Archived Abstracts
Social and demographic correlates of male androgen levels in wild white-faced capuchin monkeys (Cebus capucinus)
Authors: Franka S. Schaebs, Susan E. Perry, Don Cohen, Roger Mundry, Tobias Deschner
The Challenge Hypothesis links levels of androgens (steroid hormones responsible for the regulation of aggressive behavior and muscle mass in males) to aggressive competition among males for breeding access to females. It predicts that androgen levels should be high during periods of territory and mate acquisition and low when paternal care is provided. For primate species living in social groups, higher androgen levels are predicted when males are engaged in aggressive competition for fertile females, or – where little aggression occurs in mating contexts, but alpha males are the primary breeders – when males need to defend their high dominance rank.
We investigated how various social and demographic factors influenced androgen patterns in 18 males from 9 social groups of white-faced capuchin monkeys (Cebus capucinus) in Lomas Barbudal, Costa Rica, over a 5.25-year period. As predicted, males had significantly higher androgen levels as alphas (the primary breeders) than as subordinates. However, male androgen levels were not unaffected by (a) presence of infants, (b) the number of fertile females or adult male competitors present, or (c) the potential for instability in the alpha male position. Thus, not all predictions of the Challenge Hypothesis were supported by our results. There was a striking seasonal change in male androgen levels, which peaked close to the end of the conception season and dipped near the beginning of the conception season. Our findings suggest that seasonally changing ecological factors probably complement social factors such as dominance rank in affecting androgen profiles of male capuchins.
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