Abstract # 170:

Scheduled for Friday, August 18, 2006 07:00 PM-09:00 PM: Session 17 (Regency West 1/3 ) Poster Presentation

Positive associations between urinary testosterone, dominance rank, aggression, and behavioral style in young captive chimpanzees

S. F. Anestis
Yale University, P. O. Box 208277, New Haven, CT 06520, USA
     The juvenile and adolescent age classes are relatively understudied in the field of primate social behavior and behavioral endocrinology. In particular, associations between testosterone and behavioral variables have been measured in adults, but not in young animals, perhaps because of an assumption that hormone levels during juvenility and subadulthood are primarily tied to age and not to social behavior. In this study I tested several hypotheses about the association between baseline urinary testosterone levels and behavior in young male chimpanzees (Pan troglodytes) living at the New Iberia Research Center in Louisiana. The chimpanzees were studied over the course of four research periods, each separated by one year. Testosterone levels were assessed using a human testosterone iodine radioimmunoassay kit modified and validated for use with chimpanzee urine. A total of 710 samples from 17 males ranging from four to ten years of age were assayed. After controlling for age, testosterone levels were significantly positively associated with both dominance rank (p < 0.01) and rates of aggression directed at other group members (p < 0.01), and significantly negatively associated with rates of aggression received (p < 0.02). I also tested the hypothesis that urinary testosterone was related to behavioral styles previously found to vary in these chimpanzees. There was a positive association between testosterone and the mellow behavioral style (a style characterized by low reactivity to neutral approaches and received aggression), although this effect was partially explained by the confounding factor of dominance status. Hormone-behavior relationships in primate juveniles and adolescents should be further explored, as the period preceding adulthood is important in both physiological and social development.