The monkeys appear to keep the peace through play.

Howler monkeys live in the dense rainforests of Mexico and Costa Rica. Scientists have seen howler monkeys perform crazy antics. When they are playing with each other, they hang upside down by their tails and pull funny faces. Incidentally, not only young monkeys play with each other; adults also seem to enjoy themselves regularly. And now we finally know the reasons behind it.

energy guzzling

Playing is an energy-guzzling activity for howler monkeys. That’s because – due to their mostly leaf-based diet – they tend to lead quite lazy lives. Yet it appears that howler monkeys regularly get involved in an intensive play session. To find out more, researchers decided to study two subspecies: the Mexican howler monkey (Alouatta palliata mexicana) and the gold-cloaked howler monkey (Alouatta palliata palliata)†

Howler monkeys playing. Image: Norberto Asensio

It leads to an interesting discovery. For example, it appears that the amount of time adult monkeys spend playing increases the larger the group to which they belong, according to the trade journal. Animal Behavior† Moreover, it appears that adults play with each other more than young people. Finally, females spend more time playing than males.

Fruit

What is particularly noticeable is that adults play with each other more the more time they spend looking for fruit. Fruit is a highly valued but scarce food source, which can lead to competition within a group. And then all the puzzle pieces fell into place.

keep peace

Howler monkeys have no fixed social hierarchy; something that often leads to the resolution of competition and conflict in other monkeys. Also, howler monkeys do not groom each other – unlike other monkeys who use it for group bonding and stress relief. Instead, the researchers believe howler monkeys use play to keep the peace. It may play a key role in regulating relationships within their social group.

conflict resolution

It means that through play, howler monkeys reduce group tensions and avoid conflict. That also explains why mainly adults play with each other. “Because young people do not threaten or compete in fruit trees, we believe that adult play is a way to resolve conflict within the group,” said researcher Norberto Asensio. “This works in a similar way to other primates grooming each other.”

Play is therefore not only a way to develop yourself or to use up your energy. “Despite our own perception of what play means, it doesn’t always have to be associated with frivolity or parenting,” said study researcher Jacob Dunn. “Instead, we think it performs an important function in howler monkey society by decreasing tension when there is competition over scarce resources.”