Bonobos and chimpanzees appear to recognise photographs of former group members – even animals they haven’t seen for over 20 years. Which means these apes have the longest social reminiscence ever recorded in any animal apart from people.

Nice apes, similar to gorillas, chimpanzees and bonobos, are identified to have spectacular recollections – for instance, some chimps can keep in mind the exact location of specific fruit trees in a forest, and anticipate what occurs subsequent in a movie they’ve considered earlier than. Researchers have additionally seen hints that nice apes keep in mind people for a very long time.

“After we return to ape populations that we’ve labored with up to now, we seen that they appear to recognise and keep in mind us,” says Laura Lewis on the College of California, Berkeley.

To research how lengthy this social reminiscence lasts in apes, Lewis and her colleagues put 12 bonobos and 15 chimps, residing in zoos within the UK, Japan and Belgium, to the take a look at.

For every animal, the staff flashed side-by-side photographs of two completely different apes on a display screen for 3 seconds. One of many photographs was of an ape that they’d lived with no less than one 12 months in the past and the opposite was a stranger.

Utilizing eye-tracking know-how, the staff discovered that every one the individuals would have a look at the pictures of former group members round 1 / 4 of second longer on common than they did for those of strangers. For former colleagues that they’d optimistic relationships with, as described by zookeepers, they’d linger on their photographs even longer.

The discovering signifies that these apes keep in mind acquaintances even after a prolonged time aside. “It’s not so completely different from strolling down the streets in a significant metropolis, unexpectedly encountering somebody you went to high school with, and also you do this double take,” says staff member Christopher Krupenye at Johns Hopkins College in Maryland.

In probably the most excessive case, a bonobo referred to as Louise appeared to recognise her sister Loretta and nephew Erin after greater than 26 years of separation.

“That’s the longest long-term social reminiscence ever recorded in a non-human animal,” says Lewis.