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How capuchin monkeys break open cashew nuts

Tiago Falótico Laterally placed cashew nut allows for more efficient breakingTiago Falótico

Capuchin monkeys of the species Sapajus libidinosus are very resourceful. At Serra da Capivara National Park in the Brazilian state of Piauí, these monkeys use stones and branches as tools to process and obtain food, thereby ensuring researchers’ attention for hours on end as they study this rare behavior in the animal world. One such specialist is biologist Tiago Falótico of the Psychology Institute at the University of São Paulo, first author of a paper that describes one aspect of how the monkeys break open cashew nuts (Folia Primatologica, March 1, 2017). Falótico observed that six adult capuchins (out of a group of 30) sometimes position the nut laterally so it can be cracked open by a stone using less force. In some cases, the monkey needs to bite off one of the lobes in order to balance the nut on a rock that serves as a base. In the researchers’ interpretation, as they get older, some monkeys acquire an understanding of how to break open the nut more easily. This perception is thought to be one more element in the behavior of these animals, which adapt the weight of the stone and the type of tool according to the hardness of the nut.