Social network dynamics in a group of unrelated adolescent rhesus macaques: from the moment of association to the onset of reproductive period

Abstract

Introduction. The formation of a stable hierarchical structure in primate groups leads to a decrease in problematic social aggression. Network analysis of dynamic relationships allows for a deeper understanding of the mechanisms of formation and maintenance of dominance-subordination hierarchies in communities. The aim is to trace the dynamics of affiliation and agonistic networks in a group of unrelated rhesus macaques (Macaca mulatta) from the moment of unification until reaching reproductive age.

Materials and methods. Longitudinal observations of a community of 9 unrelated macaques were performed using the group scanning method and focal observations of each pair of interacting individuals with the construction of agonistic and affiliation network matrices in three sections: after the unification of macaques at the age of 14-18 months, after six months and after a year and a half of cohabitation. The main network indicators were evaluated and significant changes in social behavior were revealed as individuals grew up.

Results and discussion. Affiliation networks revealed temporal dynamics in the relationship between older and younger individuals, with a significant increase in the second slice and a significant decrease in friendly contacts between them in the third slice. Agonistic networks clearly reflected the hierarchy of dominance and subordination directed from the elders to the younger within the same sex in all three time slices, however, in the second period there was a significant increase in intersex aggression from the two youngest females to males close in age, and in the third period a medium-ranking female-male pair with a significant increase in bilateral aggression between them was revealed.

Conclusion. The dynamics of adolescent relationships revealed instability between the sexes at the level of low- and medium-ranked young individuals, which led to outbreaks of collective aggression and trauma in younger females. The results allow us to assess the impact of the dominance-subordination hierarchy in a community of unrelated monkeys on the health, survival and reproductive success and are of interest for understanding the foundations of human sociality.

Acknowledgements. The authors would like to thank the staff of laboratory for their help in conducting daily observations of macaques.

Funding. The research was carried out at the expense of a grant from the Russian Science Foundation (project № 25-28-02525).

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