When times get tough, howler monkeys turn to playtime to ease tension

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CAMBRIDGE, England — A little levity can go a long way during tough times, even for monkeys. A new study reveals that some monkeys play to reduce tension and avoid conflict. In fact, the amount of playfulness actually increases when resources are scarce, scientists say.

Researchers studying howler monkeys find that the primates play more when they have to come together to forage for scarce food. The research team found play among Mexican howler and golden-mantled howler monkeys grows in line with the amount of time they spend foraging for fruit.

They looked at seven groups of the howlers in the rainforests of Mexico and Costa Rica to form their findings. They also found the amount of adult play is linked to the number of potential playmates and increases in line with the size of each group.

Howler monkeys tend to eat leaves, and fruit is a highly-prized treat which generates competition among the creatures. They have no fixed social hierarchy within which they can navigate competition and conflict, and they do not groom each other. Some primates often turn to grooming to diffuse tension and build group cohesiveness.

Instead, the researchers believe play plays a key role helping the creatures regulate relationships within their social group and avoid conflict. Adults spend more time playing with other adults, rather than juveniles, and adult females spend more time playing than adult males.

‘Levels of play highest when howler monkeys are feeding on fruit’

The international team of researchers from the United Kingdom, Spain and Brazil examined how play varies with age and looked at the amount of time adults spend playing with older adults and young monkeys in their group.

Howler monkey play involves the animals hanging from their tails and making facial expressions and signals, such as shaking their heads. Play is very energy-intensive for howler monkeys, whose leaf-based diet means they can afford a lazy lifestyle.

“Despite its appearance and our own perception of what play means, play is not always associated with frivolity or education,” says study co-author Dr Jacob Dunn said in a statement. “Instead, we think it fulfills an important function in howler monkey society by reducing tension when there is competition over scarce resources. 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. 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.”

Adds lead study author Dr Norberto Asensio: “One theory for the positive effect of fruit consumption on play is that a fruit-based diet simply provides the howler monkeys with more energy compared to their typical diet of leaves. However, if this was the case, we should have observed adults engaging in more play with all members of the group during fruit foraging, rather than just with other adults. Because juveniles do not pose a threat or provide competition at fruit trees, we believe that play amongst adults is a mechanism for solving conflicts within the group, in a similar way that grooming is used by some other primate species.”

The findings were published in the journal Animal Behavior.

South West News Service writer Gwyn Wright contributed to this report.


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