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Monkeys are social animals. Understanding the behavior of monkeys helps us to recognize deviation in behavior. This is not only important for scientific behavior research but also to manage our breeding and experimental colonies. To improve our knowledge, we work together with a group of behavioral scientists from the University of Utrecht.

The behavior of female rhesus macaques to a new male



Newcomers in groups have to establish their social relationships with resident group members. The introduction of new, unfamiliar, males into captive monkey groups is necessary to prevent inbreeding but can also bear social risks. To minimize these risks, it is crucial to understand the social behavior accompanying male introductions. While the behavior of new males entering a group is generally understood, information on resident female behavior during introductions is lacking.

We studied female behavior towards immigrant males during introductions of three adult male rhesus macaques — each into a different captive group. All three males were successfully introduced; and respectively 100%, 92%, and 83% of the females tolerated the immigrant as a group-member at the end of the introductions. Older females started tolerating the male significantly faster than younger females, while no effect of female dominance rank, fertility, or the number of female coalitionary partners was found. During immigration, female aggression and submission towards the immigrant male, and male mating access decreased, while female affiliation toward the male increased.

In general, the process of tolerance and the changes in social behavior were similar between the introductions, indicating a general pattern in female behavior during male introductions.

Based on these results, we suggest that female submission towards immigrant males may constitute a criterion to assess the risk of leaving a male in the group full-time. Overall, we conclude that female behavior to a new male is important and can provide valuable information about the immigration process during male introductions. Therefore, female behavior should not be overlooked.

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