Diet and habitat overlap in two sympatric primate species, the Tana crested mangabey Cercocebus galeritus and yellow baboon Papio cynocephalus

Diet and habitat overlap was studied in two sympatric primate species sharing two neighbouring patches of fragmented gallery forest in Tana River, Kenya. Systematic data on feeding and ranging behaviour was collected on one group each of the Tana crested mangabey Cercocebus galeritus and yellow baboon Papio cynocephalus between August 1992 and February 1993. When rainfall was low and fruit resources scarce, yellow baboons spent most of their foraging time in the open woodlands while mangabeys foraged within the forest. At this period, diet and habitat overlaps between the two species were low. As rainfall increased, followed by a gradual rise in fruit availability, yellow baboons shifted their foraging range and both species became confined to the forest habitat. Consequently, both diet and habitat overlaps increased, peaking at the end of the rainy season. Mangabeys showed a reduced within-group dispersal and also spent significantly less time foraging in a given forest patch when yellow baboons were also present within the same forest patch. Increased habitat and diet overlaps during the wet season need not have resulted in increased interspecific competition for food because at this period, fruits were readily available in the forest.