UC Berkeley

Cooperative behavior in reproductive contexts is rare among animals, especially males. Tamarins exhibit a rare breeding system called cooperative polyandry, in which a single breeding female mates with two or more males to produce fraternal twins and the males cooperate in caring for the infants by carrying young for the first 10 weeks of their lives. This peculiar breeding system raises questions about the adaptive consequences of male behavior. The nature of the breeding system also prompts questions about the ecological context and genetic consequences of this social organization. My research attempted address fundamental questions in behavior, ecology and evolutionary biology through the lens of individual behavior. Tamarins oftentimes inhabit disturbed habitats, however detailed space use within fragmented habitats is not well characterized. I used fine scale spatial and behavioral data in order to quantify habitat preference of S. geoffroyi in a heterogenous urban-forest landscape in central Panama. Using home range- based analyses and a novel method, first passage time analysis, I showed that tamarins spend significantly more time in secondary forest habitat and are more likely to forage and engage in social behavior in forest as compared to human-modified habitats. I examined the role of two aquatic barriers of varying age in creating population genetic structure in S. geoffroyi. I found that there was significant population differentiation across the Chagres River, an older, established riverine barrier and smaller, but detectable population structure across the Panama Canal, a recent anthropogenic riverine barrier. Finally, I examined the possible adaptive benefits of cooperative male parental care using genetic analyses of paternity and relatedness. I found that males in a group are often related and that they share paternity over multi-year associations. My results suggest that indirect and direct fitness benefits may play a role in maintaining male-male cooperation in tamarins.