South of the taiga, Eurasian biomes become less clearly defined. Much of the area is flat and treeless. In the west, where rainfall is adequate, grass grows thickly. But deep in the continent's interior, the land becomes a desert. Here, thousands of miles from the moderating effects of the ocean, temperatures can climb well above 38°C (100°F) in summer, and plummet far below freezing in winter.
Animals must make drastic adjustments to these climatic extremes. One of the most common is migration. Herders move their domestic herds and flocks, following the seasons, and many of the wild grazers also make similar journeys, with predators following along.
The animals which are permanent residents have adapted to the heat, cold and aridity of this area. The saiga, an antelope-like animal, has nostrils pointing downward to help keep out dust. Inside each of its nostrils the saiga has a sac which is believed to warm and moisten the air.
The Bactrian camel of Mongolia and China has adapted to its environment by growing a thick, shaggy, winter coat; broad, split hooves to keep from sinking into the sand; and two humps for storing fat when foraging is poor.
Several species of wild asses are native to the interior of central Asia. Among these are the Mongolian kulan and Iranian onager. Asses are smaller than true horses and characterized by long ears, deep-set eyes coarse, wiry manes, small feet and tails tipped with long hairs. They can survive longer without water than other members of the horse family and are able to get along on a small amount of food. Because of their sure-footedness and endurance they are valuable beasts of burden and have been domesticated for centuries.
The Eurasian grassland is home to the heaviest of all flying birds, the 20 kg (45 lb) great bustard. And the world's smallest crane, the demoiselle which stands just 1 m (39 in) tall, breeds on grasslands from southeastern Europe into central Asia.
Several species of wild sheep and goats live on the grasslands and adjacent mountains. Markhors and turs, both goats, range from Spain to India and northward into Mongolia and Siberia. The tahr, a goatlike animal, is found in the high Himalayas. Goats differ from sheep in that they have beards, feet with scent glands, convex foreheads, and a definite odor among the males.
Some of the world's most unusual mammals live in the mountains which separate central Asia from India. One of the best known is the giant panda, once considered a member of the raccoon family and now thought to be related to bears. This animal lives on a diet consisting mainly of bamboo shoots. For unknown reasons the bamboo is dying, which threatens the pandas' future. The Chinese government has commissioned a team of biologists to study the situation. Although giant pandas have rarely reproduced in western zoos, a number of babies have been born in the Beijing zoo through natural conception, and artificial insemination has recently been successful.
The giant panda shares its bamboo forest with the lesser panda. This animal looks like a raccoon but is related to the giant panda.
Central Asia is isolated from India and Burma by the Himalaya mountain range, the highest mountains on earth. The area is so remote that little is known about the behavior of many of its animals. It is the home of a collie-sized gazelle, several species of wild sheep, and a member of the cow family, the yak. The yak is also domesticated and has been a beast of burden and supplier of milk, wool and fuel for many centuries.
One of the most beautiful of all Himalayan animals is the snow leopard, or ounce. Its fur is in great demand and poaching has placed it in grave danger of extinction.
The snow leopard's main prey is the bharal, or blue sheep, which lives in the Himalayas and other high mountains in eastern Asia.
As one moves south from the high country, the character of the land and its animals change. Rugged mountains give way to forested foothills. This country is the northern edge of the sloth bear's range which also includes other parts of India and Sri Lanka (Ceylon). Termites are a part of the sloth bear's diet, and it sucks them in by a "vacuuming" process. The bear rips open the termites' nest with its claws, then blows away the dirt and dust, and starts sucking. Its lips protrude; its nostrils close to keep out dirt.
Beyond the foothills, seasonal forests give way to semi-arid plains and desert in India. Axis deer, nilgai (India's largest antelope) and blackbuck live here. In the Gir Forest is the last remnant population of the lions which once roamed from the Atlantic through the Near East and into Asia. But lions have been gone from most of this range for many centuries and exist today only in a protected reserve in the tiny Gir Forest in western India, where a few hundred individuals survive.
Where one finds lions and other predators, scavengers will also be found. In India they include striped hyenas, foxes, dholes (wild dogs), and Indian white-backed vultures. These animals perform a vital function in the balance of nature, cleaning up carrion left by the hunters, thus helping to prevent the spread of disease.
Still farther south lies India's tropical forest, actually two of them — a rain forest and a seasonally deciduous forest. They are home to a large variety of monkeys, mainly of two groups — the short-tailed, stout-bodied macaques, which are primarily terrestrial, and the long-tailed, slender-bodied arboreal langurs.
The macaques include the rhesus monkey of India, sacred to the Hindus, and critical to science. The existence of the Rh blood factor was first demonstrated in rhesus monkeys, and a rhesus was the first living being shot into space in the United States' space program. In Europe, the only wild monkeys are the Barbary apes, actually macaques, of Gibraltar. Legend has it that when these animals disappear — there are approximately 30 of them — Britain's reign over the Rock will come to an end.
The second large group of Asian monkeys, the lan-gurs, are also called leaf-eating monkeys. There are more than a dozen species, among which the douc langur is considered to be one of the most beautiful of all monkeys. The word "douc" means "monkey" in Vietnamese.
Three of the surviving five species of rhinoceroses live in southeastern Asia. Two, the Sumatran and Javan rhinos, could be extinct in the wild. The third, the Indian rhino, exists in small numbers in Assam. Because of the heavy folds of skin and the bumps, called tubercules, on its hips and shoulders, this rhino appears to be wearing a suit of armor.
The Chinese believe that rhino blood, urine, and horn (which is not a true horn at all, but is composed of hair-like material) have medicinal and aphrodisiacal powers. This superstition has resulted in heavy poaching of rhinos, placing them in grave danger.
Among the better-known snakes of southeastern Asia are the Indian and king cobras and the pythons. A king cobra can measure 3.5 m (12 ft) or more. It feeds mainly on other snakes. The closely related Indian, or Asian, cobra is appreciably smaller. The pythons are non-venomous constrictors. Contrary to popular belief they do not crush their victims to death but, through constriction, cause death through suffocation.
Southeastern Asia is the home of some of the showiest of all birds — the pheasants. Although native to Asia, they have been introduced elsewhere and now are among the most widely distributed of birds. One of the most widespread is the ringneck pheasant. An old legend claims that ringnecks were introduced into Greece by Jason, famous for his quest of the golden fleece. Ringnecks were brought to the United States in the mid-1800's and are now game birds. Several species of pheasants are exhibited at the Zoo, two of them roaming freely on the grounds.
The first is the blue peafowl. The male, called a peacock, is the traditional symbol of vanity and false pride because of its almost constant displaying and strutting. The peafowl has been semi-domesticated for ages. A Greek myth relates how the bird got the eye-like spots on its tail. The peacock was a favored pet of Juno, wife of Jupiter. She became angry at her one-hundred-eyed servant, Argus, because of a misdeed on his part. To punish him and to make sure the world remembered his offense, she snatched out his hundred eyes and scattered them on the tail of her pet peacock. There they remain to this day.
The other pheasant that wanders the Zoo grounds is the junglefowl. It looks much like a domestic chicken — understandably since it is the chicken's ancestor.
Anthropologists think the chicken was first domesticated about 4000 B.C. as a fighting bird. Evidence suggests that the first chickens in the New World came with Polynesian sailors. The most ornamental of all domestic chickens are the long-tailed birds bred by the Japanese, some having tail feathers 6 m (20 ft) long.
The hot, humid rain forests of southeastern Asia hold a profusion of wildlife, much of it arboreal. Among these tree dwellers, primates reign, and within this group, the anthropoid — manlike — apes are royalty. Two of earth's four kinds of manlike apes live in southeastern Asia.
The smallest and most agile of these are the gibbons and siamangs. These apes are light-bodied, long-armed and have long, slender hands. Their generic name, Hylobates, means "tree dweller." They are truly champion acrobats, swinging hand over hand and leaping more than 9 m (30 ft) from one branch to the next. On large branches they usually walk upright, holding their arms aloft for balance. Gibbons live in family groups of two to six animals within well defined territories. Their morning whooping, often heard at the Zoo, is a territorial call to warn off other gibbons. The second anthropoid of southeastern Asia is the slow, retiring orangutan. Its name means "old man of the forest," and the orang does seem the most human of the apes. Unlike the gibbon, it is a loner. The species used to be widespread throughout the islands of southeastern Asia but extinction came early on all but Borneo and Sumatra. If we read the evidence correctly, prehistoric man hunted orangutans for food and could have been partly responsible for their disappearance from most of the range. Today fewer than 5,000 individuals remain, and despite strenuous efforts to save them, their numbers continue to drop. The forests they need are falling to the ax, so if the species survives, it will be in zoos and wildlife reserves.
Among the rain forest's arboreal creatures, there are a number of interesting "flying" animals — snakes, frogs and lizards. None of these animals actually flies. They glide with varying degrees of aerodynamic facility. The snake spreads its ribs and arches its body to produce a crude airfoil that allows it to glide at a steep angle. The other animals have folds and strips of skin which, when stretched, produce taut membranes that slow descent.
The second largest of all land animals, the Asian elephant, lives in the tropical forest. A bull can weigh 5,000 kg (11,000 Ib) and stand 2.5 to 3 m (8 to 10 ft) tall at the shoulders. Asian elephants have been domesticated for centuries — for riding, war, and as beasts of burden.
The Asian elephant's only natural enemy is the tiger. Although this cat attacks elephants, especially calves, it also preys on just about anything it can catch, including the crocodiles that live in the forest's sluggish rivers. One of its chief prey is the Malay tapir.
Tapirs originated in the New World, crossed on the land bridge into Asia and now exist on both continents. The obvious difference between Old World and New World tapirs is the large, white saddle-shaped patch of hair on the Malay tapir's body. American tapirs are a solid brown color.
Of the many species of birds in the tropical forest, among the most bizarre are the hornbills. There are 45 species, distributed throughout tropical and subtropical Africa and Asia. One of the bird's more fascinating behavioral habits is the manner of nesting. In most species of hornbills, when the female is pregnant and ready to lay, she enters a natural cavity in a tree. She and the male plaster over the cavity's opening with a mixture of droppings, mud and regurgitated food. They leave a narrow opening just wide enough for the female to poke her beak through, but too small for predators to enter. The plastered wall hardens, and the female, her eggs, and later the chicks, are safe. The male spends the time feeding his mate. When the nestlings are half-grown, both parents chip away the wall and the female emerges. She then helps her mate feed the baby birds, which remain in the nest until they are fledged. During the time the nest is occupied, it is kept clean and disease-free by insects and microscopic scavengers.
THE ANIMALS OF THE AMERICAS
North and South America comprise the only continuous land mass that reaches from the north to south polar regions, a distance of more than 14,500 km (9,000 mi). The combined area of the two continents is 41.4 million sq km (16 million sq mi), in which are found all terrestrial biomes.
The two continents have been joined for the past two or three million years. Earlier South America was an island, set apart from the northern land mass for at least 60 million years. This gave time for animal species unique to the continent to evolve. After the Isthmus of Panama emerged, there was an interchange of animals between North and South America, much as that experienced by Eurasia and America during the Ice Ages. One of the animals found in both Eurasia and America is the polar bear. Its habitat is along the entire Arctic coast. It has even been sighted hunting seals on ice floes hundreds of miles at sea. The polar bear's heavy coat insulates it from the icy water and air. Thick hair growing between its toes keep it from slipping on the ice. The thick, white pelt made the animal a prized trophy and reduced its population. The bear is now protected throughout its range.
The musk ox, resident of the far north, also has had to be protected from excessive hunting. At one time it came very close to extinction. A member of the cow family, the musk ox has adapted to the bitter cold by developing a heavy, shaggy coat consisting of two parts — a coarse outer covering of long guard hairs and a soft inner coat so dense that neither cold nor moisture can penetrate.
Musk oxen form a defensive ring when threatened. Adults stand along the perimeter, heads and horns pointing out, and the calves cluster together inside. This defensive posture works well against the ox's chief enemy, wolves, but is of little avail when high-powered rifles are the enemy.
Wolves prey on many species in the north — musk ox, caribou, moose, deer, hares, and even rodents. These carnivores are among the most maligned of all animals, victims of false myths and legends and systematic programs of extermination. They are accused of attacking humans and destroying entire herds of domestic animals. But their depredations of livestock are less severe than often claimed. And unprovoked attacks by healthy wolves in North America on humans are unknown. Those recorded from Europe's Middle Ages are thought to have been made by rabid animals or hybrids.
The world will be a far lonelier place if the last wolf dies. As biologist Ernest P. Walker wrote in his book, Mammals of the World, "The howl of the wolf and coyote, which to some people is of more enduring significance than superhighways and skyscrapers, should always remain a part of our heritage."
Some Arctic wolves remain snow white year round, an adoption to their environment. Three other predators of the far north— the snowy owl, Arctic fox, and weasel— are white at least part of the year.
The life cycle of the snowy owl demonstrates the close relationship which can exist between predator and prey. This owl hunts hares and lemmings. When these mammals are plentiful, female owls lay clutches of seven to ten eggs. When the food supply drops, only one to three eggs are laid.
Lemmings are among the most plentiful animals of the far north. These tiny rodents, found throughout the Arctic, are characterized by wide fluctuations in population. When vegetation is plentiful, the lemmings' numbers skyrocket. This population density seems to trigger a drive to migrate. Hordes of lemmings move out. Nothing deters them — swamps, forests, lakes, rivers. Eventually some reach the sea, which seems just one more obstacle. They plunge in, swim out, and drown.
Each summer the far north comes alive with the millions of birds which have migrated from the south to mate, build nests and raise their young. Waterfowl make up the majority of these migrants. Shore birds, pelagic birds, geese and ducks abound in the short Arctic summer. Some have come thousands of miles. The champion migrant is the Arctic tern, which flies • 16,000 km (10,000 mi) from the Antarctic, and in autumn flies back again.