Like people, older monkeys prefer good friends

Like people, older monkeys prefer good friends

You may have found that as you get older, you're pickier about who you spend time with and what you do with that time.

It turns out that's a similar story with Barbary macaques which has led European researchers to suggest it's a stage of life which could be deeply ingrained in primate evolution.

Research published in Current Biology has proposed a perspective on why aging humans tend to be more selective in their mates -- the clock is ticking.

"An important psychological theory suggests that humans become more socially selective when they know that their remaining life time is limited, such as in old age," Laura Almeling of the German Primate Centre says.

The centre looked into how selective 100 monkeys of varying ages were in non-social and social interaction in an enclosure in Rocamodour, France.

Like people, older monkeys prefer good friends

An old female macaque gets groomed (Julia Fischer / German Primate Centre)

To get an idea of how curious they were about new things, the monkeys were presented with a number of novel objects such as animal toys, colourful plastic cubes and tubes with food inside.

The monkeys in early adulthood lost interest in the novel objects, though all but the oldest monkeys were still keen on the tube with food.

Their social preferences were also tested by showing photos of newborn monkeys, "friends" and "non-friends" and played with the associated vocalisations. They also looked at how long and how often the monkeys, which in the wild live in Algeria, Morocco and Gibraltar, interacted with each other.

Researchers found:

Ms Ameling, a doctoral student, says it's assumed monkeys aren't aware of their own mortality.

"Therefore, if they show similar motivational changes in old age, their selectivity cannot be attributed to their knowledge about a limited future time.

"Instead, we should entertain the possibility that similar physiological changes in aging monkeys and humans contribute to increased selectivity," she says.

The study suggests that, like humans, monkeys become more selective as the get older -- they choose social over non-social information and pickier in whom they interact with.

Principal investigator Julia Fischer suggests the older monkeys may spend less time socialising because they find it "increasingly stressful and therefore avoid them".