Jacinta Beehner: University of Michigan Department of Anthropology

The arrival of a new dominant male can be a tumultuous time for females in a primate social group – particularly when this male is likely to be infanticidal. Females of many taxa where infanticide occurs have developed counterstrategies to this threat. In sharp contrast with the behavioral counterstrategies reported for many primate species, we discovered that female gelada responses are almost entirely physiological. Using 7 years of demographic and hormonal data from a population of wild geladas living in the Simien Mountains National Park, Ethiopia, I will detail two of these strategies – “false fertility” employed by lactating females, and pregnancy termination (a “Bruce effect”) employed by pregnant females. Completing the trifecta, I will present preliminary data that adolescent females exhibit yet a third physiological response to the arrival of a new male – the sudden onset of maturation (a “Vandenbergh effect”). I revive a term previously proposed for these same effects (the “hoo haa effect”) because there is likely a singular mechanism mediating all three outcomes.