Occupancy of Sympatric Central Chimpanzee (Pan troglodytes troglodytes) and Western Lowland Gorilla (Gorilla gorilla gorilla) in Campo Ma’an Conservation Area, Southern Cameroon

Abstract

Sympatric primate species coexist in tropical communities through interactions with the abiotic environment and other species. Determining the factors that influence primate species co-occurrence can help to inform conservation practices. Our study focused on the ecological interactions of central chimpanzees (Pan troglodytes troglodytes) and western lowland gorillas (Gorilla gorilla gorilla) with each other and their environment in a multiuse landscape. We assessed species-specific occupancy at 17 camera trap sites across different land-use types (National Park, Forest Management Units, or Community Lands) between June 2019 and May 2020 and examined the impact of fruit availability and human presence on ape presence. Across the study area, chimpanzees occupied a greater total number of sites than did gorillas, with a significantly higher proportion of occupied sites within the National Park than in other land-use types. The density of fruiting trees positively influenced the presence of gorillas but had no effect on chimpanzee presence. We found no effect of human presence on the presence of either chimpanzees or gorillas, although this analysis was limited to sites where apes were present. The probability of either species being present at a site during a given month remained stable under the conditional presence or absence of the other species, suggesting the absence of interactions between the two species at our study sites. These results support previous findings that the heterogeneous distribution of fruits and preferred resources allows chimpanzees and gorillas to limit direct competition by exploiting different feeding resources. Our findings provide insights on the factors influencing the occupancy of each species, including environmental variables and land-use type, information relevant when monitoring their coexistence within tropical communities.