Head and body length ranges from 28 to 33 inches in females and 30-36 inches in males. Height ranges from about 3-1/4 feet to 5-1/2 feet. Weight is from 99 pounds to 176 pounds. Captives may be heavier. Arm-spread is 50% greater than height. No tail. Face bare, skin pink in infancy darkening to black in adulthood. Baldness is frequent in adults, typically a triangle on the forehead of male, more extensive in females. Hair color is black. Infants have white tail tuft and older males (20 or over) may develop grey back patch.
GEOGRAPHICAL RANGE AND HABITAT:
Western and Central Africa, north of river Zaire, from Senegal to Tanzania, from 14 degrees north to 10 degrees south. Humid forest, deciduous woodland or mixed savanna; presence in open areas depends on access to evergreen fruit-producing forest. Found from sea level to 6500 feet.
Omnivorous. Feed on a wide variety of foodstuffs (over 80 different items have been catalogued) with the largest proportion consisting of fruit and young leaves. In long dry seasons, buds and blossoms, soft pitch, stems, galls, honey, bark and resin, seeds and nuts are also eaten. Animal prey makes up as much as five percent of the diet, with social insects, such as ants and termites, providing the largest amounts. On rare occasions small game (monkeys, pigs, and antelope) is hunted. Feeding is essentially an individual activity, but after a cooperative hunt may share morsels in response to begging by others. There seem to be "cultural" differences between groups of chimpanzees in the variety of food taken and the techniques for processing it. (West African chimps use wood and stone tools as hammers to open nuts.)
LIFE CYCLE/SOCIAL STRUCTURE:
Females in heat have prominent swelling of the pink perineal skin, lasting two to three weeks or more, and occurring every four to six weeks. Males have relatively huge testes. Puberty in both sexes occurs at about seven years, but males are not fully integrated into the social hierarchy until 15 or so. Females raised in captivity begin mating at eight to nine years and give birth for the first time at 10-11 years old. Wild females mature three to four years later. There is no breeding season. Chimpanzee females are not receptive for three to four years after giving birth, then resume sexual activities for one to six months until conception. Females mate only when in heat. For the first week or more, female chimps are promiscuous and mate on an average of six times a day. Toward the last week of estrus, when ovulation occurs, high ranking males may compete for mating rights. Occasionally, an exclusive "consortship" is formed, a female and male eluding other members of the community for days or weeks. Reproductive capability in the female may last at least until the age of 40. Maximum life span in the wild may be 60 years. The newborn is helpless with only a weak grasping reflex and needs support from the mother's hand during travel. Within a few days it clings to the mother's ventral surface without assistance, and begins riding "jockey-style" at 5-7 months. By four years, the infant travels mostly by walking, but stays with its mother until at least five to seven years old. Weaning begins in the third year. Chimp communities are made up of 15 to 120 animals. These communities lack a definite leader and are usually split into a number of subgroups which are temporary and change in composition within a matter of hours or days ("fusion-fission" groups). Mothers often travel alone with only their offspring. Males seldom or never leave the community into which they were born, whereas most females migrate to a new community during an adolescent estrus period. In male relationships, tension is routinely expressed in dominance interactions when parties meet, but males also spend much time grooming each other. They form a loose dominance hierarchy.
For sleeping at night, each chimp (except infants who nest with their mothers) constructs a nest of vegetation 9-12 meters high in a tree. Males may hunt cooperatively for baby monkeys or bush pigs and even "share" some of the meat. Dr. Jane Goodall has documented serious territorial fights.
Chimps travel mostly on the ground where they "knuckle-walk". They are one of the few mammals that manufacture and use "tools." They often feed by poking a twig or vine into a termite nest hole. When the twig has become covered with insects, they pull it out and nibble them off. They also use sticks to enlarge holes so that ants can be reached. Some populations chew leaves to make them more absorbent and dip for water from holes in trees. Many also use leaves to clean the body. West African chimps use stones to crack hard seeds.
The chimpanzees can be found in the Tropical Rainforest.
STATUS IN WILD:
Although there may be as many as 35,000 chimps in the wild, chimp populations have been reduced and fragmented by human encroachment into their habitats. In addition, hunting by people for food or commercial exportation for the animal trade has led to them being placed on Appendix II (threatened) of CITES, listed as endangered by the IUCN, and considered endangered by the U.S. Fish and Wildlife Service.