Social Network Analysis of a Chimpanzee (Pan troglodytes) Group in Captivity Following the Integration of a New Adult Member

Abstract

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 4 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 2 and 3. 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.

Evaluation of social compatibility in an all‐male group of chimpanzees (Pan troglodytes) by means of social network analysis

“…It should be noted that, although these males experienced abnormal rearing conditions (ARC), most of them showed strong affiliative interactions. This partially agrees with the idea that chimpanzee sociality seems to be negatively affected by ARC (Bloomsmith et al, 2006; Díaz et al, 2020; Fritz & Howell, 2001; Levé et al, 2015). It seems that their introduction into a social group upon arrival to FM allowed them to establish familiarity with other chimpanzees.…”

Aggressive, Submissive, and Affiliative Behavior in Sanctuary Chimpanzees (Pan Troglodytes) During Social Integration

“…In another study at Chimp Haven that looked specifically at wounding rates during social introductions, males received 64% of all wounds, and larger groups with more males experienced significantly more wounding [ 36 ]. In another study of social integration, males also directed more agonistic behaviors at others than females; however, they were not specifically directed towards other males, as we observed in this study [ 60 ].…”

“…Although we do not have complete introduction histories for all of the chimpanzees at Chimp Haven, it is also likely that many of this captive population has undergone social integrations in their past and may have some experience with changing social groups either due to births, deaths, or even research protocols that required them to be removed from and then reintegrated into social groups [ 57 , 58 , 59 ]. In another study, when a female chimpanzee was integrated into an existing group at Chester Zoo, they found that each chimpanzee was involved more often in affiliative interactions per hour (mean = 0.79) than agonistic interactions (mean = 0.50) [ 60 ]. The chimpanzees in this study were very interested in one another, with the most common affiliative behavior being approach and contact behaviors such as mouth and touch occurring multiple times during the first hour of being introduced.…”

“…Given that there are many more chimpanzees to meet in a larger group, it is possible that it took more time to develop aggressive interactions. In some studies that looked at social integrations over time, they witnessed an increase in agonistic behavior over time [ 60 , 75 , 78 ]. In this study, groups of seven to 12 individuals were observed to engage in the highest levels of affiliative behavior lending additional support to the recommendations of both the AZA and the NIH that chimpanzees should be maintained in groups of seven to nine chimpanzees.…”

Chimpanzee communities differ in their inter- and intrasexual social relationships

“…SNA has been previously applied to describe social relationships of several primate, species including humans (Dufour et al, 2011;Gradassi et al, 2022;Migliano et al, 2020;Pasquaretta et al, 2014;Puga-Gonzalez et al, 2019;Salali et al, 2016;Schel et al, 2013;van Leeuwen et al, 2018). We collected social network data based on proximity and grooming, which are widely used predictor of chimpanzee bonds (Díaz et al, 2020;Kanngiesser et al, 2011;Roberts & Roberts, 2016a;Schel et al, 2013;van Leeuwen et al, 2018;Wakefield, 2013). However, some studies have reported that proximity and grooming networks differentially predict other social behaviours, such as successful transmission of information (Hasenjager et al, 2021;Hoppitt, 2017;van Leeuwen et al, 2020).…”