Seasonal changes in the structure of rhesus macaque social networks
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Social structure emerges from the patterning of interactions between individuals and plays a critical role in shaping some of the main characteristics of animal populations. The topological features of social structure, such as the extent to which individuals interact in clusters, can influence many biologically important factors, including the persistence of cooperation, and the rate of spread of disease. Yet, the extent to which social structure topology fluctuates over relatively short periods of time in relation to social, demographic, or environmental events remains unclear. Here, we use social network analysis to examine seasonal changes in the topology of social structures that emerge from socio-positive associations in adult female rhesus macaques (Macaca mulatta). Behavioral data for two different association types (grooming and spatial proximity) were collected for females in two free-ranging groups during two seasons: the mating and birth seasons. Stronger dyadic bonds resulted in social structures that were more tightly connected (i.e., of greater density) in the mating season compared to the birth season. Social structures were also more centralized around a subset of individuals and more clustered in the mating season than those in the birth season, although the latter differences were mostly driven by differences in density alone. Our results suggest a degree of temporal variation in the topological features of social structure in this population. Such variation may feed back on interactions, hence affecting the behaviors of individuals, and may therefore be important to take into account in studies of animal behavior.
KeywordsSocial structure Social network analysis Network topology Rhesus macaques
We thank the Caribbean Primate Research Center (CPRC) for the permission to undertake research on Cayo Santiago, along with Bonn Aure and Jacqueline Buhl who assisted in the data collection. We also thank Roger Mundry for his permission to use the PSAM software and Robert Seyfarth; Dan Blumstein, an anonymous reviewer; and associate editor Joan Silk for their helpful comments on earlier versions of the manuscript. This project was funded by fellowships awarded to LJNB by the Natural Sciences and Engineering Research Council of Canada, the University of Roehampton, and the Duke Center for Interdisciplinary Decision Sciences. Additional funds were provided by the International Primatological Society, the Leakey Trust, and NIMH grant no. R01-089484-01. The CPRC is supported by a grant no. 8-P40 OD012217-25 from the National Center for Research Resources (NCRR) and the Office of Research Infrastructure Programs (ORIP) of the National Institutes of Health.
This study was approved by the IACUC of the University of Puerto Rico and by the Ethics Committee of the University of Roehampton.
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