In the wild, male rhesus macaques disperse at sexual maturity. In captivity, however, males cannotdisperse from their natal groups. Thus, the presence of natal males in captive rhesus social groups isunnatural and has the potential to negatively influence group dynamics and stability. A primarydifference between natal males and non-natal (immigrant) males is that natal males have theopportunity to form long-term alliances with their maternal kin as well as nonkin. We investigated thefactors associated with natal males' kin alliances and the impact of these alliances on measures of natalmale behavior, group dynamics, and group stability. We found that natal males more frequently formedalliances with maternal kin when they were from high-ranking matrilines, had more siblings, and wereyounger. More frequent kin alliances were associated with more frequent use of intense aggression,higher individual rank, and higher degree of integration within the male displacement network. Thus, itseems that natal males use their alliances to be more active and influential in the social group, whichmay affect group stability. It appears that juvenile natal males from high-ranking matrilines, inparticular, have the largest impact on group stability. Younger natal males from high-ranking matrilinesformed alliances with kin more frequently and used intense aggression more frequently than older orlower ranking males. Furthermore, groups with a higher proportion of juvenile males from high-rankingmatrilines also had higher rates of wounding. We suggest that the presence of natal males in rhesusgroups may act in opposition to group stability.
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