Chimpanzees share experiences, a trait previously thought to be only human

One chimpanzee doesn’t hesitate to make it clear when she wants attention. Closer cousin of humans, this species of great ape has effective means of communicating what it needs.

Researchers have often observed chimpanzees in captivity pointing at an object they want their caretakers to hand them or young chimpanzees in the wild having tantrums to get their mother’s attention.

Until now, these behaviors have only been observed when a chimpanzee wants something. Recently, however, scientists have documented footage of a wild adult chimpanzee showing a leaf to its mother, apparently just to share the experience with her, according to a report. study published on Monday (14) in the journal PNAS.

More examples of such interactions are needed to better understand the intention behind the gesture, the study researchers said, but the observation may demonstrate that chimpanzees exhibit social behavior previously thought to be specific only to their human relatives.

“Critically, she didn’t seem to want her mother to do anything with the leaf. She seems to be showing it just for the sake of it. It’s like, ‘Look, look, this is cool, isn’t it?’ And that’s very human and something that we thought was quite unique to our species,” said study co-author Katie Slocombe, professor of psychology at the University of York in the UK.

The mother-daughter chimpanzees, named Sutherland and Fiona by the researchers, are part of the Ngogo chimpanzee community in Uganda’s Kibale National Park. Slocombe and his colleagues were studying Fiona and her baby as part of a separate project in her wider social group, when they captured footage of Fiona holding the leaf out to her mother before taking it back when she caught Sutherland’s attention.

“This is the first kind of promising suggestion that this (behavior) may not be uniquely human and that chimpanzees may be able and motivated to do this,” Slocombe said.

show and tell

Fiona was engaged in what the researchers call “leaf grooming,” a common behavior in which a chimpanzee caresses and manipulates a leaf. The reasoning behind the behavior is a mystery, but Slocombe and his colleagues suspect it might be to inspect an ectoparasite, such as a tick, on top of the leaf. Often the surrounding chimpanzees are also engrossed in the action, intently watching the leaf being tended.

“When Fiona was doing it, (Sutherland) didn’t seem really interested; she wasn’t looking and wasn’t paying attention to her. Fiona then holds up the sheet to say, ‘look at it,’” Slocombe said. (Fiona) looks pleased.”

The researchers examined 84 video clips of chimpanzees raking leaves next to at least one other individual to look for possible explanations for the divergence from commonly observed behavior. The sample had a wide age range, with both male and female chimpanzees observed.

In more than 75% of cases, another individual approached the leaf trimmer or watched closely, the study team found. The vast majority of clips showed that grooming the leaf did not initiate social activity – such as grooming each other, playing together, or even eating the leaf – during or after the action, which led the researchers to believe that Fiona was simply looking for share an experience with another chimpanzee.

“Human babies, as young as 10 months old, will start to bring things that they find interesting to their caregivers. … Just like Fiona, they will reach out with the object in their hand towards their caretakers face. If the caregiver doesn’t react, they will readjust and persist until the caregiver looks,” Slocombe said.

Slocombe and his team always maintain a 7-metre distance when observing chimpanzees in the wild, so as not to disturb them. This standard practice rules out the possibility that the behavior was learned from humans.

“Chimpanzees have been observed placing ectoparasites, found during cleaning, on leaves and trying to crush them. In the clip, I can’t tell if that’s the case, but Fiona seems to take (something) out of her mouth and then puts it on the sheet and ‘shows’ it to her mother,” said Simone Pika, head of the Comparative BioCognition research group at the University of Osnabrück , in Germany.

Simone was not involved in the work, but her team is also observing chimpanzees in Ngogo and plans to continue looking for more evidence and clarification.

“We are still at the beginning of fully understanding the communicative complexity of chimpanzees and the implications for the evolution of human language and cognition,” said Simone. “We need a lot more data to clearly assess whether chimpanzees in the wild use declarative gestures and what the function is.”

This study is the first documented observation of this behavior in the wild to suggest that apes have a motivation to share experiences with one another, Slocombe said. She hopes this will encourage those who work with chimpanzees, in the wild or in captivity, to look for more examples.

“What I really hope is that the publication of this result serves as a catalyst for other people who have studied chimpanzees for a long time, maybe who have lots of videos of them, to think, ‘Oh, wait a minute. I’ve seen chimpanzees do something like this before, but I didn’t think it was really meaningful,'” Slocombe said.

“Perhaps then we can start to get multiple examples to better test whether chimpanzee motivation is similar to that of humans.”