wolf

Wolves are wild relatives of dogs and are represented by two species, the gray and red wolf, with variations within each species for a total of thirtytwo described subspecies. At one time, wolves lived throughout Europe, Asia, and North America. The gray wolf, also called the timber wolf, is the most common wolf species living in North America and can be found mostly in Canada and Alaska. Considered extinct in western Europe, with a few exceptions, gray wolves live in Russia, southeastern Europe, and Asia. Wolves’ ranges have decreased due to urbanization. Most wolves live in sparsely populated forest, tundra, wilderness, and mountain regions and tend to avoid people, approaching settled areas only when they are starving or when natural crises, such as floods, fires, and blizzards, cause their migration to populated places to seek emergency food sources. Gray wolves can attain a body length (from nose to base of the tail) of 1.2 meters (4 feet) and height of 90 centimeters (3 feet) at the shoulder. They average forty-five kilograms (one hundred pounds) in weight, with some wolves weighing twice that amount, and have sharp teeth, thick coats, tall legs, and bushy tails. Gray wolves have primarily gray coats with some black, yellow, and brown fur, although some gray wolves are solid black or white, particularly in the Arctic. An endangered species, red wolves live in the forests and brush of the south central United States and can be colored a hue ranging from reddish gray to black. Hunting of gray wolves escalated as farmers and ranchers penetrated wolf territory, their livestock offering easy targets for the wolves. Humans’ retribution threatened decimation of the gray wolf population. Efforts to replenish the number of wolves include the reintroduction of gray wolves toYellowstone National Park in 1995.
Pack Behavior
Hunting alone and in packs, wolves usually roam over large territories with a family group consisting of parent wolves and their offspring. Zoologists believe that wolves mate with the same partner for life, producing from three to nine cubs annually in late winter. Digging an underground den or appropriating a cave or hollow tree, wolves give birth and raise their cubs in this space, where the parents bring food until the cubs attain sufficient maturity to hunt. During winter and other stressful conditions, wolf families occasionally establish a larger pack of as many as thirty animals. The leader of a wolf pack, known as the alpha male, disciplines pack members. Wolves prey on both large and small animals, including deer, moose, rabbits, birds, and mice and also eat vegetables, fruit, and carrion. They tend to hunt at night and can leap over obstacles 4.9 meters (16 feet) high, and travel up to fifty-six kilometers per hour (thirty-five miles per hour) to capture prey, sustaining thirty-two kilometers per hour (twenty miles per hour) for several hours when endurance is necessary to wear down elusive prey. Wolves migrate to follow prey to other areas. Scientists hypothesize that wolves howl in order to communicate with other wolf packs.

Baleen whales belong to the order Cetacea, the only mammals which spend their entire lives in the water of the earth’s oceans. There are seventysix cetacean species, and the baleen whales make up ten of them. Among baleen whales are blue (sulfur-bottomed) whales, the largest animals that have ever lived. They grow to lengths of over one hundred feet and can weigh 400,000 pounds (200 tons). This makes them more than fifty times the size and weight of a bull elephant andmuchlarger than any dinosaur. Like all whales, baleen whales are thought to be descendants of a land animal, believed to have been an early ungulate (hoofed mammal). The huge size of the baleen whale is possible because it lives in the water. This supports its mass and frees it from the limitations of land animals, which can only grow to the sizes and weights their legs will support or their wings can carry into the skies. Whythe ancestors of baleen whales entered the oceans is not understood. It is guessed that the return to the oceans was due to the need for a new food supply or to escape frompredators. Most paleontologists believe that it happened sixty million years ago, twenty million years before the first whale fossils occur.No fossil that links baleen whales to their landbound ancestors has yet been found, although the search goes on.

Wasp and Hornet

Wasps are stinging insects of the order Hymenoptera. Many live in large colonies which have a queen, males, and sterile female workers. Such social wasps are hornets.Wasps are called solitary if they do not live in communities, but build small brood nests to hold their young. Social wasps (hornets) make paper nests. One example is white-faced hornets, found all over North America. These wasps, 1.25 inches long and black with white markings, build nests, up to halfbushel size, in tree limbs. Yellow jacket species live in colonies of many thousands, close to or under the ground. Giant European hornets, in the United States since the 1850’s, are brown with yellow streaks and nest in hollow trees. In some wasp species, no workers are born and females lay eggs in the nests of other wasps.Wasp size varies from parasitic wasps, that can develop in insect eggs, to species attaining body lengths of over two inches.

Physical Characteristics of Wasps and Hornets
Wasp bodies, which are covered by coarse hairs, have a head, thorax (midbody), and abdomen (hind body) segments. Thoraxes hold four wings and six legs. The bodies are steel blue, black, yellow, or red, with abdominal rings. Reproductive, digestive, and excretory systems are in abdomen and thorax. Females have stingers at abdomen ends. Parasitic wasps use stingers to insert eggs into hosts. Female nonparasite wasps (which are most wasps) use stingers to paralyze their prey and inject venom. The stings are painful, because the venom contains histamine and a factor that dissolves red blood cells. Wasp stings, especially by hornets, can kill allergic humans. Wasp heads contain sharp, strong mandibles (jaws), designed to chew hard things, tear up food, dig burrows, and pulp wood and earth. Wasp mouths can also lap liquids. Above the mandibles, their heads contain paired, keen, compound eyes and paired sensory antennae. Queen wasps in social species are reproductive females who use sperm obtained in mating flights to fertilize eggs that become females. Unfertilized eggs become drones (males). Production of queens-tobe or female workers depends on diet.

Wasp Nests and Life Cycles
Nests of social wasps range from combs without protecting covers, to round nests up to ten inches in diameter, having paper tiered combs and waterproof outside covers. Social wasps nest wherever possible. Small combs occur under porch roof and rafters or in trees. There are two yellow jacket types, the long-faced and short-faced species. Long-faced yellow jackets nest in trees, bushes, and roofs, while the short-faced type nests in the ground. A wasp colony lasts one year. Wasps store no food, and in fall the whole colony dies except for the future queens. They hibernate in crannies over the winter and become queens of new colonies in spring. Acolony starts after a queen makes a few cells, lays an egg in each, and feeds larvae with chewed-up insects. Next, larvae spin cocoons and pupate for several weeks, emerging as workers. After this, a queen does nothing except lay eggs. The eggs yield worker wasps until late summer, when the queen lays eggs that will become males and queens.Workers tend the young and enlarge the nests. A hornet nest may have thousands of males, females, workers, and young. Solitary wasps live alone except for breeding. Afterward, females build flat, one-comb nests. Instead of being papermaker wasps, they are mason, carpenter and digger wasps. Among mason wasps are potters and stoneworkers. Potters wasps make mortar of mud and saliva and place brood nests in trees. Mud dauber wasps mix mud with saliva and build nests under porch roofs. Stone worker wasps mix pebbles with mud and nest on rocks. Carpenter wasps tunnel into trees and digger wasps tunnel into the ground. All adult wasps eat caterpillars, spiders, beetles, flies, other insects, and nectar. Solitary wasp species feed their larvae with specific live insects. Mothers set up nurseries, paralyze prey by piercing nerve centers with their stings, and take the live food to nests. Then they lay an egg on each body. Larvae feed on the insects until they begin spinning cocoons to pupate, emerging after pupation as adult wasps.

Yellow Jackets
North American short-faced yellow jacket wasps (hornets) are 0.75 inches long, with yellow and black head, thorax, and abdomen markings that give them their name. They nest below grass level near decaying wood. Their nests are paper, made from saliva and wood. Each nest has a queen, who lays all eggs. Fertilized eggs become females and unfertilized eggs become males. Reproductive females are produced when the colony is ending its one-year life span. Sterile females tend the nest and larvae. Reproductive females eventually become queens, and males mate with queens-to-be. The yellow jacket diet is insects, fruit, and nectar. Only worker yellow-jackets hunt food, which they eat by tearing it with their mandibles. Queens live for ten months, while drones or workers only live for a few weeks.

Helpful Wasps
Most wasps help humans and the environment. They damage some fruit, but they destroy myriad caterpillars, beetles, flies and other harmful insects. Thus, they do far more good than harm. Several species pollinate farm crops. Furthermore, the parasitic varieties lay their eggs in the bodies and eggs of pests such as aphids, thereby reducing their numbers.

Vulture

Vultures comprise two groups of carrioneating birds. They are useful because they eat carrion, which otherwise might decay and endanger the health of other animals. The twenty-one vulture species inhabit temperate to tropical regions of the Americas, Europe, Asia, and Africa. All vultures exhibit similar eating habits, behavior, and appearance, including bare heads and necks. Many also have somber-colored feathers. Vultures of Europe, Asia, and Africa (Old World vultures) arise from eaglelike birds. Vultures of the Americas (NewWorld vultures), similar in appearance to OldWorld vultures, are anatomically related more closely to storks.

Some Characteristics of Vultures
Vultures have bare heads and necks and hooked bills. Carrion is their main food, and on some occasions they attack newborn or wounded animals. Most hunt by long-distance soaring to scavenge with their keen sight. New World vultures differ from OldWorld vultures in their lack of the ability to vocalize. Six species compose New World vultures. Three live in North America: turkey vultures of the southern United States and northern Mexico; black vultures of the southwestern United States and Central America; endangered California condors; king vultures; Andean condors; and yellow-headed turkey vultures of South America. There are fourteen Old World vulture species. Among the most interesting are the cinereous (with a color resembling ashes) vultures of southern Europe, northwest Africa, and Asia; the similar griffon vultures; white (Egyptian) vultures found from the Mediterranean to India; and the bearded vultures (lammergeiers) of Europe, Asia, and Africa. Vultures lack feathers on their heads and necks, which keeps them free of gore fromcarrion. Among New World vultures, several have interesting appearances. Black vultures have black heads and plumage, with white feathers under the wings. King vultures, in contrast, have feathered neck ruffs and yellow, red, white, and blue heads. California condors, the largest North American land birds, average four feet in length, with wingspans up to eleven feet. They have black neck ruffs, bald, orange to yellow heads, and black plumage except for white feathers under wings. Andean condors are similar. South American yellow-headed turkey vultures resemble North American turkey buzzards. Notable among Old World vultures are cinereous vultures, about four feet long with bare, pinkish heads and black feathers. They inhabit Europe, northwest Africa, and Central Asia. Griffon vultures are similar in size and appearance. Egyptian vultures, two feet long, have yellow heads and white feathers except for black wings. They inhabit Mediterranean areas and are found as far east as India. Bearded vultures (lammergeiers) are especially interesting. They live on Asian, African, and European mountains. They have tan plumage on the chest and stomach and dark brown wing and tail plumage. Lammergeiers have red eyes in white heads. Conspicuous black feathers surrounding the eyes end in beardlike tufts and led to the name “bearded.” These vultures average four feet long and weigh up to twenty-four pounds. Their huge wings allow soaring for hours on thermal updrafts. Lammergeiers are unusual in building large, conical nests on or in rock ledges or caves. A mated, monogamous pair uses the nests many times.

Life Cycles of Vultures
Most vultures nest on bare ground underneath mountain overhangs, or in caves. They build no nests, and females lay eggs on bare rock. After hatching, both parents feed the chicks partly digested carrion regurgitated into their mouths. For example, Andean (great) condors live in mountain caves, and females lay one or two greenish-white to bluish-white eggs on the cave floor. Both parents incubate the eggs until they hatch. The scarcity of the California condor is partly due to the fact that it lays only one egg at two- to three-year intervals. Young condors fly in six months, but parents feed them for another eighteen months. Andean condors first mate at seven years old, and at two-year intervals after that. They are monogamous and maylive for forty-five to fifty years. Lammergeiers, as noted, are unusual in building several nests used over and over. The female lays her eggs, incubates them, and feeds chicks with the help of the male.

Marabous: Storks or Vultures?
Marabou storks (marabous) combine stork and vulture anatomy and occur throughout Africa. Adults are five feet tall. They have long, storklike legs and sharp, straight bills. Their heads and necks are vulturelike. Most marabou food is deer, antelope, and zebra carrion. Marabou plumage is gray on the back and wings, with white bellies and ruffs encircling red necks. Most inhabit African wetlands, rivers, and lakes. Pairs build nests in trees or on rocky terrain. Usually, three eggs are laid and incubated by both parents. Chicks hatch during dry season when carrion is plentiful. They stay with their parents for six months. Marabous live for over twenty years. Vultures consume carrion, preventing decay and danger to health. This activity is one of their main ecological functions. Some vultures (such as condors) eat live food, giving them another ecological function, killing injured or weak members of other species. This helps the species that are eaten to select for individuals which enhance long-term survival.

Turtle and Tortoise

Turtles, tortoises, and terrapins are all turtles. The term "tortoise" is used for terrestrial turtles with high-domed shells and elephantine hindlimbs, whereas the term "terrapin" is used properly for some highly aquatic turtles (genus Malaclemys) of eastern North America, although it frequently is used in error for American box turtles in the genus Terrapene. Turtles are easily recognized and distinguished from all other vertebrates by their shells. Shells are composed of a dorsal carapace and a ventral plastron. These are usually rigidly connected on the sides by bridges. Shells are composed of bony plates that form within the skin. These are fused to underlying vertebrae and ribs. Most shells have a covering of horny plates made of keratin, a protein which, in other vertebrates, forms scales, hair, nails, claws, or horns. In some turtles, the plates of bone and keratin are reduced or absent, and the shell is covered by leathery skin. Many turtles have one or more hinges in their shells, usually in the plastron. These allow the shell to completely enclose the withdrawn head, limbs, and tail. The plastron of males in many species is indented to accommodate the female's shell during mating.

Turtle Lifestyles
Shell shape largely determines the lifestyle of its owner. Terrestrial (land-dwelling) turtles such as box turtles (Testudo) and tortoises (Geochelone) have high-domed shells. These reduce surface area through which water is lost and also are difficult for predators to grasp and break. Most aquatic and all marine turtles have relatively flat, streamlined shells for ease in swimming. However, African pancake tortoises (Malacochersus) have flat shells that allow them to hide in rocky crevices, and some bottom-dwelling aquatic turtles, such as the mud turtles (Kinosternon) of the southeastern United States, have high-domed shells. Snapping turtles in the genera Chelydra and Macrochelys have rough shells on which algae grow. This camouflages these turtles as they wait to ambush prey. Limbs also provide clues to lifestyles. Aquatic turtles have webbed feet, and sea turtles have forelimbs modified into flippers that allow them to "fly" through water. In contrast, terrestrial turtles often have spadelike feet for digging and/or columnlike limbs to support them as they walk. Regardless of shape or function, the girdles to which the limbs attach are enclosed by the ribs and shell. Turtles are the only vertebrates with this skeletal arrangement. Other anatomical modifications include nostrils on top of the snout or at the very tip of a long proboscis; these allow aquatic turtles to breathe at the surface with minimal exposure. Modern turtles, like modern birds, lack teeth. Instead, they have horny beaks of keratin variously shaped to cut leaves, tear flesh, or crush the shells of snails or clams. Because the shell prevents expansion and contraction of the thorax when breathing, turtles compress or expand the lungs by altering the location of other internal organs to which the lungs are attached. Shells limit mobility to a great extent; consequently, turtles have long and flexible necks. These allow them to reach up to browse or down to graze, or to quickly extend their necks in order to ambush quicker prey. In addition, neck vertebrae are modified to allow the head to be withdrawn into the shell, either by pulling it straight back while the neck assumes an S-shape (cryptodiran turtles) or by laying it to the side under the overhanging lip of the carapace (pleurodiran or sideneck turtles).

Origins and Future of Turtles
Fossil turtles are known from the Jurassic. Most systematists (biologists who study evolutionary relationships) group turtles with some extinct relatives in a clade called the Parareptilia. Although turtles traditionally have been considered reptiles, many expertsnowplace them a separate vertebrate class. Regardless, the ancestors of turtles arose from the first amniotes before the ancestors of other reptiles. This and their many unique features justify placing turtles into their own class. Unlike many reptiles, turtles are perceived positively by most people. Nevertheless, many species are threatened or endangered. Habitat destruction and alteration are responsible in most cases. Aquatic habitats are drained or polluted and nesting sites, especially beaches, are developed, rendering them unusable by turtles. Many species are exploited as food, either as eggs or adults, and others are killed for their shells or body parts, which are thought by some cultures to have medicinal or aphrodisiac qualities. Exotic predators, such as rats and dogs, dig up nests and kill adults. Hundreds of thousands of wild-caught turtles die each year in the pet trade, much of it illegal. Many species become roadkills when they migrate to new habitats or breeding sites. Only a few species are formally protected in at least some parts of their ranges, and several, including the sea turtles,maybe nearing extinction in spite of efforts to conserve them.

Turkey

Triceratops

Triceratops became the first genus of horned dinosaur known to science when its skull was described by Othniel C. Marsh in 1889. The remains of its horns were originally attributed to the high-horned bison (Bison alticornis), and its occipetal condyle was originally named Ceratops montanus. In his preliminary description of the skull, Marsh named its owner Ceratops horridus and felt it was related to the stegosaurs. After the skull had been cleaned, Marsh changed the name to Triceratops horridus. Thirteen species of Triceratops have been described, but only one (or possibly two) species actually occurred in nature. Triceratops lived in western North America at the end of the Cretaceous, between 68 and 65 million years ago.

Characteristics
The most characteristic feature of the animal was its large, V-shaped head which terminated in an elongate frill. The skull can be more than 6 feet long (2.2 meters). Only whales have larger skulls. The frill allowed an animal to recognize members of the same species as well as members of the opposite sex. Since Triceratops had color vision, the frill was probably pigmented, and its ornamentation was designed for visual display and not for protection or to serve as a point of attachment for the jaw muscles. The head bore three horns that functioned in display, ritual combat, and protection frompredators. One short horn arose over the nose, and two others, the longest, arose over the eyes. Males had large, erect horns while females had smaller, somewhat forward-pointing horns. The large number of skulls that have been found indicates that Triceratops was an abundant, gregarious species. No complete skeletons are known. A composite, presumably female, skeleton on display at the Science Museum of Minnesota is 26 feet (7.9 meters) long and 9 feet, 7 inches (2.9 meters) high. With a weight of 8.5 metric tons (9.4 tons), Triceratops was three times heavier than a rhinoceros. The shin bone (fibia) was notably shorter than the thigh bone (femur). The size relationship between these two bones is the reverse of what is seen in animals that are fast runners. Evidence from ceratopsian trackways and the anatomy of its shoulder (the hind legs were located directly below the hips while the forelimbs sprawled outward and were not located below the shoulders) also indicates that Triceratops was rather slow. Its running speed has been estimated at about 4.2 kilometers per hour (2.6 miles per hour).

tiger

The first tigers were members of the Felidae family of big cats that lived in northern Asia during the Late Pleistocene epoch. They migrated south and east and evolved into specific types of larger tigers according to their habitats. The ancient saber-tooth tigers were not ancestors of modern tigers. Three of the eight tiger subspecies, Bali, Caspian, and Javan, became extinct during the twentieth century.

Anatomy
Tigers range in weight according to their subspecies and gender. Sumatran male tigers are the lightest, weighing 110 kilograms (250 pounds). Females weigh approximately twenty kilograms less. Siberian male tigers weigh as much as 225 kilograms (500 pounds). The heaviest known tiger weighed 465 kilograms (1,025 pounds). From head to the base of the tail, tigers measure from1.4 to 2.8 meters (4.5 to 9 feet) long, and their tails are from 90 to 120 centimeters (3 to 4 feet). They use their tails to balance and to communicate. Tiger skulls have a big saggital crest which anchors a large jaw muscle. Tigers' vertebra and joints are flexible. Their hind legs are longer than their front legs, providing impulsion and assisting leaping when they are chasing game. They have five toes on their front paws and four toes on their hind paws. Each toe has a retractable claw which is 80 to 100 millimeters (3 to 4 inches) long and helps them restrain prey and climb trees.Mature tigers have thirty teeth. The canine teeth are 75 to 90 millimeters (2.5 to 3 inches) long. Tigers have triangular, erect ears set atop broad skulls, with their eyes positioned on the front of their face. Tigers' eyes have reflecting retinas which enable excellent night vision. Tigers' sense of smell is also acute; they can distinguish different animals by smell and exhibit the flemen response. Tigers have nineteen pairs of chromosomes, which determine genetic patterns. Their coats are colored shades of orange, with black or brown stripes of varying widths and lengths and white accents around the eyes, ruffs, and other body parts. Rarely, Bengal tigers with the two necessary alleles are born with a white foundation coat and blue eyes. They are not albinos or a separate subspecies. Tigers' stripes vary according to subspecies, with Sumatran tigers having the most and Siberian tigers having the fewest. Each tiger's stripes are unique and function as camouflage. Fur thickness varies with seasonal changes and geography. Siberian tigers have almost twice the number of hairs per square centimeter than Sumatran tigers.

Behavior
Tigers are solitary, preferring to hunt alone.Amale tiger's territory averages twenty-six to seventyeight square kilometers (ten to thirty square miles), depending on the availability of prey. Some Siberian tigers roam territories of 1,036 square kilometers (400 square miles). Tigers' territories often overlap, with several females sharing territorial space with one male. Tigers scratch on trees, leave fecal droppings, and spray urine to mark their territory. Male tigers occasionally fight. Tigers have several vocalizations to communicate aggression and receptiveness to other tigers. Females attain sexual maturity at age three and males at age four. After a four-month gestation, females have litters of two to five cubs which are born blind and are vulnerable to predators such as pythons. The cubs drink their mother's milk for two months, then feed at her kills until they are about two to three years old and capable of hunting alone. Tigers can catch and kill prey as large as 160 to 900 kilograms (440 to 2,000 pounds). They stalk and ambush ungulates, knocking prey to the ground and biting the neck or throat to sever the spinal cordor suffocate the animal.Tigers can consume twenty to twenty-five kilograms (sixty to seventy pounds) of meat daily. They drag carcasses into vegetated areas and gorge on a kill, then fast. Tigers also eat termites and snakes. Some tigers, especially in the Sunderbans river delta of India and Bangladesh, have attacked and killed humans.

Conservation
Adult tigers are hunted by poachers for their hides, bones, teeth, and body parts or for sale to exotic pet traders. Much of their jungle habitat has been destroyed during wars or for agricultural use. As a result, only about five thousand to seven thousand tigers are alive in the wild. Authorities estimate that an equivalent number are kept as exotic pets in North America and in zoos, sanctuaries, and circuses. Tiger censuses have been taken by counting pugmarks in known tiger habitats. In captivity, tiger hybrids include ligers, the hybrid of lion fathers and tiger mothers, and tigons, produced by tiger fathers and lioness mothers. Conservation breeding programs are aspiring to preserve and increase the tiger population.

Tasmanian devil

The Tasmanian devil belongs to a primitive group of mammals, the marsupials, which are found today primarily in Australia, Tasmania, New Guinea, southern Mexico, Central America, and South America. The name "marsupials" refers to the animal's marsupium, the pouchlike structure to which the immature young move after they are born, becoming attached for several months as they complete their development. The well-known pouch of kangaroos is the classic example of a marsupium, although it should be noted that a few marsupials do not have pouches and in some, including the Tasmanian devil, the pouch opens downward. During their long geological separation from the rest of the world, marsupials in Australia and South America underwent adaptive radiation, which produced an enormous diversity of forms as species became adapted to various habitats. As a result, many marsupials resemble placental mammals although they are not closely related. Thus, there are marsupials that resemble flying squirrels, moles, woodchucks, cats, and dogs. The Tasmanian devil, although a marsupial, has many similarities in structure and behavior to a dog.

Physical Characteristics
The devil belongs to a family of marsupials known as the Dasyuridae, which are found in Tasmania, Australia, New Guinea, and some nearby islands. The group includes the Tasmanian wolf or tiger, the numbat or banded anteater, and shrewlike, catlike, and ratlike forms. The Tasmanian devil is distinctive even within this distinctive group of marsupials. It received its name, "The Devil", from the early European settlers to Tasmania, who were awed by its fierce behavior and loud vocalizations. The devil actually is a stocky but short-limbed animal, doglike in shape, and only weighs between 4.5 and 12 kilograms, standing only about 30 centimeters tall. Its dark, mostly black color also contributes to its "evil" reputation. The animal does have a voracious appetite. It has a large head and very powerful jaws with long canine teeth. The devil is the largest carnivorous marsupial, extremely strong for its size; it can feed on animals larger than itself, including small kangaroos. It usually rests during the day and seeks food at night. Its food is varied and may include amphibians, lizards, rodents, insects, and poultry. The devilmayprey on live animals or may feed on carrion. Its nightly movementsmaycover distances up to ten miles or more. The legs are short and the animal usually moves along slowly, although it is capable of running quickly for short distances.

Early Life
As is true of all marsupials, the young are born alive after a relatively short gestation period- about three weeks. Breeding usually takes place in early spring. The newborns travel from the birth canal to the pouch, which is backward- opening in this species, and attach themselves to a nipple,where they remain secure for about four months. For the next several months, the young will venture outside of the pouch at times and, finally, become weaned and independent by the end of the year. Breeding usually commences between the second and third year. Reproduction is somewhat limited, as the mother has only four nipples and usually more than four young are born. It is not unusual for only two young to survive to weaning. The Tasmanian devil has had a persecuted history, especially with the advent of European settlers. Its fierce appearance, loud screeches, and occasional predation on domestic livestock and poultry caused it to be hunted, trapped, and poisoned to the point of near extinction. Its value in cleaning up carcasses was not appreciated. The Tasmanian devil finally became protected by law in 1941. Going from outlaw to icon, the Tasmanian devil was selected as the symbol of the Tasmanian National Parks and Wildlife Service.

Salamanders

Salamanders and newts comprise one of three groups of amphibians living today. The other two, the caecilians (Gymnophiona) and the frogs and toads (Anura) can be readily distinguished by their body forms. Like other amphibians, salamanders and newts have glandular skin that lacks scales, feathers, or hair. Considering only species living today, salamanders and newts are a small group compared to the number of species of frogs and toads. Whereas frogs and toads are represented by about four thousand species, only about four hundred species of salamanders and newts are living today. Systematists, biologists who study the classification of plants and animals, recognize ten families of salamanders. Newts are simply salamanders that are classified in the family Salamandridae; they can be distinguished fromother salamanders by many osteological (bony) features and by their generally rough skin, compared to the smooth skin of other salamanders.

Anatomy of Salamanders and Newts
Salamanders have long, lizardlike bodies with long tails and four small legs. Many species have costal grooves along the sides of the body; the number of these grooves varies among species and can help with identification. Olfaction (sense of smell) is used during courtship, and males of many species have specialized glands on the body. Males of many species of lungless salamanders have a gland on the chin that is used to deliver hormones to the female during courtship. Salamanders have a larval stage, but unlike frogs and toads, in which the tadpole is very different from the adult frog, larval salamanders are similar in body form to adults. Larval forms are frequently found in water and retain external gills, which are lost at metamorphosis (transformation to the adult stage). Species that breed in ponds, where oxygen levels are low, have large, bushy gills for added surface area to increase the intake of oxygen. In contrast, species that breed in streams, which have high oxygen levels, have larvae with short gills. One of the most successful groups of salamanders are the Plethodontidae, the lungless salamanders. Most species of these salamanders live and breed on land, never entering water. They have no lungs, and oxygen uptake occurs primarily through the thin, porous skin. One requirement for this gaseous exchange is moisture, and these salamanders live primarily in damp, cool forests.

Life History of Salamanders and Newts
Primitive families of salamanders deposit eggs in water and have aquatic larvae. Other families of salamanders are unique among amphibians in producing a spermatophore for the transfer of sperm from the male to the female. The spermatophore is a gelatinous structure with a sperm cap resembling a tiny mushroom. The spermatophore is transferred from the male to the female in an elaborate courtship ritual. In some species, the male rubs secretions from a gland under his chin over the body of the female and entices her to follow him about. He then deposits a spermatophore on the substrate of the pond, which the female straddles and picks up with her cloaca. Fertilization is therefore internal in those species that produce a spermatophore. Lungless salamanders are active on the forest floor during moist or humid periods. Males are antagonistic to one another and appear to establish small territories that they defend from other males. The territorial encounters include biting and chasing and can result in injuries, including loss of part of the tail.

Defense Against Predators
Like other amphibians, salamanders and newts have toxic skin secretions produced by skin glands that are used in various ways as defense mechanisms to repel predators. In some species of newts, glands are concentrated on the dorsum, and when disturbed by a predator, the salamander displays an "unken reflex." This display includes bending the body in a U-shape and showing bright coloration of the underbelly. At the same time, the animal becomes immobile, thus decreasing the chance that a predator will attack. Other species have glands concentrated on the tail and engage in tail lashing or tail undulation. In tail lashing, the salamander violently whips its tail toward the predator, which attacks the tail and tastes the noxious secretions. In tail undulation, the body of the salamander remains immobile while the tail is waved in a sinuous fashion above the body. The tail in these species can be autotomized, or broken from the body by the salamander. Thus, if a predator attacks the waving tail, the salamander loses the tail but escapes with its life. Other species actively defend themselves if attacked by a predator. Amphiumas are large, powerful salamanders that live in ponds, swamps, or marshes in the southeast United States. Adults reach one meter in length and can inflict a painful bite with their sharp teeth. In a unique manner of defense, slender salamanders can secrete copious amounts of an adhesive substance from their glands. When attacked by a garter snake, the salamander's secretions glue the snake's body to itself, and it is unable to swallow the salamander.

Ratfish

The other major subgroup of cartilaginous fishes, the subclass Holocephali, comprises about twenty-five or thirty living marine species, most or all of which are placed in a single family, the Chimaeridae. They have a single gill opening on each side, like the bony fishes, but unlike them have a soft (rather than bony) gill cover. These fishes, commonly called chimaeras or ratfish (because of their long, slender tails), live and feed on the ocean bottom, usually in deep water. They have pavementlike teeth for crushing their mollusk and crustacean food, and they have a venomous spine on the leading edge of the first dorsal fin (the forwardmost of the unpaired fins on the upper surface of the body) for defensive purposes. Male ratfishes have a fingerlike barbed clasper, of unknown function, on the top of the head, and two pairs of claspers on the ventral (belly) side of the body.At least one pair of these ventral claspers is involved in mating. The female lays eggs in leathery capsules somewhat like skate egg cases.

Ichthyology
The study of sharks, rays, and related species is part of the larger discipline known as fish biology, or ichthyology. This science has its origins in the writings of Aristotle more than twenty-three centuries ago. He was the first to report, for example, that the sex of sharks can be determined by the structure of the pelvic fins, that is, by the presence of claspers in the male. Aristotle also contrived some rather fanciful interpretations of shark anatomy and behavior, as in his explanation for the fact that the shark mouth is on the under side of the head, far back from the tip of the snout, unlike the mouths of most other fish. In his view, this made it difficult for the shark to feed on its prey, requiring it to turn on its back, and thus nature allowed some chance for the poor animals to escape the jaws of this ravenous predator. Modern study of cartilaginous fishes, like fish biology in general, involves several disciplines. Ichthyology, or systematic ichthyology, is particularly concerned with the naming and classifying of species and higher taxa (taxonomic categories) and determining their interrelationships. Living cartilaginous fishes are probably better known (that is, more of the extant species have been discovered) than living bony fishes, simply because they tend to be larger, more conspicuous, and less secretive.Yet it was not until 1976 that one of the largest shark species, a deep-water filterfeeding species called the megamouth shark (Megachasma pelagios), was discovered near Hawaii. There may exist many additional Chondrichthyes species in deep ocean waters and remote coral reef areas. Chondrichthyes systematics (that is, the classification of the fishes) has undergone many changes and revisions as more has become known about fossil representatives and about the characteristics of the anatomy, biochemistry, and the like, of the living species. Studies of fossil cartilaginous fishes are limited almost entirely to samples of teeth, since these are virtually the only body parts durable enough to be preserved in the fossil record. Nevertheless, there is enough information in the characteristics of the teeth so that knowledge of the interrelationships of fossil species, both among one another and with living species, is quite advanced. It is known, for example, that the enormous hand-sized fossil teeth of Carcharodon megalodon, which lived about twenty million years ago, are so similar to the smaller teeth of the white shark (Carcharodon carcharias) that they both belong in the genus Carcharodon. Systematic study of modern species requires collection of specimens, generally by means of nets, traps, hooks, and lines, or spearing. Specimens are then preserved in some way and maintained in a museum collection. Entire specimens, if they are relatively small, can be maintained in diluted alcohol after fixation in formalin (formaldehyde solution). Other specimens, especially large ones, are dissected, and only certain parts are preserved, particularly the head skeleton with jaws and teeth. Certain new techniques provide taxonomic information from samples of living tissue. Karyotyping (analysis of the chromosomes), protein analysis (determination of the amino acid sequence), and DNA hybridization (estimation of genetic similarities) are all techniques that can elucidate interrelationships among the Chondrichthyes. Other disciplines concerned with the study of cartilaginous fishes include fisheries biology (the science of management and exploitation of commercially important fish species) and comparative physiology.

Reindeer

Reindeer are large deer, native to subarctic and arctic regions of northern Europe and Asia. They are related to North American caribou, as both are variants of the species Rangifer tarandus. Reindeer can be domesticated and have long been valuable possessions of humans in those regions of the world. They yield meat, cheese, butter, clothes, and draft animals able to carry heavy burdens. Many Eurasian reindeer still run wild and are trapped for domestication. Whether wild or domesticated, reindeer are herbivores, eating only plants. Their diet is grass, moss, leaves, twigs, and lichens. They often obtain food by scraping snow cover with their antlers and hooves. Reindeer are diurnal, meaning that they are active only during the day. They spend most of their time seeking food. Their preferred habitats are barren, open plains (tundra), forests, grasslands,andmountains.

Physical Characteristics of Reindeer
Reindeer differ from most deer in having large, deeply cleft hooves, hairy muzzles to help to keep them warm, and antlers on both males and females. Reindeer have long bodies and legs. Their hooves are broad, to provide footing on snow and ice. Male reindeer are four feet tall at shoulder height and weigh up to six hundred pounds. Females are shorter but reach similar maximum weights. Both genders grow up to seven feet long. Their thick, waterproof fur is brown in summer and gray-brown in winter. White fur covers their rumps, tails, and the lower portions of their legs. Males have white neck manes during mating season. Reindeer do not see well, but they have an excellent sense of smell. Reindeer antlers have pointed branches (points). In females, they grow to two-foot lengths, while males' antlers reach five-foot lengths. Very large male antlers have forty points. Those of females only have a few points. As in other deer, reindeer antlers are shed and regrown each year. Males lose their antlers in winter and females lose their antlers in late spring. The antlers that grow back are larger than those replaced. Antlers are important during mating season, when males fight for mates. Fights can damage antlers, so if they were not shed and regrown each year, many males would be unable to fight well, lose fights, and be unable to mate. Reindeer are also ruminants, animals that chew and swallow their food more than once. After a little while, food that was swallowed reenters the ruminant mouth from the stomach. Reindeer and other ruminants chew the food, swallow it again, and the food enters a different stomach for additional digestion. The process, also called cud chewing, helps reindeer to get maximum amounts of nutrients and vitamins from their difficult-to-digest food. Reindeer are social animals. They live in groups of about 20 most of the year. The groups consist of a male, his mates, and their young. Reindeer migrate great distances each fall and spring to feeding and mating grounds, travelling in herds of up to 100,000 and migrating about twenty miles per day. Reindeer mate mostly in October. Gestation is about eight months long. The female leaves the herd to give birth to one calf, in May or June. The calf weighs up to twenty pounds. Mother and calf then rejoin the herd and the calf nurses for six months.Acalf can mate when three years old. The life span of reindeer is up to fifteen years.

North American Reindeer Imports
Reindeer are excellent sources of food, clothes, and draft animals, as the Laplanders of Finland food source for the Inuit of Alaska, who live in a comparable environment with a similar social structure, the U.S. Office of Education imported thirteen hundred reindeer from Siberia near the end of the nineteenth century. Several million reindeer are now found throughout Alaska. In 1935, the Canadian government set up a herd of reindeer in the Yukon Territory to benefit Native Americans and Inuit. This herd also flourished and Native Americans and Inuitnowownall reindeer herds in North America. The deer satisfy many of their basic needs, becoming a valuable North American resource.

Rhino

Rhinoceroses (rhinos), which are among the world's largest land animals, belong to the ungulate family Rhinocerotidae. There are three Asian and two African species existing today; the fossil record shows several dozen extinct species as well. The name of the animal comes fromGreek rhino + ceros, meaning "nose-horned."

Physical Characteristics of Rhinoceroses
Rhinos weigh up to four tons and have short, thick, supportive legs. Rhino skin is thick, gray to brown in color, hangs loosely on the body, and is almost hairless. In the Asian species, skin folds at the junctures of the neck and limbs make them look armored. The Asian species also have have incisors and canine teeth, which are missing in the African species. Rhinos have long, prehensile upper lips, for grasping branches and removing leaves, which they eat. Depending on the species, rhinos have one or two nose horns. In two-horned species, the horn closest to the end of the snout is longer. The horns are made of keratin, a fibrous substance that also composes hair. The horns are used for digging food, for defense, and in mating combats. Rhinos are ungulates with three toes per foot, each of which ends in hooflike nails. Each front foot has a vestigial fourth toe. Rhinos, which are ruminants related to horses, eat grass, bulbs, leafy twigs, and shrubs. Although they look clumsy, rhinos can run as fast as horses. They have sharp vision, very good smell, and excellent hearing. Their keen hearing is due in part to their funnelshaped ears, that swivel in different directions.

Rhino Life Cycles
Most rhinos are both diurnal and nocturnal, active in daylight hours as well as after dark. They eat during the cool mornings and evenings, staying in mud wallows during hot afternoons. Rhinos have few enemies because of their size and their dangerous horns-an angry rhino charges its attackers. Humans are rhinos' great enemies, killing them for their horns, which are used in jewelry or medicinally. Most rhinos, especially males, live alone except during mating. There are some exceptions to solitary living: mothers live with their offspring, and young males or females may form same-sex groups. Males have territories, which are marked and defended. They fight each other for mates. While rhinosmaynot live with others of theirown species, they almost always have symbiotic birds, called oxpeckers, living on and around them. The birds eat insects from the rhinos' skins. This gives the birdfood, and frees the rhino fromthe insects. Mating takes place year round, and gestation lasts up to fifteen months. The female gives birth to a baby that weighs between 100 and 150 pounds. The young rhino stays with mother for 2.5 years, though it can feed itself in 2.5 months. Rhinos mate at seven to ten years of age. Females wait for approximately three years between gestations, only becoming pregnant after the previous offspring has left them. Rhinos live for up to fortyfive years.

Rhinoceros Species
There are five rhino species: three in Asia and Malaya, and two in Africa. African rhinos are twohorned and classified as "black" or "white", though all are bluish-gray. Black rhinos live in habitats from mountain forests to scrub lands. Their maximum body length is 10 feet, their height is 5 feet at the shoulder, and they weigh 1.75 tons. Each has a front horn up to 3.5 feet long. The rear horn is shorter. Black rhinos are mostly nocturnal, eating in the cool morning and evening hours and wallowing in river mud during the hot daylight hours. They eat grass, leaves, herbs, fruit, branches, and twigs. In the wild, a male has a marked territory, which he defends. When the territories of several males overlap, they form groups that share resources and defend the combined territory from strangers. White rhinos, similar to black rhinos, are the largest land mammals except elephants. Their maximum length is 13 feet, shoulder height is 6.75 feet, and they weigh 4 tons. Females use their horns for digging, defense, and guiding their offspring. Nearly extinct, white rhinos exist only in preserves. Indian rhinos-the largest Asian rhino species- average 10 feet in length and 5.5 feet in shoulder height, and weigh 2.75 tons. They have one thick, foot-long horn; their skin is sprinkled with knobs, and folds at the limb joints make them look as though they have armor. Females, although 75 percent the weight of males, have similar body heights and lengths. These rhinos live in marshy jungles and eat reeds, grass, twigs, and plant shoots. There are 1,500 Indian rhinos, all living in preserves and protected by legislation. Javan rhinos are similar to the Indian species, but smaller. They occur only inWestern Java, though they once lived in forests of Bengal, Burma, Borneo, Java, and Sumatra. Sumatran rhinos, the smallest rhinos, have two horns. They are approximately 4 feet tall, and weigh about 1 ton. Unlike the smooth-skinned African rhinos, they are hairy, especially on the tail and ears. The few living Sumatran rhinos are in Sumatra's forested hills. Rhinoceroses are reputedly dangerous. However, they are usually peaceful and timid, except when threatened. Legally protected rhinos suffer from the market for rhino horn, reputed to be a medicine and aphrodisiac in traditional Asian medicinal practice. This market has been a major factor in driving four of the five rhino species into endangerment.

Rodents

Rodents, comprising about two thousand species, form the largest, most abundant mammal order. They are found almost everywhere on the earth. Most are ground dwellers and many rodent species dwell underground in burrows or tunnel networks of varying complexity and size. However, rodents also dwell in tree nests (squirrels) or lodges in ponds and streams (beavers), or simply run in herds (capybaras). Judging from fossil remains, rodents were widespread and plentiful fifty million years ago. It is believed that they evolved from small, insect-eating mammals, and did not develop into large species until a million years ago. The largest ancient rodents were giant, bear-sized beavers. Contemporary rodents are usually small. However, the largest modern rodents are herbivorous capybaras, which grow to approximately 100 pounds as adults. Rodents also show remarkable diversity in their diets. These range from the vegetarian capybaras to the all-encompassing diet of omnivorous rats, which will eat meat. Rodents have many roles relative to humans. Hamsters and other small rodents are pets, capybaras are eaten as food, chinchillas are fur sources, and a few, such as rats and mice, are pests that compete with humans for their food crop supplies. The tremendous adaptability of rodents, especially rats, explains their wide geographical distribution in areas differing hugely in climate.

Physical Characteristics of Rodents
Among the two thousand known rodent species, size varies widely. Some small adult mouse species weigh about a fifteenth of a pound. At the other extreme, capybaras, largest of contemporary rodents, are the size of pigs. Regardless of size, all rodents possess pairs of large, chisel-like front teeth in both the upper and lower jaws. The roots of these incisor teeth are located far back in rodent jawbones and grow continuously. Rodents lack the tearing teeth (cuspids) of carnivores as well as several premolars. Therefore, a large space exists between their incisors and molars. This allows the incisors to operate well in gnawing. The design of rodent dentition also allows the gnawed food to be transferred easily to the molars for efficient grinding. In addition, the muscles of the rodent lower jaw are arranged so as to enable its easy movement backward, forward, and laterally. This optimizes grinding of gnawed food. Rodent incisors are different from those in other animals. Their continued growth from the root is valuable, especially because only the front surfaces of these teeth are protected by enamel, the hardest material in teeth. Thus, gnawing food causes the rear surfaces of the teeth to wear down faster than their front surfaces. This wear pattern is the basis for development of the chisel-like incisor edges. It continues as long as a rodent eats regularly, keeping the incisors sharp. Another interesting aspect of rodent mouths is that cheek fur grows inside the mouth and fills up the space between incisors and molars. This hair acts as padding and filters out food chunks too large to be swallowed comfortably. Other than the special development of "gnawing machinery" of the mouth and teeth, rodents are anatomically unspecialized, with no other ubiquitous anatomic features. Where any special characteristic has developed in some rodents, it appears to be due to environmental need. For example, claws and front paws of burrowing rodents, such as woodchucks and moles, make them efficient diggers. In addition, gliding adaptations in some squirrels allow them to "fly" (or actually glide) from tree to tree. Furthermore, leaping rodents such as the kangaroo rat use both hind feet together to enhance leaping capability. Yet another such adaptation is the webbed feet seen in beavers.

The Lives of Rodents
Rodents, like all other mammals, are warmblooded. They carry offspring to term in a uterus where each fetus is connected to the mother via the placenta, give birth to them, and nurse them. Depending on the rodent, the sequence of events between fertilization and the end of the nursing period takes between 5.5 weeks for a small mouse, to well over a year for large rodents. The process is easiest to describe for rats, although it is quite similar for mice and hamsters. After fertilization, rat eggs make their way into a complex uterus which can hold eight to sixteen fetuses. There, each attaches to the uterine wall and develops, over three weeks, into a rat pup. The pups are born pink, hairless, blind, and incompletely developed. They are then nurtured by their mothers, who have the instinct of all mammals to care for their offspring. Rats breast-feed their pups for three weeks. At the end of this time, they are fully covered in hair, have full vision, and have begun to eat foods other than milk. In another month the pups are sexually mature and can breed. This makes it clear why omnivorous wild rats pose a threat to humans.Anypair of rats can produce up to eighty offspring per year. Furthermore, within six weeks after birth, any two offspring can, and do, reproduce. Inbred laboratory rats live for two to three years, depending on the strain. Males are much larger than females (often twice their size) and may attain body weights up to two pounds. In the wild the life expectancy of rats varies greatly. However, reports of animals living for over five years occur. Some males have been reported to be as large as small cats or dogs. Wild rats live in complex tunnels as colonies of a hundred or more animals. Other rodents live different versions of the life of rats. Litter size, gestation time, group organization all vary. For example, the larger rodents have only a few offspring per litter, and some rodents live in tree nests (squirrels) or lodges in ponds (beavers). Life expectancies may be ten years or more, assuming death by natural causes.

Destructive and Beneficial Rodents
Rats and mice interact extensively with humans in a destructive fashion. The problems involved are competition for food, and disease transmission fromrodents to humans. Rats and mice, viewed as pests, are known to eat 10 to 25 percent of grain crops grown, harvested, and stored worldwide. This percentage varies depending upon the extent of use of rodenticides, such as warfarin, in various nations and the extent of agricultural technology. Very careful use of rodenticides is important because they are quite toxic to humans. Rodents are disease vectors, historically causing outbreaks of serious epidemics of the bubonic plague and tularemia. This was especially serious during the Middle Ages, when rats were responsible for the transmission of the Black Death. Currently, most sporadic outbreaks of rodent-derived infectious disease are handled by use of rodenticides to kill carriers and antibiotics to destroy rodent-borne microorganisms that infect humans. Most often it is not the rodents themselves that cause disease outbreaks. Rather, infection occurs as contaminated fleas and ticks move from rodents to humans. Rats are seen as the main disease vectors because they abound near and in human habitations. However, mice and any other infected rodents can be disease vectors. Concerning beneficial use of rodents, one can point to the myriad rats, mice, hamsters, and guinea pigs utilized as laboratory animals in testing and developing pharmaceuticals, the identification of toxic cosmetic, paint, and food components, isolation of disease cures, and so on. This aspect of research is likely to become less common because a large segment of the population deems it morally inappropriate to submit animals to these testing procedures. Another benefit of rodents that is becoming morally unacceptable is harvesting rodent fur. Beaver fur was once hugely important to the world fur trade. Presently, as beaver are nearly extinct, the use of rodents to provide fur for human use has shifted to muskrats, nutria, and chinchillas, which are valued for their attractive, luxuriant coats.

Raccoon

All members of the raccoon family have small bodies, long tails, ringed tails, and facial markings. Kinkajous lack markings, but have prehensile tails that aid arboreal movement. Raccoons are carnivores of the genus Procyon. They are common throughout the United States and also inhabit southern Canada, Central America, and South America. They are foxlike in appearance, with a broad head, a pointy muzzle, and short, erect ears. Raccoons have long fur and bushy tails. They are gray to brown above and lighter beneath. Black cheek patches and white whiskers adorn their heads. Their tails are marked with dark rings. Each paw has five toes, and most raccoons are about 3.5 feet long, including a 1- foot tail. The crab-eating raccoon, a species of Central and South America, is larger than common raccoons and has dark gray fur with yellow patches. Common U.S. raccoons inhabit trees near ponds and streams, or near human homes. They hunt at night for poultry, rodents, bird eggs, insects, fish, frogs, carrion, nuts, and fruit. Those that live near human habitations are particularly fond of scavenging in garbage cans and raiding bird feeders. In northern areas, raccoons winter in dens, rarely emerging. Males are solitary except for mating, while females and young live in groups. Raccoons mate in winter. The following spring, they give birth to up to six young, born in tree dens. Young raccoons depend on their mothers for five months. Mothers and offspring stay together for a year.

quail

The quail is a relatively small, very fast-flying bird that is found in the western hemisphere as well as Europe, Asia, and northern Africa. It is a ground bird that prefers to hunt for seeds, bugs, insects, and other food on the ground near cover. Quails need a high-protein source of feed because of their fast heartbeat, so they usually hunt meaty invertebrates. The quail is generally monogamous in nature. When babies arrive, both parents tend to the offspring. There are several closely related varieties of quail in the world. All have adopted a slightly different way of living, but are recognizable by their general patterns of flight, group activity, and food-hunting tactics. Quail belong to the Phasianidae family, which includes pheasant, turkeys, and several other fowl. The males and females are similar in color and size. Quail are nonmigratory and will establish a territory in which they want to live and stay. Quail are sportsmen's favorite bird because they are fast flyers and elusive. They serve as a challenge.

Porcupine

Agile and armed, although they may seem slow, a porcupine is quick to make its point with its defensive quills. Porcupines do not throw or cast their quills into a potential predator; instead, quills penetrate a predator's body on contact with the porcupine's prickly body. The more than thirty thousand quills on a porcupine's back and sides are actually modified hairs (one of the characteristics of mammals). Other common names of porcupines are quillpig and pricklepig. North American porcupines are arboreal or semiarboreal, spending much of their day climbing trees and consuming tree bark. These herbivores ingest a variety of plant materials, from buds to roots. On occasion, porcupines may eat shed antlers of deer or elk for the various minerals, such as calcium, that they contain. Second in size only to the beavers in the class Rodentia, adults porcupines weigh between four and six kilograms, although much larger ones have been reported. The length attained by adults ranges from about sixty to one hundred centimeters. While color variations occur, most individuals have dark colored pelage. Porcupines are mostly nocturnal, butmaybe observed during the day either on the ground or in trees.

Porcupine Life Cycle
Adult porcupines are solitary mammals for most of the year, except during the breeding season, between September and November. Female porcupines begin reproductive activities at about 1.5 years of age. It is common to find several males around a female during her brief (eight- to twelvehour) time of receptivity. Mating is brief and occurs on the ground, with the female raising her tail over her back. After the male has inseminated her, each porcupine goes its separate way. Usually only one porcupette, as the young are sometimes called, is born after the lengthy gestation period.Weighing between four hundred and five hundred grams at birth, newborn porcupines are quite precocial. Their eyes are open and their quills are present, as are their incisors and premolar teeth. Although capable of consuming vegetation within a week of birth, the young are nursed by their mother through the summer months. Porcupines consume the inner bark of trees and shrubs, especially in the fall and winter when the plants on the ground are becoming dormant or dying. It is easy to observe porcupine feeding sites in the forests by observing the limbs and trunks of trees. If the outer bark has been stripped away, the whitish colored areas beneath are quite apparent. During the spring and early summer, porcupines spend more time on the ground feeding on tender shoots and buds of emerging plants. While their vision is not acute, their olfactory (smell) and auditory (hearing) senses are well developed. Some researchers have reported observing porcupines standing up on their hind legs and sniffing their surroundings. If a porcupine detects a potential predator, it will form a defensive posture of lowered head and back, at the same time raising the tail for swinging. The heavy muscular tail can drive quills deep into a predator's face and head.

Pronghorn

The pronghorn, or American antelope, can sprint sixty miles per hour and run at forty miles per hour. Pronghorns are fast almost from birth. For example, two-day-old pronghorns can outrun humans. Pronghorns are the only living members of the artiodactyl sub-family Antilocapridae, related to antelope. They are not true antelope and reportedly are almost unchanged from ancestors of two million years ago. Pronghorns inhabit open grasslands in plains and semideserts and depend on keen eyesight to detect enemies (wolves and coyotes) and on speed to escape them.Whenpronghorns are afraid, their white rump hairs rise and are visible for miles. An endangered pronghorn also emits warning odors from rump scent glands. This gives other pronghorns time to seek safety. Pronghorns are ruminant herbivores. In the summer they eat herbs, sagebrush, and grasses. During winter, pronghorns dig under the snow for hidden grass and woody plant twigs. When water is scarce, they get needed moisture by eating cacti. Pronghorns are sociable creatures, and their groupings reflect living conditions. In summer, males form single-sex groups, and females live with offspring. In winter, pronghorns form large herds containing both genders.

Physical Characteristics of Pronghorns
Pronghorns are graceful, tan to reddish-brown animals, with solid, chunky bodies, strong but slender legs, and short tails. Their bellies, rump patches, and throat bars are very white. Male pronghorns (bucks) grow to body lengths of 4.5 feet, shoulder heights of 3.5 feet, and weights of 155 pounds. Bucks have back-curving horns with prongs, which is the source of the species name. The horns are up to 1.5 feet long and made of a bone core over which a black horny covering grows. The covering is shed and renewed every year, and horn core is retained. Females have much smaller horns and also shed the coverings. Pronghorns are the only known animals that shed horn covers. Pronghorns are artiodactyl herbivores (others include cattle, pigs, goats, deer, and antelope), which walk on two toes. Their ancestors had five toes, but evolution removed the first toe, and the second and fifth toes are vestigial. The support toes—the third and fourth toes—each end in a hoof. Many artiodactyls are ruminants that chew and swallow vegetation, which enters the stomach for partial digestion, is regurgitated, chewed again, and reenters the stomach for more digestion. Bovids, including pronghorns, have true horns (called horns henceforth). They are permanent, hard, pointy skull outgrowths that usually occur only on heads of males. Horns of females, where present, are smaller. All have bone cores, and atop the core is a tough skin layer rich in keratin, a durable covering for underlying bone. In pronghorns, horn coverings are shed and regrownevery year, allowing horns to enlarge.

The Life Cycle of Pronghorns
In the spring, pronghorn herds separate according to age and gender. Does live in small herds and bucks live in breeding territories that they mark with scent from glands under their ears. Each buck tries to attract mates and scare away rivals by bellows or charges. Sometimes very violent battles arise over territories. In August and September, does begin to pass through individual male territories. Some stop and mate with a buck; others move to the next breeding territory. Gestation lasts eight months and usually produces twin offspring (fawns). Fawns weigh 7 to 8.5 pounds at birth. They develop quickly and are weaned in five months. Pronghorns live about ten years in the wild and up to fourteen years in captivity When North America was settled by Europeans, over fifty million pronghorns lived on the continent. In the early twentieth century, it was estimated that their population was only twenty thousand to twenty-five thousand, due largely to indiscriminate hunting. At that time pronghorns were protected by severely limiting their hunting. This control and careful wildlife management have raised the pronghorn population to 500,000. Wyoming, Montana, andNewMexico permit limited hunting of pronghorns.

Platypus

When the first platypus pelt arrived at London's Natural History Museum in the late 1790's, it was thought to be a fake made from bits of animals sewn together. This unusual mammal has a leathery bill, webbed feet, and fur, and it is one of only three mammals that lay eggs. Its body length is about eighteen inches, and its broad, flat tail is about seven inches long. The reclusive platypus spends most of its time in streams, rivers, and some lakes, foraging for food in the evening and sleeping during the day in burrows dug into the river banks.

Platypus Life
The unusual anatomical features of the platypus provide perfect adaptations for its life in water. The webbed feet are efficient paddles for swimming through the water. Claws on the feet help the platypus to dig burrows. Dense, waterproof fur covers the entire body except the feet and bill. The eyes and ear holes of the animal lie in folds that close when the animal is submerged, and the nostrils are located toward the end of the beak and also close under water. The bill is highly sensitive to touch, and is equipped with electrosensors that detect weak electrical fields produced by prey. Thus, the platypus can locate and capture prey in murky river bottoms without relying on vision, hearing, or smell. Bottom-dwelling invertebrates, especially crustaceans, aquatic insects, and insect larvae, compose the majority of the platypus diet. Behind the bill are located two internal cheek pouches containing horny ridges that substitute for teeth, which are lost early in the life of the platypus. The pouches are used to store food while it is being chewed and sorted by the animal. Amale platypus has a spur on each rear ankle that is connected to a venom gland in the thigh. The spur is used against attackers, but also against competing males during the mating season. The venom is not fatal to humans, but can cause a great deal of pain. This feature makes the platypus one of very few mammals that are venomous.

From Egg to Adult
Courtship and mating occur in the water. After initial approaches by the female, the male chases and grasps her by the tail and inseminates her. After mating, a female will lay two to three eggs and incubate them in a special nesting burrow, which may extend one hundred feet away from the water. The female blocks the entry to the nesting burrow with soil plugs to protect the eggs and young from predators and flooding. She removes and replaces the plug each time she leaves to forage for food. When the eggs hatch, in seven to fourteen days, the young are about one inch long and totally dependent on the mother. Platypuses do not have nipples, but milk is produced in themammaryglands and expressed through openings in the abdominal wall. The young suck the milk directly from the fur. At about five months of age, the young emerge from the nesting burrow and begin learning to search for prey themselves. A typical platypus in the wild will live about ten years.

Pigs and Hogs

Pigs are estimated to have evolved about 38 million years ago in central Europe, and about 25 million years ago to have become established in Africa and Asia. Pigs became domesticated in China about 5000 b.c.e. The reason for the delay in agricultural domestication is believed to be that pigs were unwilling to adapt to a nomadic lifestyle, as dogs, sheep, and goats did. The domesticated pig is thought to have descended fromtwo different lines of wild hogs. It is believed that the East Indian pig (Sus vittatus) has had major influence on the swine of China and the surrounding region. The European wild boar has probably had major influence on the rest of the various breeds of pigs in the world. The domestic pig is a compact, solid-looking animal with a large head, short, fast-moving legs, a rough coat, and a small tail. The color of a pig can vary greatly, fromwhite or black to brownish-red, and any combination thereof, including spotted, solid colored, and banded. Some may reach a height of only twelve inches at the shoulder, others may reach all the way to four feet. The weight of a pig also can vary, with some weighing only about 60 pounds, where others can go over 900. The average meat pig falls in the range from225 to 300 pounds. Humans use pigs in many different ways. From the point of view of the percentage of the carcass used, the pig is the most utilized of all domesticated animals. The hair is used for brushes because it is very strong, yet flexible. The hide is used for numerous products, from shoes to purses; in general it is lightweight and durable. The blood and offal are used for fertilizers, soaps, and medical supplies. Domestic pigs have been used by mankind for centuries as a main supplier of dietary protein.

Types of Pigs
Pigs are cloven-hoofed ungulates, and are closely related to the hippopotamus. As mentioned, the domestic pig (Sus scrofa) isnowfound worldwide. They are omnivorous, eating almost anything. However, pigs generally prefer to eat soft tissue plants, especially roots and tubers, which they dig up with their noses. They will also eat leaves, seeds, bugs, and anything that is found on the ground, including bird eggs, baby birds, snakes, and carrion. There are hundreds of different breeds of pigs in the world. Most of the breeds that the various departments of agriculture recognize as major contributors to current swine production come from the United States or Europe. The pigs can be identified as being either meat, lard, or bacon types. Lardtypes have lost a great deal in numbers over the past fifty years, and have been bred into a style more like meat. The pig population in the world is large, and is approaching almost one billion in number, with China having the largest number, 250 million. Russia and the United States are tied in second place with about 60 million each. Brazil would be fourth with 35 million. The largest consumer of pork per capita is Denmark (105 pounds annually), followed by Hungary, Germany, Austria, Luxembourg-Belgium, and the United States. In the United States, the state of Iowa leads in production of hogs, followed by Illinois, Missouri, Indiana, and Minnesota. Pigs are very smart domesticated animals. Their abilities are thought of as being greater than those of the domestic dog. Indeed, pigs make fine pets, as is evidenced by the pot-bellied pig of Southeast Asia.

Polar Bear

Protected from cold by a thick fur coat and a layer of blubber, the polar bear hunts seals in open areas in the Arctic sea ice.Astrong swimmer, the polar bear uses its large front paws as paddles. Its white fur blends in with the ice and snow as it stalks or still-hunts seals. Ringed seals are the polar bear's primary food, but it also consumes bearded seals, and occasionally walruses, belugas, narwhals, musk oxen, and carrion (dead terrestrial and marine mammals). Although largely carnivorous, when on land the polar bear may eat grasses, kelp, berries, and lichens. Males and nonpregnant females do not make dens or hibernate, but spend the winter hunting on the sea ice. The polar bear evolved from the terrestrial brown bear about 100,000 to 200,000 years ago. In captivity, polar bears and brown bears have interbred and produced fertile offspring. This shows a high degree of genetic relatedness. In nature, however, these two species are geographically isolated fromone another and would rarely meet. Swimming in icy water among the ice floes of the Arctic, quietly stalking a resting seal, then killing it with a crushing blow of its forepaw, the polar bear is an impressive example of an animal's ability to adapt to and live in one of the harshest environments on earth.

Physical Characteristics of Polar Bears
Male polar bears are up to five feet high at the shoulder while on all fours and up to ten feet long. When standing on its hind legs, a male can be eleven feet tall. Adult males are generally much bigger than females: 1,100 to 1,770 pounds for males, 330 to 770 pounds for females. Like other bears, polar bears are plantigrade. Mating takes place in late March to late May. This is the only time that the male is with the female. Other than family groups of females with their cubs, polar bears are solitary. Pregnant females dig snow or earth dens in which they will give birth to one to three cubs in late November to early January. The mother's milk is very rich, with an average fat content of 33 percent. The cubs, which weigh 1 to 1.5 pounds at birth, grow quickly and weigh 22 to 33 pounds when they emerge from the den with their mother in late February to early May. Polar bear cubs usually leave their mother at 2.5 years of age, at which time the mother is ready to breed again. Therefore, the female usually gives birth every third year.

Conservation
By the 1960's, polar bear populations were in serious decline due to sport hunting. In 1967, the five "polar bear nations" (the United States, Canada, Denmark, Norway, and the Soviet Union) limited hunting to the Inuit (Eskimo) people. By 2001, polar bears had recovered, and there were twenty thousand to forty thousand in the world. A 1999 study by longtime polar bear biologist Ian Stirling and his colleagues shows that polar bears at Hudson Bay are 10 percent thinner and have 10 percent fewer cubs than they did twenty years ago. In 1999, the ice on Hudson Bay melted three weeks earlier than it did twenty-five years earlier. Polar bears must wait for ice to form each fall to hunt ringed seals, their main food source. Hudson Bay polar bears fast six to eight months each year and then hunt seals intensively during the ice season. The three-week reduction of hunting time has not yet resulted in significant decline of the polar bear population, but is expected to do so if the climate trend continues.