Primates of West Africa : a field guide and natural history
West Africa, from the coast of Senegal to Lake Chad and Cameroon's Sanaga River, is home to 60 primate species and subspecies, 46 of which occur nowhere else. They range from the nocturnal angwantibo, pottos, and galagos, to the mangabeys, baboons, and the drill, to guenons and colobus monkeys. In addition, no less than three of the great apes are restricted to this region, including two chimpanzees and the Cross River gorilla.