Chimpanzees use stones to crack open hard-shelled nuts in Cameroon’s Ebo Forest, more than 1,700 kilometers (1,000 miles) east of a river previously thought to have prevented the inland spread of this behavior.
Until now, nut cracking had been reported only in chimp groups living west of the N’Zo-Sassandra River, which cuts vertically through Côte d’Ivoire not far from Africa’s west coast.
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