The chimpanzee (Pan troglodytes) is a member of the order Primates, a group embracing more than 200 living species. They range from creatures as primitive as tarsiers and lemurs at one end of the spectrum, to man at the other.
The chief anatomical characteristics shared by chimpanzees, orangutans and gorillas (which set them apart from lesser primates), are the absence of a tail, a more or less upright posture and the high degree of development of the brain. However, these primates vary widely in way of life: orangutans live almost entirely in the trees, gorillas live primarily on the ground, but the chimpanzee--alone among the anthropoid apes--is equally at home in the trees and on the ground.
Habitat: Chimpanzees are found in the forests of Central and West Africa. They thrive in steamy, lowland rainforests, in mountainous forests and, in the western part of their range, the savannah.
Development: Chimps weigh about five pounds at birth (the gestation period is about seven-and-a-half months). Like a human baby, a chimp is almost completely helpless at birth and for the first 12 months, but at a few days old it is able to cling to its mother. By the age of eight or nine, a chimp may weigh 88 pounds and is sexually mature. Growth continues until the animal is about 13 years old. An average adult chimp stands about four feet tall, females weight about 99 pounds, the male, 121 pounds; larger individuals can weigh nearly twice as much. Chimps often live 40 years or longer.
Dependent infancy and the long childhood of chimps are indications of their close relationship to man. Other characteristics are the chimp's hands, which have an opposable thumb so they can pick up objects between thumb and forefingers and, most importantly, a brain large in relation to body size and weight.
A baby chimpanzee learns by watching its mother. For two to three years it shares a nest with its mother, usually built in the treetops and fashioned from branches; sometimes it is crafted of grass blades on the ground. The baby travels with its mother six to eight hours daily to feed on fruit, leaves, bark and, on occasion, meat. In the trees, chimpanzees swing can swing easily from branch to branch; on level ground or on thick aerial branches they move about on all fours.
By the age of two, a young chimp will begin to find part of its food itself. Researchers have observed young chimps begging food from their mothers or other females. Chimps live in groups of up to 40 individuals. Within this group, a mother and her young comprise the most stable social unit. Males are not tied to infant care and, if they are not needed for defense, may range far afield in search of food, sometimes killing small game.
Currently, the social behavior of chimps has been observed in the wild for many consecutive years by scientists. Dr. Jane Goodall, a recipient of World Wildlife Fund 's annual Getty Prize, and her colleagues have spent more than 30 years in what is now Gombe National Park in Tanzania. Goodall has observed chimps making tools--carefully selecting sticks, stripping them of leaves and dipping them into termite mound holes to enjoy a tasty feast. They also pluck leaves off trees, chew them up and use the resultant mass as a sponge. Water, in the natural bowl of a tree, is soaked up into the "sponge" and squeezed into the chimp's mouth.
Mothers examine the fur of their babies for foreign particles, spending more and more time on the task as the babies grow older and venture further afield. Adult females within the group get along well with each other, often taking turns "babysitting." Chimps do not pair off in monogamous relationships, nor does the high-ranking male keep or protect a harem of females. Females in heat will mate with several males in a row. Chimps reproduce only every three years, since a nursing mother cannot conceive.
Predators: Of all the animals that live in its territory, the leopard is the only real predator of the chimpanzee. It is strong, fast and a stealthy killer. To test chimps' reactions to leopards, a scientist placed a dummy leopard along a forest trail. As the troup approached, the dummy was pulled upright and its tail "wagged." The chimps reacted with terrified screams, and some tore up small trees and began threatening the pseudo-leopard.
Endangerment and Conservation: Man is the main threat to the chimpanzee's survival. The species is considered vulnerable in all of West Africa and parts of East Africa where most populations are now reduced to small remnants surviving mainly in restricted forests and in some parks and reserves. The species is possibly abundant in some areas of Central Africa, but little or nothing is known about populations that might occur in the interior forests of Cameroon, Gabon, the Congo Republic and Zaire. The principal reason for the decline in the number of chimpanzees is the progressive destruction of their environment. More than 110,000 square kilometers of tropical rainforest are currently destroyed each year for timber and to provide farmland. Not only do the animals lose their habitat, but the former forest areas are seriously degraded and are often unfit for cultivation for more than a few years.
Chimpanzees are threatened in other ways. Because they so resemble humans in physiology and in behavior, they are in heavy demand for scientific research. Chimps have the same A-B-O blood groupings as humans and are used for compatibility studies for tissue transplants, for hepititus research and for other medical studies. The more commercial trade in chimpanzees for zoos and the pet trade has diminished somewhat in recent years, thanks to the Convention on International Trade in Endangered Species of Wild Flora & Fauna. This convention, respected in more than 100 member countries, prevents international trade in wild-captured chimpanzees for primarily commercial purposes. The trade in live chimpanzees represents a heavy drain on the wild population, for often whole families are killed to obtain a few babies, and the mortality rate among these babies during capture and transport is high. There is, therefore, a growing realization in many research centers that self-perpetuating chimp colonies are a necessity.