Ontogenetic change in determinants of social network position in the spotted hyena
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Social development is crucial in the ontogeny of animals living in complex societies and has lasting consequences in adulthood. Spotted hyenas (Crocuta crocuta) live in fission-fusion societies as complex as those of cercopithecine primates. The social positions adult hyenas hold within their groups are complex and varied, but little is known about how those positons emerge and change over the course of development. Using social network analysis (SNA), we tested predictions of hypotheses suggesting that sex and dominance status affect the social network positions of young hyenas across three stages of ontogeny: (1) while living at the communal den, (2) den independent but pre-reproductive, and (3) early adulthood. By examining rates at which hyenas were found alone and their association networks, aggression networks, and affiliation networks, we observed striking changes in individuals’ network positions across ontogeny, as well as pronounced sex differences. With the exception of rates at which individuals were found alone, which increased over ontogeny, most social network position metrics decreased greatly from infancy to adulthood. However, females showed considerably more rank-related variation in this trajectory than did males. Overall, social rank had stronger effects on the development of social network positions in females than males. Thus, females and males have different social development trajectories that appear to prepare them for their different respective futures of integrating into their natal clan or dispersing to a new one.
Social development is difficult to study, particularly in long-lived gregarious mammals, so little is known about the variables shaping the emergence during ontogeny of social roles played by adults. We used social network analysis to investigate how sex and rank affect the social positions of maturing spotted hyenas as their positions change across ontogenetic development. Females develop more complex social positions than males early in life, with strategies that vary with their dominance status. Although males are just as well connected to group-mates as females when they are cubs, they generally disengage from the natal clan as they mature; males clearly do not disperse because they are aggressively expelled from their natal group. Our data suggest for the first time that social development appears to prepare females and males for their alternative futures of philopatry or dispersal.
KeywordsSpotted hyena Social network Social position Social development Ontogeny Social bonds
We thank the Kenyan National Commission for Science, Technology, and Innovation for permission to conduct this research and the Kenya Wildlife Service, Narok County Government and the Senior Warden of the Masai Mara National Reserve for assistance. We are indebted to all those who have contributed to long-term data collection on the Mara Hyena Project. Special thanks to T. Getty, L. Smale, J. Neal, and A. Wolfe for helpful comments along the way. We would also like to thank three very thoughtful anonymous reviewers for their comments. This research was supported by National Science Foundation Grants DEB1353110 and OISE1556407 to KEH, a Student Research Grant from the Animal Behavior Society to JWT, a Grant-in-Aid from the American Society of Mammalogists to JWT, and a Dissertation Continuation Fellowship to JWT from the College of Natural Science at Michigan State University.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving animals were in accordance with the ethical standards of Michigan State University and following all applicable guidelines in Kenya. Ethical approval for use of animals in this study was issued by Michigan State University under IACUC approval no. 05/11-110-00 on 22 August 2013.
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