Apes have the astonishing ability to recognise long-lost companions, found new research. If you’re wondering why this is astonishing, it’s because this challenges the conventional understanding of social memory in non-human animals. This actually happens to be the longest-lasting social memory to be documented outside the human species.
The research
Research published on Monday in the Proceedings of the National Academy of Sciences found that chimpanzees and bonobos could recall and respond positively to images of former group mates over 25 years after their last encounter.
The research was conducted by Christopher Krupenye, an assistant professor at Johns Hopkins University, and lead author Laura Lewis from the University of California, Berkeley.
In conversation with CNN, Krupenye revealed that the inspiration for the study arose from his personal experiences with apes. He said he could sense that the apes recognised him even years after their last interaction.
To test this, the researchers used high-quality photographs of deceased or departed apes from various zoos, presenting them alongside images of strangers to participating apes at Edinburgh Zoo in Scotland, Planckendael Zoo in Belgium and Kumamoto Sanctuary in Japan.
Photos of apes ranged from nine months to 26 years. They then used noninvasive eye-tracking technology to measure the apes’ gaze duration on each photo.
Beyond the study’s scientific implications, the authors said that they hope it will help spread awareness of the impact of poaching and deforestation on ape communities, emphasising the importance of conservation efforts.
“We hope that these results will provide people more empathy with our closest living cousins,” said Lewis.
Humans and apes aren’t that different after all
The results were striking, demonstrating that the apes looked “significantly longer” at familiar faces, regardless of the time that had elapsed since their last meeting. The gaze was even more extended for those with whom they had shared a friendly relationship.
As per Krupenye, this phenomenon parallels human experiences, akin to unexpectedly encountering a long-lost high school friend.
“It’s a very familiar experience for humans too,” he said.
Notably, one bonobo named Louise exhibited a “robust bias” towards her sister Loretta and nephew Erin, whom she hadn’t seen in 26 years.
As per a news release, she “showed a strikingly robust looking bias toward both of them over eight trials.”
The researchers speculate that apes’ social memory might surpass 26 years, possibly rivalling the human capacity to remember individuals for up to 48 years. The release also points out that humans start forgetting people after 15 years.
As per CNN, the study sets a new benchmark for the longest social memory documented in non-human animals. Previously, dolphins were known for remembering individuals after 20 years. This challenges the notion that social memory is a uniquely human trait and emphasises that it may be a characteristic we share with our closest relatives: apes.
(With inputs from agencies)
