Chimpanzees (Pan troglodytes), along with bonobos (Pan paniscus), belong to the genus Pan. Molecular analysis of both nuclear and mitochondrial DNA confirms these closely related species to have been separated around 1.2 – 2.7 million years ago. Currently, there are four recognized chimpanzee subspecies: Pan troglodytes verus, Pan troglodyres vellerosus, Pan troglodytes troglodytes, and Pan troglodytes schweinfurthii.
Chimpanzees show a slight sexual dimorphism with males being slightly larger than females. Adult males and females weight around 40-60 kg. and 32-47 kg., respectively. Chimpanzees are covered by black hair although some individuals turn grey in some areas of their body (e.g., legs) with age. Infants have light faces that get darker as they mature and a white tuft of hair in their anal region that disappears at around 3-5 years of age. Current population estimates place the number of west African chimpanzees between 96.000 and 180.000 and that of eastern African chimpanzees between 173.000 and 300.000.
Distribution and ecology
Chimpanzees inhabit a wide variety of habitats in sub-Saharan Africa ranging from dry woodland savannah, and grassland to secondary and primary rain forest.
Like bonobos, chimpanzees subsist primarily on plant food, including fruits, seeds, sprouts, leaves, flowers, bark, stems, pith, roots, and mushrooms. In addition, chimpanzees hunt small terrestrial mammals such as antelopes or more commonly arboreal monkeys. In some populations hunting is done cooperatively by groups of males while in other populations hunting is an individual activity.
Chimpanzees are a mainly terrestrial species although they spend a considerable part of their day in the trees where they forage and rest. Similar to all other great ape species, chimpanzees build sleeping nests in trees where they sleep or just rest. The average day range of chimpanzees is 1900-4600m with a home range of around 25km2.
Social structure and behaviour
Similar to bonobos, chimpanzees live in fission-fusion polygynous societies, in which they temporarily split into small parties that reunite at a later time. Thus, this is a fluid society in which party membership (but not community membership, especially for males) may change from day to day depending on factors such as food availability or the presence of estrous females among other factors.
The society of chimpanzees centres around the adult males, who form the strongest bonds and actively defend their territory against males from neighbouring communities by patrolling the border of their own territories. The females can be described as ‘individualistic’ and less ‘gregarious’ and leave their natal group upon reaching sexual maturity. In contrast, males stay in their natal groups and become integrated in adult male dominance hierarchy.
For a more detailed overview and references see Call & Tomasello, 2007.