Chimpanzee

The chimpanzee is the animal that first forced scientists to admit humans are not unique. Chimps make and use tools, wage territorial war, pass local traditions between generations, comfort each other, deceive rivals, and grieve — and they share almost 99% of our DNA.

Overview

Chimpanzees live across a broad band of equatorial Africa, from the dry woodlands of Senegal in the west to the forests of western Tanzania in the east. They occupy rainforest, swamp forest, montane forest, and open savanna woodland, and their behaviour varies with all of it. There are four recognised subspecies, and the species as a whole has been studied continuously in the wild since Jane Goodall began at Gombe, Tanzania, in 1960.

Physical characteristics

An adult male chimpanzee weighs 40–70 kg and, though only about human height when upright, is several times stronger in the upper body. Chimps have long arms for swinging and reaching, opposable thumbs and big toes for gripping, black hair that greys with age, and bare faces that range from pink to nearly black. They move on the ground by knuckle-walking and can stand or run bipedally for short distances.

Society

Chimpanzee communities of 15 to 150 individuals occupy and defend a shared territory, but the whole group is almost never together. Instead they travel in constantly changing parties — a fission–fusion society — that split and merge through the day depending on food and social opportunity.

Males stay in their birth community for life and form the core social network, ranked in a hierarchy topped by an alpha male who holds his position through a mix of strength, aggression, and carefully maintained alliances. Females usually transfer to a neighbouring community as they mature. Relations between communities are hostile: bands of males patrol boundaries and will attack and kill lone individuals from rival groups, a pattern first documented as the “Gombe chimpanzee war.”

Tools and culture

More than any other non-human animal, chimpanzees show culture — behaviours that are learned, shared within a group, and different between groups. Termite fishing, nut cracking with stone hammers, using leaf sponges to drink, medicinal leaf-swallowing, and specific grooming handclasps all vary from one population to the next in ways that cannot be explained by genetics or environment alone.

Diet

Chimpanzees are omnivores built around fruit. Ripe fruit makes up roughly half the diet, supplemented with leaves, seeds, flowers, bark, and pith, plus insects — termites, ants, and bee larvae — and, seasonally, hunted meat.

Reproduction and life cycle

Females give birth to a single infant, rarely twins, after an eight-month pregnancy, and there is a long gap of five to six years between births. Infants cling to the mother’s belly, then ride on her back, and nurse for four to five years while learning the community’s foraging and social skills. This slow reproduction — a female may raise only three or four surviving offspring in a lifetime — is a major reason chimp populations recover so slowly from any loss.

Threats and conservation

The chimpanzee is listed as Endangered and declining across its range:

• Habitat loss from logging, agriculture, and mining, which also fragments populations and opens roads for hunters.
• The bushmeat trade and live capture of infants for the illegal pet trade, which usually involves killing the mother.
• Disease. Chimpanzees catch human respiratory viruses, and Ebola has devastated communities in Central Africa.

Long-term research sites, national parks, community forest management, and sanctuaries for orphaned chimps are the pillars of conservation, but the western chimpanzee subspecies in particular has declined by around 80% in recent decades.