Abstract # 93:

Scheduled for Thursday, August 18, 2005 07:00 PM-09:00 PM: (Cambridge/Oxford Room) Poster Presentation

Determinants of dominance rank in a large sample of captive female baboons

S. M. Ramirez, L. Brent, E. Sosa, A. Comuzzie and J. Rogers
Southwest Foundation for Biomedical Research, Southwest Foundation for Biomedical Research, PO Box 760549, San Antonio, TX 78245, USA
     The benefits and determinants of dominance rank in nonhuman primates have been the subject of much study and debate. Interpretations regarding females are complicated because subjects are often related and rank is inherited from the mother in many matrilineal primate societies. We analyzed the dominance rank of 326 captive female baboons (Papio hamadryas sp.) that were part of a large multigenerational pedigree. All subjects had been weaned from their mothers (mean 5.8 months) and placed in peer groups with generally unrelated youngsters, reducing the influence of maternally inherited rank. All subjects were adults (average 11.3 years) living in social groups at the time of dominance rank assessment. Ranks of all females in the group were determined based on the directionality of aggressive, submissive and affiliative social behavior and summarized into quintiles. Heritability analysis indicated that genetic variance was related to variation in dominance rank (h2 = 0.45, P < 0.00008), but that when age and body weight were included as covariates, the heritability was no longer statistically significant (h2 = 0.12, P < 0.07). Previous studies found that body weight was highly heritable in this population. Weaning age was not a significant covariate in the genetic analyses. We conclude that genetic variation does influence rank in this population, but that much of the effect is driven through genetic effects of body size.