Social network changes during space restriction in zoo chimpanzees

Nicola F Koyama,Filippo Aureli

doi:10.1007/s10329-018-0675-6

Nicola F Koyama, Filippo Aureli

Open Access

https://doi.org/10.1007/s10329-018-0675-6

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Journal: Primates	Publication Date: Jul 17, 2018
Citations: 16	License type: open-access

Affiliation: Liverpool John Moores University, Universidad Veracruzana

Abstract

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.

Highlights

We found that the density of unidirectional grooming ties was significantly lower in the restricted period compared to the control period
Four of the five males showed the same outdegree pattern as females did by grooming fewer partners during space restriction (7.8 ± 3.7) compared to the control period (11.5 ± 3.0), whereas the alpha male increased the number of partners he groomed from 5 to 10 partners during space restriction
This is the first study to investigate the effect of reduced space availability on primate social networks

Summary

Introduction

Much research has demonstrated how nonhuman primates flexibly use various coping strategies to avoid conflict and reduce social tension in response to reduced space availability (Anderson et al 1977; Aureli et al 1995; Aureli and de Waal 1997; Caperos et al 2011; Caws and Aureli 2003; Cordoni and Palagi 2007; Crast et al 2015; de Waal 1989; Duncan et al 2013; Judge and de Waal 1993, 1997; Judge et al 2006; Nieuwenhuijsen and de Waal 1982; Sannen et al 2004; Tacconi and Palagi 2009; Videan and Fritz 2007; van Wolkenten et al 2006). As the change in actual space use by the chimpanzees was less pronounced than in other studies focusing on the responses to reduced space availability, Caws and Aureli (2003) reported subtler behavioral changes They did not find differences in overall aggression rates and allogrooming patterns between the period with a reduction of escape opportunities and the control period. These findings suggest that chimpanzees may adopt a selective inhibition strategy when escape opportunities are limited

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