Deforestation changes social behavior in monkeys

Deep in the rainforest, monkeys are known for their lively social interactions. But a new study reveals a worrying trend: when deforestation disrupts their habitat, monkeys are forced to change their social behaviors in order to survive.

“One trend we’re seeing with primates worldwide is that when their forests are cut down, they’re either able to adapt in some way, or their population declines,” explained Dr. Laura Bolt, a primatologist at the University of Toronto Mississauga.

Monkey behavior changes

One might wonder, why focus on monkey social behavior? Much like humans, monkeys are social creatures and their interactions are important for survival, learning, and social structures. 

Since changes in their environment may impact these interactions, the researchers studied how monkeys adapt to living near forest edges caused by human activities. 

Focus of the study 

The study took place in Costa Rica at La Suerte Biological Research Station. Scientists observed three monkey species – spider monkeys, capuchin monkeys, and howler monkeys – from 2017 to 2023. 

The team documented the monkeys’ social behaviors, such as grooming, playing, and communication, both deep inside the forest and near the edges. The aim was to see if the monkeys behaved differently in the natural forest interior compared to the disturbed edge zones. 

Spider monkey behavior changes 

Spider monkeys played and groomed each other less often in the edge areas compared to the deeper parts of the forest. This difference suggests the monkeys might not feel as safe or comfortable socializing on the edges.

The researchers speculate that the monkeys are saving energy in these harsher edge areas. This could be because there’s less food or because there are more dangers around, like predators or people. 

The forest edge is closer to humans, so it might not be as good of a habitat as the inner forest. There is likely less food and fewer big trees for the monkeys to swing through and hide in. 

Spider monkeys prefer the inner forest 

Another thought is that spider monkeys just prefer the thicker, inner parts of the forest for socializing. They might feel safer moving around high up in the tree canopy, away from the trouble and dangers at the forest edge. 

The canopy is like a 3D maze of branches that the monkeys can swing through easily. It also has fruit trees, making it a great place to hang out with friends and share food.

Behavior changes in capuchins 

The experts found that white-faced capuchin monkeys engaged in behavior that wouldn’t draw attention to themselves. These monkeys fought and vocalized less often while living along the forest edge.

Capuchins eat a variety of foods, so they might be able to find more to eat at the forest edge, which could affect how they interact with each other. Also, being quieter and less aggressive might help them avoid predators in these open areas. 

“If they’re in an area with smaller trees, where it’s easier for predators to see them, they’re especially vulnerable,” said Dr. Bolt. “It makes sense that the capuchins would try to avoid getting eaten, essentially.”

Howler monkey behavior remained the same

Unlike the other monkeys, howler monkeys behaved the same way in both the center of the forest and at the edges. 

This could mean that howler monkeys are very adaptable and can handle these changes well. Or, it might be that they can’t adjust their behavior very easily to new situations.

Howler monkeys mostly eat leaves, which are easy to find even in disturbed areas. This flexible diet might be why they act the same way regardless of their surroundings. 

Long-term concern for howler monkeys 

The study suggests that howler monkeys might do well in damaged forests without changing how they interact with each other. Unfortunately, this stability could also mean they have trouble adapting to environments that change quickly or become badly damaged. 

“This could be a concern long-term for howler monkeys. They might be only capable of living one way and then they persist until suddenly, they die out because they’re not able to cope,” said Dr. Bolt.

Monkey social behavior and conservation

Dr. Bolt’s research helps us understand how well monkeys can cope with change. This knowledge allows us to pinpoint which primates are most at risk from fragmented forests and how changes in their natural behavior might affect their survival.  

“Understanding how species behave is a way of better understanding them, and better understanding how to conserve them,” said Dr. Bolt.

The study is published in the American Journal of Primatology. 

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