US EPA

7433174 

Journal Article 

Alpha Male Capuchins (Cebus capucinus imitator) as Keystone Individuals 

Jack, KM; Fedigan, LM; , 

2018 

91-115 

10.1007/978-3-319-98285-4_6 

http://link.springer.com/10.1007/978-3-319-98285-4_6
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A keystone individual is defined as an individual that has a disproportionate impact on group dynamics relative to its representation in the population. Here we use over 30 years of behavioural, physiological, paternity, and demographic data collected on the Santa Rosa, Costa Rica, capuchin population to address the question of whether or not alpha male white-faced capuchins (Cebus capucinus imitator) are keystone individuals. Within groups of white-faced capuchins, the alpha male is easily distinguished from other adult males. He is usually of prime age (10–15 years) and often the largest male due to his pronounced secondary sexual characteristics. He is the most central adult male and the recipient of the highest rates of grooming. He is also the most active participant during encounters with predators and extragroup individuals. Using naturally occurring dispersal events, we assess the impact of the removal of an alpha versus subordinate adult male on group dynamics, specifically infant mortality. We found that infant mortality following the removal of an alpha male was more than double the rate observed following the removal of a subordinate adult male. The removal of an alpha male has additional consequences for group success, individual life histories, and population conservation that extend far beyond the immediate aftermath of an alpha male replacement. Based on these findings, we conclude that alpha male white-faced capuchins are keystone individuals, and future research should focus on identifying the factors that enable some males to attain alpha status while others live out their lives as subordinates.