Necessity creates opportunities for chimpanzee tool use

Although social transmission mechanisms of animal cultures are well studied, little is known about the origins of behavioral innovations, even in established tool users such as chimpanzees. Previous work has suggested that wild chimpanzees are especially prone to engaging with tools during extended periods of low food availability and after long travel, supporting the hypothesis that cultural innovation is facilitated by necessity revealing opportunities. Here, we tested this hypothesis with a field experiment that directly compared subjects' immediate variation in measures of current energy balance with their interest in a novel foraging problem, liquid honey enclosed in an apparatus accessible by tool use. We found that the previous distance traveled directly predicted subjects' manipulations of both the apparatus and the tool, whereas previous feeding time was negatively correlated to manipulation time. We conclude that necessity augments chimpanzees' likelihood of engaging with ecological opportunities, suggesting that both factors are scaffolding foraging innovation in this and potentially other species.