First evidence of underground extractive tool use by chimpanzees in Kibale National Park, Uganda.

Chimpanzee behavior, including tool use, varies widely among communities and populations. Tools made by chimpanzees for extracting products from the underground nests of stingless bees are among the most complex used by the species. They have rarely been described in East Africa and have never been observed in three chimpanzee communities in the Kibale National Park, Uganda-two at Ngogo and one at Kanyawara community-that have been studied for over 30 years. In the current study, we present the results of a 15-year study of a fourth community of chimpanzees ranging at Sebitoli, in the northern part of Kibale, and the insects they consume. We identified the stingless bees and carpenter bee species on which they feed. In addition, we collected the tools used by the Sebitoli chimpanzees. Of the 443 tools used in 152 episodes to extract products from insect nests, 332 were used by chimpanzees to explore or exploit underground or arboreal nests of Meliponula sp.. In addition, individuals sometimes left sticks vertically inserted into the entrances of underground bee nests. We discuss the implications for the transmission of the tool use behavior for subterranean extractive task within this social group, given that it appears to be absent in the other three Kibale Forest communities being studied. Our results highlight the importance of taking small-scale cultural variation into account in understanding chimpanzee behavioral repertoires as well as planning and implementing conservation strategies. We dedicate this article to the chimpanzee Hugo, who loved honey the most. He was slaughtered with machetes by poachers on April 3, 2026.