Chimpanzee seed dispersal in a montane forest fragment in Rwanda

Primate seed dispersal plays an important role in forest regeneration. It may be particularly important to anthropogenically disturbed habitats such as forest fragments. However, few studies have examined primate seed dispersal in these types of environments. Chimpanzees (Pan troglodytes) are frugivorous and large-bodied, and are therefore able to disperse both large and small seeds, making them an important seed dispersal species. We examined chimpanzee seed dispersal in Gishwati forest, a 14 km2 montane rainforest fragment in Rwanda. We systematically collected ≤24-hr-old fecal samples and counted the number of seeds of each fruit species. We also recorded observations of seeds found in wadges. We found that chimpanzees dispersed at least 18 fruit species in 14 families in their feces. Ninety-five percent of feces had seeds, the most common of which were Ficus spp., Myrianthus holstii, and Maesa lanceolata. We estimated that the Gishwati chimpanzee community with a density of 1.7 individuals per km2 dispersed an average of 592 (>2 mm) seeds km−2 day−1. We also found that chimpanzees dispersed the seeds of at least two fruit species, Ficus spp. and Chrysophyllum gorungosanum, in their wadges. In addition, 17% of the tree species recorded in our vegetation plots were chimpanzee-dispersed. This study emphasizes the importance of chimpanzees as large seed dispersers in regenerating forest fragments. RESEARCH HIGHLIGHTS Chimpanzees in Gishwati disperse a significant number of large seeds. Large-bodied seed dispersers, like chimpanzees, are particularly important in regenerating forest fragments.