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Scientists find that apes can remember long-lost friends despite decades apart
- Scientists showed bonobos and chimpanzees side-by-side photos of a stranger ape and a long-time associate from the past.�
- They tacked eye movements using technology to figure out signs of recognition.�
- The great apes were found to remember and recognize other apes they previously knew, even if they had not seen them in years.
Researchers said that some apes even stopped drinking their juice and simply stared at the photo when noticing an old friend or family member.�
The monkeys remembered others way further back than expected
Scientists involved in the research claimed that they were already aware of the monkeys recognizing and remembering those from the past. They were however taken aback by just how far those memories spanned.
Bonobo Louise, for example, hasnt seen her sister Loretta in over 26 years. When a photo of her was shown, however, she showed clear signs of recognition. Scientists described the moment as evidence of the longest-lasting nonhuman social memory on record.
Its not surprising that they remember others for years. What was surprising is how long their memory seems to last, Laura Simone Lewis, lead author of a study published in the journal Proceedings of the National Academies of Sciences, told Mongabay.
Lewis told the publication that her intrigue over the subject began when she worked with great apes, noticing how they seemed to recognize her and others. The animals seemed to still recognize humans months and sometimes years later.
Positive relationships make them more likely to remember
Having a positive and close relationship seemed to impact how well the animals remembered the other.
Their social relationships seem to shape their memory, Lewis told Mongobay. The apes would focus more attention on the apes they have a positive relationship with during their time together.
These apes are not referred to as friends like humans, but instead close positive social bonds.
How the ape study worked
The study, published in December, researched and analyzed bonobos and chimpanzees from Edinburgh Zoo, Plackendael Zoo in Belgium, and Kumamoto Sanctuary in Japan. 26 great apes became subjects of the study.�
To test the animals, they were lured with a bottle of fruit juice. Content with the bottle, the apes would sit still drinking, which is the perfect opportunity to show them the photos. Apes were shown images of other bonobos or chimpanzees on a monitor in front. One image would be a close-up shot of a former groupmate who had either died or been moved to a different group. The second photo was one they had never seen before.
Researchers then used infrared cameras to closely track eye movements, tracking how long they spent on each image.
Lewis told Mongabay that she could see the apes recognized their group mates, even before she saw the results. Some bonobos, she said, would stop drinking their juice and instead stare at their recognized individual. I hadnt seen the data yet, but to me, it seemed like they clearly recognize these individuals, just from their behavior during the experiment, she said.
