Marilyn A. Norconk - US grants

Students of evolutionary biology are involved in testing predictions about how animals make a living. `Making a living` is shorthand for studying how animals search for food, avoid predators, and reproduce successfully. It is assumed that, like us, animals do not have time to perform an infinite variety of tasks; some are more important than others. Finding food and avoiding predators are critical to survival even before reproduction can become an issue, and food fuels all of these activities. Since most primates need to refuel every day, the ability of each individual to find food is an essential daily activity. This study examines how Venezuelan white faced saki monkeys (Pithecia pithecia) solve the problem of finding and using food. White faced sakis live in small social groups that travel together from morning to evening. Finding food is thus both an individual and social problem. We will employ interdisciplinary methods to examine how female sakis, who like all female mammals are under stronger energy constraints than males, balance nutritional needs in different reproductive states (estrous cycles, pregnancy and lactation). Traditional behavioral methods of observation will be combined with recently developed laboratory techniques to help us understand how females make individual choices based on reproductive status and nutritional value of the foods.

In non-human primates, groups often engage in between group aggression. Despite the integral role these social interactions play in models predicting and explaining primate behavior, our knowledge of why individuals choose to engage in this risky behavior remains somewhat limited. In general, aggression between groups is attributed to defense of resources or defense of mates and infants. This project will investigate the factors underlying aggression during between-group encounters in a territorial South American primate: the white-faced saki monkey. This arboreal primate occupies small home ranges which are actively defended from neighboring groups along home range boundaries. In order to comprehensively test the function of this aggression, this project will gather data on between-group encounters among white-faced saki groups at Brownsberg Nature Park, Suriname. Variation in aggression and individual participation in these interactions will be assessed in terms of dependence upon food abundance, female reproductive state, and within group social bonds. Such data will provide valuable information on a little known primate species as well as serve as a case study to help develop models of primate social behavior. The broader impacts of this study include collaboration with the National Herbarium of Suriname and the training of a Surinamese student. This project will also integrate lines of evidence from often distinct aspects of primatology (feeding behavior, social behavior, and endocrine analysis) in order to comprehensively examine a behavioral trait. This doctoral dissertation research project will contribute to the academic training of a female graduate student.