by JESSICA WARD LYNCH A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Anthropology) at the UNIVERSITY OF WISCONSIN - MADISON 2001 ABSTRACT I evaluated social relationships, sexual behavior, male endocrinology, and seasonal subgrouping patterns in one group of tufted capuchin monkeys, Cebus apella nigritus, at the Estacao Biologica de Caratinga, Minas Gerais, Brazil. In order to characterize intra- and intersexual relationships, data were collected on social distance, dyadic aggression, coalition formation, participation in intergroup encounters, grooming, and play behaviors. All adult males were dominant to all adult females. High-ranking females were the alpha male's most frequent coalition partners and grooming partners. All males participated together in intergroup encounters. The alpha male was aggressive to other males, and had agonistic alliances with them, but showed no active affiliative behavior towards them. In contrast, subordinate adult males were never aggressive to one another, and were affiliative towards one another in both grooming and play. In many aspects of male-male behavior, the capuchins at EBC were more similar to white-faced capuchin monkeys, Cebus capucinus, from Costa Rica, than to tufted capuchins at other field sites. Capuchin sexual behavior is unusual, because females actively solicit alpha males for copulations, but these males may delay sexual activity for hours or days. This study tested whether male sexual reluctance is season-specific. The influences of season and rank were analyzed for male consortship participation, solicitation of females, latency to copulation, and copulation frequency. Thirty-two copulations were observed, occurring over 9 months of the year. The alpha male was solicited for the most consortships, but his mating success did not differ from other adult males. In the dry season, males showed some contest competition for mates, a higher rate of alternative mating strategies, and an increase in the monitoring of female condition. However, no males ever mated more than one time per day, even at the peak of female sexual activity. Male capuchin sexual behavior was affected by both season and rank, and there was evidence for limitations on ejaculatory frequency throughout the year. The temporal pattern in male testosterone and cortisol production was compared to ' female sexual activity and male-male aggression. The alpha male did not differ from other adult males in testosterone or cortisol concentration. As expected, there was a clear elevation of testosterone in all males during the onset of adult female sexual activity. Cortisol concentration was positively correlated with testosterone concentration, suggesting that cortisol does not inhibit testosterone in this species. The seasonal frequency of female-maintained consortships was the best predictor of mean adult male testosterone concentrations. The sustained high-magnitude increase in steroids during the peak of adult female sexual activity was associated with a relatively low frequency of male-male intragroup aggression. Subgrouping patterns in tufted capuchin monkeys were compared to those in other Cebid and Cercopithecine species. Across the study period, 159 different subgroups of the main group were recorded, on a total of 105 days, out of 201 days of observation. Multi-male multi-female groups with associated juveniles were the most common subgroup type. In the wet season, low-ranking matrilines split off frequently from the main group, accompanied by low-ranking males. The fluidity of subgroup size and membership, and seasonal differences in subgroup patterns, were best predicted from the model of other Cebidae species. The bimodal distribution of group size and the composition of subgroups matched predictions based on Cercopithecine subgroups. CONTENTS Abstract ii Acknowledgements iv Chapter 1: Introduction 1 Chapter 2: Social relationships in wild tufted capuchin monkeys, Cebus apella nigritis 10 Chapter 3: Male mating strategies of wild tufted capuchins (Cebus apella nigritus) in Brazil's Atlantic forest 56 Chapter 4: Individual and seasonal variation in fecal testosterone and cortisol levels of wild male tufted capuchin monkeys, Cebus apella nigritus 92 (co-authored by T. E. Ziegler and K. B. Strier) Chapter 5: Seasonal subgrouping patterns in one group of tufted capuchin monkeys, Cebus apella nigritus 126 Chapter 6: Conclusions 163 HOW TO OBTAIN: To borrow this document, contact Joanne Brown (brown@primate.wisc.edu), Head of Technical Services, Wisconsin Primate Research Center Library and Information Service, University of Wisconsin-Madison. Fax: 1-608-263-3512
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