1Department of Anthropology, Tulane University, 2National Primate Research Center, University of Wisconsin-Madison
Friday 8:45-9:00, Ballroom A
In many wild primates, male dominance rank is correlated with reproductive success. However, not all males compete successfully, suggesting that the costs of obtaining and maintaining high dominance are significant. Testosterone (fT) and dihydrotestosterone (fDHT) are androgens that facilitate male aggression and sexual behavior. Glucocorticoids (fGC) are associated with the stress response and mobilization of energy stores, but chronically elevated levels are associated with immunosuppression. We investigated the hormonal mechanisms underlying reproductive competition in alpha and subordinate male white-faced capuchin monkeys (Cebus capucinus) across female reproductive phases. From July 2008–October 2009, we collected weekly fecal samples (N=989) from all adult and subadult males (N=14) residing in three habituated groups in the Santa Rosa Sector of the Area de Conservación Guanacaste, Costa Rica. Fecal samples were also collected from females to identify periovulatory phases (POP) using progesterone and estradiol assays. Males responded to the presence of ovulatory females with increases in fT, fDHT, and fGC regardless of dominance status (GLMM, fT: F=70.352, P<0.001; fDHT: F=8.474, P<0.001; fGC: F=8.474, P=0.004), suggesting that all males experience increased competition and stress during POPs. Alpha males had higher fT, fDHT, and fGC than subordinate males independent of female reproductive state (GLMM, fT: F=161.313, P<0.001; fDHT: F=78.774, P<0.001; fGC: F= 1.367, P<0.001). These findings suggest that while alpha males may benefit from increased competitive ability associated with elevated fT and fDHT, high fGC levels indicate that there are also costs associated high dominance status.
Research support was provided by the Fonds Québecois de la Recherche sur la Nature et les Technologies (VAMS), The LSB Leakey Foundation (VAMS), National Geographic Society (VAMS #8652-09), National Science Foundation (VAMS #0926039), and Tulane University’s Research Enhancement Fund (KMJ), Department of Anthropology (VAMS and KMJ), Stone Center for Latin American Studies (VAMS and KMJ) and Middle American Research Institute (VAMS). The NIH provides partial support to the Wisconsin National Primate Research Center for the cost of analysis (TEZ #RR000167).