Planning abilities of wild chimpanzees (Pan troglodytes troglodytes) in tool-using contexts

Planning is a type of problem solving in which a course of future action is devised via mental computation. Potential advantages of planning for tool use include reduced effort to gather tools, closer alignment to an efficient tool design, and increased foraging efficiency. Chimpanzees (Pan troglodytes troglodytes) in the Goualougo Triangle use a variety of different types of tools. We hypothesized that procurement strategy (brought to the termite nest, manufactured or acquired at the termite nest, or borrowed from others) reflects planning for current needs, with tool transport behavior varying by tool type and by age and sex class. It is also possible that chimpanzees anticipate the need for tools at future times, which would be evidenced by transporting multiple tool types for a sequential task. One year of video recordings at termite nests were systematically screened for tool procurement; data comprised 299 tool procurement events across 66 chimpanzees. In addition, we screened video recordings of leaf sponging and honey gathering, which resulted in another 38 procurement events. Fishing probes, which are typically used during a single visit, were typically transported to termite nests, while puncturing tools, which are durable and remain on site, were more often acquired at termite nests. Most tools transported in multiples were fishing probes, perhaps in anticipation that a single probe might not last through an entire foraging bout or might be transferred to another chimpanzee. We further documented that chimpanzees transported tool sets, comprising multiple different tool types used in sequence. Mature chimpanzees transported tools more often than did immatures. These observations suggest that chimpanzees plan tool use flexibly, reflecting the availability of raw materials and the likelihood that specific tool types will be needed for particular tasks. Developmental studies and further integration of behavioral, spatial, and archaeological data will help to illuminate the decision making and time depth of planning associated with tool technologies in living primates and hominin ancestors.