When it comes to reducing tension and resolving conflicts within their groups, howler monkeys have come up with a nifty solution – playtime.


During a play session, howler monkeys can be seen hanging upside down from their tails and making funny faces and gestures at one another. But thanks to their mainly leaf-based diets, these play activities are relatively energy-costly.

To investigate the potential benefits of this monkeying around, a team of researchers from Spain, Brazil and the UK observed the interactions of seven different groups of howler monkeys living in the rainforests of Costa Rica and Mexico.

They found that the amount of time that the adult monkeys spent playing increased as the size of the group they belonged to went up, with the adults spending more time playing than the youngsters and females spending more time playing than males.

They also noticed that play increased among the adults when they spent more time foraging for fruit - a highly prized food resource that can lead to competition amongst the group.

This suggests that play has a key role in helping the animals reduce tension in the group and avoid conflict, the researchers say.

“Despite its appearance and our own perception of what play means, play is not always associated with frivolity or education. Instead, we think it fulfils an important function in howler monkey society by reducing tension when there is competition over scarce resources,” said the study’s co-author Dr Jacob Dunn, Associate Professor in Evolutionary Biology at Anglia Ruskin University.

“We found that levels of play are at their highest when howler monkeys are feeding on fruit – which is a valuable and defendable resource – and female adults play more than males. This is striking, as females would be more vulnerable to food competition than males.

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"Howler monkeys are a particularly energy-conservative species, and we would have assumed females would have played less, as they are also constrained by the energy requirements of reproduction.”

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Jason Goodyer
Jason GoodyerCommissioning editor, BBC Science Focus

Jason is the commissioning editor for BBC Science Focus. He holds an MSc in physics and was named Section Editor of the Year by the British Society of Magazine Editors in 2019. He has been reporting on science and technology for more than a decade. During this time, he's walked the tunnels of the Large Hadron Collider, watched Stephen Hawking deliver his Reith Lecture on Black Holes and reported on everything from simulation universes to dancing cockatoos. He looks after the magazine’s and website’s news sections and makes regular appearances on the Instant Genius Podcast.