Doctoral Dissertation Improvement: The Impact of Seasonal Variation in Food Resources and Ranging Patterns on the Reproductive Physiology and Behavior of Female Spider Monkeys

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In both humans and great apes it has been demonstrated that a female's reproductive cycle varies in response to energy balance. In particular, research has shown that levels of ovarian steroids, such as estrogen and progesterone, fall when diet quality is poor or in response to sustained physical exertion, potentially resulting in infertility. But while this pattern has been documented in humans and their closest relatives, the so-called ecological energetics hypothesis (EEH) has not been tested in any other non-human primate. Spider monkeys provide an excellent model to test this hypothesis because in contrast to many New World monkeys, they share a number of relevant traits with the great apes including non-seasonal breeding, extended reproductive parameters, and a high degree of food specialization. Previous research on spider monkeys has demonstrated a consistent pattern whereby females fail to conceive during times when ripe fruit abundance is low. To date, however, no study has adequately demonstrated a clear link between diet, activity levels, and reproductive condition. This research tests the EEH in free ranging black-handed spider monkeys on Barro Colorado Island, Panama. Diet quality is assessed by combining female spider monkey foraging behavior data with available information on local fruit abundance and nutritional content. These values are then compared to monthly changes in the reproductive cycles of known females. Results from this study contribute to a better understanding of spider monkey reproductive biology and behavior and improve our understanding of how seasonal changes in resources impact primate evolution. Furthermore, by focusing on specific fruiting species important to spider monkeys the research has the potential to inform future conservation management decisions. Finally, this doctoral dissertation research project also contributes to the professional development of a female, Hispanic graduate student and will involve collaboration with Latin American researchers.