat will be used tomake sausages or left asentire cuts.

100%Meat breed

100%Maternal breed

50% Meat breed 50% Maternal breed

100% Maternal breed

100% Meat breed

75% Maternal breed25% Meat breed

FAT62.5% Meat breed

37.5% Maternal breed

MEAT BREEDShave high weight gain, agood build, and a highfood-conversion efficiency.

MATERNAL BREEDSThey are very prolific,have good maternal skills,and produce a largenumber of piglets.

Landrace

Yorkshire

Hampshire

Duroc

Pietrain

CROSS TO OBTAIN A HOG FOR CONSUMPTION

210 to 220 pounds(95-100 kg)

IS THE WEIGHT OF A PIGWHEN IT IS READY TO BE

SLAUGHTERED.

FOOT

BACON LOIN AND CHOP TAIL

HAMRIBSSHOULDERBLADE

FEEDIt is common to use growth hormones toincrease food conversion efficiency and thelean-meat content in the dressed carcass.

GestationOnce impregnated, they aretaken to the gestation room,where they will remain for114 days, or until two orthree days before givingbirth. To prevent problemswhen they give birth, theyreceive a restricted diet sothey do not get fat.

2

MaternityThey give birth to litters of 10to 12 animals and can produceover 3 gallons (12 l) of milkdaily. Feeding is unrestricted sothat the sow is not leftweakened after weaning.

3

RaisingThe recently weanedpiglets enter nurserycrates kept at anambient temperatureaveraging 77º F (25° C).They are given an initialration and remain herefrom day 21 to day 45.

4

SlaughterOnce they weigh between 210 and220 pounds (95-100 kg), the pigs aretransferred to the slaughterhouse.There they are given an electric shock

that renders them unconsciousbefore they are killed. They are

scalded in hot water to detachtheir hair, are bled, and arethen eviscerated, and thecarcass is prepared for finalbutchering.

6

FatteningThis period lastsapproximately 90days. When the pigsare 150 days old, theyweigh about 210pounds (95 kg).

5

MountingsOlder sows coming fromthe breeding room andyoung replacement giltsenter pens where they willbe naturally or artificiallyimpregnated.

1

1.MILKING AND MILKPRESERVATIONAT THE FARMMechanicallymilked milk comesout at about 99º F(37° C). It isimmediately cooledto less than 39º F(4° C) to preventspoilage.

2. COLLECTIONThe milk is pHcontrolled to preventcontamination, and it isremoved from the farmin large tanker trucks.

MECHANICAL MILKING

MAIN DAIRY BREEDS

MILK PRODUCTS

3. ANALYSIS Once in the plant,the phosphatasetest is done: if it ispositive, the milkis raw and has notbeen heated.

4. RECEPTION ANDSTERILIZATIONMilk is heated tobetween 135º and154º F (57-68º C) fortransportation orprocessing, eliminatinggerms while retainingthe properties of rawmilk.

6. HOMOGENIZATIONensures that theproduct is uniform inconsistency. It consistsof the dispersion ofthe milk's fat globulesby means of frictioncreated under veryhigh pressure.

7. PASTEURIZATIONensures that potentially harmfulmicroorganisms are eliminated from the milkbut does not change the milk's properties. Itbegins with rapid heating from a source ofindirect heat, followed by circulation througha cold pipe for quick cooling.

8. BOTTLING Peroxide solutions are used tosterilize the containers, andreagent strips are used to ensurethat no peroxide residue remains.

Louis Pasteur1822-95French chemist. Amongother things, hediscovered that thedecomposition of foodis caused by bacteria,and he invented the firstways to keep substancesfrom spoiling.

High-pressure streams of milkcollide with a piston, reducingthe size of the fat particles.

MilkPipeline

Piston SmallerParticles

MilkEntrance

HEATING COOLING

Cold Water 39º F(4° C)

Hot Water 162º F(72° C)

5. SEPARATIONMilk and cream are separatedcentrifugally. Next, milk products areobtained. For butter and whippedcream, the cream is heated to 260ºF (127º C) to reduce its watercontent. For yogurt and cheese,proportions of milk and cream aremixed together and appropriatebacteria cultures are added.

Until the 18th century, milk was a little-consumed product becauseit could be kept for only a few hours without spoiling. It wasnot easy to offer a supply of fresh milk to meet urban needs.

Only in the 20th century, after the discovery of pasteurization,allowing milk to be preserved, did milk become a universallypopular drink produced industrially.

Milk Production

COOLINGROOM

CHEESE YOGURT BUTTER

ICE CREAM CREAM DULCE DELECHE

Milk Status

Raw

Sterilized

Skimmed

Cream

Homogenized

Pasteurized

REFRIGERATEDTANKER

SEPARATOR

HOMOGENIZER

WATER HEATER

HEAT EXCHANGE

PACKER

Pasteurized,Homogenized

Milk Tank

CreamTanks

Skim MilkTank

KEY

HOLSTEIN-FRIESIANFrom Germany. Formore than 300 years,these black andwhite cows haveadapted todifferent climates.

JERSEYThe mostwidespread Englishbreed. Its angularframe makes itideal for milkproduction.

AYRSHIREFrom southwesternScotland. The oldestof the milk breeds(17th century). Theyare notable for theirred spots.

SEALING MACHINEis maintained in asepticconditions. Processing andexpiration dates arestamped on the container.

Internal layers of theseparator where creamparticles are decantedas grainy sediment

FILLING MACHINEExcept in the case of long-life milk, the machine fillscontainers that will allowthe milk to be preserved fortwo weeks underadequately cold conditions.

CONTROL ROOMThe various steps of theprocesses carried out in

modern plants are automatedand controlled by computers

from a central office.

ANNUAL PRODUCTIONOF FRESH MILK

140billiongallons


STEEL TEAT CUP

Vacuum Pump

The difference in pressure extractsthe milk.

Teat

Milk

MilkHose

Milking Stall

Pulsator Line

TEAT CUPS

MilkHose

MAMMALS 89

135

8075 72

39 38 35 32 29

0

20

40

60

80

100

120

140

Indonesia India Brazil China Cameroon Tanzania Russian Federation

Thailand U.S.

Over the next 30 years, almost a quarter of the mammals could disappear from theface of the Earth, according to the United Nations. The eminent collapse reflectsan unequivocally human stamp: hunting, deforestation, pollution, urbanization,

and massive tourism. Experts calculate that more than 1,000 mammals areendangered or vulnerable, and 20 areas of theplanet have been identified whereprobabilities of extinction mayexist in the near future.


Giant PandaAiluropoda melanoleuca

One thousand bears survive in reservescreated in China. The disappearance of theirhabitat—caused by the felling of bamboo,their natural food—as well as the extremedifficulty they have reproducing in captivity(because of their timidity) are the principalreasons for the decrease in this species.

HippopotamusThese are among themost vulnerable animals.From 1994 until today,their population in Zambiaand the DemocraticRepublic of Congo hasfallen by 95 percent.

MAMMALS OF THE WORLD

583Vulnerable

162Critical

4,319Speciesthat are notthreatened orfor which thereis no information

1,097Threatenedspecies

348Endangered

Affected RegionsThere are 781 threatened species in theregion of sub-Saharan Africa, and in South

Asia there are 726. South America containsanother 346 endangered species, and Central andNorth America have 63 endangered mammals.

MAMMALS AT CRITICAL RISK

UP TO 10 SPECIES ALREADY EXTINCT

MORE THAN 10 SPECIES ALREADY EXTINCT

KEY

Southern Right WhaleEubalaena australis

inhabits a broad band extending from20º S to 60º S. They are sought fortheir high quantities of body oils, andthey are relatively easy to capture. It isestimated that only 3,000 exist today.

Extinct

In the Wild

Critically Endangered

Endangered

Vulnerable

Has not been seen for 30 years

Survives in captivity

500 individuals

1,000 to 2,000 individuals

Up to 5,000 individuals

IS THE NUMBER OFEXISTING MAMMAL

SPECIES.

5,416

Dama GazelleThe degradation of theirhabitat, as well asunregulated hunting, threatentheir existence. In the Sahara,their population fell by 80percent in only 10 years.

OrangutansPongo pygmaeuspygmaeus (Borneo)Pongo pygmaeus abelii (Sumatra)

Found in the tropical forests of the islandsof Borneo and Sumatra. Indiscriminatelogging, mining, and forest fires isolatethem from nature, as does the illegalcapture of their young, which are then soldas pets.

Sea OtterEnhydra lutris

Once a continuous line of sea ottercolonies stretched from the KurilIslands of Japan to California. Todayonly a few colonies remain in Alaskaand in the lower United States.

Families of PrimatesTwenty-five percent of the 625species and subspecies of

primates are in danger of extinction.The principal causes are deforestation,indiscriminate commercial hunting,and illegal trafficking of animals. Inthe countries of Gabon and Congo,where the majority of chimpanzeesand gorillas live, the populationdecreased by more than half between1983 and 2000.

The Human Threat

More than one out of every five speciesof mammals is endangered: 20 to 25percent of existing mammalian species.

DEGREE OF THREAT

Hainan Black-crested GibbonNomascus nasutus sp. hainanusThese primates are among the fivespecies in most danger of extinction.Only 30 black-crested gibbons areknown to exist.

ChinchillaChinchilla brevicaudataThey live in the AndesMountains of Chile and Peru.Indiscriminate hunting hasdecreased the species, and itis endangered.

ENDANGERED BY COUNTRYIndonesia has the most endangeredspecies, followed by the “country oftigers,” India. In Latin America,Brazil is first and Mexico second.

FAMILY HYLOBATIDAE

Gibbon Siamang

Gorilla Chimpanzee

Titi Orangutan

CetaceansGray whales, which inhabit the waters of the northern Pacific and the

Arctic, are protected. In 1970, sperm whaleswere declared endangered, and today huntingthem is prohibited. The Indian Ocean has beendeclared a whale sanctuary in an effort tocurb hunting, but 7 out of 13 great whalesremain in danger of extinction, as do a similarnumber of dolphin species.

Blue Whale

Fin WhaleGray Whale

Sperm Whale

Dolphin

The World ConservationUnion was created in1948, bringing together81 nations and nearly10,000 specialists.

Atlantic

Ocean

A S I A

O C E A N I A

A F R I C A

E U R O P E

Indian

Ocean

Pacific Ocean

Pacific Ocean

N O R T HA M E R I C A

C E N T R A LA M E R I C A

S O U T HA M E R I C A

Harbor Porpoise

FAMILY PONGIDAE

92 GLOSSARY MAMMALS 93

Glossary

AbomasumLast of the four chambers into whichruminants' stomachs are divided. It secretesstrong acids and many digestive enzymes.

AgoutiRodent mammal of South America measuringapproximately 20 inches (50 cm) and havinglarge feet, a short tail, and small ears.

AlbuminProtein found in abundance in blood plasma. Itis the principal protein in the blood and issynthesized in the liver. It is also found in eggwhites and in milk.

Alveolar GlandFunctional production unit in which a singlelayer of milk-secreting cells is sphericallygrouped, having a central depression called alumen.

BiomeLand or water ecosystem with a certain typeof predominant vegetation and fauna.

BipedAdjective applied to species of mammals thatwalk on two feet.

BradychardiaLowering of cardiac frequency to below 60beats per minute in humans.

BunnyThis is a young or growing rabbit.

CarnassialA typical sharp premolar present incarnivorous animals that helps them cut andtear the flesh of their prey more efficiently.

CarpusBone structure of the wrist, located between

the bones of the forearm and the metacarpus.It is made up of two rows of bones.

ChiridiumA muscular limb in tetrapods. It is a long bonewhose anterior end articulates with thescapular belt. The posterior end articulateswith two bones that connect to the joints ofthe digits.

CloacaThe open chamber into which the ducts of theurinary and reproductive systems empty.

CochleaA structure shaped like a coiled spiral tube,located in the inner ear of mammals.

ConchaThe arched, osseous plate found in each of thenostrils.

ConesThe photoreceptor cells in the retina ofvertebrates. They are essential fordistinguishing colors.

ConvolutionEach of the slight elevations or folds thatmark the surface of the cerebral cortex.

CortexThe outer tissue of some organs, such as thebrain and kidney.

Counter ShadingThe characteristic of protective coloration inthe hair or fur of certain mammals that aredorsally dark and ventrally lighter.

CynodontsAnimals that, beginning in the Triassic Period,start to exhibit characteristics essential to thelives of warm-blooded animals, making them

EndemismThe characteristic of a specific area whereanimal or plant species are natively andexclusively found.

EndothermyThe ability to regulate metabolism to maintaina constant body temperature independent ofthe ambient temperature.

EpidermisThe outer layer of the skin formed by epithelialtissue covering the bodies of animals.

ErythrocyteA spherical blood cell containing hemoglobin,which gives blood its characteristic red colorand transports oxygen throughout the body. Itis also known as a red blood cell.

EstrusThe period of heat, or greatest sexualreceptivity, of the female.

EthologyThe science that studies animal behavior.

EumelaninOne of the types of melanin, a darkish browncolor pigment.

EutheriaOne of the infraclasses into which the Theriasubclass is divided, applied to animals thatcomplete their development in the placenta.

Fetlock JointIn quadrupeds, the limb joint between thecannon bone and the pastern.

FollicleA small organ in the form of a sac located inthe skin or mucous membranes.

GestationThe state of an embryo inside a woman orfemale mammal from conception until birth.

GlomerulusA ball-shaped structure such as the renalglomeruli, which are formed by a tiny ball ofcapillaries and which filter the blood.

HabitatThe set of geophysical conditions in which anindividual species or a community of animals orplants lives.

HibernationThe physiological state that occurs in certainmammals as an adaptation to extreme winterconditions, exhibited as a drop in bodytemperature and a general decrease inmetabolic function.

HockThe joint located between the metatarsal andtarsal bones of the hind limbs of a quadruped.

HomeostasisThe set of self-regulating phenomena thatkeeps the composition and properties of anorganism's internal environment constant.

HomeothermyThermoregulation characteristic of animalsthat maintain a constant internal temperature,regardless of external conditions. Bodytemperature is usually higher than that of theimmediate environment.

HoofHorny, or cornified, covering that completelyenvelops the distal extremity of horses' feet.

IrisThe membranous disk of the eye between thecornea and the lens that can take on different

coloration. In its center is the pupil, which isdilated and contracted by the muscle fibers ofthe iris.

KeratinA protein rich in sulfur, it constitutes the chiefelement of the outermost layers of mammals'epidermises, including hair, horns, nails, andhooves. It is the source of their strength andhardness.

LactationThe period in mammals' lives when they feedsolely on maternal milk.

LitterAll the offspring of a mammal born at onetime.

MammaliaformesSee Cynodonts.

MammalogyThe science of studying mammals.

Mammary GlandOne of a pair of external secretion organscharacteristic of mammals. It provides milkto the young during lactation.

MarsupialMammals whose females give birth to unviableinfants, which are then incubated in the ventralpouch, where the mammary glands arelocated. They belong to the Metatheriainfraclass.

MarsupiumThe pouch, characteristic of female marsupials,that functions as an incubation chamber. It isformed by a fold of the skin and is attached tothe outer ventral wall. The mammary glandsare found there, and the offspring completethe gestation period there.

relatives of true mammals. They include theMammaliaformes.

DendriteThe branched elongation of a nerve cell bymeans of which it receives external stimuli.

DermisThe inner layer of the skin, located under theepidermis.

DichromaticRefers to mammals, such as mice and dogs,that have two types of cones in their retinasand can only distinguish certain colors.

DigitigradeRefers to animals that use only their digits towalk. One example is dogs.

DimorphismTwo anatomical forms in the same species.Sexual dimorphism is common between malesand females of the same species.

DomesticationThe process by which an animal populationadapts to human beings and captivity througha series of genetic changes that occur overtime, as well as by means of adaptationprocesses brought about and repeated overgenerations.

EcholocationThe ability to orient and maneuver by emittingsounds and interpreting their echoes.

EcosystemA dynamic system formed by a group ofinterrelated living beings and their environment.

EmbryoA living being in the first stages of itsdevelopment, from fertilization until it acquiresthe characteristic appearance of its species.

94 GLOSSARY MAMMALS 95

MelaninThe black or blackish-brown pigment found inthe protoplasm of certain cells. It givescoloration to the skin, hair, choroidmembranes, and so on.

MetacarpusThe set of elongated bones that make up theskeleton of the anterior limbs of certainanimals and of the human hand. They arearticulated to the bones of the carpus, or wrist,and the phalanges.

MetatheriaThe infraclass of the Theria subclass, itcontains species that reproduce partially insidethe mother and then continue theirdevelopment inside the marsupium.

MoltThe process by which certain animals shedtheir skin or feathers; or, when plants shedtheir foliage.

MonotremataThe only order of the Prototheria subclass, itconsists of egg-laying mammals with amarsupium in which they incubate their eggs.The mammary glands are tubular and similarto sweat glands. They are distributed in fourfamilies, half of which are now extinct.

MultituberculateA group of mammals that lived predominantlyduring the Mesozoic Era and that becameextinct during the early part of the CenozoicEra.

NeuronA differentiated cell of the nervous systemcapable of transmitting nerve impulses amongother neurons. It is composed of a receptorsite, dendrites, and a transmission (or release)site—the axon, or neurite.

NostrilEach of the openings of the nasal cavities thatlead to the outside of the body.

OmasumA ruminant's third stomach chamber. It is asmall organ with a high absorptive capacity. Itpermits the recycling of water and mineralssuch as sodium and phosphorus, which mayreturn to the rumen through the saliva.

OviductThe duct through which the ova leave theovary to be fertilized.

OviparousRefers to animals that lay eggs outside themother's body, where they complete theirdevelopment before hatching.

PapillaEach of the small, conical elevations on skin ormucous membranes, especially those on thetongue, by means of which the sense of tastefunctions.

Pasteur, Louis(1822-95) The French chemist who developedpasteurization and other scientific advances.

PasteurizationThe process that ensures the destruction ofpathogenic bacteria and the reduction ofbenign flora in milk without significantlyaffecting its physicochemical properties.

PatagiumThe very fine membrane that joins the fingersand anterior limbs with the body, feet, and tailof bats.

PheomelaninOne of the types of melanin, a yellowish-redpigment.

QuadrupedRefers to a four-legged animal.

Rabbit WarrenA burrow that rabbits make to protectthemselves and their offspring.

ReticulumThe second chamber of a ruminant's stomach.It is a crossroad where the particles that enterand leave the rumen are separated. Only smallparticles of less than a 12th of an inch (2 mm)or dense ones greater than 1 ounce per inch(1.2 g per mm) can go on to the third chamber.

RetinaThe inner membrane of the eyes of mammalsand other animals, where light sensations aretransformed into nerve impulses.

RodAlong with cones, rods form the photoreceptorcells of the retina of vertebrates. They areresponsible for peripheral and night vision,though they perceive colors poorly.

RumenThe first chamber of a ruminant's stomach. Itis a large fermentation vessel that can hold upto 220-265 pounds (100-120 kg) of matter inthe process of being digested. Fiber particlesremain there between 20 and 48 hours.

RuminateThe process of chewing food a second time,returning food to the mouth that was alreadyin the chamber that certain animals(ruminants) have.

ScapulaTriangular bone, also called the shoulder blade.With the clavicle, it forms the scapular belt.

ScavengerAnimals that eat organic forms of life thathave died. They help maintain the equilibriumof the ecosystem by feeding upon deadanimals, breaking them down.

SpermacetiA waxy substance contained in the organ thatbears the same name, located in the head ofthe sperm whale. It is believed that it aidsdeep dives, although some specialists believethat it may assist echolocation.

Spinal CordAn extension of the central nervous system.Often protected by vertebrae, this soft, fattymaterial is the major nerve pathway thatcarries information to and from the brain andmuscles.

SynapsidsThese are also known as therapsids and aredescribed as mammal-like reptiles. They are aclass of amniotes that were characterized by asingle opening in the cranium (fenestra) behindeach eye in the temple. They lived 320 millionyears ago, during the late CarboniferousPeriod. It is believed that modern mammalsevolved from them.

Tapetum LucidumA layer of cells located behind the retina ofsome vertebrates that reflects light towardthe retina, increasing the intensity of the lightit receives. It heightens the perception of lightin near-darkness.

TrichromaticRefers to mammals whose eyes have threeclasses of cones—sensitive to red, green, orblue.

Trophic ChainSystem formed by a group of living beings thatsuccessively feed on each other.

UdderSaclike organ containing the mammary glandsof certain female mammals.

UngulateA mammal that supports itself and walks onthe tips of its digits, which are covered by ahoof.

UropatagiumThe membrane that bats have between theirfeet. It also encloses the tail.

ViviparousRefers to animals in which the embryonicdevelopment of offspring occurs inside themother's body and the offspring emerge asviable young at birth.

Vomeronasal OrganAn auxiliary organ of the sense of smelllocated in the vomer bone between the noseand the mouth. Sensory neurons detectdifferent chemical compounds, usuallyconsisting of large molecules.

WarrenA burrow where certain animals raise theiryoung.

WeaningThe process by which a mammal ceases toreceive maternal milk as its subsistence.

WhiskersVery sensitive hairs of many mammals. Theyare often located near the mouth, like amustache.

PheromoneA volatile chemical substance produced by thesexual glands and used to attract an individualfor reproductive purposes.

PhylogenyThe origin and evolutionary development ofspecies and, generally, genealogies of livingbeings.

PlacentaThe spongy tissue that completely surroundsthe embryo and whose function is to allow theexchange of substances through the blood. Italso protects the fetus from infections andcontrols physiological processes duringgestation and birth.

PlacentaliaThe name by which the species in the Eutheriainfraclass orders are also known.

PlantigradeRefers to mammals that use the entire foot inwalking. Humans are plantigrade.

PolyandryRefers to the relationship in which a femalecopulates with various males during onebreeding period.

PolyestrousRefers to an animal that has multiple annualbreeding, or reproductive, periods.

PolygynyThe social system of certain animals, in whichthe male gathers a harem of females.

PrototheriaA subclass of the mammal class, it has a singleorder, Monotremata.

96 INDEX MAMMALS 97

Index

Aacoustical guidance system

bats, 72See also echolocation

Africa, endangered species, 90-91aggressive mimicry, 74, 75American beaver, 70-71antler, 36-37Arabian camel (dromedary camel), 64-65Arctic fox, 30artificial insemination, 86-87Asia, endangered species, 91Australia, 10-11, 84-85, 91Ayrshire (breed of cattle), 88

Bbacteria, ruminants, 53Bastet, 83bat, 23, 31, 60, 72-73bear

brown, 15grizzly, 15polar, 6-7, 16-17, 31

beaver, 12, 70-71bellow, 37

See also communicationBengal tiger, 18-19binocular vision, 14, 26, 51, 57biomass, 54birth, 44blood, 67blowhole, 67blue whale, 5body temperature, 14, 16-17

balling up, 62-63camel, 64dormice, 62fur, 8hibernation, 15, 62

See also homeothermybonding phenomenon, 45bone: See skeletonBorneo, 91bottlenose dolphin, 14, 76-77bradycardia, 67brain, 15, 77breathing, 66-67breeding, 86brown bear (grizzly bear), 15buffalo, 55burrow, rabbits, 78-79

Ccall, 72

See also communicationcamel, 15, 61, 64-65camouflage, 30, 74-75carnivore, 50-51, 54cat (feline)

balance, 68-69camouflage, 74-75cheetahs, 24-25, 55companion to humans, 80-81domestic, 68-69equilibrium, 69flexibility, 69Geoffroy's cat, 55history, 80lions, 50-51, 55mythological, 83paws, 23skeleton, 68small-spotted genet, 54tigers, 19, 26-27, 74-75vision, 26-27

caudal fin, 76Cerberus, 82cetacean (aquatic mammal), 15, 23, 66-67, 76-

77, 90-91See also dolphin; sea lion; seal; whale

diving, whales, 67dog

developmental stages, 44-45dingoes, 84-85field of vision, 27greyhound, 24mythological, 82nose, 29paw, 22sense of hearing, 28sense of smell, 28-29sense of taste, 29

dolphin, 14, 76-77domestic cat, 68-69dormouse, 60-61, 62-63dorsal fin, 76dromedary camel (Arabian camel), 64-65

Eeagle, 57ear

anatomy, 8, 28bones, 15cats, 69cochlea, 69dogs, 28

eastern cottontail rabbit, 34eating

giraffes, 32-33ruminants, 52

echidna, 10, 35, 38-39echolocation, dolphins, 77ecology, 54-55ecosystem, 54-55egg, 32, 35, 38elephant seal, 13, 15endangered species, 5, 90-91endolymph, 69energy, trophic pyramid, 54epidermis (skin), 30-31equilibrium, 69, 84-85

erythrocyte (red blood cell), 64Europe, endangered species, 90Eutheria: See placental mammalevolution, 74extinction, 90-91

causes, 81polar bears, 7See also endangered species

extremity, 22-23fins, 23opposable thumbs, 49wings, 23

eye, 26-27

Ffalling, feline equilibrium, 68-69family, 59farming, 86fat reserve, 17fat storage, 62-63, 65fatty tissue, 30feline: See catferret, 55fin, 23, 76finger, 49flexibility, 68-69flight, 24-25, 72-73flying squirrel, 24-25food

dormice, 62lions, 51pork, 86-87

food chain, 54-55, 84-85foot, 9, 20fossil, 11fox, 30fruit bat, 73fur, 30-31

body temperature, 14camel, 64camouflage, 30, 74-75

functions, 19, 30, 75hair types, 31mimicry, 75polar bear, 15, 16, 17

Ggame

chimpanzees, 48wolves, 59

gazelle, 55, 90genet, 54genetics, 86Geoffroy's cat, 55gestation, 11, 35, 42giant panda, 91gibbon, 91giraffe, 13, 32-33, 74gland

milk-producing, 46-47sebaceous, 31sweat, 14, 30

goat, 22Gondwana (continent), 11gorilla, 14-15, 91gray whale, 90-91greyhound, 24grizzly bear (brown bear), 15growth hormone, 87

Hhabitat, 15, 90-91Hainan black-crested gibbon, 91hair

body temperature, 14camel, 64camouflage, 30functions, 19, 30, 75

cheetah, 24-25, 55chimpanzee, 22-23, 48-49, 91chinchilla, 30, 90chipmunk, 14, 75Chiroptera (bat), 23, 72-73circulatory system, 14claw, 23, 25coati, 31cochlea, 28, 69coloration, 74-75colostrum, 44communication

bats, 72chimpanzees, 48, 49deer, 37dolphins, 76-77meerkats, 57playing, 48-49rabbits, 78underwater, 76-77wolves, 58

companion animal, 80-81consumer, trophic pyramid, 54continent, 11corpuscle, 31cottontail rabbit, 34cow, 46-47, 52-53, 88cranium (head), 15Cretaceous Period, 8, 12

Ddairy farm, 88-89dam, 70-71Dama gazelle, 90deer, 36, 52-53defense mechanism, 74-75dentition: See teethdermis, 30-31digestion, 52-53digitigrade (foot), 22dingo, 84-85

98 INDEX MAMMALS 99

mimicry, 75polar bear, 15, 16, 17types, 31

hand, 9hare, 27, 30hazel dormouse, 62hearing, 28

See also earherbivore, 52-53, 54hibernation

bats, 73body temperature, 5, 15dormice, 62polar bear, 17weight loss, 63

hierarchy, social, 58-59hippopotamus, 91hog (pig), 86-87Holstein (breed of cattle), 88homeostasis, 16homeothermy (body temperature)

balling up, 62-63dormice, 62hibernation, 5, 15polar bears, 16-17See also body temperature

hominid, 15homogenization, 89hoof, 20, 22horn, 36-37horse, 20-21, 22, 24, 82, 83human

adaptation, 15animal relationships, 80-91brain, 77classification, 15destructiveness, 5feet, 22-23field of vision, 27survival, 4-5, 15

huntingcheetahs, 24lions, 50-51tigers, 26wolves, 59

hyena, 55

IIndonesia, 91insulation, 31IUCN (World Conservation Union), 91

Jjackal, 56jaw, 15Jersey (breed of cattle), 88Jurassic Period, 8, 12

Kkangaroo, 40-41, 84-85kidney, 64koala bear, 35

Llactation

cows, 46-47distinguishing feature, 46kangaroo, 40marsupials, 40placental mammals, 44platypus, 39rabbits, 34weaning, 34

language

extinction, 7, 81, 90-91extremities, 22family, 59fastest, 24features, 8-9feeding, 34: See also lactationflying, 24-25, 72-73food chain, 54-55, 84foot, 9fur: See furhabitat, 15hair: See hairhand, 9herbivores, 52-53, 54hierarchy, 58-59humans: See humaninsulation, 31lactation: See lactationlife cycle, 34life span, 34, 35marsupials: See marsupialmimicry, 74-75monotremes: See monotrememovement, 20-21, 22, 79mythological, 82-83nocturnal, 72-73number of species, 5, 14, 90omnivores, 13, 55origins, 4-5, 7, 8placental: See placental mammalplaying, 48-49, 59, 76posture, 9prominence, 12reproduction: See reproductive cycle;

sexual reproductionrunning, 20, 24-25, 51sense of smell, 28-29senses, 19, 28-29skeletal structure, 20-21skin, 30-31slowest, 74social groups, 56-57, 58-59socializing, 48-49species, 5, 14, 91subclasses, 10

tail, 9, 21, 25, 51types, 9ungulates, 20vertebrate, 21vision, 14, 18water conservation, 64-65

Mammaliaformes, 8mammary gland, 15, 46-47mandrill, 13marsupial, 9, 10

defining characteristics, 11gestation, 35kangaroo, 40, 84-85koala bear, 35opossum, 11pouch, 40-41Tasmanian devil, 11wallaby, 35

marsupium, 40-41mating, 36-37meerkat, 56-57melon, dolphins, 76, 77Merkil's disk, 31metabolism, 17, 25Metatheria: See marsupialmigration, polar bears, 17milk, 15, 34, 40, 46-47, 88-89

See also lactationmilk production, 88-89mimicry, 30, 74Minotaur, 82, 83monkey

chimpanzee, 22-23, 48-49endangered, 91gibbon, 91hanging, 49macaque, 30mandrill, 13

monocular vision, 14monotreme, 9, 10, 32, 35, 38-39morganucodon, 8-9mouth, 15movement, 22

multituberculate, 9muscle, 20myoglobin (protein), 67myth, 82-83

Nnest, 63, 78-79Newton, Isaac, 68night vision, 18, 26-27North America, endangered species, 90nose

camel, 64dog, 28-29

OOceania, 10-11offspring, 34-35omnivore, 13, 55opossum, 11opposable thumb, 49orangutan, 91organ, 64otter, 90oxygen, 66, 67

Ppack, 58-59panda bear, 91pant-hoot, 48Pasteur, Louis, 89pasteurization, 88-89pastureland, 84-85patagium, bats, 73

monkeys, 49underwater, 76-77See also communication

legend, 82-83life cycle, 34-35, 40life span, 34ligament, 20limb

fins, 23functions, 15, 22wings, 23

lion, 50-51, 55, 83livestock

cows, 88hogs, 86-87sheep, 84-85

locomotion, 22, 79longevity, 35loop of Henle, 64Luperca, 82-83

Mmacaque monkey, 30mammal

aquatic: See cetaceanAustralian, 84-85beginnings, 4-5, 7, 8body temperature: See body temperature;

homeothermybone structure, 8-9camouflage, 30, 74-75carnivores, 50-51, 54circulatory system, 14classifying, 22coloration, 74-75common characteristics, 14-15, 16-17, 46-47communication: See communicationdentition: See teethdiversity, 5, 60-79education, 48-49endangered, 5, 90-91

100 INDEX

paw, 23, 25pectoral fin, 76Pegasus, 82pet, 80-81photosynthesis, 54physiology, 15pig (hog), 86-87placenta, 42, 43placental mammal, 9, 10, 11

branches, 12defining characteristics, 12-13, 42-43development, 42-43lactation, 44life cycle, 34

plantigrade (foot), 22platypus, 10, 35, 38-39playing, 48-49, 59, 76polar bear, 6-7, 16-17, 31porcupine, 31pork, 86-87pouch, 40-41predator, 54prehensile digit, 22primate

characteristics, 15chimpanzee, 22-23, 48-49endangered, 91feet, 22-23gibbon, 91gorilla, 14-15hanging, 49hominid, 15human: See humanmandrill, 13

producer, trophic pyramid, 54protective mimicry, 74protein, 67Prototheria: See monotremepulmonary collapse, 67pupil, 26puppy, 44-45

Qquill, 31

Rrabbit, 34, 78-79, 85raccoon, 12rat, 42-43red deer, 36-37red kangaroo, 40regurgitation

ruminants, 52weaning, 45

reproductive cycleechidnas, 35, 38-39kangaroo, 40koala, 35length, 35marsupial, 40monotremes, 35, 38-39placental mammals, 12, 42-43platypus, 38-39rabbit, 34rat, 42-43

reptile, 8respiration

cheetah, 24underwater, 66-67

retina, 27rodent

beaver, 70-71chipmunk, 14dormice, 60-61, 62-63flying squirrel, 24-25gestation, 42-43multituberculates, 9rat, 42-43semi-aquatic, 70-71squirrel, 24-25

ruminant, 52-53rumination, 52-53

running, 20, 24-25, 51

Sscavenger, 55sea lion, 31sea otter, 90seal, 13, 15sexual reproduction, 32

echidna, 38-39marsupial, 35mating, 36-37monotremes, 38-39pigs, 86-87platypus, 38-39red deer, 36

sheep, 52-53, 84shelter

beaver dam, 70-71rabbit burrow, 78-79

short-beaked echidna, 35shrew, 5siamang, 91Siberian flying squirrel, 24-25sight: See visionsign language, chimpanzees, 49skeleton

cats, 68horses, 20-21

skin, 15, 30-31slaughterhouse, 87sloth, 25, 74small-spotted genet, 54smell, sense of, 28-29social structure

meerkats, 56wolves, 58-59

socialization, chimpanzees, 48-49sound wave, 77South America, endangered species, 90southern right whale, 90-91species

endangered, 5, 90-91number, 5, 14, 91

sperm whale, 66-67, 90spermaceti organ, sperm whales, 66spiracle, 66, 76squirrel, 24-25stereoscopic vision, 18sternum, 20stomach, ruminants, 52-53Sumatra, 91sweat gland, 14, 30

Ttail

cheetah, 25lion, 51rodent, 9structure, 21

Tasmania, 11Tasmanian devil, 11taste, 29teat, 46teeth

beavers, 70, 71carnivores, 50growth, 14herbivores, 52horses, 20Mammaliaformes, 8types, 14whales, 66

temporal bone, 69tendon, 20territory, 57Tertiary Period, 8Theria (mammal subclass), 10thoracic collapse, 67three-toed sloth, 25thumb, 49tiger

Bengal, 18-19

camouflage, 74-75vision, 26-27

titi monkey, 91tongue, 29tool, chimpanzees, 49tooth: See teethTriassic Period, 8Trojan horse, 82trophic pyramid, 54-55tunnel, 78-79

Uudder, 46ungulate, 20, 22unicorn, 83uropatagium, 73UV radiation, 30

Vvertebra, 21vision

binocular, 14, 26, 51, 57lions, 50-51monocular, 14night, 18, 26-27stereoscopic, 18tigers, 26-27

WWales, 4wallaby, 35warren, rabbits, 78water conservation, camels, 64-65

weaning, 45whale

blue, 5fins, 23gray, 90-91life span, 34southern right, 90-91sperm, 66-67, 90

wing, 23, 72-73wolf, 30, 55, 58-59, 82-83wool, 31, 85World Conservation Union (IUCN), 91

Zzebra, 51, 55, 60-61, 74

MAMMALS 101

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MAMMALS

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