On an evolutionary scale, the chimpanzee (Pan troglodytes) is the closest living relative of humans (Homo sapiens), both shared a common ancestor sometime between 5-8 million years ago.

The chimpanzee is listed as Endangered in the IUCN Red List of Endangered Species (IUCN, 2008). The Robust Chimpanzee (Pan troglodytes) is an omnivorous ape found in a variety of wooded habitats across equatorial Africa. Typically, chimpanzees inhabit evergreen forests, but marginal populations also thrive in deciduous woodland and grassland and savanna habitats, interspersed with gallery forest.

There are four sub-species of the Robust Chimpanzee. These exhibit mutually exclusive geographical ranges and include: The Western Chimpanzee (P. t.verus), which is the sub-species most endangered with extinction, second to the Nigerian Chimpanzee (P.t.vellerosus), and the Central African Chimpanzee (P.t.troglodytes) and finally the Eastern Chimpanzee (P.t.shweinfurthii). Recent evidence suggests that the Western Chimpanzee may, however, in fact be a separate species altogether (Morin et al., 1994).

The majority of the populations of the Western Chimpanzee are found in the Upper Guinea Forests. These forests are among the most biologically rich in the world. They are unfortunately also among the most threatened. The Guinean Forest has been designated as one of the world's 25 hotspots for biodiversity (Myers et al., 2000).

BOSSOU is one of six long-term chimpanzee field sites in Africa.