Predictors of Colobus Abundance: How Populations Respond to Stress

University Of Florida, Gainesville FL

Investigators

Abstract

A fundamental issue in ecology is determining factors that regulate the density of animal populations. The importance of understanding determinants of animal abundance has increased with the need to develop informed management plans for endangered or threatened species. With respect to primates, these issues are critical because tropical forests occupied by primates are undergoing rapid anthropogenic transformation. However, understanding and predicting factors that determine primate abundance has proven extremely difficult. Numerous studies of forest primates have revealed a high degree of inter-site variation in density, but there are few direct tests of general hypotheses proposed to account for this variation. Notable exceptions are studies of folivorous primates, where the protein/fiber ratio of available leaves has been used to predict folivorous primate biomass. In a previous NSF, Colin Chapman showed that this relationship applied to small spatial scales, and he was able to predict the biomass of neighboring populations of colobine monkeys inside Kibale National Park, Uganda. He also demonstrated diet selection for foods with high protein to fiber ratios and tested two alternative hypotheses (colobines are energy limited or restricted by the availability of particular minerals). However, finding single factor explanations for complex biological phenomena, like determinants of colobine abundance, is unlikely. Rather, recent long-term studies have highlighted the importance of multifactoral explanations. As a result, this current project will explore the possibility that nutrition and parasitism operate synergistically to influence colobus population dynamics. Two approaches will be taken. First, in a system of forest fragments monitored since 1995, this project will test if the size of population change is a function of changes in the availability of quality foods and the level of parasitic infections. To partially evaluate assumptions made when taking the second approach, levels of stress hormones, isolated from fecal samples, will be relate to the magnitude of population change. Secondly, using long-term observation of a stable population, the degree to which periods of stress, as indexed by levels of cortisol metabolites in fecal material, correspond to periods of food scarcity and/or increased parasite infections will be assessed. The broader impacts of this study are many. For example, this information will be useful in construction of informed management plans for folivorous primates around the world. Funding will also facilitate long-term monitoring in Kibale, building the infrastructure of Makerere University Biological Field Station, promoting Ugandan student training and conservation (2 students have been identified), graduate and undergraduate training at the University of Florida, and dissemination of this information to the public by assisting the development of nature films (particularly with the BBC).