Anthropogenic disturbance and chimpanzee (pan troglodytes) habitat use in the Masito-Ugalla ecosystem, Tanzania

Abstract

The habitat quality of chimpanzee (Pan troglodytes), including the availability of food and nesting resources, is important to ensure the long-term survival of chimpanzees. Botanical composition of vegetation is spatially variable and depends on numerous biotic and abiotic factors. There are few data regarding the availability of chimpanzee plant food and nesting species in the Masito-Ugalla ecosystem (MUE), and how these resources vary with human disturbance. It was hypothesized that chimpanzee plant food species richness, diversity, and abundance, decline with increasing disturbance. Further, it was predicted that chimpanzee abundance and habitat use is influenced negatively by disturbance. Published literature from Issa Valley, Gombe, and Mahale Mountains National Parks, was used to document plant species consumed by chimpanzees, and quantify their richness, diversity, and abundance, along 32 transects totaling 63.8 km in length across four sites of varying human disturbance in MUE. A total of 102 plant food species was documented and found significant differences in their species richness (H = 55.09, P < 0.001) and diversity (H = 36.81, P < 0.001) across disturbance levels. Chimpanzees built nests in 17 tree species. The abundance of nesting tree species did not vary across survey sites (H = 0.279, P > 0.964). The least disturbed site exhibited the highest encounter rate of chimpanzee nests km -1 , with rates declining towards the highly disturbed sites. Thus, severe anthropogenic disturbance in MUE is associated with the loss of chimpanzee plant food species and negatively influences chimpanzee habitat use, a relationship that threatens the future of all chimpanzee populations outside national parks.