Alexis Amann

Preliminary abstract: Hamadryas baboons are perhaps the most sexually coercive primate species, with a unique multi-level social system in which males aggressively transfer females between social units, a system that may closely reflect that which evolved in our hominin ancestors. Hamadryas male-imposed takeovers are costly to females and are often followed by infant mortality. I hope to elucidate female reproductive strategies that may function to counteract this coercion and high risk of infanticide. For example, lactating females may display false signals of sexual receptivity to males post-takeover, thereby preventing the loss of a dependent infant. In addition, pregnant females may use a strategy of pregnancy termination post-takeover, thus mitigating the eventual loss of investment in offspring. This project will take place at the only long-term field site with habituated and individually-identified wild hamadryas baboons, Filoha in Ethiopia. Using behavioral and fecal hormonal data, I will seek behavioral and physiological evidence of deceptive swellings and adaptive pregnancy failure (the Bruce Effect) in hamadryas baboons. For decades, baboons have been used as models for human evolution due to shared features of their ecology and physiology, and the hamadryas social system in particular — female defense polygyny within a larger multilevel social system — may closely mirror the social system that evolved in early Pleistocene hominins. Thus evidence of hamadryas female ability to counteract male reproductive strategies within the context of this coercive multi-level system may lend insight to the evolution of the interacting male and female reproductive strategies in our own ancestors.