Black howler monkey (Alouatta pigra) nutrition: Integrating the study of behavior, feeding ecology, and the gut microbial community

This dissertation describes an integrated 10-month field study investigating the behavioral and physiological mechanisms used by non-human primates to satisfy nutritional demands in response to changes in diet and physiology. Specifically, it examines the relationship between behavior, physiology and nutrition in two groups (N = 16 individuals) of wild, black howler monkeys (Alouatta pigra) in Palenque National Park, Chiapas. The first chapter explores patterns in black howler monkey nutritional intake across time to determine whether howlers employ a foraging strategy that regulates energy and/or nutrient intake and whether this strategy changes in response to the amount of ripe fruits or leaves in the howler diet. The second investigates the response of the howler monkey gut microbial community to changes in diet composition across time and the potential effects of changes in the gut microbial community on howler digestive efficiency and nutrition. Finally, the third chapter examines differences in activity, diet, and the gut microbiota among adult male, adult female, and juvenile howler monkeys to determine whether behavioral or physiological mechanisms allows adult females and juveniles to compensate for the increased nutritional demands of reproduction and growth.;The data presented in this dissertation suggest that although they are able to consume large quantities of leaves periodically, on an annual basis, black howler monkeys consume more ripe fruits than leaves. They also exhibit a protein-regulating foraging strategy similar to that of ripe-fruit-specialist spider monkeys and consume more protein energy and more total energy than spider monkeys. These results indicate that black howler monkey feeding ecology is similar to that of other primates that consume mostly fruit and that both fruits and leaves are critical to understanding howler monkey nutrition and feeding ecology. Additionally, data from this dissertation show that the impacts of the gut microbial community must be considered when discussing howler monkey ecology and evolution. The howler gut microbial community shifts in response to changes in the howler diet over time, contributing additional energy during periods of reduced energy intake. Similarly, adult female and juvenile howler monkeys are characterized by bacteria that produce more energy and vitamins compared to adult males. These differences, together with differences in nutritional intake, may play a role in allowing females and juveniles to meet the increased nutritional demands of reproduction and growth. As a result, while behavior and foraging patterns are important in understanding how howler monkeys respond to temporal variation in food availability while maintaining activity, ranging and life history patterns, the nutritional contributions of the gut microbiota are also critical.;Understanding how primate behavior, feeding ecology, and gut microbial processes relate has important implications for the study of primate ecology and evolution. The resources provided by the gut microbial community are typically not accounted for in traditional studies of behavior and feeding ecology but are crucial for understanding primate nutrition. By pinpointing both the causes and effects of changes in gut microbial community composition and improving the understanding of how foragers adjust to changing nutritional demands in variable environments, we can approach studies of primate behavior, nutrition, and health more effectively. While the patterns and mechanisms involved may differ across primate populations in response to differences in phylogeny or habitat, improved knowledge of both nutrition and physiology is critical for primate research worldwide. (Abstract shortened by UMI.).