DISSERTATION RESEARCH: The effects of removing large herbivores on the ecology of infectious diseases

Stanford University, Stanford CA

Investigators

Abstract

Large animals play crucially important roles in ecological systems, but they are declining in abundance worldwide. This project will explore how declines in large herbivores in Africa, including elephants, giraffes, and zebras are affecting human risk of exposure to infectious diseases. Removing large herbivores causes a doubling of rodent densities because large herbivores compete with smaller ones for food. These increases in rodent density can cause increases in the density of fleas that transmit human diseases such as plague. This project will use small-scale experiments in Kenya to test whether these increases in flea densities result in greater abundances of fleas infected with disease-causing pathogens. The researchers will also test whether these associations occur in several regions of Tanzania. The experiments in Tanzania will be carried out in landscapes in which large mammals are protected and landscapes in which they are not. Using this combination of careful experiments and large-scale comparisons will allow the researchers to test first whether the effects of large herbivores on infectious disease transmission can occur, and then whether they actually do occur. The results of this study will advance our understanding of the ecological consequences of worldwide declines in the abundance of large mammals. The project will also improve the ability of scientists and managers to respond to such population declines by giving them information about specific consequences that could result. In addition, three African field assistants and two undergraduate students will be trained in field and laboratory protocols as a result of this project.