Social network analysis of a chimpanzee (Pan troglodytes) group in captivity following the integration of a new adult member

Management of primates in captivity often presents the challenge of introducing new individuals into a group, and research investigating the stability of the social network in the medium-term after the introduction can help inform management decisions. We investigated the behavior of a group of chimpanzees (Pan troglodytes) housed at Chester Zoo, UK over 12 months (divided into three periods of four months) following the introduction of a new adult female. We recorded grooming, proximity, other affiliative behaviors and agonistic behaviors and used Social Network Analysis to investigate the stability, reciprocity and structure of the group, to examine the effect of rearing history on grooming network position and the role of sex in agonistic behavior. Both the grooming and agonistic networks correlated across all three periods, while affiliative networks correlated only between periods two and three. Males had significantly higher out-degree centrality in agonistic behaviors than females, indicating that they carried out agonistic behaviors more often than females. There was no significant difference in centrality between hand-reared and mother-reared chimpanzees. Overall, the group structure was stable and cohesive during the first year after the introduction of the new female, suggesting that this change did not destabilize the group. Our findings highlight the utility of Social Network Analysis in the study of primate sociality in captivity, and how it can be used to better understand primate behavior following the integration of new individuals