By Serge K. Soiret, GAP correspondent in West Africa, from Ivory Coast

We can only say that it is extraordinary. Nuts in forest are an important potential food source. But it ends up raising a problem for chimpanzees, because their shells are so hard that their teeth can not overcome them.

At Tai forest, chimpanzees (males and females) seem to have solved this problem by breaking the nuts following a very specific technique: firstly they grapple nuts that they carry in one hand, both hands or hands and mouth. Then they filed the nut near a root or a stone that will act as an anvil and stabilize the nuts in a hollow of the anvil. With a stone they hit the nuts with a gesture energy (but not too much) to break the shell without the almond crumble.

Young people attend their parents during the cracking and often try to open nuts. We have seen a male adult hit a child because he took his hammer stone. It must be said that good stone hammers in the forest are rare, so it must protect its tool for not losing it.

This technique of nut cracking, signed by primatologist Christophe Boesch (1994), is limited by a natural border of the river N’zo Sassandra (Ivory Coast).

Reference: Boesch, C., Marchesi, P., Marchesi, N., Fruth, B., and Joulian, F. (1994). Is nut cracking in wild chimpanzees a cultural behaviour? J. Hum. Evol. 26: 325-338.

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