Vervet monkeys deal with social norms and peer pressure too

A new study reveals that vervet monkeys exhibit diverse social “norms” and behaviors that are comparable to human customs, varying significantly across different communities. 

Led by Elena Kerjean from the University of Lausanne, the research team spent nine years observing vervet monkeys and their unique social dynamics.

“Over the last decades, animal tradition studies not only helped researchers to better understand the diversity of intra-species behavioral repertoires, but also to unravel the evolutionary roots and the selective pressures leading to the emergence of culture,” wrote the researchers.

Social customs

The study provides new insights into the social behaviors of these primates. Kerjean explained that the research has uncovered behavioral traditions of social customs in vervet monkeys that are stable across nine years.

This discovery challenges the previous understanding of animal behavior, as it demonstrates a complex social structure within vervet monkey groups, similar to human societies.

Social atmospheres

One of the key findings of the study is the identification of different “social atmospheres” within vervet monkey groups. 

These atmospheres, characterized by varying social customs, are passed down through generations, indicating a form of social learning. 

Social conformity 

The team also discovered a notable aspect of social adaptation: when male monkeys moved to a new group, they quickly adapted their social behaviors to align with the norms of their new community. This behavior suggests an element of social conformity and peer pressure among vervet monkeys.

“Males adapted their sociality to the group they integrated with, which we believe is a good example of social conformity,” said Kerjean. 

“This normative rule – act like others – probably helps them to get better integrated in a new group. This conformity effect had been previously shown through a novel food experiment, but this is the first time that we observed that with social behavior.”

Distinct behaviors

Kerjean, along with her colleagues Erica van de Waal and Charlotte Canteloup, analyzed over 84,000 social interactions among nearly 250 vervet monkeys. 

The analysis revealed distinct social behaviors in one group, named Ankhase (AK), where monkeys showed a higher tendency for reciprocal grooming compared to other groups. In this group, grooming was more fairly exchanged, with individuals reciprocally grooming each other, creating a more balanced social interaction.

“You can think about it like massage exchanges between individuals,” explained Kerjean. “If I give you a massage 100 times a year but you only did it two times, I may feel that our relation is quite unfair. That’s the kind of differences we observed between our groups.”

Study implications 

The research sheds light on the social structures and norms of vervet monkeys. It also offers new perspectives on animal behavior and social learning. 

The team’s findings indicate that social norms among vervet monkeys are not only diverse but also stable over time, suggesting a deeper level of social complexity than previously understood.

Looking ahead, the researchers would like to learn more about how social traditions are introduced and passed on. They are especially curious to explore the role of key individuals or leaders in pressuring newcomers to follow incidence.

The study is published in the journal iScience.

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