Insect applications to open wounds by chimpanzees in the wild: first insights from East African chimpanzees

Medicative behaviours are widespread among animals, and chimpanzees in the wild may exhibit a newly identified form involving the application of insects to open wounds. To date, insect applications to wounds have only been reported in a single community of Central chimpanzees (Pan troglodytes troglodytes). Thus, we report observations of similar behaviours in Eastern chimpanzees (P. t. schweinfurthii) of the Ngogo chimpanzee population, in Kibale National Park, Uganda. Between November 2021 and July 2022, we observed six individuals (three males, three females) applying flying insects to their own wounds (N = 5) and, in one instance, to the wound of a conspecific. These observations demonstrate a generally consistent sequential pattern of insect applications in both Eastern and Central chimpanzees. Although the extent and potential medicinal function of this behaviour remain unclear, we propose three hypotheses to inform future research, focusing on insect selectivity, social transmission, and prosociality. In conclusion, the findings suggest that insect applications are more widespread than currently documented, and provide a basis for investigating their acquisition, social dynamics, and potential relevance to the evolution of human medicinal behaviours.