APE

any of the tailless, manlike primates of the families Hylobatidae (gibbon and siamang) and Pongidae (chimpanzee, bonobo, orangutan, and gorilla), found in the tropical forests of western and central Africa and Southeast Asia. Apes are distinguished from monkeys by the complete absence of a tail, by the presence of an appendix, and by their more complex brains. Apes typically move about by swinging, or brachiation; they also display a tendency to stand erect and, occasionally, to move bipedally, especially when carrying an object. The gibbon, siamang, and orangutan (qq.v.) are arboreal, while the gorilla, chimpanzee, and bonobo (qq.v.) spend some or much of their time on the ground. Pongids travel on the ground by quadrupedal knuckle-walking, in which the long fingers of the forelimbs are folded under to provide support for the body. Fruits and other vegetal materials are the chief foods, though small invertebrates and even small vertebrates are eaten occasionally. Most apes lodge at night in trees, all except gibbons building sleeping nests for the purpose. Group size ranges from the virtually solitary orangutan to the sociable chimpanzees and bonobos, who may live in bands of up to 100 members. Destruction of their forest habitats and hunting by humans have resulted in severe population declines among the apes, all species of which have been classified as endangered by the U.S. Department of the Interior. The evolutionary history of the apes includes numerous extinct forms, many of which are known only from fragmentary remains. The earliest known fossils date from the Oligocene Epoch (beginning about 36.6 million years ago) in Egypt and include such forms as Aeolopithecus, a possible ancestor of the gibbon, and Aegyptopithecus, a possible ancestor of the great apes. Later deposits have yielded such fossils as the gibbonlike Pliopithecus and Limnopithecus and the great-ape-like Dryopithecus (including Proconsul). Apes are intelligent animals and are more closely related to humans than any other living primates. The gorilla, chimpanzee, bonobo, and orangutan are called great apes in recognition of their comparatively large size and manlike features, while the gibbon and siamang are called lesser apes. The term ape is also used in a less-restricted sense to refer to certain large tailless monkeys, such as the Celebes black ape (q.v.).