Howler monkeys use toys to avoid conflict over resources

When we’re young, playtime is as natural as breathing. Then as we get older, something seems to change. It may be the level of responsibility, or that we simply have fewer opportunities to engage in play with our peers. Whatever the reason, some of this youthful exuberance is being lost. As far as we can tell, the same trend is happening in non-human animals as well.

This is certainly the case for the howler monkeys in the rainforests of Mexico and Costa Rica. Playtime is mostly devoted to the young monkeys or adults they are teaching, but this is not always the case. Norberto Ascencio of the Department of Clinical Psychology and Research Methodology at the University of the Basque Country and colleagues found that howler monkeys play with each other as a way to reduce stress and conflict. Their findings were published in the journal Animal Behavior.

Scientists have observed the Mexican howler monkey and the gold-covered howler monkey at Los Tustlas Biosphere Reserve in Mexico and the Guanacaste Conservation Area in Costa Rica for more than 1,800 hours to learn when and why they play.

Howler monkeys are often sedentary as a result of their paper-based diet. They spend most of their time either eating the leaves or resting during digestion. As such, engaging in play is an energy costly activity that they don’t often do. In fact, the total playing time was less than 1% of the total notes. It suggests that when they play, there is a good reason for it.

Unlike some other primates, howler monkeys do not have strict social hierarchies to which they can refer when faced with a conflict, nor do they conduct social grooming as a way to establish and maintain relationships. This poses a potential problem when the potential for combat increases, as in the presence of scarce and required resources.

“Through social play, adults can decide who eats first, and establish a precise hierarchical order to access food, and play will be an alternative to fighting here to decide who wins without aggression,” Asensio told SYFY WIRE. “Play also mitigates the inherently competitive situation.”

While howler monkeys mostly eat leaves, they feed on fruit when the opportunity presents itself. In these cases, the fruit becomes a valuable property that the monkeys will defend from others in their group. The researchers found that when fruit was more available, levels of play increased among howling adults. Playtime is believed to fill the space where social hierarchies or social grooming would be. It is a way to remind everyone that they are friends or to display physical abilities in a non-violent way.

Play is presented most often with monkeys hanging by their tails and making faces on each other, which we can frankly understand.

“It’s one of the communicative cues that animals use to say, ‘Hey, I came with friendly intentions, this wouldn’t be aggression. “It consists in showing teeth with a comfortable mouth. Another sign of play is head shaking. Laughter would be a sign of play in humans, and howler monkeys would have something similar if you were close enough to hear it,” Asensio said.

Importantly, the researchers did not see any increase in play between adults and juveniles in the presence of increased fruit availability, likely because adults do not view juveniles as a threat to their resources. This seems to indicate that the increased play is not a direct result of the additional energy provided by the high-energy fruit.

Moreover, play has also increased as a result of larger group sizes. The more monkeys in a given area, the more likely adults are to play with each other. There are two possible explanations for this relationship. The first is that larger groups offer more opportunities to play. Basically, you are more likely to find a friend worth playing with in a larger group. The second is that larger groups have a higher chance of conflict and playtime appears again as a way to manage this.

“It could be both of these reasons, opportunity as well as necessity. Opportunities come with more possibilities for selection and individual preferences may emerge, and necessity may come in trying to get to know everyone in your group and maintain cohesion,” Asensio said.

In some ways, that may mean that howler monkeys aren’t much different from us. Spending casual playtime with friends can sometimes feel like expensive energy, and while we have social hierarchies, some people believe that the invention of sports and other games arose from a desire to display physical prowess without engaging in violent conflict.

Maybe the next time you get into a brawl, you should spin a tag game or something and just see what happens.

It’s something of a fan
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