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 corprehistoric man hunted orangutans for food and could have been partly responsible for their dis-appearance 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 facil-ity. 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 domestifor 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, includ-ing 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 conti-nents. 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 subtropiAfrica 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 microscavengers.