Trachypithecus delacouri inhabit an unusually harsh environment in Vietnam where they move and feed on rough, sparsely vegetated karst (limestone) formations. These remarkable, critically endangered primates are virtually unstudied and little is known about feeding ecology in karst forests. This study will provide data on the dynamics between soil quality, plant chemistry, and food selection, that is, how do plant-eating mammals balance their nutritional requirements with the poisonous compounds present in the plant foods they eat. The soil influences the chemical nature of its plants. Herbivores make feeding and locomotor decisions based on such plant constituents as well as on the efficacy of accessing food. The fact that a leaf-eating monkey in a food-limited habitat is restricted both by challenging substrates and harsh soil conditions that produce stunted vegetation has important implications for adaptation. While there is an abundance of evidence suggesting how plant-eating primates make feeding decisions in other types of environments, there is no evidence as to what factors influence feeding decisions in a karst habitat. Determining the role of soil type, plant defensive compounds, and substrate availability on the foraging of Delacour's langurs in a geographically and food-limited environment has far-reaching implications for the locomotor and dietary adaptations of all primates. Further, this project will shed light on how these monkeys, and thus plant-eaters in general, adapt to karst's presumed low resource environment. Soil, leaf, and behavioral analyses will be used to analyze the food selection of two groups of free-ranging Delacour's langurs on an isolated karst mountain in northern Vietnam. These data will be used to evaluate the resource availability hypothesis, the idea that plants invest heavily in defenses in environments where resources for plant growth are limited. Support for the resource availability hypothesis comes from several herbivorous mammals in non-limestone habitats, but has not been evaluated in mammals that live on plants that grow on limestone soils. The inclusion of this harsh habitat is necessary to relate soil conditions in a wide variety of environments to the behavioral ecology of a diverse array of plant-eating mammals. Feeding data from this limestone habitat will be compared with the available primate dietary and locomotor adaptations from habitats with a wide range of soil, vegetative, and substrate distributions. This project will broaden the participation of underrepresented groups in science through an international collaboration with students and colleagues from Vietnam National University (VNU), Hanoi University of Science (HUS), and the Institute of Ecology and Biological Resources (IEBR) in Hanoi. Local villagers will be employed and trained in this project. Second, in addition to enhancing scientific knowledge about Delacour's langurs and their limestone habitat, this project will improve protection of this critically endangered species by determining habitat requirements, habitat usage, and long-term viability of the population. The entire known population of Delacour's langurs is found in this northern Vietnam region. Finally, support for this project will further the training of a female graduate student in physical anthropology.
