Chimpanzees narrow their social circle and increasingly seek peace and quiet in the same way as humans as they age, a major study has found.
A study into wild chimpanzees, based on 78,000 hours of observation, found that the apes focused on fewer, but more meaningful friendships in their later years.
Researchers claim it is the first evidence that a species other than humans alter how they socialise depending on their age.
Scientists from the Harvard department of human evolutionary biology looked at the social interactions of 21 chimps between the ages of 15 and 58 in a study spanning 1995 to 2016.
Their work was based at Kibale National Park in Uganda and focused specifically on male chimps, which build stronger social bonds and are more socially active than females.
It was found that older chimps preferred spending more time with - and grooming - chimps they had developed mutual friendships with over the years.
Younger chimps, however, had more one-sided relationships where grooming wasn't always returned.
Older males were also more likely to spend more time alone but interacted with more important social partners like their ageing mutual friends, the study, published in the journal Science, found.
Much like humans in their later years, the older chimps sought out peace and quiet more regularly and tended to make their social interactions more positive than negative.
Alexandra Rosati, an assistant professor of psychology and anthropology at the University of Michigan and one of the paper's lead authors, said: "The really cool thing is that we found that chimpanzees are showing these patterns that mirror those of humans."
She added: "There's really a pressing need to understand the biology of ageing.
"More humans are living longer than in the past, which can change the dynamics of ageing."
Richard Wrangham, professor of biological anthropology and founder and co-director of the Kibale Chimpanzee Project, said: "Even though chimps are very smart, they do not understand they're going to die.
"Much more likely something else is going on in chimps to explain why their relationships become more positive as they get older. And then the question is what applies to chimps the same as what applies to humans."