Often, chimps acquire new talents by trial and error. For example, when trying to crack nuts, they might strike one stone onto an anvil stone and miss the nuts all together. Or they might use their hands to strike the nut, which is ineffective. But the Bossou chips couldn't have learned how to deactivate the snares this way, as one mistake could be fatal.

"The observations indicate that chimpanzees can learn some manners without trial and error," says Mr Ohashi.

The researchers speculate that the chimps may have learnt how the snares work by observing them over time, and this information has been passed down generations.