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Chimpanzees Using Leaves as Sponges

By Russell Tenofsky

A fascinating new study has shown chimpanzees in the wild learning to use new tools by watching other chimpanzees use them first, a clear sign that chimpanzees possess culture.Image of a chimpanzee culture using a leaf as a sponge

A team of scientists directly observed individual members of the Sonso chimpanzee community of Uganda’s Budongo Forest learning to use “leaf sponges” by watching other chimpanzees dipping the tools into the water to drink. The chimpanzees either created leaf sponges on their own by folding up leaves or moss, dipping them in the water and then chewing the leaves; or they re-used leaf or moss sponges discarded by other chimpanzees.

Primatologists have been studying the Sonso chimpanzees for over twenty years and they had not previously observed any form of leaf sponging. However, scientists were recently lucky enough to videotape Nick, an alpha male, make a moss sponge while Nambi, one of the dominant adult females, observed him.

“We were very lucky, I must say,” said co-author Thibaud Gruber, a primatologist at the University of Neuchâtel in Switzerland. “The chimpanzees just decided to display this novel behavior right in front of us, and we only needed our camcorders to capture the scenes.”

Quick Learners

“This shows that chimpanzees can be really fast in adopting new tools!”According to the researchers, the new behavior spread like wild fire and over the next six days an incredible seven more chimpanzees had made and used moss sponges. The scientists also observed eight other chimpanzees reuse discarded sponges.

“The spread of the behavior was very fast,” Dr. Gruber said. “This shows that chimpanzees can be really fast in adopting new tools!”

“Researchers have been fascinated for decades by the differences in behavior between chimpanzee communities — some use tools, some don’t, some use different tools for the same job,” said lead study author Catherine Hobaiter, a primatologist at the University of St. Andrews in Scotland. “These behavioral variations have been described as cultural, which in human terms would mean they spread when one individual learns from another. But in most cases, they’re long established, and it’s hard to know how they originally spread within a group.”

A Unique Culture

According to the all of the study’s authors, the development, use, reuse and continued expansion of a new tool is a definitive sign of chimpanzee culture.

“Our results provide strong evidence for social transmission along the chimpanzees’ social network, demonstrating that wild chimpanzees learn novel tool use from each other and support the claim that some of the observed behavioral diversity in wild chimpanzees should be interpreted as cultural,” said study co-author William Hoppitt, a senior lecturer in zoology at Anglia Ruskin University.

As if the other scientists had not made the point clearly enough, Dr. Gruber drives the point home that chimpanzees do indeed possess culture and that there is an evolutionary link between chimpanzee and human culture.

“There has been an ongoing debate about whether chimpanzee culture and human culture are evolutionary linked,” said Dr. Gruber. “My answer is yes. Our findings here strongly support the idea that the last common ancestors of chimps and humans could learn cultural behaviors from each other, in a similar way as the Sonso chimpanzees did.”

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