Sex differences in the use of natural hammers by wild chimpanzees: A preliminary report

The chimpanzees of the Tai National Park, Ivory Coast, use clubs and stones to open different species of nuts. An intriguing sex difference has been observed in this behavior. It is almost exclusively females that open Coula nuts directly in the tree and crack the very hard Panda nuts. Both techniques are difficult and imply either anticipating the need of a hammer and its transport, or exact positioning of the nut and precise dosage of the hits. The efficiency of females is superior to that of males in the technique of cracking Coula nuts on the ground, which is performed by both sexes. Possible implications for the evolution of tool-use in humans are discussed.