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

大型动物在生态系统中扮演着至关重要的角色，但它们的数量在全球范围内正在减少。该项目将探索非洲大型食草动物，包括大象、长颈鹿和斑马的数量减少如何影响人类接触传染病的风险。移走大型食草动物会导致啮齿动物密度翻一番，因为大型食草动物会与较小的食草动物争夺食物。这些啮齿动物密度的增加会导致传播鼠疫等人类疾病的跳蚤密度增加。该项目将在肯尼亚进行小规模实验，以测试跳蚤密度的增加是否会导致感染致病病原体的跳蚤数量增加。研究人员还将测试这些关联是否出现在坦桑尼亚的几个地区。坦桑尼亚的实验将在大型哺乳动物受到保护的环境中进行，而在没有保护大型哺乳动物的环境中进行。利用这种仔细的实验和大规模比较的结合，研究人员将能够首先测试大型食草动物是否会对传染病传播产生影响，然后再测试它们是否确实发生了。这项研究的结果将促进我们对全球大型哺乳动物数量下降的生态后果的理解。该项目还将提高科学家和管理人员应对这种人口下降的能力，向他们提供可能导致的具体后果的信息。此外，由于这一项目，三名非洲外勤助理和两名本科生将接受实地和实验室礼仪方面的培训。

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.