Doctoral Dissertation Improvement: The Reproductive Trajectories of Geladas (Theropithecus gelada)

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Strong male bonds are rare among primates, especially for female-bonded species. Thus, the relationship between male bonding and reproductive strategies remains largely unexamined in female-bonded species. Geladas (Theropithecus gelada) provide an ideal model for understanding how male bonds influence male reproductive trajectories in a female-bonded species. Prior to acquiring reproductive access to females, "bachelor" geladas live in cohesive all-male groups. Eventually, males graduate from these groups to gain sole reproductive access to a group of females (one-male unit). Bachelors acquire one-male units using one of several strategies: (1) directly overthrowing the leader male, (2) submissively entering a unit and attempting to pare females away from the unit over time, or (3) capitalizing on the chaos of a recent takeover to opportunistically mate with females. Additionally, bachelors have been observed to cooperate in attempts to overthrow leader males and enter one-male units with former members of their all-male group - yet only one male eventually reaps the reproductive benefits. This project investigates the behavioral and hormonal factors that shape the reproductive trajectory of gelada males as they move from an all-male group to a one-male unit. The researchers will(i) describe the social interactions among bachelors within their all-male group; (ii) determine the behavioral and hormonal factors that influence bachelor participation in takeover attempts of leader males, and (iii) determine whether bachelor quality predicts a reproductive strategy. Behavioral data and noninvasive fecal hormone sampling will document the reproductive trajectories of male geladas. Additionally, digital photographs will be taken of male chest patch color - a feature that may indicate male quality - to document changes in color as males move from their bachelor groups to one-male units. Results from this research will inform conservation decisions regarding these rare primates, and the investigator's presence in the Simien Mountains National Park help deter illegal activities in this World Heritage Site that is in danger. This project provides income and training to local Ethiopian field assistants and the co-PI has arranged to explain gelada behavior to high school students in several U.S. states.