Dietary Ecology of the Nigeria-Cameroon Chimpanzee (Pan troglodytes ellioti)

Examining the diets of primate populations inhabiting different habitat types could be useful in understanding local adaptation and divergence between these populations. In Cameroon, the Nigeria-Cameroon chimpanzee (Pan troglodytes ellioti) is subdivided into two genetically distinct populations that occupy different habitat types; one occurs in forests to the west and the other in a forest-woodland-savanna mosaic (ecotone) in the center of the country. We used macroscopic fecal sample assessment to investigate dietary differences in relation to monthly fruit availability among P. t. ellioti communities in both habitat types: at Ebo Forest (rainforest) and Mbam and Djerem National Park (ecotone). We collected data simultaneously across three sites: Bekob and Njuma (rainforest) and Ganga (ecotone) from January 2016 to December 2017. In the dry season, fruits were the most important dietary component at Bekob and Njuma, while nonfruit plant material (leaves, pith, and bark) were most important at Ganga. In the wet season, the proportion of fruits in the diet was greatest at Ganga, while nonfruit plant material dominated chimpanzee diets at Bekob and Njuma. Chimpanzees at Bekob ate more fruits from introduced and secondary forest plant species than those at Njuma and Ganga, especially during periods of fruit scarcity. Animal consumption was higher at Ganga and was inversely associated with fruit consumption. These observations link habitat diversity to differences in feeding ecology among genetically distinct populations of P. t. ellioti. We speculate that dietary differences reflect broader socioecological variation between these populations, and collectively, that these factors promote intraspecific divergence.