Abstract

Central chimpanzee (Pan troglodytes troglodytes) and western lowland gorilla (Gorilla gorilla gorilla) are two endangered great ape species that are sympatric over much of their geographic range. Protecting areas of high conservation value and the development of responsible ecotourism are two main strategies for the continued preservation of these species, and both strategies require up to date knowledge on areas currently occupied by great apes and their activity patterns. The occupancy of chimpanzees and gorillas across three land type designations in a multi-use landscape in Southern Cameroon was assessed and we analyzed whether there was an overlap in species occupancy on the monthly scale. We also tested whether fruit availability or human presence influenced the activity of chimpanzees or gorillas at different locations across the study area. Chimpanzees occupied more sites across the whole study area, with a significant difference among land use types, with the highest proportion of occupied sites being in the National Park. No evidence of spatio-temporal overlap was found between gorillas and chimpanzees on the monthly scale. The probability of either species occupying a site during a given month remained stable under the conditional presence or absence of the other species, suggesting there is neither a positive nor negative interaction between the species. No effect of human presence on the activity levels of either chimpanzee or gorilla was found, although activity analyses were limited to sites where apes were present. The density of fruiting trees positively influenced the activity of gorillas but had no effect for chimpanzees. This study adds to our understanding of gorilla and chimpanzee occupancy and activity across the CMTOU, which may be useful for further monitoring of both species. Our results are in support of previous work showing the heterogeneous distribution of ripe fruits and preferred feeding resources acting as a mechanism allowing these two sympatric ape species to coexist. This is the first study that we are aware of to simultaneously investigate occupancy and activity of two sympatric ape species across a multi-use landscape.