Doctoral Dissertation Improvement: Nutritional ecology of Mexican black howler monkeys: The role of nutrient mixing, plant secondary metabolites, and behavioral flexibility

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Many primate species exploit low quality and difficult to process resources year-round or as fallback foods during food-limited times of the year. In addition to anatomical specializations, primates have developed behavioral and cognitive solutions that serve to increase foraging efficiency or reduce energetic requirements when exploiting low quality foods. Optimal Foraging Theory has been used to explain foraging behavior in primates, and predicts that individual food choice is best described in terms of maximization of energy intake. However, according to recent nutritional ecology models, a nutrient mixing framework may provide a stronger explanation of primate foraging strategies. This study examines the nutritional ecology of Alouatta pigra, an endangered primate that feeds on low quality resources and yet is characterized by rapid growth rates and a high reproductive output compared to closely related species. Specifically, by integrating nutritional, energetic, ecological, and behavioral data, this research investigates how factors such as food and patch choice, food intake rates, the nutritional composition of plant resources, seasonal changes in food availability, the nutritional requirements of reproduction, and within-group feeding competition affect male and female foraging strategies in two neighboring groups of black howler monkeys living in Southern Mexico. The explanatory power of three models will be tested using a Geometric Framework for nutrition. This will be accomplished by detailed behavioral observations of marked individuals; vegetation assessments and determination of food availability in the groups' home ranges; and phytochemical analyses of foods collected from feeding trees.While there are data on howler monkey feeding ecology, the precise nutritional factors affecting male and female food choices are poorly understood. By constructing complete dietary profiles for each focal animal, and analyzing individual foraging decisions using a nutritionally explicit model, this research provides critical insight into the importance of nutrient balancing in assessing primate food choice and decision-making. The project also will provide valuable nutritional information for the management of captive primates, strengthen partnerships between Mexican and US universities, and offer training opportunities for Mexican undergraduates, including female students in science.