Wild capuchin monkeys adjust stone tools according to changing nut properties

Wild bearded capuchin monkeys (Sapajus libidinosus) in Brazil's Serra da Capivara National Park demonstrate the ability to adjust their stone tool use based on the maturation stage of cashew nuts. The study found that while fresh, caustic cashew nuts are easier to crack, the monkeys prefer using larger stones to process them, likely to minimize contact with the hazardous substance. This indicates a sophisticated adaptation in foraging behavior, as capuchins distinguish between nut stages within the same species and modify their tool selection accordingly. Researchers conducted field experiments using stones of varying weights and two maturation stages of cashew nuts to test this hypothesis, revealing nuanced cognitive flexibility in wild primates.

Luncz, L. V., Falótico, T., Pascual-Garrido, A., Corat, C., Mosley, H., & Haslam, M. (2016). Wild capuchin monkeys adjust stone tools according to changing nut properties. Scientific Reports, 6(1). https://doi.org/10.1038/srep33089