Contrary to the implication of one of its common names, "pygmy chimpanzee," this species is not particularly diminutive when compared to common chimpanzees (Pan troglodytes). The "pygmy" modifier may instead refer to its location: it lives in an area inhabited by people often referred to as such.
Unlike its closest cousins (common chimpanzees), bonobos are not divided into subspecies. Bonobos are apes about two-thirds the size of humans, with dark hair covering their bodies. The hair is generally longer than in common chimpanzees, and is particularly noticeable on the cheeks, which are relatively hairless in P. troglodytes. The portions of body not covered with hair (i.e. mid-face, hands, feet) are darkly colored throughout life. This contrasts with common chimpanzees, which have lighter skin, particularly during the younger years.
Bonobos are primarily knuckle-walkers, although at times they walk bipedally and do so more frequently than P. troglodytes. Bonobos have longer extremities, particularly hind legs, as compared to common chimpanzees. Although sexual dimorphism exists with males around 30% heavier (37 to 61 kg, 45 kg average) than females (27 to 38 kg, 33.2 kg average), bonobos are less sexually dimorphic than many primates, and skeletons are nearly the same size. Average height is 119 cm for males and 111 cm for femals. Average cranial capacity is 350 cubic centimeters.
Range mass: 27 to 61 kg.
Average mass: 39 kg.
Range length: 104 to 124 cm.
Average length: 115 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger