DISSERTATION RESEARCH: The alteration of landscape nutrient flows by human-induced increases in generalist omnivores

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All organisms require nutrients, such as nitrogen, potassium, and phosphorus, and movements of these nutrients among habitats may fundamentally alter their availability for plant growth, and ultimately for the animals dependent upon these plants. Animals can be important avenues of nutrient movement across space. Humans have altered these nutrient flows, both by eliminating some species, and by introducing others which can lead to many direct and indirect impacts on ecological function. Feral swine - a species which was first introduced to the New World by the Spaniards and are now widespread and abundant - is a classic example of a species that can potentially have large impacts upon nutrient flows among habitats. A detailed study of impacts of feral pigs upon ecosystem nutrient flows is being undertaken in the Lower Suwannee National Wildlife Refuge, located on the Gulf Coast of Florida. The landscape consists of forested islands interlaced in salt marsh. The pigs use the islands as refuges, and their intense use of these areas has led to high deposition of fecal material in the island forest habitats. Surveys revealed higher nutrient levels in the island forest soil compared to mainland forest soil, and there appear to be considerable impacts upon local plant communities. Exclosures have been set up to determine whether feral hogs are indeed responsible for increased nutrients in these refuges areas, and to examine their impact on the plants. To determine the source of the deposited nutrients, the diet of the hogs is being determined through analysis of fecal and bone samples. Genetic analysis of DNA in the feces will permit an estimation of population size and, combined with the effect the population has on nutrient deposition, will allow a 'per hog' expression of the impact of feral hogs on the nutrient flows. Feral and wild pigs are found globally and are often very abundant in the southeastern U.S.A. Refuge and park managers consider them to be very destructive, but past work has not quantified the magnitude of their impacts on nutrient flows, even though it is clear that they can profoundly alter local ecological processes. The results of this study should have wide applicability, providing basic knowledge that can assist management of many disturbed ecosystems. The project also enriches science education. Undergraduates will be involved in both in the fieldwork and in laboratory analysis. Students will be encouraged to develop their own related projects. One student will examine the imprint of periodic food scarcity as well as disease recorded in tooth enamel and bones. The student will eventually apply the results to the archaeological remains of human populations. One unusual aspect of the educational experience provided by involvement with this project is that students will be interacting with a wide range of non-academic users of the refuge, for instance by the preparation of educational materials and Powerpoint presentations made available to the general public via organizations like the Friends of Lower Suwannee and the National Wildlife Refuge system.