Savanna chimpanzee tool and fruit transfers facilitate the transmission of technological behaviours at Dindefelo, Senegal

Abstract

Social learning is a key factor in the transmission of technological behaviours amongst primates. We studied chimpanzee (Pan troglodytes verus) social interactions in the context of tool and proto-tool use behaviours in the savanna site of Dindefelo, Senegal. Between 2017 and 2025, we obtained 14 h 58 min of camera trap footage at 14 locations where chimpanzees performed tool-use behaviours, namely algae fishing (for filamentous green algae: Zygnemataceae), ant dipping (for army ants: Dorylus sp.), and termite fishing (for termites: Macrotermitinae). We also obtained 30 min of camera trap footage at 11 locations where chimpanzees carried baobab (Adansonia digitata) fruit, which they pound against stationary anvils (i.e., proto-tools), a behaviour called baobab pounding. In total, we recorded 33 tool transfers and four fruit transfers. Transfers occurred mostly between mothers and their offspring. Most tool transfers were recoveries and tolerated takes. We compared the behaviour of initial tool possessors and tool recipients 30 s after and 30 s before each transfer. We excluded recoveries because in these cases the initial possessor does not interact with the recipient before abandoning the tool. We fitted Linear Mixed-Effects Models to test whether initial possessors and recipients exhibited different proportions of time using tools, insertions per second, and mouthfuls per second, after versus before a transfer. Initial possessors spent a significantly lower proportion of time using tools and performed significantly fewer insertions per second after transferring a tool, whereas recipients spent a significantly higher proportion of time using tools, and performed significantly more insertions and mouthfuls per second after receiving a tool. In addition, we detail two cases that highlight social learning of technological behaviours, in the context of ant dipping and baobab pounding, respectively. In line with previous research, we found that tool transfer constitutes a type of teaching in Dindefelo. Our results support the idea that teaching and facilitation, mainly from mothers, contribute to the acquisition of technological skills in immature chimpanzees.