Chimps and orang-utans are well known for their ability to develop tool-using tricks and transmit these within their social groups. But because gorillas are comparatively poorly studied, it's unclear whether they develop such "traditions". A study now suggests they do.
Richard Byrne at the University of St Andrews, UK, and colleagues looked at how captive-bred gorillas picked apart stinging nettles to eat them. They noticed that the apes never detached the stinging leaf stalks and reduced their exposure to stings by squeezing nettles together.
"This fascinated us because, while wild gorillas in Rwanda also pick apart stinging nettles, they do so by removing stalks and folding, rather than squeezing, the nettles," says Byrne.
You can see the difference in the video above. In the first clip a captive lowland gorilla in Port Lympne, Kent, strips nettle leaves off their stem, but doesn't twist off the stalk. Then he rolls and scrunches the bundle. The ape tucks in the leaf tips to tidy up his bundle before eating it.
In the second clip a wild mountain gorilla from Karisoke, Rwanda, strips the leaves from the stem, twists off the sting-infested stalks that attach the leaves to the stem, and then carefully folds the bundle over her thumb, underside up so that the stinging topsides are tucked away – rather than scrunching it – and pops the tidy package into her mouth.
Byrne argues that each group developed its own tactics and spread them among themselves. "The perfect study would compare only wild gorillas or only captive ones, but when that is not possible, studies like these are valuable," says primatologist Elizabeth Lonsdorf at the Lincoln Park Zoo in Chicago. "I think we've only scratched the surface of gorilla learning abilities."
Journal reference: Animal Cognition, DOI: 10.1007/s10071-011-0403-8
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