Animal Life : Secrets of the Animal World Revealed

49

STRAWBERRY POISON FROG
Found in the rain forests of Costa Rica,
Nicaragua, and Panama, the strawberry
poison frog (Oophaga pumilio) is
3⁄4–1 in (2–2.5 cm) long and may
exhibit remarkable color variation.

50

VERTEBRATES REPTILES DIAPSIDS TUATARAS
Page 37 Rhynchocephalia
Reptilia Thick-skinned tetrapods with amniotic eggs or Diapsida All reptiles, other than turtles, including birds.
internal development of young. They include warm-blooded Body forms vary but are often elongated, with scaly or Species 2

birds and other scaly, cold-blooded reptiles. feathered coverings and, commonly, four limbs. LEPIDOSAURS

Lepidosauria Diapsids that shed their skin in large pieces
or as a whole.

HIDDEN-NECKED IGUANAS ANOLES
TURTLES AND TORTOISES Iguanidae Polychrotidae
Species 398
Cryptodira Species 38
Species 255
IGUANAS AND RELATIVES
TURTLES
Iguania Lizards that have four functional limbs and use
Testudines Reptiles with bodies contained within their tongues to capture and grab food.
upper and lower bony, boxlike shells. There are aquatic,

semiaquatic, and terrestrial species.

SIDE-NECKED
TURTLES
Pleurodira
Species 54

ARCHOSAURS AGAMAS AND 6 OTHER
CHAMELEONS FAMILIES
Archosauria Reptiles with teeth sunk into sockets. This
group includes many extinct dinosaur groups, with birds and Acrodonta Species 570

crocodilians being the only living archosaurs. Species 567

BIRDS

Archosaurs with asymmetrical flight feathers (lost in CROCODILIANS LIZARDS AND SNAKES
some flightless species). Many dinosaurs had feathers, Lizards and snakes are closely related
but they were not flight feathers. More recently evolved Crocodylia Elongated, limbed reptiles covered with thick and make up the group Squamata. It is
leathery plates under which are bony plates on their top thought that snakes evolved from lizards,
birds—not including the primitive tinamous and possibly from burrowing species, and the
ratites—have many more shared features, including a surface. All are semiaquatic predators. differences between them are slight.

horny, toothless bill and a keeled breastbone.

Aves PAGE 56
Species 9,500

REPTILES LIZARDS LIZARDS
AND
SNAKES

Reptile groups SNAKES

The oldest groups of reptiles are the turtles and archosaurs, widespread group of lizardlike reptiles, and the squamates, a
which first appeared about 220 million years ago. huge group that includes all lizards and snakes. This
Archosaurs include crocodilians and birds, which are diagram represents one hypothesis of reptile relationships.
feathered reptiles, but also the extinct dinosaurs. Controversy surrounds the relations between squamates
Lepidosaurs include the tuataras, relics of a once and the placement of turtles. Not all families are shown here.

51 REPTILES

LIZARDS AND SNAKES WORM LIZARDS GECKOS AND RELATIVES
AND RELATIVES Gekkota
Squamata Scaly reptiles of many forms, also known Species 1,073
as squamates. Males have paired copulatory organs Amphisbaenia

called hemipenes. Species 166

SKINKS AND RELATIVES SCLEROGLOSSANS
Scincomorpha
Species 2,000 Scleroglossa Squamates that use their jaws rather than
their tongue to catch food, and their tongue for smelling.
AUTARCHOGLOSSANS
This group includes all squamates except iguanians.
Autarchoglossa Squamates with highly developed
olfactory capabilities involving the tongue and a sensitive
scent organ (Jacobson’s organ) in the roof of the mouth.

KNOB-SCALED GLASS
LIZARDS LIZARDS
Anguidae
Xenosauridae
Species 114
Species 6

ANGUIMORPH LIZARDS

Anguimorpha A diverse group of squamates. Many have
bony plates (osteoderms) beneath their scales
and some species lack legs.

BEADED MONITOR
LIZARDS LIZARDS
Helodermatidae Varanidae

Species 2 Species 63

MONITORS AND RELATIVES

Varanoidea Includes squamates with an excellent sense of
smell, and well-developed teeth, upper jaw, and neck. Most
are efficient predators that use long tongues to track prey.

SNAKES

Serpentes Elongated squamates with no limbs (although
the skeletons of some snakes show evidence of hind
limbs), no moveable eyelids, and no external ears.

BLIND SNAKES TRUE SNAKES
Scolecophidia Alethinophidia
Species 473 Species 2,500

ANIMAL KINGDOM 52 Reptiles higher temperatures than endothermic (“warm-
blooded”) birds and mammals. Some reptiles
What most people understand by the term “reptile” is an egg-bearing may also survive temperatures as low as
vertebrates that has a tough skin with a covering of hard, dry scales. freezing, although in these conditions their
In fact, the term also includes birds, with their covering of feathers. bodily functions operate at a very reduced rate.

Living reptiles include turtles and tortoises, purposes of this catalog, the birds have been Extreme habitats
tuatara, squamates (lizards, amphisbaenians, profiled separately from the non-avian reptiles
and snakes), crocodilians (crocodiles, alligators, (see pp.58–67) By obtaining all their heat from external sources
and caimans), and, perhaps somewhat such as the sun, ectothermic reptiles can
surprisingly, birds. In fact, crocodilians are more Temperature control survive easily on one-tenth of the amount
closely related to the birds than to the other of food needed by an endothermic animal
reptiles, and together they form a group known Reptiles occur throughout the world but are of the same size—endotherms use up a large
as the Archosaura (“ruling reptiles”), which also more common in tropical habitats. Most non- proportion of the energy obtained from their
contains several extinct groups of dinosaurs and avian reptiles are ectothermic, meaning they food just to maintain a constant body
pterosaurs (flying reptiles). Birds, then, are cannot generate metabolic heat. However, some temperature. This gives non-avian reptiles a
warm-blooded reptiles with feathers. For the regulate their internal body temperature through great advantage in habitats where conditions
behavior, such as sunning, and can operate at are extreme and food is in short supply, notably
deserts, where lizards are often the most
common form of vertebrate life.

Turtles and tortoises Alligator snapping turtle Big-headed turtle Green sea turtle
Chelonia mydas
Order Chelonia Macroclemys temminckii Platysternon megacephalum 31 in–3 ft 3 in (80–100 cm)
151⁄2–31 in (40–80 cm) 51⁄2–8 in (14–20 cm)
Turtles and tortoises comprise the order Chelonia.
They are heavily armored reptiles with bony shells that
originate from their ribs and cover the top and bottom
of their bodies. This gives them excellent protection
from predators but limits their speed and agility on land.
They all lack teeth and instead use a sharp horny “beak”
to break up their food, which may consist of animal or
vegetable material, or both, depending on the species. Turtles
occur on the land (where they are often known as tortoises), in
freshwater, and in the sea. They all lay nearly spherical eggs,
with some marine species laying up to 100 in a clutch.

Starred tortoise
Geochelone elegans
12–15 in (30–38 cm)

Red-eared turtle Yellow mud turtle
Trachemys scripta elegans
8–11 in (20–28 cm) Kinosternon flavescens
41⁄2–61⁄2 in (12–16 cm)

Hermann’s tortoise Leopard tortoise Chinese soft-shelled turtle Common snake-necked turtle
Testudo hermanni Pelodiscus sinensis Chelodina longicollis
6–8 in (15–20 cm) Geochelone pardalis 6–12 in (15–30 cm) 8–10 in (20–25 cm)
171⁄2–28 in (45–72 cm)

Tuatara Tuatara

Order Rhynchocephalia Sphenodon punctatus
191⁄2–26 in (50–65 cm)
Both surviving members of the order Rhynchocephalia live
on islands off the coast of New Zealand. Despite their lizardlike
appearance, they are not squamates and belong to an ancient
group of reptiles that was formerly spread over much of the world.
Their teeth are fused to their jawbones and those on the tip of their
upper jaw are modified into a beaklike arrangement. Tuataras also
lack the hemi penis (double penis) unique to squamates. They lay
eggs, which take about a year to hatch, and have long life spans.

Lizards and snakes 53 REPTILES

Order Squamata Australian frilled lizard Thai water dragon
Physignathus cocincinus
The lizards, snakes, and amphisbaenians (worm-lizards) Chlamydosaurus kingii 31–39 in (80–100 cm)
comprise the Squamata. This is the largest group of ectothermic 231⁄2–35 in (60–90 cm)
reptiles, with the widest distribution. Most squamates lay eggs
but a sizable proportion bear live young. Lizards are the most
numerous group and are distinguished by the presence
of legs, although limblessness has evolved many times
among squamates. They also have eyelids and external
ear openings. Squamates have adapted to many
habitats and filled many ecological niches. The worm-
lizards are burrowing squamates restricted to warm
climates. Their scales are arranged in annuli (rings) and
their skulls are bony, allowing them to force their way
through hardened soil. Most worm-lizards have no limbs,
but the ajolotes or mole lizards (Bipedidae) have front limbs
that they use to dig. Snakes are elongated squamates
lacking legs, eyelids, and external ear openings. These
constraints have resulted in specialized methods of
locomotion and hunting. All snakes are carnivorous,
feeding on animals ranging from ants to antelopes.

Spiny dab lizard Inland bearded dragon Common agama Flying lizard
Draco spilonotus
Uromastyx acanthinurus Pogona vitticeps Agama agama 6–8 in (15–20 cm)
12–151⁄2 in (30–40 cm) 12–191⁄2 in (30–50 cm) 12–151⁄2 in (30–40 cm)

Thorny devil Warty chameleon Jackson’s chameleon
Moloch horridus Furcifer verrucosus Chamaeleo jacksonii
6–7 in (15–18 cm) 4–10 in (10–26 cm) 8–12 in (20–30 cm)

Collared lizard Plumed basilisk
Crotaphtus collaris
8–14 in (20–35 cm) Basiliscus plumifrons
231⁄2–28 in (60–70 cm)
Green iguana
Iguana iguana Desert horned lizard
5–61⁄2 ft (1.5–2 m)
Phrynosoma platyrhinos
31⁄4–41⁄2 in (8–11 cm)

Marine iguana
Amblyrhynchus cristatus
3ft 3in–51⁄2 ft (1–1.7 m)

Green anolis
Anolis carolinensis
41⁄2–8 in (12–20 cm)

ANIMAL KINGDOM 54 Tokay gecko
Gekko gecko
7–14 in (18–35 cm)

Kuhl’s flying gecko Northern leaf-tailed gecko Nicobar blind lizard Armadillo lizard
Ptychozoon kuhli Dibamus nicobaricus 4–5 in (10–13 cm)
7–8 in (18–20 cm) Phyllurus cornutus Cordylus cataphractus
6–81⁄2 in (15–21 cm) 61⁄2–81⁄2 in (16–21 cm)

Rough-scaled plated lizard Tegu lizard Ocellated lizard
Gerrhosaurus major 16–19 in (41–48 cm) Tupinambis teguixin
31–39 in (80–100 cm) Lacerta lepida
Eyed skink 231⁄2–31 in (60–80 cm)
Chalcides ocellatus
7–12 in (18–30 cm) Yellow-spotted night lizard European glass lizard
Lepidophyma flavimaculatum Ophisaurus apodus
8–12 in (20–30 cm) 3ft 3in–4 ft (1–1.2 m)

Black-and-pink-striped gila monster Savanna monitor

Heloderma suspectum Varanus
12–191⁄2 in (30–50 cm)
exanthematicus
21⁄2–4 ft (0.8–1.2 m)

Komodo dragon TEXAS THREADSNAKE SOUTH AMERICAN PIPESNAKE
Varanus komodoensis Leptotyphlops dulcis grows to a length of 6–101⁄2 in (15–27 cm). Anilius scytale is 28–35 in (70–90 cm) long. The sole
81⁄4–101⁄4 ft (2.5–3.1 m) member of its family, its markings mimic those of
It is a member of the Leptotyphlopidae, a family of small, venomous coral snakes that live in the same region.
Black-and-white
amphisbaenian burrowing snakes that live in the soil and feed mainly on termites.
Amphisbaena fuliginosa
12–171⁄2 in (30–45 cm)

55 REPTILES

Sunbeam snake Mexican burrowing snake Rosy boa
Xenopeltis unicolor Loxocemus bicolor
3ft 3in–4 ft (1–1.3 m) 3ft 3in–4 ft (1–1.3 m) Charina trivirgata
2–31⁄2 ft (0.6–1.1 m)

Anaconda Burmese python Emerald tree boa Cuban woodsnake
Eunectes murinus Tropidophis melanurus 31 in–39in (80–100 cm)
20–33 ft (6–10 m) Python molurus Corallus caninus
161⁄2–23 ft (5–7 m) 5–61⁄2 ft (1.5–2 m)

Arafura filesnake Gaboon viper WESTERN DIAMONDBACK RATTLESNAKE Puff adder
Bitis gabonica 4–61⁄2 ft (1.2–2 m) Crotalus atrox is a large and formidable pit viper, Bitis arietans
Acrochordus arafurae 3–7 ft (1–2.1 m) long, common in the arid American 3–6 ft (0.9–1.8 m)
5–81⁄4 ft (1.5–2.5 m) Southwest. It is active mainly at night.
Egyptian cobra
Cornsnake Naja haje
Elaphe guttata 5–73⁄4 ft (1.5–2.4 m)
3–6 ft (1–1.8 m)
Bibron’s burrowing asp
Atractaspis bibroni Eastern coral snake
20–28 in (50–70 cm) Micrurus fulvius
28–39 in (70–100 cm)

Crocodiles, alligators, and gharials Nile crocodile
Crocodylus niloticus
Order Crocodilia 161⁄2–21 ft (5–6.5 m)

Crocodilians are one of the two surviving groups from an
evolutionary line that also contained the extinct dinosaurs, the
other survivors being the birds. Crocodilians are covered with
thick bony plates and are semiaquatic predators. Their social
behavior, complex displays, and vocalizations set them apart
from all other reptiles. All species lay eggs, and females show
a high degree of parental care. Most crocodilians live in
freshwater rivers, lakes, and lagoons, while a few species
inhabit tidal reaches and may venture out to sea.

American alligator Spectacled caiman Gharial
Gavialis gangeticus
Alligator mississippiensis Caiman crocodilus 13–23 ft (4–7 m)
91⁄4–161⁄2 ft (2.8–5 m) 81⁄4–93⁄4 ft (2.5–3 m)

56

VERTEBRATES BIRDS NEOGNATHS
Page 37
Aves Feathered vertebrates with forelimbs modified into Neognathae All living birds except the tinamous and the
wings (in most cases), and a horny toothless bill. Birds also flightless ratites. A huge variety of forms has evolved,

lay hard-shelled eggs. including the passerines (perching birds).

PIGEONS AND
DOVES

Columbiformes
Species 298

SANDGROUSE
Pteroclidiformes

Species 16

TINAMOUS HUMMINGBIRDS
Tinamiformes AND SWIFTS
Apodiformes
Species 46 Species 429

OSTRICH EMUS AND FOWL NIGHTJARS
Struthioniformes CASSOWARIES AND RELATIVES
Casuariformes Galliformes Largely terrestrial birds, with short, stout,
Species 1 decurved bills, and strong legs and feet. Short wings Caprimulgiformes
Species 4 typically give short bursts of low flight. This group includes Species 115
the jungle fowl, from which domestic fowl were derived.
WOODPECKERS
RATITES
Piciformes Neoaves with feet having two toes pointing
Ratitae Flightless birds with reduced flight muscles, no forward and two backward. They have chisel-like bills, and
developed flight feathers, and a breastbone with no keel. many have stiff tail feathers acting as a prop when perched

This group includes the largest living birds. on upright branches.

KIWIS RHEAS WATERFOWL MOUSE BIRDS
Apterygiformes Rheiformes Coliiformes
Species 2 Anseriformes Water or waterside birds with three toes Species 6
Species 6 on each foot joined by webs. Their bills vary from slender
and serrated to broad and triangular. This group includes TROGONS
Trogoniformes
ducks, geese, and swans.
Species 39

KINGFISHERS

Coraciiformes Tiny to medium-sized, dry-land
or waterside birds, with two toes fused at the base,
typically a short, square tail, an upright stance, and

a horizontal bill. Many have striking colors.

Bird groups

Birds number close to 10,000 species, ranging from the rails, may appear to have little in common. Recent DNA
primitive tinamous and ratites to perching birds, the most studies have helped resolve some of the relationships,
recently evolved group. Outward appearances make some producing dramatically revised groupings. Surprises have
groupings such as penguins and hummingbirds obvious, included the close relationship between New World
but birds within other groups, such as the cranes and vultures and storks, rather than other birds of prey.

57

NEOAVES GREBES FLAMINGOS STORKS, IBISES,
Podicipediformes Phoenicopteriformes HERONS, AND NEW
Neoaves All neognaths except the fowl and the Species 5 WORLD VULTURES
waterfowl. The relationships between groups within Species 22 Ciconiiformes
FALCONS
the neoaves remain largely unresolved. Falconiformes PELICANS
Species 60
BIRDS OF PREY Pelicaniformes Relatively large sea- and freshwater
Accipitriformes CRANES AND RAILS birds, with long, angular wings, a bare and flexible throat
Species 225 Gruiformes pouch, a dagger-shaped or hooked bill, forward-facing
Species 199
eyes, and webbing joining all four toes.

PARROTS WADERS AND RELATIVES LOONS PENGUINS
Psiitaciformes Gaviiformes Sphenisciformes
Species 352 Charadriiformes Shore and seabirds, with bill shape Species 5 Species 17
and leg length adapted to their feeding techniques. Feet
CUCKOOS may be fully or partially webbed, or unwebbed. Found ALBATROSSES, PETRELS,
Cuculiformes AND SHEARWATERS
Species 138 worldwide, they include long-distance migrants. Procellariiformes

TURACOS Species 107
Musophagiformes

Species 23

HOATZIN
Opisthocomiformes

Species 1

OWLS
Strigiformes
Species 194

PERCHING BIRDS SUBOSCINES

Passeriformes Birds with four unwebbed toes joined at Tyranni A group of South American passerines, divided
the heel, three pointing forward and one backward. Also from songbirds by physical features including the detailed

known as passerines, they vary hugely in form. structure of the vocal organ (syrinx).

NEW ZEALAND WRENS NEW GUINEA
Acanthisittidae BERRYPECKERS
Species 3 Melanocharitidae

LYREBIRDS Species 12
Menuridae
Species 2 NEW ZEALAND HONEYEATERS CORVIDS
WATTLEBIRDS AND RELATIVES
Meliphagidae Corvidae Passerines with strong, heavily scaled feet and
Callaeatidae a stout, versatile bill. With loud and hoarse calls, they are
Species 174
Species 2 often social birds and highly developed mentally. This
group includes crows, jays, and magpies.
SONGBIRDS
PASSERIDS
Passeri A group of passerines, ranging greatly in size, with
a complex vocal organ (syrinx) that gives many species a Passerida A group of songbirds comprising an
sophisticated vocal range and control. extremely varied mixture of species. Some subgroups are

AUSTRALASIAN LOGRUNNERS very distinct but the true relationships between the
BABBLERS Orthonychidae different groups are yet to be resolved. They include
Species 3
Pomatostomidae about one-third of the world’s bird species.

Species 5

AUSTRALIAN BOWERBIRDS
TREECREEPERS Ptilonorhynchidae
Species 18
Climacteridae

Species 7

ANIMAL KINGDOM 58 Birds the tracts are harder to define. Feathers provide
insulation, enable flight, and need to be replaced
Birds are lightweight but remarkably tough animals, with a high metabolic rate regularly through the process of molting,
and often fast, high-energy lifestyles. They are found throughout the world, usually once or twice a year.
except for the most extreme polar areas, and in nearly every surface habitat.
Counting toes
Modern birds trace their descent back to dinosaurs feather. Feathers developed from modified scales,
and have much in common with reptiles, but all and grow in well-defined tracts. On most birds By using detailed physical and behavioral
bird species are warm-blooded. Most species these tracts form a regular pattern, described by features to trace common descent, birds
can fly, but there are some flightless ones. All such terms as ear coverts, scapulars, primaries, are grouped into 227 families to create an
species lay eggs that are incubated externally, and tail feathers. Overlying the body, smaller evolutionary family tree. Physical characters
and have horn-sheathed bills. There is, however, contour feathers smooth the bird’s outline. On include the structure of the feet: most birds
another feature that is unique to birds: the some species, including penguins and kiwis, have four toes, the majority having three facing
forward, one back. A substantial number of
species have just three toes and a few,
including the ostrich, have just two toes.

Tinamous Ostrich Rheas Cassowaries and emus

Order Tinamiformes Order Struthioniformes Order Rheiformes Order Casuariiformes

This ancient South American family of The world’s largest birds are Rheas are flightless, polygamous These flightless birds, found in
ground-living, quail-like birds lives mostly flightless and can run at birds that are ostrichlike in form Australia and New Guinea, are
in dense, tropical forest as far north as up to 40 mph but have three toes and are somewhat ostrichlike, but with
Mexico. Some species live in open (65 kph). considerably smaller, up to 5 ft a longer, lower profile and
grasslands. Elusive but often (1.5 m) tall. They live in open three toes. Cassowaries can
heard, they eat insects, seeds, habitats in South reach 6 ft (1.8 m) in height
and berries, and range from America. They and emus, the world’s
6–191⁄2 in (15–50 cm) eat leaves, second-largest
in length. shoots, seeds, birds, can reach
and some 61⁄2 ft (2 m) and
Red-winged tinamou Ostrich invertebrates. weigh up to
100 lb (45 kg).
Rhynchotus Struthio camelus Greater rhea
7–91⁄2 ft (2.1–2.8 m) Rhea americana Southern cassowary
rufescens 3–5 ft (0.9–1.5 m) Casuarius casuarius
151⁄2 in (40 cm) 6 ft (1.8 m)

Kiwi Brown kiwi Gamebirds and relatives California quail
Apteryx australis Callipepla californica
Order Apterygiformes 151⁄4 in (40 cm) Order Galliformes 10 in (25 cm)

Three species of small flightless birds make up Gamebirds occur in many habitats, Chukar
this order. Females are larger than males, and including semi-desert, grassland, Alectoris chukar
their especially large eggs are each up to 25 savanna, woodland and forest, and 121⁄2–151⁄2 in (32–39 cm)
percent of the female’s body weight. They are even high peaks and northern tundra.
nocturnal, and find food, especially earthworms, They are all small-headed, large-bodied
by touch and scent, using facial bristles and nostrils birds with short, stout, arched bills and
at the tip of a long bill. often marked sexual differences. Some
cold-climate species have feathered
feet and turn white in winter.

Wildfowl Northern bobwhite Western capercaillie

Order Anseriformes Colinus virginianus Tetrao urogallus
91⁄2–11 in (24–28 cm) 231⁄2–33 in (60–85 cm)
This group consists of ducks, geese,
swans, and screamers. Wildfowl are Mute swan
mostly water or waterside birds,
many of which feed on dry land Cygnus olor
and retreat to water for safety. 41⁄2–51⁄4 ft (1.4–1.6 m)
Swans are the largest, geese mostly
intermediate, and ducks smaller. Ducks
can be freshwater, marine, or both, and
feed on land and in water.

Eurasian wigeon
Anas penelope
30–34 in (75–86 cm)

Plumed whistling-duck Red-breasted goose Grey francolin Temminck’s tragopan
Dendrocygna eytoni 151⁄2–171⁄2 in (40–45 cm) Branta ruficollis 21–211⁄2 in (53–55 cm) Tragopan temminckii
Francolinus pondicerianus 25 in (63 cm)
131⁄2 in (34 cm)

Penguins Loons 59 BIRDS

Order Sphenisciformes Order Gaviiformes

Although some species venture as far Loons (also called divers) are Northern Hemisphere water
north as the Equator, these distinctive birds, nesting by freshwater, but spending much
flightless seabirds are most typically time at sea. Their strong legs, set far back on the
associated with the very cold body, are ideal for swimming underwater, but
conditions and rich marine food make walking on land impossible.
sources farther south in the
Southern Ocean. Most species Rockhopper penguin Adelie penguin Arctic loon
breed in large colonies, some Pygoscelis adeliae Gavia arctica
consisting of hundreds of Eudyptes chrysocome 18–24 in (46–61 cm) 231⁄2–28 in (60–70 cm)
thousands of birds. Penguins 191⁄2 in (50 cm)
have plump bodies and can Grebes
weigh between 21⁄2 and 66 lb
(1–30 kg). They have short Order Podicipediformes
legs, webbed feet, and wings
that are flattened to serve as These birds are widespread worldwide and
flippers. All species stand found on freshwater and at sea on sheltered
upright and waddle on land, inshore waters. They have slim, daggerlike bills,
but are superb swimmers, their feet are broadly lobed, and their legs are
reaching speeds of up to set far back for underwater
9 mph (14 kph). They are propulsion.
also deep divers, pursuing
fish and krill. Jackass penguin Humboldt penguin Great crested grebe
Spheniscus humboldti Podiceps cristatus
King penguin Spheniscus demersus 23 in (58 cm) 18–20 in (46–51 cm)
Aptenodytes patagonicus 231⁄2–28 in (60–70 cm)
35 in (90 cm)

Albatrosses, petrels, and shearwaters Flamingos

Order Procellariiformes Order Phoenicopteriformes

From tiny storm-petrels to the wandering albatross (which Flamingos are tropical and temperate waterside birds
has the longest wingspan of any bird), albatrosses, shearwaters, that live and breed socially, within very
and petrels are all characterized by tubular nostrils. They spend few, large breeding colonies. Tens
much time over open sea, but come to land to breed. Smaller or hundreds of thousands gather
species, effectively unable to walk, visit nests only under cover to feed in very restricted
of darkness, and even the larger species are weak on land, but areas with favorable
all show great mastery of oceanic conditions. conditions. They are
long-legged, long-
ROYAL PAIR necked, and have
A breeding pair of royal albatrosses (Diomedea remarkable,
epomophora ) on their nest. angled bills
used for filtering
food from the water as they
wade, or sometimes swim.

Northern fulmar Cory’s shearwater European storm-petrel Greater flamingo
Phoenicopterus ruber
Fulmarus glacialis Calonectris diomedea Hydrobates pelagicus 4–43⁄4 ft (1.2–1.45 m)
171⁄2–191⁄2 in (45–50 cm) 171⁄2–22 in (45–56 cm) 51⁄2–61⁄2 in (14–17 cm)

Storks, ibises, and herons Black-crowned night-heron
Nycticorax nycticorax
Order Ciconiiformes 23–63 in (58–65 cm)

This is a varied group of waterside birds that includes herons, European spoonbill
bitterns, egrets, storks, ibises, and spoonbills. They are widespread, Platalea leucorodia
but some species are localized, restricted to tiny areas of suitable 32–37 in (80–93 cm)
habitat such as reed beds. Most are long-legged, long-necked

birds, with daggerlike bills for grasping, not
stabbing, fish. Spoonbills have flattened
bills with sensitive, spoon-shaped tips
used to detect food in shallow water.

Scarlet ibis
Eudocimus ruber
22–27 in (56–68 cm)

European white stork Cattle egret Grey heron
Bubulcus ibis Ardea cinerea
Ciconia ciconia 18–20 in (45–50 cm) 35–39 in (90–98 cm)
3–31⁄2 ft (0.95–1.1 m)

ANIMAL KINGDOM 60 Pelicans and relatives

Order Pelecaniformes

A widespread group in tropical and temperate regions, these Brown pelican Northern gannet Great cormorant
Phalacrocorax carbo
birds all share long, angular wings, flexible throat pouches, and Pelecanus occidentalis Morus bassanus 31–39 in (80–100 cm)
31⁄2–5 ft (1–1.5 m) 35–393⁄4 in (89–102 cm)
forward-facing eyes. All but the frigatebirds have webbing joining

all four toes (unlike ducks or gulls). Many are seabirds, but some

are freshwater species. Colonies sometimes number many

thousands of pairs.

Great frigatebird Shoebill
Fregata minor
33–41 in (85–105 cm) Balaeniceps rex
31⁄2–41⁄2 ft

(1.1–1.4 m)

Birds of prey Cranes and rails

Orders Accipitriformes, Cathartiformes, and Falconiformes Order Gruiformes

A diverse group, birds of prey include birds smaller than a thrush Characterized by the tall, upright, long-legged,
as well as some of the world’s largest flying birds. Many are powerful cranes, these birds are strongly
predatory, others scavengers, and some are largely migratory and social. The group includes birds
vegetarian. Most species have muscular legs, as varied as rails and crakes, many of which
sharp talons, and a sharp, hooked bill. are waterside birds; the bustards, which inhabit
various open grassland habitats; and oddities
such as the limpkin and seriemas. The order
is widespread, but many species are secretive,
and some are relatively little-known.

Great bustard

Otis tarda
31⁄2 ft (1.1 m)

Turkey vulture Andean condor
Cathartes aura
25–32 in (64–81 cm) Vultur gryphus
4–41⁄4 ft (1.–1.3 m)

Little bustard Kagu Buff-banded rail
Rhynochetos jubatus 211⁄2 in (55 cm) Gallirallus philippensis
Tetrax tetrax 11–13 in (28–33 cm)
151⁄2–171⁄2 in (40–45 cm)

Southern caracara Common kestrel Harris’s hawk
Falco tinnunculus 12–15 in (30–38 cm) Parabuteo unicinctus
Caracara plancus 30 in (75 cm)
191⁄2–23 in (49–59 cm)

Water rail Common moorhen
Gallinula chloropus
Rallus aquaticus 121⁄2–14 in (32–35 cm)
81⁄2–11 in (22–28 cm)
Purple swamphen
Porphyrio porphyrio
15–191⁄2 in (38–50 cm)

Secretary bird Common crane
Grus grus
Sagittarius 3–4 ft (0.95–1.2 m)

serpentarius
41⁄4–41⁄2 ft (1.3–1.4 m)

White-bellied sea eagle Haliaeetus Egyptian vulture (immature) Neophron Limpkin
Aramus guarauna 22–28 cm (56–71 cm)
leucogaster 28 in (70 cm) perncopterus 23–28 in (58–70 cm)

Waders, gulls, and auks 61 BIRDS

Order Charadriiformes Eurasian oystercatcher Masked lapwing Black-necked stilt
Vanellus miles 13–15 in (33–38 cm) Himantopus mexicanus
This large and varied order, found worldwide, includes some Haematopus ostralegus 14 in (35 cm)
of the greatest long-distance migrants of the bird world. The core 151⁄2–171⁄2 in (40–45 cm)
groups are wading birds or shorebirds, including plovers and
sandpipers; the more marine gulls and terns; and true seabirds,
the auks, including guillemots and puffins, which breed in
spectacular coastal colonies. Waders show great variation
in size, bill shape, and leg length, according to their various
foods and habitats. They spend most time
close to water, but breed on
tundra, moorland, marshland,
or even farmed habitats.

Wattled jacana

Jacana jacana
61⁄2–10 in (17–25 cm)

Little ringed plover Eurasian curlew

Charadrius dubius Numenius arquata
51⁄2–6 in (14–15 cm) 191⁄2–231⁄2 in (50–60 cm)

Pied avocet Common gull Inca tern Long-tailed jaeger Atlantic puffin
Stercorarius longicaudus Fratercula arctica
Recurvirostra avosetta Larus canus Larosterna inca 19–21 in (48–53 cm) 10 in (25 cm)
161⁄2–171⁄2 in (42–45 cm) 15–171⁄2 in (38–44 cm) 151⁄2–161⁄2 in (39–42 cm)
Kea
Sandgrouse Pin-tailed sandgrouse Parrots and cockatoos Nestor notabilis
Pterocles alchata 18 in (46 cm)
Order Pteroclidiformes 11 in (28 cm) Order Psittaciformes
Black-winged lory
The sandgrouse are a small group of Widespread tropical birds, which are Eos cyanogenia
terrestrial birds found in warm or hot, found mostly in scrub, woodland, or forest. 4 in (10 cm)
open steppe or semidesert habitats. They are often social, and feed on fruit and
These short-legged, stout-bodied, long- seeds. All have short legs, strong feet with
winged birds are weak walkers but swift two toes pointing backward, and stout,
fliers. They often live socially, making hooked bills with bare skin (a “cere”) at the
regular morning or evening flights to water. base, somewhat like falcons and pigeons.
They can carry water back to their chicks
in their soaked belly feathers. White cockatoo
Cacatua alba
18 in (46 cm)

Pigeons and doves Speckled pigeon Brown lory
Columba guinea
Order Columbiformes 131⁄2 in (33 cm) Chalcopsitta dulvenbodei
121⁄2 in (32 cm)
A large group of species, which is found Pink-spotted
worldwide on land, except in areas of fruit dove
extreme cold and desert conditions. The Ptilinopus
order comprises pigeons and doves (there perlatus
is no clear separation between the two) 10 in (26 cm)
and includes two well-known extinct
families, the dodo and solitaires.

Croaking ground Mourning dove
dove
Columbina Zenaida macroura
cruziana 9–131⁄2 in
6 in (15 cm)
(23–34 cm)

Red-fronted lorikeet St. Vincent parrot
Charmosyna rubronotata 4 in (10 cm) Amazona guildingii 151⁄2 in (40 cm)

ANIMAL KINGDOM 62 Cuckoos and turacos Red-crested turaco

Order Cuculiformes Tauraco erythrolophus
151⁄2–17 in (40–43 cm)
This group is found widely around the world, some cuckoos
being long-distance migrants between tropical and temperate
regions. Turacos are residents of tropical
forests, and the hoatzin lives in South
American forests. Many cuckoos lay
their eggs in the nests of other
species and play no part in
raising their own young.
Cuckoos feed on insects,
especially caterpillars.

Common cuckoo TREE DWELLER
Cuculus canorus 121⁄2–13 in (32–33 cm) This primitive South American hoatzin (Opisthocomus
hoazin ) lives in trees and feeds almost entirely on
leaves. It is 24–28 in (62–72 cm) in length.

Owls Nightjars and frogmouths

Order Strigiformes Order Caprimulgiformes

Owls and barn owls are mostly crepuscular or nocturnal, Nightjars and frogmouths are found around the world, together
but some feed by day. Most owls have excellent hearing with localized species of Caprimulgiformes, such as the oilbird.
and eyesight; adapted to almost silent flight, they are able They are active at dawn and dusk or in darkness, usually
to pinpoint prey by sound in near darkness or under hunting for flying insects. Nightjars and frogmouths are
snow. They occupy tundra and desert, dense rain forest, characterized by tiny legs, tiny bills with huge gapes,
and open scrub. Found worldwide, the barn owl is large eyes, and highly cryptic plumage patterns. By
among the most widespread of land birds. day they rely on their camouflage to hide against
bark, in foliage, or on the ground.

European nightjar Tawny frogmouth Common potoo
Caprimulgus europaeus 10–11 in (26–28 cm) Nyctibius griseus
Podargus strigoides 13–15 in (33–38cm)
131⁄2–21 in (34–53 cm)
Andean hillstar
Eagle owl Spectacled owl Tawny owl Hummingbirds Oreotrochilus
Bubo bubo and swifts estella 5–6 in
23–29 in (59–73 cm) Pulsatrix perspicillata Strix aluco (13–15 cm)
17–201⁄2 in (43–52 cm) 141⁄2–151⁄2 in (37–39 cm)

Order Apodiformes

Swifts are the world’s most aerial Pallid swift
birds, some not coming to land for
two or three years, and then only Apus pallidus
to nest. They catch insects, despite 61⁄2–7 in
having tiny bills. The hummingbirds
eat nectar, having highly adapted (16–18 cm)
bill shapes. The world’s most
maneuverable birds, they hover,
dash forward, or can even fly
backward. This group includes
the world’s smallest birds.

Great grey owl Eurasian pygmy owl
Strix nebulosa
23–33 in (59–85 cm) Glaucidium passerinum
6–71⁄2 in (15–19 cm)

Ural owl Mousebirds
Strix uralensis
23–24 in (58–62 cm) Order Coliiformes

Northern hawk-owl Just six species, all found in tropical
Surnia ulula Africa, make up this order. They are
14–16 in (36–41 cm) characteristic of open bush in the great
savanna plains. Mousebirds have small,
decurved bills, short but strong feet,
and long, slender tail feathers. They
are highly social birds, feeding close
together. This is one of only two
orders of birds exclusively native
to Africa. The other is the ostrich.

Barn owl Blue-naped mousebird Speckled mousebird
Urocolius macrourus
Tyto alba 13–14 in (33–36 cm) Colius striatus
111⁄2–171⁄2 in (29–44 cm) 12–151⁄2 in (30–40 cm)

Trogons Kingfishers and relatives 63 BIRDS

Order Trogoniformes Violaceous trogon Order Coraciiformes European roller
Trogon violaceus Coracias garrulus
Despite being found in the widely 9–10 in (23–26 cm) Kingfishers, motmots, bee-eaters, rollers, hoopoes, 12 in (30 cm)
separated tropical regions of Africa, the and hornbills as a group are represented almost worldwide,
Americas, and Indo-China, all trogons but only kingfishers are really widespread. Few kingfishers
are remarkably similar in appearance. actually eat fish, many catching insects or reptiles in
They are essentially green above, often woodland, as do the Australasian kookaburras. Bee-eaters
barred black-and-white on the tail, and take insects on the wing; rollers drop from perches to the
bright red, pink, orange, or yellow below. ground to catch their prey; hoopoes and some hornbills
They have short, stout bills, and short legs. feed on the ground. Kingfishers range from tiny to
Most species prefer forest or woodland medium sized, whereas ground hornbills are
habitats and feed on insects. huge birds. These species all nest in holes of
various kinds, either tunneled into earth or
Resplendent quetzal ready-made in tree cavities.
Pharomachrus mocinno
14–151⁄2 in (35–40 cm) Toco toucan Laughing kookaburra Common kingfisher Pied kingfisher
Alcedo atthis 61⁄2 in (16 cm) Ceryle rudis
Woodpeckers and toucans Ramphastos toco Dacelo novaeguineae 10 in (25 cm)
21–231⁄2 in (53–60 cm) 161⁄2 in (42 cm)
Order Piciformes

Puffbirds, barbets, honeyguides, toucans,
and woodpeckers form a group with zygodactyl
feet—meaning that they have two toes facing
forward and two toes facing backward.
They have strong bills and often rather
bold, noisy behavior. Honeyguides
lead other animals to bees’ nests
and benefit from the other animals
breaking into the hives. Toucans
are characterized by remarkable,
colorful, long but lightweight
bills. Woodpeckers use their
tails as “props” to support them
against upright branches, and
“drum” against branches with
their bills, using this instrumental
communication in place of
conventional song. Only the
woodpeckers are widespread
on several continents.

Blue-crowned motmot European bee-eater
Momotus momota 181⁄2 in (47 cm) Merops apiaster
12 in (30 cm)

Jamaican tody

Todus todus
41⁄2 in (11 cm)

Common hoopoe
Upupa epops
10–11 in (26–28 cm)

D’Arnaud’s barbet Greater honeyguide
Trachyphonus darnaudii Indicator indicator
8 in (20 cm) 8 in (20 cm)

Northern wryneck Middle spotted woodpecker Rufous-tailed Southern yellow-billed hornbill Great hornbill
jacamar Buceros bicornis
Jynx torquilla Dendrocopos medius Galbula ruficauda Tockus leucomelas 5 ft (1.5 m)
61⁄2 in (16 cm) 71⁄2–81⁄2 in (19–22 cm) 10 in (25 cm) 191⁄2–231⁄2 in (50–60 cm)

ANIMAL KINGDOM 64 Passerines Rifleman Green broadbill African pitta
Calyptomena viridis Pitta angolensis
Order Passeriformes Acanthisitta chloris 8 in (20 cm) 8 in (20 cm)
31⁄2 in (3 cm)
By far the largest order of birds, all
passerines have four unwebbed toes with
three pointing forward, one backward.
They are otherwise hugely variable in size,
form, color, behavior, and habitat. Known
as the perching birds, they form two varied
suborders. The smaller group, the sub-
oscine passeriformes, has 12 families,
and the larger, the oscines, often called
songbirds, has 70 families. Some songbirds,
such as the crows, are not very musical,
while others, such as the Australasian
lyrebirds, Old and New World thrushes, and
various chats, including the nightingale, are
among the world’s finest songsters.

Barred antshrike

Thamnophilus doliatus
61⁄2 in (16 cm)

Three-wattled bellbird Sharpbill Eastern kingbird
Procnias tricarunculatus Tyrannus tyrannus
10–12 in (25–30 cm) Oxyruncus cristatus 8 in (20 cm)
61⁄2 in (17 cm)

Blue manakin Buff-fronted foliage-gleaner Wedge-billed woodcreeper SUPERB LYREBIRD
Chiroxiphia caudata Philydor rufum. 71⁄2 in (19 cm) Despite its extraordinary appearance, the lyrebird
5 in (13 cm) Glyphorynchus spirurus (Menura novaehollandiae ) is elusive. It is known for
51⁄2 in (14 cm) its remarkable mimicry of natural and artificial sounds.

Red-backed fairy-wren Blue-faced honeyeater Brown thornbill Grey-chinned minivet
Malurus melanocephalus Entomyzon cyanotis Acanthiza pusilla
4–5 in (10–13 cm) 12 in (31 cm) 4 in (10 cm) Pericrocotus solaris
71⁄2 in (19 cm)

Lesser grey shrike Tawny-crowned greenlet Eastern black-headed oriole
Lanius minor 71⁄2–8 in (19–20 cm) Hylophilus ochraceiceps 41⁄2 in (11.5 cm) Oriolus larvatus 81⁄2 in (22 cm)

65 BIRDS

Magpie-lark Carrion crow Blue jay
Cyanocitta cristata
Grallina cyanoleuca Corvus corone 12 in (30 cm)
111⁄2 in (29 cm) 201⁄2 in (52 cm)

Scarlet robin White-necked picathartes Bohemian waxwing Greater bird-of-paradise
Bombycilla garrulus 61⁄2 in (17 cm) Paradisaea apoda
Petroica boodang Picathartes gymnocephalus 14 in (35 cm)
43⁄4–51⁄2 in (12–14 cm) 151⁄2–191⁄2 in (39–50 cm)

Palmchat Blue tit Bank swallow Eurasian skylark
Dulus dominicus Parus caeruleus 41⁄2 in (12 cm)
7 in (18 cm) Riparia riparia Alauda arvensis
41⁄2 in (12 cm) 7–71⁄2 in (18–19 cm)

Red-whiskered bulbul Dartford warbler Red-billed leiothrix
Pycnonotus jocosus Leiothrix lutea
8 in (20 cm) Sylvia undata 6 in (15 cm)
41⁄2–5 in (12–13 cm)

Bearded tit Asian fairy-bluebird Cape white-eye Winter Wren
Zosterops pallidus 41⁄2 in (11 cm)
Panurus biarmicus Irena puella Troglodytes troglodytes
41⁄2–6 in (12–15 cm) 101⁄2 in (27 cm) 31⁄2–4 in (9–10 cm)

ANIMAL KINGDOM 66 Common starling

Sturnus vulgaris
81⁄2 in (21 cm)

Eurasian nuthatch Eurasian treecreeper Northern mockingbird
Sitta europaea Certhia familiaris Mimus polyglottos
4–8 in (10–20 cm) 5 in (12.5 cm) 9–11 in (23–28 cm)

Song thrush Rufous-gorgetted flycatcher Scarlet-chested sunbird
Turdus philomelos Chalcomitra senegalensis 6 in (15 cm)
9 in (23 cm) Ficedula strophiata
51⁄2 in (14 cm)

House sparrow Java sparrow Dunnock Richard’s pipit

Passer domesticus Lonchura oryzivora Prunella modularis Anthus richardi
51⁄2 in (14 cm) 51⁄2–6 in (14–15 cm) 51⁄2 in (14 cm) 61⁄2–8 in (17–20 cm)

Eurasian bullfinch Hooded warbler Bullock’s oriole
Pyrrhula pyrrhula Wilsonia citrina 51⁄2 in (14 cm)
6 in (15 cm) Icterus bullockii
81⁄2 in (21 cm)

Snow bunting Green honeycreeper Northern cardinal
Chlorophanes spiza 51⁄2 in (14 cm) Cardinalis cardinalis 81⁄2 in (22 cm)
Piectrophenax nivalis
61⁄2 in (16 cm)

BEARDED TIT 67
Related to Asian parrotbills rather than
true tits, the bearded tit (Panurus biarmicus )
is usually confined to reed beds. When
numbers are high in fall, some disperse
in search of new sites and may be seen
in cattails or other marsh plants.

68

VERTEBRATES MAMMALS LIVE-BEARING MAMMALS PLACENTAL MAMMALS
Page 36
Mammalia Characteristics of this group include a lower Theria Mammals that produce live young, at various Placentalia Live-bearing mammals with young that develop
jaw comprising a single bone, and skin that contains glands stages of development. This group includes both the in the uterus attached to a placenta which allows nutrients
(including mammary glands) and is usually covered with hair. and waste to pass between a mother and her offspring.
placental and marsupial (pouched) mammals.
ANTEATERS,
AMERICAN BANDICOOTS ARMADILLOS,
OPOSSUMS Peramelemorphia AND SLOTHS
Didelphimorphia Species 21
Xenarthra
Species 87 Species 31

EGG-LAYING MAMMALS MARSUPIALS LAURASIATHERIANS

Prototheria The only mammals that reproduce by laying Marsupialia Live-bearing mammals that have a pouch Laurasiatheria The most diverse group of placental
soft-shelled eggs. Their body temperature is maintained (marsupium) in which the young are nurtured on milk to mammals, ranging from whales to bats, cats
to rhionoceroses.
at a lower level than that of most other mammals. complete their development.

PLATYPUS AND ECHIDNAS KANGAROOS AND 4 OTHER
Monotremata RELATIVES ORDERS
Species 5 Diprotodontia
Species 80
Species 143

BATS HEDGEHOGS
Chiroptera AND SHREWS
Species 1,116 Eulipotyphla

SKUNKS Species 452
Mephitidae
Species 12

RACCOONS WEASELS RED PANDA CIVETS PANGOLINS
Procyonidae Mustelidae Ailuridae Viverridae Pholidota
Species 14 Species 67 Species 1 Species 35 Species 7

WALRUS TRUE SEALS CARNIVORES MALAGASY CATTLE AND CAMELS AND
Odobenidae Phocidae CARNIVORES ANTELOPES LLAMAS
Species 1 Carnivora Mainly meat-eating mammals with Eupleridae Camelidae
Species 19 well-developed canine teeth and powerful cheek teeth Species 8 Bovidae
EARED SEALS Species 4
Otariidae BEARS with a scissorlike action, called carnassials. DEER Species 143
Ursidae Cervidae
Species 16 Species 8 Species 51

MONGOOSES DOGS CATS PIGS EVEN-TOED HOOVED
Herpestidae Canidae Felidae Suidae MAMMALS AND WHALES
Species 35 Species 36 Species 38 Species 19
Cetartiodactyla Laurasiatherians with a uniquely shaped
HYENAS hock bone, known as the astragulus or talus, including the
Hyaenidae
Species 4 terrestrial ancestors of modern whales.

WHALES AND GIRAFFES
DOLPHINS Giraffidae
Cetacea Species 2

Species 84

HIPPOPOTAMUSES
Hippopotamidae
Species 2

Mammal groups

The primitive egg-laying mammals were the first group to and sizes we see today. Although many of the traditional
diverge, followed by the marsupials. The placental mammals mammal groups, such as primates and carnivores, appear
divided into three broad groups, the laurasiatherians, on this diagram, others are less familiar. These include the
afrotherians, and euarchontoglires, plus the anteaters and even-toed hooved mammals and whales, which have been
relatives, before evolving into the diverse array of forms combined quite recently using genetic and fossil evidence.

AFROTHERIAN MAMMALS HYRAXES 69 MAMMALS
Hyracoidea
Afrotheria A group representing an ancient radiation Species 4 ELEPHANTS
of African mammals. Now diversified, they bear little Proboscidea
SEACOWS Species 3
outward resemblance to one another. Sirenia
Species 5

RABBITS AND PIKAS
Lagomorpha
Species 92

TENRECS AND AARDVARK RATS AND MICE
GOLDEN MOLES Tubulidentata Muroidea
Species 1
Afrosoricida Species 1,518

Species 51

ELEPHANT SHREWS BEAVERS GOPHERS
Macroscelidea Castoridae Geomyidae
Species 15 Species 2 Species 40

EUARCHONTOGLIRES RODENTS

Euarchontoglires A group of placental mammals Rodentia Gnawing mammals with a single pair of incisor
that combines rodents and rabbits with primates, tree teeth in the upper and lower jaws that are open-rooted and

shrews, and colugos. grow throughout life.

HORSES TAPIRS TREE SHREW CAVIES, 11 OTHER
Equidae Tapiridae Scadentia CHINCHILLAS, FAMILIES
Species 4 AND VISCACHAS
Species 8 Species 20 Species 184
COLUGOS Caviomorpha
Dermoptera
Species 235
Species 2
SQUIRRELS
Sciuridae

Species 278

ODD-TOED HOOVED
MAMMALS

Perissodactyla Plant-eating mammals with an odd
number of weight-bearing toes. Cellulose-digesting

bacteria are housed in the hind gut.

RHINOCEROSES
Rhinocerotidae
Species 5

LEMURS BUSH BABIES
Lemuriformes Galagidae
Species 17
Species 37

LORISES AND PRIMATES
RELATIVES
Lorisidae Primates Mammals with grasping extremities,
Species 7 binocular vision, and large brains.

TARSIERS MARMOSETS, HUMANS, APES,
Tarsiidae TAMARINS, AND NEW AND OLD WORLD
Species 5 MONKEYS
WORLD MONKEYS
Catarrhini
Platyrrhini
Species 153
Species 128

ANIMAL KINGDOM 70 Mammals fat. Milk-producing mammary glands are also
found only in mammals. The milk provides
Despite their relatively late appearance in the fossil record, mammals have nourishment to offspring, removing the need to
diversified into an astonishing array of shapes and sizes. They are most expend energy on foraging, and initially contains
diverse and widespread on land, but have also colonized air and water. antibodies, which protect infants from disease.

About 5,000 species of mammal have been insulate the body. Mammals also have skin Key characters
described, ranging from the egg-laying duck- glands, among which are sebaceous glands
billed platypus to humans with their sophisticated that allow sweating. Mammals are endothermic, The only characters that can identify all mammals,
brain and hand dexterity, but there are similarities which means that they maintain a constant whether extant (living) or fossil, are skeletal—
that unite them all in the class Mammalia. body temperature—often above that of their among these are the possession of a single
Mammals uniquely possess fur, which protects surroundings—by producing heat through bone in the lower jaw (dentary) and having
delicate skin, provides camouflage, and helps metabolic processes, such as breaking down three bones (incus, stapes, and malleus) in the
middle ear. Any one of these features identifies
an animal as a mammal and separates it from all
other living things.

Monotremes Duck-billed platypus Short-beaked echidna
Ornithorhynchus anatinus Tachyglossus aculeatus 12–171⁄2 in (30–45 cm)
Order Monotremata 16–24 in (40–60 cm)

All other mammals produce live young,
but monotremes lay soft-shelled eggs,
which hatch after a short incubation
period. Monotremes have only a single
posterior opening, called the cloaca, into
which the urinary, alimentary, and
reproductive systems open.

Marsupials Virginia opossum Tasmanian devil Common brush-
Didelphis virginiana Sarcophilus harrisii tailed possum
Supercohort Marsupialia 15–20 in (38–50 cm) 28–42 in (70–110 cm) Trichosurus vulpecula
14–23 in (35–58 cm)
These are the so-called pouched mammals, although not all of Feather-tailed possum
the species have one. The offspring are born after a very limited Red-necked wallaby
gestation period, and then make their way to the pouch. Born Distoechurus pennatus Macropus rufogriseus
in almost embryonic form, the young attach to a nipple and 41⁄2–51⁄2 in (10.5–13.5 cm) 28–41 in (70–105 cm)

suckle milk while completing their development.
Marsupialia is divided into seven orders, including:
American opossums (Didelphimorphia);
bandicoots and bilbies (Paramelemorphia);
and koalas, kangaroos, wombats,
and possums (Diprotodontia).

Greater glider
Petauroides volans
14–19 in (35–48 cm)

Rufus bettong Common wombat
Aepyprymnus rufescens 141⁄2– Vombatus ursinus 28–47 in (70–120 cm)
201⁄2 in (37–52 cm)
HONEY POSSUM
Koala Red kangaroo This tiny Australian marsupial (Tarsipes rostratus )
Phascolarctos cinereus is only 21⁄2–31⁄2 in (6.5–9 cm) long, and gathers
26–31 in (65–78 cm) Macropus rufus pollen and nectar (“honey”) from flowers.
31⁄4–51⁄4 ft (1–1.6 m)

Quokka

Setonix brachyurus
16–211⁄2 in (40–54 cm)

Tenrecs and Elephant shrews Aardvark Hyraxes 71 MAMMALS
golden moles (Sengis)
Order Tubulidentata Order Hyracoidea
Order Afrosoricida Order Macroscelidea
This monospecific order comprises These species have a unique eye
This recently recognized group is chiefly Elephant shrews, or sengis, are only the long-eared, long-snouted structure. A part of the iris projects
supported by genetic evidence, but there characterized by a long, highly mobile aardvark. Unlike most other mammals, over the pupil. This has the effect of
are some features of the dentition that are snout, an enlarged cecum (a pouch its teeth lack an outer coating of enamel reducing the amount of overhead light
characteristic. Afrosoricids have only one connected to the large intestine) in the and are covered instead with cementum, entering the eye.
major cusp on each of the upper molars; hind gut, and cheek teeth the same tissue that coats tooth roots.
other placental mammals have several. that can grow Rock hyrax
throughout life Aardvark Procavia capensis
since they Orycteropus afer 21–23 in (30–58 cm)
have open 51⁄4 ft (1.6 m)
roots.

Common tenrec Rufous elephant shrew
Tenrec ecaudatus 10–151⁄2 in (25–39 cm) Elephantulus rufescens 41⁄2–5 in (12–12.5 cm)

Elephants Dugongs and West Indian manatee
manatees Trichechus manatus
Order Proboscidea 81⁄4–143⁄4 ft (2.5–4.5 m)
Order Sirenia
An elephant can be easily recognized by its large size, Dugong
columnar legs, and long trunk. The incisor teeth are modified These large, slow-moving creatures Dugong dugon
into continually growing tusks of dentine, while the molar are streamlined for their aquatic lifestyle. 81⁄4–13 ft (2.5–4 m)
teeth—of which there are six in each half of the upper and lower Sirenian forelimbs are modified into
jaws—erupt at the back of the jaw and migrate forward in a flippers, while the hindlimbs have been
conveyer-belt-like fashion over about 60 years. The large head entirely lost. Instead there is a horizontal,
is made lighter by the presence of air pockets in the skull. spatula-like tail. Manatees have only six
neck vertebrae compared to the seven
found in most other mammals. Entirely
herbivorous, sirenians have unusually long
guts, with bacteria for the digestion of
cellulose. This bacteria is housed in the
cecum in the hind portion of the gut, as
it is in horses. They are the only marine
mammals that feed purely on plants.
Cheek tooth replacement is similar to
that of the elephant.

African elephant Anteaters and relatives

Loxodonta africana Orders Pilosa, Cingulata
13–161⁄2 ft (4–5 m)
The order Pilosa comprises anteaters and sloths, and
the order Cingulata contains the armadillos. Both groups Two-toed sloth
are unique in having a double vena cava vein in the Choloepus didactylus
lower part of the body and additional moving joints, or 18–34 in (46–86 cm)
articulations—called xenarthrales—on the lower lumbar
vertebrae. The two groups can easily be separated
because the armadillos have an armored upper body
whereas anteaters and sloths have fur.

Armadillo Southern tamandua Silky anteater
Tamandua tetradactyla 21–35 in (53–88 cm)
Dasypus sp. Cyclopes didactylus
12–151⁄2 in (30–40 cm) 61⁄2–81⁄2 in (16–21 cm)

Asian elephant Giant anteater
Elephas maximus 111⁄2 ft (3.5 m)
Myrmecophaga tridactyla
31⁄4–61⁄2 ft (1–2 m)

ANIMAL KINGDOM 72 Rodents Canadian beaver Gray squirrel Alpine marmot
Castor canadensis Sciurus carolinensis
Order Rodentia 29–35 in (74–88 cm) 9–12 in (23–30 cm) Marmota marmota
191⁄2–211⁄2 in (50–55 cm)
These are the gnawing mammals. Most are small, but all have
characteristic teeth. Rodents have a single pair of continually
growing incisor teeth in the upper and lower jaws that are sharpened
as the lower ones sheer against the inside of the upper ones. Canine
teeth are absent, leaving a gap called the diastema. Many species
have broad, ridged cheek teeth, which are effective in grinding up
vegetation, but some rodents are carnivorous. The cavylike
rodents can be separated from the other rodents on the basis
of their jaw musculature and longer gestation periods that lead
to the birth of smaller numbers of well-developed offspring.

Springhare

Pedetes capensis
101⁄2–151⁄2 in

(27–40 cm )

Spiny mouse Striped grass mouse Malagasy giant rat
Acomys cilicius 61⁄2–7 in (17–18 cm) Hypogeomys antimena 12–14 in (30–35 cm)
Lemniscomys striatus
4–51⁄2 in (10–14 cm)

Brown rat Bank vole Red vole
Clethrionomys glareolus 31⁄4–41⁄2 in (8–11 cm) Clethrionomys rutilus 31⁄4–41⁄2 in (8–11 cm)
Rattus norvegicus
81⁄2–111⁄2 in (21–29 cm)

Forest dormouse Four-toed jerboa

Dryomys nitedula Allactaga tetradactyla
31⁄4–5 in (8–13 cm) 4–41⁄2 in (10–12 cm)

North American porcupine
Erethizon dorsatum
26–31 in (65–80 cm)

Long-tailed chinchilla Cape porcupine Naked mole-rat Capybara
Chinchilla lanigera 81⁄2–9 in (22–23 cm) Hystrix africaeaustralis 191⁄2 in (50 cm)
Heterocephalus glaber Hydrochoerus hydrochaeris
51⁄2–7 in (14–18 cm) 31⁄2–41⁄4 ft (1.1–1.3 m)

Rabbits, hares, and pikas Hispid hare North American pika
Caprolagus hispidus Ochotona princeps 61⁄2–81⁄2 in (16–22 cm)
Order Lagomorpha 15–191⁄2 in (38–50 cm)

These are herbivorous mammals that gain maximum Rabbit
nutrients from food by ingesting it twice, a behavior called Oryctolagus cuniculus
coprophagy. Rabbits and pikas also have very distinctive 14–191⁄2 in (35–50 cm)
upper incisor teeth, with a pair of small, nonfunctional,
peglike incisors behind the functional pair. Like rodents, they
lack canines, which creates a large gap through which the
lips can be drawn to prevent debris from entering the mouth
while feeding.

Primates Ring-tailed lemur 73 MAMMALS

Order Primates Lemur catta
151⁄2–18 in (39–46 cm)
Members of this order are characterized by an opposable thumb
or toe and the ability to rotate the lower arm bones (radius and Slender loris
ulna) around one another. These features allow primates to grasp
and manipulate objects. The order is generally subdivided. The Loris tardigradus
lemurs, galagos, and lorises form the strepsirhines, which depend 61⁄2-10 in (17–26 cm)
more on their sense of smell than do monkeys and apes. They
generally have longer snouts, a glandular (and therefore moist) and
naked nasal region, and comma-shaped nostrils. The tarsiers,
marmosets, monkeys, and apes form the second group, the
haplorhines, which have dry noses with ovate nostrils.

Senegal bushbaby
Galago senegalensis 6–61⁄2 in (15–17 cm)

Gray woolly monkey Red howler monkey Bolivian squirrel monkey
Alouatta seniculus
Legothrix cana 20–25 in (51–63 cm) Saimiri boliviensis
191⁄2–26 in (50–65 cm) 101⁄2–121⁄2 in (27–32 cm)

Golden lion tamarin
Leontopithicus rosalia
8–10 in (20–25 cm)

Patas monkey

Erythrocebus patas
231⁄2–35 in (60–88 cm)

Black and white colobus monkey Proboscis monkey Gelada
Nasalis larvatus 29–30 in (73–76 cm) Theropithecus gelada 28–29 in (70–74 cm)
Colobus guereza
201⁄2–221⁄2 in (52–57 cm) Lar gibbon
Hylobates lar 161⁄2–23 in (42–59 cm)

Western gorilla
Gorilla gorilla
41⁄4–61⁄4 ft (1.3–1.9 m)

Mandrill De Brazza’s monkey
Mandrillus sphinx
25–32 in (63–81 cm) Cercopithecus neglectus
191⁄2–23 in (50–59 cm)

Chimpanzee

Pan troglodytes
21⁄2–3 ft (0.75–1 m)

Siamang Orangutan
Hylobates syndactylus Pongo pygmaeus 3–3 ft 3 in (0.9–1 m)
35 in (90 cm)

ANIMAL KINGDOM 74 Tree shrews Flying lemurs Insectivores

Order Scandentia Order Dermoptera Order Eulipotyphla

These rather squirrel-like mammals have Flying lemurs, or colugos, are cat-sized, These insect-eating animals
slender bodies and long tails. In the past arboreal mammals. Their distinctive feature have a small brain, which lacks
they have been classified as insectivores is the large gliding membrane, called a the copious infolding found in
and as primates on the basis of characters patagium, which stretches from the neck other mammals. In common with
they have in common with these orders. to the front and hind digits and onto the monotremes and marsupials, they
However, genetic evidence now suggests very tip of the tail. have a cloaca, but unlike them the
that tree shrews are an ancient group with young develop longer in the womb.
an independent evolutionary history. European mole

Talpa europaea
41⁄2–61⁄2in (11–16cm)

Lesser tree shrew

Tupaia minor
41⁄2–51⁄2 in (11.5–13.5 cm)

Malaysian flying lemur European hedgehog Common shrew
Erinaceus europaeus
Cynocephalus variegatus 8–12 in (20–30 cm) Sorex araneus
13–161⁄2 in (33–42 cm) 21⁄4–31⁄2 in (5.5–9 cm)
Lesser mouse-tailed bat
Bats Rhinopoma hardwickei
21⁄4–23⁄4 in
Order Chiroptera (5.5–7 cm)

Bats are the only mammals that are capable of powered flight. Lesser horseshoe bat
Their forelimbs have very long finger bones that support the flight Rhinolophus hipposideros
membrane. Some bats, known as flying foxes, feed only on fruit 11⁄2–13⁄4 in (3.5–4.5 cm)

and nectar. They do not echolocate because they have
excellent vision and sense of smell. Most bats eat insects,
which they locate by emitting ultrasound pulses and
listening to the returning echoes. To pinpoint the
sounds these bats may have large ears with an
additional projection called a tragus.

Rodrigues flying fox
Pteropus rodricensis
14 in (35 cm)

Noctule bat

Nyctalus noctula
21⁄4–31⁄4 in (6–8 cm)

Seba’s short-tailed bat Common vampire bat
Desmodus rotundus 23⁄4–31⁄2 in (7–9 cm)
Carollia perspicillata
2–21⁄2 in (5–6.5 cm)

Daubenton’s bat Whiskered bat Brown long-eared bat Parti-colored bat
Myotis daubentonii Myotis mystacina
13⁄4–21⁄4 in (4.5–5.5 cm) 11⁄2–2 in (3.5–5 cm) Plecotus auritus Vespertilio murinus
11⁄2–2 in (4–5 cm) 2–21⁄2 in (5–6.5 cm)
Pangolins Cape pangolin
Manis temminckii
Order Pholidota 16–28 in (40–70 cm)

Distinctive, overlapping body scales
provide pangolins with a unique protective
armor. Since they feed primarily on ants
and termites, they lack teeth and the lower
jaw is much reduced. With no teeth to grind
up their food, pangolins have a tough,
muscular stomach that does this instead.

Carnivores 75 MAMMALS

Order Carnivora Least weasel Eurasian badger Raccoon
Meles meles Procyon lotor
A predominantly meat-eating group, carnivora includes Mustela nivalis 22–35 in (56–90 cm) 24–36 in (60–100 cm)
terrestrial and aquatic species. The terrestrial carnivores are 61⁄2–91⁄2 in (16.5–24 cm)
characterized by their large canine teeth and specialized
carnassials—last upper premolar and first lower molar—used
for slicing through hide, meat, and bone. In seals and walruses
the limbs are modified into flippers and the teeth are
less specialized because these animals feed on
fish and invertebrates that are swallowed whole.
Since meat is relatively easy to digest, the stomach is simple and
the intestine short. In all carnivores the clavicle bone is lost, or very
reduced, and three of the small bones in the wrist—the scaphoid,
centrale, and lunar bones—have fused to form a scapholunar bone.

Red panda California sea lion Walrus Polar bear
Ailurus fulgens Zalophus californianus
20–25 in (50–64 cm) 7 ft (2.1 m) Odobenus rosmarus Ursus maritimus
93⁄4–113⁄4 ft (3–3.6 m) up to 81⁄4 ft (2.5 m)

Brown bear Sand fox Grey wolf
Canis lupus 1–1.5m (31⁄4–5ft)
Ursus arctos Vulpes rueppellii
51⁄2–91⁄4 ft (1.7–2.8 m) 16–201⁄2 in (40–52 cm)

Cheetah Caracal Tiger
Caracal caracal Panthera tigris
Acinonyx jubatus 24–36 in (60–91 cm) 61⁄2–121⁄4 ft (2–3.7 m)
31⁄2–5 ft (1.1–1.5 m)
Lion
Panthera leo
51⁄2–81⁄4 ft (1.7–2.5 m)

Banded mongoose Meerkat
Mungos mungo 211⁄2–24 in (55–60 cm) Suricata suricatta 10–14 in (25–35 cm)

ANIMAL KINGDOMA 76 Horses, tapirs, African wild ass Brazilian tapir White rhinoceros
and rhinoceroses Equus asinus
61⁄2–71⁄2 ft (2–2.3 m) Tapirus terrestris Ceratotherium simum
Order Perissodactyla 51⁄2–61⁄2 ft (1.7–2 m) 121⁄4–13 ft (3.7–4 m)
Warthog
Odd-toed ungulates are so-called Phacochoerus africanus Collared peccary Hippopotamus
because they bear their weight on either 3–5 ft (0.9–1.5 m) Tayassu tajacu 30–39 in (75–100 cm)
one (equids) or three (rhinoceroses and Hippopotamus amphibius
tapirs) toes. Being plant eaters, they need Guanaco 103⁄4–111⁄2 ft (3.3–3.5 m)
cellulose-digesting bacteria in their guts to Lama glama
break down plant cell walls. These bacteria 3–7 ft (0.9–2.1 m) Dromedary
are housed in the cecum—a blind-ended
sac leading off the small intestine—hence Camelus dromedarius
they are referred to as hindgut digesters. 71⁄4–111⁄4 ft (2.2–3.4 m)

Terrestrial even-toed
ungulates

Order Cetartiodactyla (part)

The order Cetartiodactyla comprises
what used to be recognized as two separate
orders, Artiodactyla (terrestrial even-toed
ungulates) and Cetacea (whales, dolphins,
and porpoises—see opposite). The recent
recognition that these two seemingly
different groups belong together is based
mainly on genetic evidence, but backed up
by some fossil evidence. The land-dwelling
species are known as even-toed ungulates,
because they bear their weight on two toes,
each enclosed in a hoof of keratin. Many
species ruminate—that is they regurgitate
and further chew their plant food. They are
also called foregut digesters, as they have
digestive bacteria in their rumen, the first of
the four chambers of the stomach. A major
food source for the larger carnivores, these
ungulates have laterally situated eyes for
all-round vision and most have elongated
lower legs that enable them to be energy
efficient when running for long periods.

South African giraffe

Giraffa giraffe
121⁄2–151⁄2 ft (3.8–4.7 m)

Alpine musk deer Red deer Okapi
Moschus chrysogaster Okapia johnstoni 61⁄2–71⁄4 ft (2–2.2 m)
28–39 in (70–100 cm) Cervus elaphus
5–61⁄2 ft (1.5–2 m)

American bison Scimitar-horned oryx Mouflon
Oryx dammah 41⁄2–73⁄4 ft (1.4–2.4 m)
Bison bison Ovis musimon
7–111⁄2 ft (2.1–3.5 31⁄2–41⁄4 ft (1.1–1.3 m)

Whales, dolphins, and porpoises 77 MAMMALS

Order Cetartiodactyla (part) Ganges river dolphin Franciscana
Pontoporia blainvillei
These mammals are perfectly adapted to an aquatic lifestyle, Platanista gangetica 41⁄4–51⁄2 ft (1.3–1.7 m)
having streamlined bodies with flippers for forelimbs and a large 7–81⁄4 ft (2.1–2.5 m)
tail fluke instead of legs. The skeleton is much reduced, serving Dall’s porpoise
mainly for muscle attachment, and the neck vertebrae may be Phocoenoides dalli
fused. The whales and dolphins can be divided into two groups— 71/4–73/4 ft (2.2–2.4 m)
those with teeth and those without. The giant baleen whales filter
feed, trapping food particles in two huge baleen plates that hang Pygmy sperm whale
down from the sides of the upper jaw. Most toothed whales are Kogia breviceps 83/4–93/4 ft (2.7–3 m)
smaller and some can echolocate to find food.
Gray whale
Common dolphin Killer whale Eschrichtius robustus
Orcinus orca up to 26 ft (8 m) 43–49 ft (13–15 m)
Delphinus delphis
71⁄2–81⁄2 ft (2.3–2.6 m) Bryde’s whale
Balaenoptera edeni
Commerson’s dolphin Harbour porpoise 30–511⁄2 ft (9–15.5 m)
Cephalorhynchus commersonii Phocoena phocoena 41⁄2–61⁄2 ft (1.4–2 m)
41⁄2–51⁄2 ft (1.4–1.7 m)
Sperm whale
Narwhal Physeter catodon
Monodon monoceros 36–66 ft (11–20 m)
13–143⁄4 ft (4–4.5 m)
Northern bottlenose whale
Cuvier’s beaked whale Hyperoodon ampullatus
Ziphius cavirostris 20–33 ft (6–10 m)
23–25 ft (7–7.5 m)

Humpback whale
Megaptera novaeangliae
46–59 ft (14–18 m)

Northern right whale Pygmy right whale
Eubalaena glacialis Caperea marginata
43–56 ft (13–17 m) 18–21 ft (5.5–6.5 m)

ANIMAL



ARMORED SUPPORT
Up to 25 percent of a crab’s total weight may be
its “shell.” This is not simply an outer protective

casing, it is also its skeleton—a complex set
of supporting structures linked at flexible joints,
enclosing and moved by intricate sets of muscles.

SKELETONS AND MUSCLES 81 SKELETONS AND MUSCLES

Most members of the animal kingdom possess some kind of strong body
framework, and pulling devices with which to move it. Although the principles
and detailed structure of muscles are virtually constant across all major groups
of animals, types of skeletons show huge variety in design and construction.

Movement and structure EXTENSION

Muscle tissue is the primary means of movement in almost all animals, biceps contracts biceps relaxes
except for sponges, allowing an animal to implement its behaviors and triceps relaxes
actions. Muscle is often the most plentiful tissue in the body, and it has one triceps contracts
basic function: to shorten, or contract. As it does so, it moves parts of the FLEXION
skeleton or other body structures. Muscles power not only the movements OPPOSITE CONTRACTION
visible on the outside, they are also the basis of internal activities, such as Two muscles in a vertebrate forelimb
the pumping of the heart. For invertebrates with a hard outer framework, demonstrate a simple antagonistic
system, where each muscle opposes
or exoskeleton, most muscles are positioned on the pull of the other. If both muscles
the inside and attached to the skeleton’s inner walls. exert tension, the joint can be held
In vertebrates, the situation is reversed, with the steady in any position through its range.
muscles attaching to the outside of the endoskeleton.
In soft-bodied animals like worms, muscle tissue teams. In the simplest arrangement, one muscle pulls a skeletal element
forms its own fluid-pressurized “water skeleton.” or body part one way, while its opposing partner on the other side relaxes.
To move the part the other way, the opposing muscle contracts while the
tendon attaches first muscle relaxes. However, this two-way action is given greater range
muscle to bone since there are usually several muscles involved, attached to the skeleton
at varying places and angles, to give differing lines of pull. This allows for
main part of muscle (also movement with close control in several directions.
called belly of muscle)

MUSCLE FIBERS Joints
This scanning electron
micrograph (SEM) of a Most animals have a skeleton or similar framework made up of numerous
skeletal muscle shows parts, which move in relation to each other at joints. In arthropods, the
striations (bands) of joints are relatively simple thinnings of the exoskeleton. The cuticle
muscle fibers. forms a flexible articular membrane, but the harder, rigid layers of
chitin or mineralization are almost absent. In most
perimysium (sheath) epimysium (sheath of connective vertebrates, the bones of the skeleton are covered
fascicle tissue covering entire muscle) in their joints by cartilage, which reduces friction and
wear. The joint is enclosed in a joint capsule, inside
myofiber COMMON STRUCTURE which there is a lubricating liquid, synovial fluid, to
A vertebrate muscle is attached to the skeleton, further reduce rubbing. Strong, stretchy ligaments
myofibril are attached to the bones and allow the joint to flex.
usually at each end, and consists of bundles
(fascicles) of muscle fibers (myofibers). Each

fiber is composed of perhaps thousands of
thinner muscle fibrils (myofibrils).

Muscle arrangement extensor muscle FLEXIBLE JOINTS
The frog’s tiny joints
A typical mammal has more than 600 individual muscles, while some flexor muscle have a greater range
insects have three times that number. The inner structure of a typical
muscle is based on cellular components known as muscle fibers or cuticle of movement than
myofibers. In larger animals, some myofibers exceed 3 ft 3 in (1 m) in articular invertebrate joints.
length, yet each is thinner than a human hair. Contraction occurs when membrane
bundles of overlapping protein filaments in the fibers slide past each other. bone marrow
Because muscles only contract and pull, they are arranged in opposing bearing surface bone
or pivot ligaments
INVERTEBRATE MUSCLES muscle connecting joint capsule
In arthropods the muscle structure segments INVERTEBRATE synovial
can be quite similar to that of JOINT membrane
vertebrates, but the arrangement muscle for changing POINTS OF MOVEMENT synovial fluid
differs in that the muscles connect shape of segment The exoskeleton is flexible at an invertebrate joint, cartilage
to the inner walls of the exoskeleton. and the shape of the bearing surfaces usually
muscle for moving leg allows movement in only one plane or direction. In VERTEBRATE JOINT
a vertebrate joint, a thin layer of synovial fluid helps
prevent friction between the connecting bones.

SKELETONS AND MUSCLES 82 Water skeletons

Fluid-based skeletons are found in a huge variety of invertebrates,
especially worms and similar “soft-bodied” animals. Far from being
soft and floppy, many of these can become rigid and resistant when
muscular action compresses fluid inside an animal’s body.

Support LIMITED MOVEMENT
Most nematode worms, such as this parasitic
An animal’s hydrostatic skeleton, or hydroskeleton, employs similar principles PULSES FOR SWIMMING roundworm, have only longitudinal muscles
to hydraulic systems in machinery. In animals, a liquid in some sort of chamber Muscle fibers compress fluid within a in the body wall. As these contract on each
or container is pressurized by contraction of the muscular walls around it. jellyfish’s main body, causing contractions side alternately, they produce characteristic
The liquid is the internal body fluid of the animal. Its compression makes the C- or S-like thrashing movements.
structure become hard and rigid, forming a firm skeletal unit. The skeleton to run from the center of the bell to its
then gives support and protection to the animal’s body parts. In simpler edges. This produces a pulsing epidermis cuticle
animals the whole body covering acts as the hydroskeleton. In more movement for swimming.
complex ones, especially segmented (annelid) worms, the pressure
can be limited to selected body compartments.

edge of gastric pouch

ring canal

mucosa

alimentary canal

visceral circular muscle
peritoneum longitudinal muscle

coelem

SEGMENTED WORM ANATOMY
Each worm segment has a set of circular
muscles around it. Some longitudinal muscles
span a segment, while others run along many
segments. This allows the worm to stretch
some parts, while shortening others.

Movement

In a hydroskeleton, changes in muscle tone and the

arrangement of muscles can alter the pressure within

its chambers, thereby changing the skeleton’s shape,

and causing the structure to become rigid. This

provides a stiff base against which movements can

occur, and also produces the movements themselves.

bell In many worms, for example, there are two layers

upper of muscle in the outer body wall: ringlike circulars;
edge of
stomach and strap-shaped, longitudinal (lengthwise) muscles.

stomach gonad Contraction of circular muscles squeezes the body,

making it longer and thinner; longitudinal muscle

contraction makes it shorter and fatter; and when

Octopus suckers are able Sea cucumber tentacles rely Coral polyps use muscle fibers in Anemone tentacles bend to the BENDY APPENDAGES both sets contract, the body
the stalks to “lean” in any direction. side on which the muscle contracts. Apart from whole body becomes tense, stiff, and rigid.
movements, hydrostatic Other combinations of contractions
and hydraulic principles permit further movements. If the
can also be used to longitudinal muscles along one
move smaller body side shorten, the body curves
parts or individual to that side. Using such a system
appendages. Such of contractions, burrowing
movements allow earthworms are able to push
animals to perform tasks their way between tightly packed
such as self defense
and capturing prey.

to grasp objects firmly. on internal pressure. soil particles with great force.

Horny skeletons 83 Horny skeleTons

“Horny” describes substances that are strong, tough, and resilient, yet which sticky feet
can also be slightly compressed and flexed. In arthropods, the main horny A jumping spider has two
substance is chitin. This forms the basis of the outer body covering or cuticle,
which is the main component of the animal’s exoskeleton. foot claws and a pad of
tufted hairs that are formed
Tough exoskeleton by tiny, supple extensions of
the cuticle. These can stick
Chitin is light, strong, translucent, and pliable, and to a wide variety of surfaces.
has been compared to plastic. The substance is
chemically a polysaccharide (carbohydrate), consisting
of glucoselike sugar units. In most land arthropods
chitin is accompanied by various proteins, the
molecules of which may take many shapes, including
fibrous, sheetlike, and helical. Many hundreds of
these proteins are known in the insect group alone.
In some aquatic arthropods, such as crabs and
other crustaceans, the chitin and protein are
accompanied by minerals, especially
chalky crystals of calcium carbonate.
These make the exoskeleton or
shell harder for protection. It also
makes it heavier—which is of
less hinderance to aquatic
animals whose weight is
supported by water—
and consequently also
more brittle and liable
to fracture.

new armor many segments make spiny bristles deter Structure and layering
A spider crab’s heavily up caterpillar’s body predators
mineralized shell is hard A typical cuticle has several main layers. The outermost layer, the epicuticle,
and rigid, except for a caterpillar’s thinned body
where it thins at the cuticle allows each segment
joints. During the few to flex and change shape.
hours after each molt,
the soft new cuticle forewings modified
enlarges rapidly before it as rear-wing covers
hardens. At this time the
crab hides away because a rhinoceros beetle’s
of its increased vulnerability “horn” is formed from
until its new shell is ready. thickened, stiff cuticle.

thorax

head

is the barrier to the outside world—repelling microbes, coping with physical
wear, and reducing water loss. The procuticle is formed from chitin fibers
and mineral crystals embedded in a variable matrix of proteins. Neither of

these layers contains living cells. The epidermis beneath these is the layer
of living cells that manufactures the top two layers. Under the epidermis,
the basement membrane forms a firm support with fibers of the protein

a wasp has a typical insect collagen. The relative epicuticle
exoskeleton—with a head, proportions, compositions,
abdomen thorax, and abdomen. and strengths of these exocuticle
platelike
cuticle layers vary between
arthropod species, and
also on different body parts.

cuticle endocuticle dermal
gland cell
The procuticle layer is divided into the
epidermis
hardened exocuticle, which has many basement
membrane
compacted fibers, and the more flexible

wood lice are terrestrial crustaceans endocuticle. Dermal glands in the
with a shieldlike segmented
exoskeleton for protection. epidermis can produce chemical

repellents to deter predators.

SKELETONS AND MUSCLES 84 Chalky skeletons

The bodies of some invertebrates are supported by chalky frameworks.
These can take two forms. Mollusks, such as snails, tend to have shell-like
coverings, while echinoderms (including starfish and sea urchins) are
more likely to have what can be termed a true skeleton. In both groups,
a distinctive feature of their structure is calcium carbonate, the main
constituent of rocks such as chalk and limestone.

Composition CALCIUM DIET BRITTLESTARS
This triton trumpet is seen feeding on a crown-of- The flexible arms of the snake starfish,
Chalky body structures are usually laid down in the form of calcium crystals thorns starfish. The shell of this sea snail is made a type of brittlestar, writhe like worms
embedded in a matrix, which is usually protein based. Calcium carbonate of calcium carbonate, which it gets from its diet because their ossicles are loosely bound
may be joined by allied minerals such as calcium phosphate, magnesium and the surrounding seawater. into the pliable body wall.
carbonate, and silicates. Also, calcium carbonate itself crystallizes in a variety
of forms, such as angled, prismlike calcite and more rectangular aragonite.
Marine mollusks tend to have calcite crystals, while argonite is more common
in terrestrial mollusks, such as land snails. The predominant material in
echinoderm skeletons is calcite, whose crystals tend to lie in the same
orientation within each of the small skeletal elements, called ossicles. These
are almost bony in texture, being hard and stiff, and spongy rather than solid.

SPINY SKELETON
Echinoderm means “spiny skin,” as
exemplified by the crown-of-thorns
starfish, shown here feeding at
night on coral in the Red Sea.

ossicle plate ball-and- 85 CHALKY SKELETONS
anus socket joint

Echinoderms spine mouthparts

The standard echinoderm arrangement is a thick outer

body layer containing many embedded calcium-based

ossicles. These vary greatly in shape and size—from

microscopic to palm-sized, depending on not only the

species but also on the body part concerned. This

type of skeletal structure is technically defined as an

endoskeleton since it is not produced by the outermost spine tube feet (cover
body layers. But it functions as an exoskeleton because gonad whole body)
it encloses the main body parts. In urchins the skeletal

plates are large and locked together to form a rigid ossicle plate
covering. In more flexible types

of echinoderms, such as sea SEA URCHIN water OSSICLES AND SPICULES
cucumbers and brittlestars, The inflexible ball-shaped skeleton of a sea vascular This microscope image shows a collection of sea
the ossicles are embedded urchin is known as a test. Joints attach the canal cucumber ossicles (shaped like sheets, wheels,
in a matrix of proteins and spines to the test. The waving tube feet, spines, buckles, and crosses) and silica-based
other substances. part of the water vascular system, protrude slivers (called spicules) from a sponge’s skeleton.
through small holes in the plates.

Mollusks

A mollusk shell is secreted by a gland in the mantle, which
is the animal’s fleshy, cloaklike body covering. Shell form

varies hugely, with segmentlike plates in chitons; two-part
shells in bivalves, such as mussels and clams; a winding
helix in gastropods; and a much reduced internal structure

in cephalopods, such as squid, or no shell at all in

octopuses. The shell includes a thick central layer, the

ostracum, itself composed of two SHELL SHAPES CHITON SHELL
layers of calcium carbonate crystals. The nautilus adds
CALCIUM CARBONATE On the outside of the ostracum is the inner walls, or septa,
The highly magnified protein-rich periostracum that protects to its shell, and lives
ostracum of an abalone the calcium carbonate layers of the in the last, largest
shell reveals layers of ostracum from dissolving or chemical chamber. Chitons, or
overlapping, platelike attack. The innermost shell layer coat-of-mail shells, have
aragonite crystals. is the aragonite-rich hypostracum, eight sectional plates
and a surrounding
girdle “skirt.” Murex

which in some mollusks has a lustrous shells are among the NAUTILUS SHELL MUREX SHELL
sheen and is commonly known as most complex of jaw shell
mother-of-pearl, or nacre. gastropods and of
all mollusk shapes.

coiled shell hinge mantle
ligament
mantle tentacle

feeding
arm

shell

foot
foot

GASTROPOD BIVALVE SQUID mantle cavity
A snail shell gradually grows in diameter A bivalve shell grows as the soft, fleshy A squid’s shell is wholly internal
as new material is added, and its size mantle adds new carbonates and other and known as a pen. It is thin,
reflects the snail’s age and food supply. substances around the edge. lightweight, and pliable.

INTERNAL SUPPORT
A squid’s internal shell serves as an endoskeleton,
helping the body stay relatively stiff and giving
the muscles of its water-jet propulsion system
a firm base for their contractions.

SKELETONS AND MUSCLES 86 Bony skeletons CARTILAGE SKELETON
Sharks, skates, and rays have skeletons, but
Most vertebrate animals have an internal framework (or endoskeleton) these are made mainly of cartilage rather than
consisting chiefly of the hard, mineralized tissue known as bone. It is heavier bone. As a result, swimming is more
divided into the axial skeleton and the appendicular skeleton. The axial energy-efficient.
skeleton runs along the middle axis of the body, from head to tail. The
appendicular consists of the bones attached to the axial skeleton. thoracic vertebrae

cervical vertebrae

cranium

maxilla

axis
atlas

upper scapula
canine sternum

lower canine mandible

HARD AND SOFT Bone and cartilage humerus
Under a bone’s outer hard ulna
layer, cancellous bone tissue Bone is a complex tissue, composed of mineral crystals (mainly
(above) has many tiny calcium phosphates) along with fibrous proteins, principally radius
chambers. Cartilage (here collagen, embedded in a ground tissue or matrix of carbohydrates,
colored green) is light and salts, and other substances. It is continually maintained by cells
pliant, forming support for known as osteocytes, which can also repair damage, such as
body parts such as the ears. fractures. A typical bone has a dense, hard outer layer of
compact bone tissue; a layer of cancellous bone tissue beneath
this, which is more spongy or honeycomb-like; and a central
cavity of jellylike marrow, which stores fat and manufactures new
blood cells. Cartilage is similar to bone, with protein fibers,
carbohydrates, and other substances encased in a matrix.
However, it lacks the hard calcifying minerals of bone, making it
somewhat lighter, softer, more pliable, and less brittle.

Skeletal appendages EXTRA BONE Sea horses have an outer layer of bony carpal
Each of these animals possess plates covered by thin skin. phalanx
In addition to an internal skeleton, some bony parts or appendages that
vertebrates have associated bony parts and have developed for varying Three-banded armadillos roll into metacarpal
appendages that develop in the same way as functions, such as protection and balls for all-over body protection.
the skeleton, but elsewhere in the body. Some self-defense. The sea horse has
fishes, such as armored catfishes, have stiff, developed bony plates in its skin for
bony plates in their skin. Their decreased protection against predators. The
mobility and increased weight are offset by neck frill of the frilled lizard is spread
greater physical protection. Reptiles such as out when the lizard feels threatened,
the draco, or “flying dragon,” have long, thin and the bony plates and scutes of an
rods of bone that hold out flaps of skin. armadillo can protect its whole body.
Among mammals, physical protection in
armadillos is achieved by hard bony plates. The frilled lizard spreads out its wide
These form crosswise bands around the neck frill to deter enemies.
body and consist of dermal bone, which
has no links with the endoskeleton. It forms
within the thickness of the skin and is
covered by a layer of horn-coated, bone-
based scales, known as scutes.

87

lumbar vertebrae

sacral vertebrae

INTERNAL TIGER ilium ON THE PROWL
rib The 200-plus bones of the tiger skeleton form a pubis Each bone of the tiger’s skeleton
has a part to play in its movements
lithe, flexible inner framework for more than 600 and behavior. Opening the jaws to
muscles to pull and maneuver. The vertebral snarl, swishing the tail, and crouching
column runs from the skull to the tail tip. It acts as ready to spring are all achieved by
a flexible central support for the limbs and ribcage. teams of muscles pulling precisely
In mammals such as cats and dogs, the skeleton on particular bones.
forms about 20 percent of the body’s total weight.

costal cartilage

ischium

Highly modified skeletons femur

The typical vertebrate skeleton consists of a skull, tail
a flexible backbone, and four movable limbs, but
through evolution the basic layout has become caudal vertebrae
hugely modified for different habitats and lifestyles.
In snakes, only the skull, greatly lengthened vertebral fibula
column, and ribs remain, while most or all limb tibia
remnants are lost. Turtles and tortoises have a rigid
enclosing shell made of the domed carapace over the calcaneus
back and the flatter plastron on the underside. In birds, (tarsal)
the forelimbs are greatly altered as wings for flying, with
reduced numbers and sizes of bones, especially the fingers.
Whales and dolphins have forelimbs modified as flippers,
but lack any rear limb bones. In bony fishes, bony rods,
called rays, hold out the flexible fins.

All snakes have more than 100
vertebrae, and some possess over 400.

Swimming muscles anchor to the long The turtle’s ribs and vertebrae are Bird bones are mostly thin, hollow,
extensions of a fish’s vertebrae. fused to the inside of the carapace. and light to allow for flight.

SPECIALIZED SKELETONS phalanx metatarsal
Each of these vertebrates has a bony skeleton with
a skull, spinal (vertebral) column, and ribs. But the
other parts and proportions of the skeleton vary
hugely, for functions such as flight, swimming,
slithering, and self-defense.

NEED FOR SPEED
Cheetahs require fast, brief bursts of speed to
catch their prey. They have an extremely flexible

spine, which coils and uncoils with every
movement, propelling the animal forward. The
cheetah can reach speeds of 70 mph (113 kph),
but they are not built for stamina. They become
breathless and overheated within 30 seconds.

MOVEMENT 89 MOVEMENT

Animals display an incredible variety of movements, from the hovering

of hummingbirds to the slithering of snakes. Locomotion occurs when an

animal’s entire body moves from one place to another, as when walking,

running, swimming, flying, leaping, or crawling. In addition to utilizing

muscle power, animals can also harness a number of environmental

features, such as the wind, water currents, and gravity, to aid movement.

Land, air, water, and soil Gravity-assisted CARTWHEELING TO SAFETY
The desert arachnid called the solifuge (also known
Methods of locomotion vary dramatically, according to the substances Various animals take advantage of as the sun spider) has a clever method of escaping
or “media” an animal is traveling through. Moving across the land predators. It curls its legs around to form a wheel
necessitates contact with the ground, using body parts that range from shape and rolls down sand dunes.
legs and feet, to scales in snakes, and a slimy undersurface or “foot”
in snails. Grip against the surface provides the required forward thrust. gravity, by tumbling or sliding down

The huge variety of surface consistencies requires numerous slopes, or simply falling through the air. These methods are generally
specializations. For example, desert dwellers such as kangaroo rats
have enormous feet and toes as well as hairy soles to help them jump used as emergency measures to escape predators. A number of animals
in the soft, shifting sand. Moving through air requires large aerodynamic
surfaces, such as wings in true fliers (birds, bats, and insects), or flaps possess the ability to curl into a ball and roll away from danger, including

millipedes and wood lice. Tree-living insects, such as beetles and stick

insects, simply let go and drop to the ground. Their survival is ensured

by their small size, tough body casing, and soft landing site (leaf litter).

Metabolic rate

There is a close connection between metabolic rate (the speed of essential
biochemical processes within an animal’s body) and locomotive ability.
Birds and mammals are homeothermic (warm-blooded)—that is, they
maintain a constant high body temperature. This makes their muscles
ready for action at any time. Most other animals are ectothermic (cold-
blooded), so their temperatures vary according to the environment. When
the temperature cools, their muscle metabolism becomes less effective.
At very low temperatures, they are actually unable to move at all.

BARN SWALLOW COMMON EARTHWORM BROWN SEA NETTLE EASTERN GREY
JELLYFISH KANGAROO

of skin in gliders, such as colugos and “flying” SHAPED TO TRAVEL
squirrels. Animals have to expend a lot of Swallows have scythelike wings
energy to provide both lift (to counteract for speedy, acrobatic pursuit of
gravity) and thrust for forward movement. food. Earthworms are long and
slim, to push between soil particles.
Water is a much more resistant medium The jellyfish’s shape exploits sea
than air. In general, it requires at least twice currents, and the kangaroo’s hops
are energy-efficient on soft ground.

the amount of energy to attain the same

speed in water as it does on land. A smoothly contoured, streamlined WARMING UP FOR TAKE OFF SPRINTING ABILITY
On cool evenings, some hawkmoths have to The swordfish is able to channel natural low-level
shape becomes extremely important in water. Aquatic creatures generally “shiver” their flight muscles to generate enough heat within its body along certain blood vessels to
heat to take off. warm its muscles, enabling short bursts of speed.
have large, flat surfaces such as tails and fins to push against the heavy,

fluid medium. Locomotion in soil, sand, and mud is by far the slowest

and most energy-intensive. However, as in all forms of locomotion, there ENERGY EFFICIENCY

are benefits to offset even the

most arduous movement. For This chart shows four mammals of similar masses—about 13⁄4 oz (50 g) —that move through
land (field mouse), air (bat), water (desman), or soil (mole). It plots how far each travels in one
example, burrowing animals are second and how much energy it expends (for comparison, the field mouse’s energy expenditure
is shown as one unit). The bat uses energy most efficiently, and the mole the least.
usually less visible to predators

and are sheltered from the

weather. They may also be Distance traveled in 1 second (meters) Units of energy used per second compared to field mouse

surrounded by their common 0 1 2 3 4 5 6 7 8 9 10 Meters

food source, such as plant roots FIELD MOUSE

in the case of naked mole rats. BAT

MULTISKILLED FISH DESMAN 20 40 60 80 100 120 140 160 180 200 Energy
Some appendages are a compromise between MOLE
various forms of locomotion. The mudskipper’s 0
muscular pectoral fins can help this fish
burrow, swim, wiggle, waddle, and leap.

anImal anaTomy 90 Walking and running calcaneus metapodials
(heel bone) digits

With the exception of a few extraordinary animals that are able to walk on water or calcaneus PLANTIGRADE
along the ocean floor, walking and running are confined to land animals and require (heel bone)
the use of legs. There are many different limb actions that animals employ to achieve
locomotion on land, which are known as gaits. Individual animals often exhibit a digits
broad variety of gaits. These methods of locomotion are most obvious in larger
mammals, but they also occur in the smallest invertebrates. claws

metapodial

DIGITIGRADE

Numbers of legs Different gaits metapodial

The numbers of legs varies greatly through the animal kingdom, from Many mammals use different gaits, ELEPHANT fatty pad
two in birds and kangaroos, to the standard vertebrate number of four from a slow walk to a full-speed supports
in most mammals, amphibians, and reptiles. Insects have six legs, while run. These gaits are especially foot bones
arachnids and some crustaceans have eight. Centipedes often possess clear in hoofed mammals, such
well over 100 legs. Despite their name, millipedes do not ever have a as horses, which alter their leg single
thousand legs. Most species have between 100–400 legs, but one—the movement from walk to trot, digit
Illacme plenipes—has an incredible 750. In centipedes and millipedes, the canter, and gallop. The trot is used hoof
sheer number of legs is an arthropod adaptation to a part-burrowing way to cover long distances efficiently, UNGULIGRADE
of life. The many tiny limbs allow these creatures to push powerfully while the gallop is used to evade
through loose material, leaf debris, and soil, without the individual limbs predators. Unusual gaits include MAMMAL WALKING GAITS
needing a lot of space for their actions. The legs move mainly to and fro camel “pacing,” where both legs on Plantigrades, such as bears, walk with their heel bone,
rather than out to the side, which keeps their movement efficient. one side move simultaneously, to metapodials, and digits on the ground. Digitigrades,
give a side-to-side swaying motion. such as dogs, move with only their digits touching the
ground. Unguligrades stand on one or more toe tips.
Externally, elephants appear plantigrade, but are
actually digitigrades, since the heel bone is raised and
only their digits touch the ground.

UNUSUAL WALKERS Specialized movements S-SHAPED WALK
A crab’s sideways walk is due to the A tiger salamander’s body
direction in which its leg joints bend. A In many creatures, specialized body curls from side to side as
millipede’s legs move in coordinated “waves”— movements aid locomotion. For
a single wave involves lifting around a dozen legs example, the flexible backbone of the it walks, in a series of
up, lowering them, and then pushing backward. cheetah arches up and down to extend its “S”-shaped waves.
stride. In salamanders, newts, and lizards This pattern is
(among others), “S”-shaped sideways curves derived from
pass along the body from head to tail. This the movements
gives added swinging motion to the limbs, of fishy ancestors
which splay out to the sides. of amphibians.

Leg design Rhinoceroses have thick, sturdy limbs to carry their great bulk. compromise limBs
In spite of this, they are able to sprint surprisingly quickly.
In general, longer limbs allow longer strides Animals that move both on land and in
and greater speed. With fast runners, the water have compromise limb designs.
muscle bulk that moves the limb is near the Inter-toe webbing is an enhanced version of
main body, often in the shoulder or hip region. the standard five-toed land vertebrate foot.
This reduces the weight of the limb toward its end, It provides a broad, finlike surface for
making it easier to move to and fro at speed. Many pushing against water and is found in
invertebrates have unjointed legs, which often utilize a wide variety of semiaquatic walker-
hydraulic pressure. Caterpillars have both jointed and swimmers, including otters and desmans
unjointed legs. The latter help the caterpillar to grip,
since they contain tiny hooks that act like suction cups. among mammals, many kinds
of seabirds and waterfowl
MODES OF MOVEMENT from albatrosses to
Rhinoceroses and ostriches ducks, and many
rely on their muscle mass amphibians.
close to their main body to The degree of
achieve locomotion. Starfish webbing reflects
locomote by hydraulic the proportion of
pressure. They squeeze time spent in water—
water into each of their tiny- for example, tree frogs
tubed feet to extend them. have virtually none.

Ostriches contain their main musculature in their hips and thighs. Starfish have tiny “tubes” on the underside of their five Ostriches can sustain a speed
They can also use their wings as rudders to help change direction. or seven arms, which lift up and move forward. of 45 mph (70 kph) for up to
30 minutes, covering up to
161⁄2 ft (5 m) in a single stride.

ZEBRA “FLIGHT”
As a zebra gallops, all four hooves are off the
ground for more than half of the time taken for each
complete stride. Such minimal contact reduces
friction with the ground and allows the zebra to
“fly” in a succession of long leaps, at speeds
exceeding 35 kph (55 kph).

MOVEMENT 92 Climbing and leaping

There is a huge diversity of climbing animals, some of which have developed
extraordinary specializations, such as the acrobatic skills of gibbons or the ability of
geckos to stick to almost any surface. Leaping involves progression by alternately
speeding and slowing, in a series of jerky actions. Most animals use the same limbs
for leaping as they do for walking and running, although some invertebrates use
additional body parts specifically to leap.

Getting a grip

Moving through tree branches, and up cliffs, rocks, and walls requires

strong, mobile limbs and an excellent grip. Most climbers have muscular

limbs that can haul their body weight upward. Since it is necessary to

hang on while the other limbs are moved to new positions, some climbing

animals can support their body weight with only two or even one limb

mADAGASCAN gripping. Powerful claws, fingers, toes, and tails
DAY GECKO contain various specializations to achieve grip. For

example, a chameleon’s five toes are grouped as two

sets, of three and two, to form a “pincer” that clings

onto a twig with a vicelike hold. Some animals,

including a number of monkeys, possess “prehensile”

tails, which are able to grasp and hold objects.

RIDGES, STALKS, AND SPOONS
Geckos have ridged toes (left) with thousands of
minuscule stalklike bristles, dividing into billions of
microscopic spoonlike hairs (right). These hairs
mesh with the tiny irregularities of the surface the
gecko is climbing and provides it with grip.

SPIDER SPECIALIZATION mEXICAN RED-
The tip of a tarantula’s foot KNEED TARANTuLA
has two claws, a hook,
and serrated hairs, all
of which grip strongly
to most surfaces.

PRIMATE HANDS AND FEET

Primates have adapted limbs not just for branches very well. The greatly elongated
locomotion—chiefly in trees—but also for middle fingers of the aye-aye pick out grubs
feeding and grooming. The chimpanzee’s from under bark. The indri lemur has evolved
muscular, semi-opposable toe and thumb grip a grooming claw on its second toe.

foot hand foot hand foot hand A proboscis monkey’s feet are
ChImPANZEE AYE-AYE INDRI LEmuR partially webbed, making them
very effective swimmers.

Brachiation 93

Locomotion by brachiation (arm-over-arm swinging) STEP 1 STEP 2 STEP 3 STEP 4
occurs chiefly in tree-living primate mammals,
and most spectacularly in gibbons. There KING OF THE SWINGERS
are 14 different species of gibbons, which 1 At the start of each swing, the siamang’s body
are found in the tropical rain forests of gains speed and energy as it swings forward.
Southeast Asia. The siamang (right) is the 2 Its body swings around to allow the free hand to
largest of them. It is perfectly equipped for grab the next branch. 3 The long, muscular arms
brachiation, having long-palmed, hooklike hands and the momentum from the swing propel the
with much-reduced thumbs, elongated, powerful siamang to the next branch. 4 The grasping feet
arms, muscular shoulders, and flexible joints. reach for a lower branch as it comes to a halt.
This is aided by stereoscopic distance-judging
vision, which helps locate the next handhold.
When swinging, the siamang’s body moves forward
in a series of arcs, like a traveling pendulum. It is an
energy-efficient form of locomotion because it involves
maintaining momentum.

Energy-efficient locomotion

The energy efficiency of leaping is improved by
structures in the limbs, such as ligaments around joints,

and tendons, which anchor muscles to the skeleton.
These structures contain rubbery,
elastic substances, including the

proteins elastin and resilin. As
ligaments and tendons stretch or
compress in preparation for the

EMERGENCY EXIT leap, they store energy like a coiled BACK FLIP TAKEOFF
Some species of monkey, including spring. The energy is then released Before a jump, this cat
the proboscis monkey, make their during the leap, in a catapult action flea compresses blocks
longest leaps to escape danger. that assists the muscles. As a of resilin at the bases
Both fingers and toes are adapted kangaroo lands after even a small of its legs.
for grasping, and the tail functions hop, its body weight stretches its
as a balancing rudder. leg tendons and ligaments, storing
energy for the next hop.
How animals leap
13 in The leap of a 1⁄16 in
Prodigious leapers, including, hares, kangaroos, frogs, fleas, and
grasshoppers, usually have one pair of specially adapted limbs that are (2 mm) cat flea—170 times
larger and stronger than the others. Each limb unfolds sequentially at its its own body length.
joints as a series of levers, from the hip and thigh, to the knee and shin,
to the ankle and foot, and lastly, to the toes. This flings the animal up pronking
and forward in a series of leveraged pushes, achieving a rapid gain in
momentum. In addition to avoiding predators and other dangers, leaps Certain hoofed mammals perform stiff-limbed, springlike vertical
are used in many other contexts—for example, to clear obstacles, reach leaps, as though bouncing along with their legs held straight. This
a nearby branch, or as a display of fitness when courting or defending motion is known as “pronking” and is derived from the Afrikaans word
territory. Desert-dwelling animals often use short, quick leaps as an “pronk,” meaning “to boast.” It occurs particularly in antelopes, such
efficient way to move over soft, shifting sand. as the springbok (shown here) and impala, as well as many gazelles.
This behavior is thought to be a
BOUNDING SIFAKA display of fitness, showing
When on the ground, predators that the
some lemurs and sifakas, individual is healthy,
such as this Verreaux’s and not worth
sifaka, move with targeting.
sideways bounds of their
long, muscular legs. They
raise their arms up and
outward for balance. This
remarkable form of
locomotion can propel
the sifaka over 161⁄2 ft
(5 m) in a single leap.

MOVEMENT 94 Burrowing, slithering, and sliding

Some forms of locomotion involve progress in tiny, often
continuous stages, with a large area of body in contact
with the surface. These movements include sliding
and slithering, which are undertaken mainly by limbless
creatures. Many animals are capable of burrowing and
this occurs through many different types of terrain.

Burrowing and tunneling BURROWING Piddocks are bivalve mollusks that have shells with Shipworms are bivalve mollusks that possess tiny,
THROUGH DIFFERENT ridged “teeth” to rasp into rock. serrated shells, which enable them to bore into wood.
There are many subterranean animal species that Naked mole rats use their large, constantly growing
employ a variety of methods and body parts to push SUBSTANCES incisor teeth to bite through dry soil.
aside particles of soil, mud, sand, or similar material Some animals use
and force themselves forward. This is by far the slowest
and most energy-expensive method of animal specialized body
locomotion. However, there are benefits of the fossorial
(underground) mode of life for creatures that habitually parts to burrow through
spend their lives tunneling or burrowing. A truly
fossorial animal is relatively safe, since it is out of sight, hard surfaces, such as
hearing, and scent of surface predators. It is also
sheltered from extreme conditions, such as droughts wood and rock. Softer
and blizzards. Also, many burrowing creatures exploit
underground food sources such as roots, bulbs, and substances also
other subterranean plant parts.
present challenges.

Sand collapses as the

burrower passes, leaving

no permanent tunnel.

This means that creatures Sandfish (a species of skink) wiggle like fishes to
“swim” through loose sand and soil.
like sandfish must
continually expend

energy as they go.

65ft The length of tunnel

an average European mole
excavates in a single day.

DIGGING SPECIALIST
The sharp claws on the European
mole’s enormous front feet work like
shovels. The mole anchors itself with
its back feet and scoops soil sideways
and backward. When it nears the
surface, this shoveling action pushes
the soil up, forming a “molehill.”

Burrowing methods 95

A typical burrower needs to push aside particles of the Slithering and sliding CONVEYOR BELT
surrounding ground, using muscle-powered pressure A slug travels using small waves of muscle
from one part of its body, while at the same time Snakes, slugs, snails, flatworms, and similar animals contraction, passing from head to tail along its
anchoring another part of its body to generate sufficient move smoothly and continuously along a surface, as broad, slime-coated foot, pushing it forward
burrowing force. Vertebrates, such as moles, have like a conveyor belt.
powerful limbs that work like shovels to shift soil. Many
invertebrates, such as subterranean termites, have saw-
toothed mouthparts, which they use to cut through the
soil. Some bivalve mollusks, such as the razor shell,
have muscular feet, which expand and contract to
enable it to burrow through mud and sand. Aided by its
streamlined shape, which minimizes resistance, this

burrowing method allows the razor shell
to dig 3 ft 3 in (1m) in under 10 seconds.

a result of many tiny muscular contractions. Some

snakes tilt their scales to gain purchase against objects and

undulations on the surface. Gastropod mollusks, such as

snails, slugs, and limpets, slide on a film of mucus using

rhythmic actions of their foot muscle layers. These actions

move the foot along in undulating waves. The suction achieved

by the sticky mucus allows them to grip

onto many different surfaces, including SLOW PROGRESS
rocks and loose soil. It even enables If this garden snail moved
them to travel upside down. continuously, it would take it over
a week to cover 0.6 miles (1 km).

FOOT EXTENDED FOOT CONTRACTED SNAKE LOCOMOTION In sidewinding,
The razor shell pushes its valves The foot swells at the tip to form a the snake lifts its
(shell halves) slightly open and lower anchor point, then the foot In contrast to animals with legs, snakes have no head and extends
extends its long, fleshy foot into contracts, the valves close together, concentrated point to push off from. Instead, they have it forward. The
the sand to thrust downward. and the shell slides down. a complex system of muscles, which allows them to move rear of the
using four distinct methods. Often, the method used varies snake’s body lies
according to the size of the snake, the kind of surface they side-on to the direction
are traveling on, and how quickly they need to move. Most of movement, allowing for
snakes can perform each of these types of locomotion as better leverage. This is
the situation arises. Sidewinding is the only exception, employed on smooth or
which is unique to the caenophidian family of snakes. slippery surfaces.

In rectilinear locomotion, the belly scales are lifted, tilted to grip the In lateral undulation, the snake
surface, then pulled forward, in a succession of waves along the body. exploits surface irregularities, such
This method is mainly used by heavy snakes. as rocks, tree trunks, and hillocks,
by adjusting the angle of contact
In concertina locomotion, to gain forward thrust.
the rear body folds in sideways
curves, which act like a
frictional anchor. The head
then extends forward, and
the rear is drawn along.

LOCOMOTIVE VARIETY
Most species of snakes,
including this Burmese
python, are able to vary
their style of locomotion
according to the terrain
they are traveling on.
This python is utilizing
concertina locomotion,
most often used when
climbing, or traveling
through tunnels.

MOVEMENT 96 Flying and gliding

The three main animal groups to have mastered the air are insects, birds, and bats. AERODYNAMICS
They are considered to be “true fliers,” since they all capable of staying airborne by
flapping their wings. Some other animals are able to employ temporary airborne A bird’s wing forms a curved shape along its
locomotion but they are considered gliders because they are not capable of powered upper surface, known as an airfoil. Air
“flapping” flight. Gliding is also employed by some of the true fliers as an energy-efficient passing over the upper surface has to travel
method of locomotion. Some birds are able to use thermals (columns of warm air) to slightly farther at a faster pace than the air
soar for hundreds of miles. This means that they hardly ever need to flap their wings. passing along the lower surface. The slow-
moving air beneath the wing exerts a
Insect flight Bird flight greater pressure, which effectively pushes
up the wing from below. The faster-moving
Almost all the main insect groups have the power Bird wings create much of their lifting force by forward air above the upper surface of the wing
of flight. Typically they are four-winged, such as movement through the air, using the airfoil design (see produces lower air pressure and sucks the
dragonflies, mayflies, butterflies, caddis flies, moths, panel, right). The main power for flapping comes from wing up from above. This creates a
bees, and wasps. In the true flies—more than 120,000 the pectoralis major (breast) muscles in the chest. continuing force of lift that true fliers need
species of houseflies, blowflies, gnats, midges, These anchor to the sternum (breastbone) at the center to counteract the downward pull of gravity.
mosquitoes, hoverflies, crane flies, and others—the of the chest, and at the other end to the inner wing
hindwings have actually become tiny, drumsticklike bones. As these muscles contract, they pull the whole faster air low air
secondary wings. These vibrate or twirl rapidly, adding wing down and back. Muscles within the wing, aided flow pressure
stability and control, while the forewings actually by long tendons running out through the leading edge,
provide lift and thrust. The flight muscles are located in can flex or warp the whole wing, change the angle slower air high air cross section
the thorax (middle body section). Some insects directly of the feathers, and alter the wing’s curvature for flow pressure of bird’s wing
contract and relax these muscles to pull the wing bases precise control.
up and down. Other insects actually change the shape UPSTROKE AND DOWNSTROKE
of their thorax in order to move their wings up and A barn owl raises its wings on the upstroke.
down. For both techniques, muscles at the wing bases It twists its feathers to allow air through, thereby
determine the direction of flight by adjusting the angle reducing resistance. It then lowers its wings
of each stroke. Wing motion is not just up or down, strongly on the powerful downstroke. The feathers
but also to and fro, to generate both lift and thrust. flatten to overlap and form a continuous airproof
surface. This ensures maximum lift and thrust.
AEROBATIC FLIERS
Among the fastest,
most aerobatic insects
are dragonflies. They
can rapidly accelerate
to speeds of more than
40 mph (65 kph).
Dragonflies are also
able to beat their two
sets of wings alternately,
which increases
maneuverability.

flexor muscles tendon
biceps muscle
alula pectoral
digit muscle

primary flight triceps
feathers muscle

WING PROTECTION LIFT, SPEED, AND AIRFLOW secondary flight tendon
In beetles, such as The primary feathers fan or fold to control feathers
ladybugs, the forewings
have become hard, protective speed and direction. The secondary
covers, called “elytra.” Before feathers form the main airfoil for lift. The
takeoff, these are raised and held
clear as the larger, delicate, hind alula (digit covered by 3–5 feathers)
wings unfold for flight. disrupts smooth airflow at the leading

edge to reduce speed for landing.

Gliding specialists CALIFORNIA FLYING FISH 97 FLYING AND GLIDING

There are a number of animals—such as flying squirrels, flying possums, WALLACE’S FLYING FROG
ASTONISHING GLIDERS
flying lizards, flying frogs, and flying fishes—whose names suggest they California flying fish use their pectoral and pelvic
fins as gliding surfaces. Wallace’s flying frog
can fly. They are not, in fact, true fliers, since they cannot remain airborne extends its webbed toes as four mini-parachutes
to slow its fall, as it jumps from a tree.
in a sustained way and gain height under their own power. These

remarkable creatures employ winglike structures with large surface areas,

which function as parachutes to increase air resistance. They can also

generate small amounts of lift that reduce descent speed. Tilting or

changing the shapes of these surfaces gives a certain amount of control

over distance and direction. The most impressive mammal gliders are the

flying lemurs (neither true fliers nor true lemurs) of Southeast Asia, which

can travel more than 330 ft (100 m) and land with pinpoint accuracy.

SOARING
When the sun warms the
ground, the air above it
also warms. This creates
columns of warm air,
known as “thermals.”
“Updrafts” are formed in
mountainous terrain
by deflected wind. Both
thermals and updrafts
enable birds to soar
with minimal need to
flap their wings. This
energy-efficient method
of locomotion is used
by eagles, vultures,
condors, and storks
among others.

Wing aspect ratio EUROPEAN SPARROWHAWK

A wing’s aspect ratio refers to the relative proportion of its span
(length from the body to the wing tip) to its width (from leading to
trailing edge). Long, narrow wings have a high aspect ratio and
are most effective for long-distance gliding and soaring. Flapping
is minimized, since the air currents provide much of the lift
needed to sustain flight. Many birds feature this wing design,
including albatrosses, gulls, and to a lesser extent condors and
eagles. Low aspect-ratio wings are shorter and wider. These are
used for rapid acceleration, fast
turns, and precise control, as in
sparrowhawks. Curved,
scythelike wings with
tapering, drag-reducing
tips are used for sustained,
speedy aerobatics, as seen
in swallows and swifts.

FIGURE-EIGHT FLIGHT ANDEAN CONDOR
Hummingbirds flap their wings in a figure-eight
pattern, providing the necessary downflow of air to SPARKLING VIOLET-EAR
allow them to hover. With slight adjustments, they HUMMINGBIRD

can fly sideways and even backward.

MOVEMENT 98 Swimming

Swimming is remarkably similar to flying in a number of respects. SCHOOL SWIMMERS
Both air and water are fluid media, and many of the same principles Juvenile blackfin barracudas
apply to fins as to wings, such as the need to push broad surfaces often swim in large schools.
backward in order to propel an animal forward. One significant They have long, streamlined
difference is that water is 1,000 times denser than air, bringing many bodies with very powerful
drawbacks, but also benefits. tails, which allow them to
accelerate rapidly.

Staying afloat forward, offsetting a tendency to sink. Sharks also
have a large, oil-rich liver that adds to their buoyancy,
An advantage of water over air is that it provides plenty since oil is lighter than water. In cephalopods, such as
of support, so unlike aerial animals, aquatic species do nautiluses, cuttlefish, and squid, the shell (which is
not need to generate powerful lift. However, they do internal in the latter two) contains gas-filled spaces that
need buoyancy control, as well as propulsion, in order can be filled or emptied to adjust buoyancy. Diving and
to rise, descend, or “hover” in the water at a certain swimming birds have adaptations that enable them to
depth. Bony fishes adjust their buoyancy using an sink quickly in order to catch food. Cormorants, for
organ called the swim bladder, the gas content of example, have feathers that can hold a lot of
which can be adjusted. Cartilaginous fishes, such as water, reducing the air trapped in their plumage.
sharks and rays, lack a swim bladder. Their angled fins
provide them with hydrodynamic lift as they move

siphuncle swim bladder ovale
gas gland

gas-filled
chamber

rete mirable (network
of capillaries)

BUOYANCY CHAMBERS SWIM BLADDER intestines
Each chamber of a nautilus’s shell is filled with fluid, which is
absorbed and replaced by gas. An opening in each chamber allows A bony fish regulates its buoyancy by exchanging gas between its
the nautilus to control the volume of gas inside, and therefore
regulate its buoyancy. The siphuncle removes excess water. bloodstream and its swim bladder. Gas is secreted into the swim

bladder from the gas gland, which is supplied by the rete mirabile.

The gas is removed and reabsorbed into the blood by the ovale.

Swimming styles steering and to provide stability. However, some forward
fishes use them for their main propulsion, including movement
Most large aquatic animals, such as marine mammals seahorses, which swim by rippling the dorsal fin, and
and big fishes, swim using the muscles in their bodies rays, which undulate their large, winglike pectoral fins. of fish
and tails to push against the water. Some cartilaginous A fish’s body shape usually reflects its swimming style.
fishes, bony fishes such as eels, and sea snakes swim Powerful, fast movers have muscular, torpedo-shaped
with an undulating or wriggling motion, as “S”-shaped bodies that are elongated and tapered at both ends.
waves travel along the entire body. Most bony fishes Fishes that live in quiet waters and do not need to
swim by moving their rear body and tail (caudal fin) move at high speeds, except in short bursts, tend to
from side to side. The other fins—dorsal on the back, be laterally compressed (narrow from side to side).
anal on the underside, the paired pectorals at the front, Bottom dwellers are usually vertically compressed,
and pelvics toward the rear—are generally used for (narrow from top to bottom) for example flatfishes
and angel sharks.

A shark’s tail fin has an Bony fishes have a TAIL FINS sideways
uneven shape, generating symmetrical homocercal The shape of a movement
both lift and thrust. tail fin. fish’s tail reveals the of tail
swimming style of its
owner. Most bony diagonal
fishes have a resultant force
“homocercal” tail
shape, with upper BODY PROPULSION
and lower tail lobes As a fish’s tail moves, it generates both sideways
approximately equal. and backward thrust in the water. The resultant
force acts diagonally halfway between the two.
TRUNK SWIMMERS A tuna’s tail fin lowers A pike’s tail fin has a large As the fish moves its tail from side to side, the
Seals like the Hawaiian monk seal move by drag for fast cruising. surface area for fast acceleration. resultant diagonal thrusts to left and right produce
undulating the rear body and “kicking” with a net backward thrust, so the fish will swim in
their rear flippers. Eels, such as the white- a straight line.
margined moray, utilize serpentine locomotion
—moving in a series of muscular waves
passing from head to tail. This is aided by a
flattened tail, which generates more thrust.