Shifting through the forest: home range, movement patterns, and diet of the eastern chimpanzee (Pan troglodytes schweinfurthii) in Nyungwe National Park, Rwanda.

Populations of the endangered eastern chimpanzee (Pan troglodytes schweinfurthii) are declining throughout their range. Although Nyungwe National Park (NNP) harbors the largest remaining eastern chimpanzee population in Rwanda, we know little about their space use and dietary patterns. We studied home range, movement, and diet of two communities of chimpanzees in NNP using daily tracking data (6:00 am to 6:00 pm) collected from 2000 to 2015. One community, Mayebe, resided in the forest center, and the other community, Cyamudongo, inhabited a forest fragment located about 10 km from the main forest. Home range estimated with the 95% kernel density estimation (KDE) method was 21 km2 for the Mayebe community and 4 km2 for the Cyamudongo community. Chimpanzee home range sizes were smaller during the dry versus wet season and varied monthly throughout the year. The Mayebe community had an average hourly step length of 75 ± SE 5 m with a daily movement range of 987 ± SE 71 m, while the Cyamudongo community had a shorter hourly step length of 52 ± SE 3 m with a daily movement range of 651 ± SE 71 m. Both chimpanzee communities fed primarily on Ficus spp. Other important dietary items included fruits of Symphonia globulifera, Syzygium guineense, and Chrysophyllum gorungosanum for the Mayebe community and Trilepisium madagascariense for the Cyamudongo community. Food choice varied monthly and seasonally for each chimpanzee community. Our study provides the first estimates of home range size and movement parameters for chimpanzees in Rwanda and documents their food habits and seasonal variations therein. We also identified the 50% core home range for each chimpanzee community and suggest this area as the focus of management actions. These results could help park management reduce threats to chimpanzees and other sympatric species by improving the efficiency of ranger patrols.

Structure of Chimpanzee Gut Microbiomes across Tropical Africa.

Understanding variation in host-associated microbial communities is important given the relevance of microbiomes to host physiology and health. Using 560 fecal samples collected from wild chimpanzees (Pan troglodytes) across their range, we assessed how geography, genetics, climate, vegetation, and diet relate to gut microbial community structure (prokaryotes, eukaryotic parasites) at multiple spatial scales. We observed a high degree of regional specificity in the microbiome composition, which was associated with host genetics, available plant foods, and potentially with cultural differences in tool use, which affect diet. Genetic differences drove community composition at large scales, while vegetation and potentially tool use drove within-region differences, likely due to their influence on diet. Unlike industrialized human populations in the United States, where regional differences in the gut microbiome are undetectable, chimpanzee gut microbiomes are far more variable across space, suggesting that technological developments have decoupled humans from their local environments, obscuring regional differences that could have been important during human evolution. IMPORTANCE Gut microbial communities are drivers of primate physiology and health, but the factors that influence the gut microbiome in wild primate populations remain largely undetermined. We report data from a continent-wide survey of wild chimpanzee gut microbiota and highlight the effects of genetics, vegetation, and potentially even tool use at different spatial scales on the chimpanzee gut microbiome, including bacteria, archaea, and eukaryotic parasites. Microbial community dissimilarity was strongly correlated with chimpanzee population genetic dissimilarity, and vegetation composition and consumption of algae, honey, nuts, and termites were potentially associated with additional divergence in microbial communities between sampling sites. Our results suggest that host genetics, geography, and climate play a far stronger role in structuring the gut microbiome in chimpanzees than in humans.