Rachel Perlman is a PhD candidate from Stony Brook University. She was awarded a Leakey Foundation research grant during our spring 2016 cycle for her project entitled “The energetics of male reproductive strategies in geladas (Theropithecus gelada).”
That energy limits the reproductive success of females, but not males, is a central tenet of primate socioecology. Often male primates invest comparatively fewer resources into each offspring. Yet at the same time, males may also face energetic constraints, particularly when reproductive strategies involve direct competition. The way in which such constraints affect male reproduction is, however, poorly understood.
My research examines the energetic dynamics of male reproductive strategies in a wild nonhuman primate, the gelada (Theropithecus gelada). Two kinds of males are distinguished: harem-holding leader males siring 83-100% of offspring and bachelor males in all-male groups with no reproductive opportunities. To gain reproductive access, bachelors must take over a leader’s unit. Because takeovers involve intense chases and fighting, energetic condition likely mediates male reproductive success. Intriguingly, the annual takeover season occurs at the end of the dry season when the main food source (grass) is less plentiful. This suggests that bachelors may target leaders when they are energetically vulnerable.
I will collect data from a population of wild geladas living in the Simien Mountains National Park, Ethiopia. I will combine non-invasive hormone analyses (thyroid hormone, C-peptide, testosterone) with behavioral observations to examine seasonal energetic variation, how energetics relates to male social status, and whether energetic condition influences testosterone and male mating effort. By examining the effects of energetics on the allocation of male reproductive effort, this project will shed light on the selective pressures and potential influence of energetics in shaping nonhuman primate and human life history.