Determinants of Colobine Abundance: Implications for Theory and Conservation

University Of Florida, Gainesville FL

Investigators

Abstract

A fundamental issue in ecology is determining what factors regulate the density of animal populations. This issue has become increasingly important as ecologists are asked to apply their knowledge to assist conservation biologists to construct informed management plans for endangered species. With respect to primates, the importance of these theoretical issues has become critical, because most primates are found in tropical forests that are increasingly impacted by humans. Furthermore, primates constitute a major component of the vertebrate community in most tropical forests, and their ecological role is of considerable importance. However, understanding and predicting factors that determine the abundance of primate species has proven extremely difficult. Numerous studies of forest primates have revealed a high degree of variation among sites in density, but there have been few direct tests of general hypotheses proposed to account for this variation. The objective of this project is to build upon extensive long-term data on the red colobus (Procolobus badius) and black-and-white colobus monkeys (Colobus guereza) of Kibale National Park, Uganda to provide insight into the fundamental question of what determines primate abundance. To address this question the researcher will take two approaches. 1) Behavioral Responses to Changing Food Availability and Quality - In areas where food is scarce and of low quality primates should behave differently than in areas where high quality foods are readily available. These behavioral differences should provide insight as to how different components of food availability and quality influence primate density. Chapman will take advantage of seasonal (24 months) and spatial (pristine forest, logged forest, forest fragments) variation in food availability and quality to examine behavioral responses to changing environmental conditions. 2) Correlating Primate Abundance to Food Abundance and Quality for Populations at Equilibrium - The most direct means of examining the relationship between population density and food availability/quality would be a correlational one. However, this approach requires knowing that the populations are at equilibrium. If some populations were not at the carrying capacity because a factor, such as a disease, has temporarily reduced their numbers, then food availability and quality would not correlate with primate density, when in fact it may typically regulate primate numbers. Long-term research at Kibale offers a means to circumvent this limitation. In the foothills of the Rwenzori Mountains adjacent to Kibale National Park, there are approximately 40 crater lakes. These crater lakes represent a series of "experimental test-tubes" in that the forest in that each varies in extent and composition, and one can investigate how this variation in forest structure influences their primate populations. In 1995, the researcher surveyed primate communities in 20 of these forest fragments to determine the abundance of black-and-white colobus and the presence or absence of red colobus. He will repeat this survey with two goals: 1) For the black-and-white colobus populations that are found to be at equilibrium, they will directly test for relationships between indices of food availability/quality and black-and-white colobus density. 2) For red colobus populations they will see if indices of food availability and quality can predict their presence or absence in a patch.