The influence of ecology on chimpanzee (<i>Pan troglodytes</i>) cultural behavior: a case study of five Ugandan chimpanzee communities

The influence of ecology on the development of behavioral traditions in animals is controversial, particularly for chimpanzees (Pan troglodytes), for which it is difficult to rule out environmental influences as a cause of widely observed community-specific behavioral differences. Here, we investigated 3 potential scenarios that could explain the natural variation in a key extractive tool behavior, "fluid-dip," among several communities of chimpanzees of the <i>Pan troglodytes schweinfurthii</i> subspecies in Uganda. We compared data from previous behavioral ecological studies, field experiments, and long-term records of chimpanzee tool-using behavior. We focused on the quality of the available food, dietary preferences, and tool sets of 5 different communities, and carried out a standardized field experiment to test systematically for the presence of fluid-dip in 4 of these communities. Our results revealed major differences in habitat, available diet, and tool use behavior between geographically close communities. However, these differences in ecology and feeding behavior failed to explain the differences in tool use across communities. We conclude that ecological variables may lead both to innovation and loss of behavioral traditions, while contributing little to their transmission within the community. Instead, as soon as a behavioral tradition is established, sociocognitive factors likely play a key maintenance role as long as the ecological conditions do not change sufficiently for the tradition to be abandoned.