Chimpanzees

Chimpanzeesare one of the two species of the genus Pan, the other being the bonobo. Together with gorillas, they are the only exclusively African species of great ape that are currently extant. Native to sub-Saharan Africa, both chimpanzees and bonobos are currently found in the Congo jungle.

Distribution and habitat

There are two species of the genus Pan, both previously called Chimpanzees:

1. Common Chimpanzees or Pan troglodytes, are found almost exclusively in the heavily forested regions of Central and West Africa. With at least four commonly accepted subspecies, their population and distribution is much more extensive that the Bonobos, in the past also called 'Pygmy Chimpanzee'.
2. Bonobos, Pan paniscus, are found only in Central Africa, south of the Congo River and north of the Kasai River (a tributary of the Congo), in the humid forests of the Democratic Republic of Congo of Central Africa

Anatomy and physiology

A chimpanzee's arms are longer than its legs. The male common chimp stands up to 1.2 m (3.9 ft) high. Male adult wild chimps weigh between 40 and 60 kg with females weighing between 27 and 50 kg. When extended, the common chimp's long arms span one and a half times the body's height. The bonobo is slightly shorter and thinner than the common chimpanzee, but has longer limbs. In trees, both species climb with their long, powerful arms; on the ground, chimpanzees usually knuckle-walk, or walk on all fours, clenching their fists and supporting themselves on the knuckles. Chimpanzees are better suited for walking than orangutans, because the chimp's feet have broader soles and shorter toes. The bonobo has proportionately longer upper limbs and walks upright more often than does the common chimpanzee. Both species can walk upright on two legs when carrying objects with their hands and arms.

The chimpanzee is tailless; its coat is dark; its face, fingers, palms of the hands, and soles of the feet are hairless. The exposed skin of the face, hands, and feet varies from pink to very dark in both species, but is generally lighter in younger individuals and darkens with maturity. A University of Chicago Medical Centre study has found significant genetic differences between chimpanzee populations. A bony shelf over the eyes gives the forehead a receding appearance, and the nose is flat. Although the jaws protrude, a chimp's lips are thrust out only when it pouts.

The brain of a chimpanzee has been measured at a general range of 282–500 cm³. The human brain, in contrast, is about three times larger, with a reported average volume of about 1330 cm³.

Chimpanzees reach puberty between the age of eight and ten years. A chimpanzee's testicles are unusually large for their body size, with a combined weight of about 4 oz (110 g) compared to a gorilla's 1 oz (28 g) or a human's 1.5 ounces (43 g). This relatively great size is generally attributed to sperm competition due to the polyandrous nature of chimpanzee mating behaviour.