Social network changes during space restriction in zoo chimpanzees.

Several studies across anthropoid species have demonstrated how primates respond to the increased risk of conflict during space restriction with various behavioral strategies. Three strategies have been proposed relating to tension regulation, conflict avoidance, and inhibition. Prior research supporting these strategies has focused on individual- and dyadic-level analyses, yet group-living animals live within a web of inter-individual connections. Here, for the first time, we used a network approach to investigate how social structure and individuals' connectedness change during space restriction. We collected grooming and aggression data during a 6-week control period and a 5-week period of space restriction in a large group of zoo chimpanzees. We compared network density and individual centrality measures (degree, eigenvector, and betweenness centrality) between these two periods using permutation tests. The density of the unidirectional grooming network was significantly lower during space restriction, indicating fewer grooming partners and a less cohesive network. This was mainly due to a reduction in females' grooming partners (degree) and an increase in females' betweenness centrality. We found no differences in the mutual grooming or aggression networks. Our findings are consistent with a conflict avoidance strategy and complement previous findings from the same dataset based on individual behavioral rates that supported a selective inhibition strategy. The results highlight the dynamic nature of social structure and its inherent flexibility to respond effectively to short-term changes in the environment.