9628943 Adler An important issue in ecology is to determine what limits densities of animal populations. This problem is particularly acute in the tropics where there are few long-term experimental studies of population limitation. Rodents are ideal organisms for testing hypotheses of density limitation because they are often abundant and easily sampled. This study will test five theories of density limitation in the spiny rat Proechimys semispinosus, a common rodent in tropical forests in Central America. This species is of particular interest because it is an important predator and disperser of tree seeds and may therefore influence forest regeneration. Twelve islands in the Panama Canal will serve as experimental systems in which food abundance and rat densities will be altered. Responses to the experiments will be monitored over a four-year period. This study will advance our understanding of animal populations in tropical forests, and the results may be applicable to many other organisms. Spiny rats are also important hosts for many infectious agents that cause diseases in humans, including leishmaniasis and Chagas' disease. Better knowledge of host populations will aid in finding points in the transmission cycles of these pathogens that are most vulnerable to intervention and that decrease the risk of transmission to humans.
