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

Appendix 1: Description of honey extraction from trees at Ngogo

On June 24th, 2016, a party of chimpanzees found an Apis nest in a hole the trunk of a fallen tree. The nest seemed to be old (not many bees were present) and apparently did not contain a large quantity of honey. Adult females CEC and SEN both harvested small amounts of honey by hand. SEN then broke a branch, about 80 cm long, from a small tree next to the fallen trunk. About halfway along its length, this branch divided into multiple smaller branches that had leaves; without removing these, SEN inserted the bare woody half into the hole and used it to scrape out some of the remaining honey. She continued this for four minutes, while multiple other chimpanzees, including her infant and young adolescent sons, watched, before abandoning the tool and moving away from the nest. Adult male GA then picked up her tool and used it in similar fashion for another 10 min, during which time he was also closely watched by other chimpanzees. When he abandoned the tool, young adult male BEN retrieved it and used it for five minutes, after which he abandoned it and his younger brother YY retrieved it and also used it for three minutes. Finally, YY’s infant sister JOY retrieved the tool after he dropped it and moved off. JOY, who was now alone at the bee nest, used it as a probe for another three minutes before moving off rapidly, still carrying the tool, in pursuit of her mother. All five chimpanzees obtained only small amounts of honey by using the tool.

Appendix 2: List of plant species used as tools by Sebitoli chimpanzees (Kibale national park, Uganda)