Bonobos (Pan paniscus), along with common chimpanzees (Pan troglodytes), belong to the genus Pan. The name probably derived from a misspelling on a shipping crate going to Bolobo, Zaire (now Democratic Republic of Congo). 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.
Bonobos constitute the least sexually dimorphic ape species with the males having longer canines than the females. In addition, adult male bonobos weigh on average 39 kg and have an average body length of 730—830 mm. Adult female bonobos weigh on average 30 kg and have an average body length of 700—760 mm. The pelage color is black and may turn more of a grayish color with age.
Bonobos are sometimes called pygmy or dwarf chimpanzees. Comparisons of anatomical features, however, show bonobos not to be smaller than chimpanzees, but to differ in distinct body proportions: their upper limbs are shorter and their lower limbs are longer than those of chimpanzees, they have a narrower chest, and their skull is more gracile. The face of bonobos is black from birth and a white tail tuft is seen in adults and infants.
Distribution and ecology
Bonobos exist only in the Congo Basin of the Democratic Republic of Congo (DRC, formerly Zaire), and population estimates range from only 5,000 to 100,000 individuals. Bonobos are thought to be restricted by the Congo-Zualaba River in the west, north and east, and by the Kasai-Sankuru River in the south. Preferred habitats include primary, secondary and swamp forests.
Like chimpanzees, bonobos subsist primarily on plant food, including fruits, seeds, sprouts, leaves, flowers, bark, stems, pith, roots, and mushrooms. Bonobos divide the time they spent feeding and traveling between the ground and trees, and build their sleeping nests in trees. The average day range of bonobos is 1200—2400 m with a home range of around 20.5 km2. Home ranges of neighboring communities overlap extensively (Fruth, 1995).
Social structure and behaviour
Similar to common chimpanzees, bonobos live in fission-fusion polygynous societies composed of several males, several females, and their offspring. In contrast to the more patrilineal society of chimpanzees, the society of bonobos centres around the adult females.
Furthermore, it can be characterized by egalitarian relationships between the sexes and large parties, which are biased towards females. As young females approach adolescence, they become less social than males and disperse. In contrast, males stay in their natal groups, and mother and mature son are linked together by continuing strong bonds.
For a more detailed overview and references see Pika, 2007.