Abstract # 6218 Poster # 175:

Scheduled for Friday, June 19, 2015 06:00 PM-08:00 PM: (Cascade AJBCD) Poster Presentation


SUPPLY-AND-DEMAND OR SOCIAL INVESTMENT? CONTEST COMPETITION AND GROOMING EXCHANGE AMONG FREE-RANGING RHESUS MACAQUES

K. N. Balasubramaniam1,2, B. A. Beisner1, H. Fushing1, B. J. McCowan1 and C. M. Berman2
1University of California at Davis, 1 shields avenue, Davis, CA 95616, USA, 2University at Buffalo, SUNY
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     In nonhuman primates, (allo)grooming is frequently exchanged either reciprocally for itself or interchangeably for access to rank- or fitness-related benefits (infant-handling, feeding/drinking-tolerance) to varying degrees. One explanatory framework for such variation combines socio-ecological and biological-markets principles: reciprocity prevails when the costs of within-group resource competition (WGC) are low, and interchange prevails when high WGC-costs generate a strong demand for rank-related benefits. We examined evidence for this dynamic among free-ranging rhesus macaques (Macaca mulatta) on Cayo Santiago. Data on agonistic, affiliative, and contest-competitive behavior were collected on adult females (n=30) of group S using focal-animal and all-occurrences sampling. Rowwise matrix correlations showed both significant grooming reciprocity (Kendall’s T=0.42,p<0.001) and interchange for receiving drinking-tolerance (Kendall’s T=0.26,p=0.005). GLMs showed moderate evidence for positive relationships between WGC-costs (feeding on scattered, low-quality food: B=0.567,p=0.02) and interchange, but not when controlling reciprocity (B=-0.085,p=0.72). Jointly modeling grooming and drinking-tolerance social networks showed that greater-than-expected numbers of grooming dyads also codrank, but independently of direction (Chi2(9)=25.03,p<0.005). Our findings point to social-investment rather than biological-markets: when WGC-costs are high, macaques with strong grooming relationships also tend to cooperate or tolerate each other more when drinking, but without keeping track of exact transactions (who owes whom).