1Department of Evolutionary Anthropology, Duke University, 2Department of Structural Biology, Stanford University, 3Vaccine Research Center, National Institutes of Health, 4Sanofi, Sanofi, 5Departments of Medicine and Microbiology, Perelman School of Medicine, University of Pennsylvania, 6School of Human Evolution and Social Change, Arizona State University
March 26, 2015 9:30, Grand Ballroom E/F/G
In many species of non-human primates, males form friendly social bonds while simultaneously competing with each other for high rank in a dominance hierarchy that determines mating access to females. While studies reveal a clear link between female bonds and fitness in female philopatric species, few studies have investigated such a relationship in males. Those studies that exist suggest that the connection between bonds and fitness may be mediated by coalitionary aggression in males, but in chimpanzees coalitionary aggression is relatively infrequent. Here, we investigate whether male social bonds themselves facilitate fitness benefits in one population of wild, free ranging chimpanzees. We created indices of dyadic bond strength based on grooming and associations in two-year periods from 1994 to 2011, and used these to determine total bond strength, number of bonds, and betweenness centrality in the grooming and association networks for each male. We ran a linear mixed model to determine whether, controlling for current rank and age, bond strength predicted rank change (measured by Elo score) within each period. Surprisingly, number of grooming partners significantly predicted rank change within each period (p = 0.02), while total bond strength and betweenness centrality in grooming and association networks were not significantly related to rank change. This suggests that males increase their rank by forming a higher number of grooming relationships with other males, but not by investing in strong grooming relationships. Future analyses will account for the influence of coalitionary aggression and investigate the influence of bonds on male reproductive success.
Funding provided by the Jane Goodall Institute, NSF (DBS-9021946, SBR-9319909, BCS-0452315, IOS-LTREB-1052693), NIH (R01 AI050529), NSF GRFP (DGE-1106401), and the Kirschstein Research Service Award (NIH F32 AI085959-03).