Sunday, 30 April 2017

Chimps pass on sponge drinking trick like a family tradition


26 April 2017

By Sam Wong

Six years ago, a chimpanzee had the bright idea to use moss to soak up water, then drink from it, and seven others soon learned the trick. Three years later, researchers returned to the site to see if the practice had persisted to become part of the local chimp culture.

They now report that the technique has continued to spread, and it’s mostly been learned by relatives of the original moss-spongers. This adds to earlier evidence that family ties are the most important routes for culture to spread in animals.

After the first report of chimps using moss as a sponge in Budongo Forest, Uganda, researchers rarely saw the behaviour again, and wondered whether chimps still knew how to do it. So they set up an experiment, providing moss and leaves at the clay pit where the chimps had demonstrated the technique before.

Then they watched to see whether chimpanzees would use leaves – a more common behaviour – or moss to soak up the mineral-rich water from the pit.

Most of the original moss-spongers used moss again during the experiment, and so did another 17 chimps, showing the practice had become more widespread. The researchers wondered what factors influenced which individuals adopted it: were they connected socially, or through families, for instance?
Keeping it in the family

This group of chimps has been observed for a long time, so the researchers were able to look through field data to calculate an index of how much time each chimpanzee spent with other individuals. It turned out that this metric wasn’t a good predictor of which chimps would use the moss sponge. Instead, moss-sponging was strongly correlated with having moss-sponging relatives.

The chimpanzees didn’t only learn from their parents: it was spread between any family members in either direction. “It’s like the family is the [crucible] where the behaviour is transmitted,” says Thibaud Gruber of the University of Geneva, Switzerland, one of the study authors.

But there were also individuals who learned the technique from non-family members. “Once a behaviour has been developed and spread to a few individuals, the majority of transmission will appear in the family, but if you hang out with some tool users, you’re still likely to develop a behaviour by social learning,” says Gruber.



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