Social network and dominance hierarchy analyses at Chimpanzee Sanctuary Northwest

Abstract

Different aspects of sociality bear considerable weight on the individual- and group-level welfare of captive nonhuman primates. Social Network Analysis (SNA) is a useful tool for gaining a holistic understanding of the dynamic social relationships of captive primate groups. Gaining a greater understanding of captive chimpanzees through investigations of centrality, preferred and avoided relationships, dominance hierarchy, and social network diagrams can be useful in advising current management practices in sanctuaries and other captive settings. In this study, we investigated the dyadic social relationships, group-level social networks, and dominance hierarchy of seven chimpanzees (Pan troglodytes) at Chimpanzee Sanctuary Northwest. We used focal-animal and instantaneous scan sampling to collect 106.75 total hours of associative, affiliative, and agonistic data from June to September 2016. We analyzed our data using SOCPROG to derive dominance hierarchies and network statistics, and we diagrammed the group’s social networks in NetDraw. Three individuals were most central in the grooming network, while two others had little connection. Through agonistic networks, we found that group members reciprocally exhibited agonism, and the group’s dominance hierarchy was statistically non-linear. One chimpanzee emerged as the most dominant through agonism but was least connected to other group members across affiliative networks. Our results indicate that the conventional methods used to calculate individuals’ dominance rank may be inadequate to wholly depict a group’s social relationships in captive sanctuary populations. Our results have an applied component that can aid sanctuary staff in a variety of ways to best ensure the improvement of group welfare.

Early life experience and alterations of group composition shape the social grooming networks of former pet and entertainment chimpanzees (Pan troglodytes)

“…Most studies on chimpanzees define the social networks by scoring dyadic grooming interactions [44,76,90], or by recording information of dyadic spatial association [43]. Due to the database available for this study and based on the fact that grooming is an important social behaviour in chimpanzees [52] we created matrices of directed dyadic grooming interactions obtained for each time period and group composition.…”

“…Social network analysis (SNA) allows us to statistically describe, quantify and compare the social relationships of individuals within a group [40][41][42]. Although it has been proven to be an extremely useful tool for describing complex social systems and investigating welfare of animals, few studies have focused on former pet and performer chimpanzees in zoos and rescue centres to date [43,44]. By detecting social patterns on a group level and analysing asymmetries of certain individuals under specific conditions, we can go further and identify factors influencing social interactions and social group structures.…”

The multidimensionality of female mandrill sociality—A dynamic multiplex network approach

“…Furthermore, in both observation periods, different layers had different edge overlap values, which were globally small, and different individuals were the most central across interaction types and at the multiplex level. It is expected that individuals within primate groups are connected differently and have a varying engagement with different interaction types [23][24][25]. Thus, each interaction type encompasses potentially variable meaningful information about the relationships between dyads.…”

“…These unique characteristics make SNA the most comprehensive and powerful method available to investigate social relationships. Whereas the most common social network approaches tend to focus on a single type of interaction (e.g., grooming: [21]; spatial proximity: [22]) or to analyse different interaction types via aggregated networks or individual networks separately [e.g., [23][24], recent developments now allow for the analysis and representation of multiple interconnected networks into a single mathematical object [25][26]. This methodological advance facilitates the study of the multidimensional nature of primate social relationships.…”

Considering Social Play in Primates: A Case Study in Juvenile Tibetan Macaques (Macaca thibetana)

“…SNA has been used to characterize these relationships in primate social groups, as well as identify clusters of individuals, subgroups, isolated group members, and, overall, diagram of the group's social network (e.g., Clark 2011; Farine and Whitehead 2015; Funkhouser et al 2018a;Sueur et al 2011a). For example, using SNA, researchers have examined the correlation between juvenile play network positions, ontogenetic social development, and later-life social connectedness (P. troglodytes, Shimada and Sueur 2014; M. fuscata, Shimada and Sueur 2017; Macaca spp., Sueur et al 2011b).…”