Omnivory, defined as feeding on more than one trophic level (e.g., a diet that includes both animals and plants), is suggested to contribute to the stability of natural communities following natural and man-made disturbances or changes in resource availability. However, the mechanisms determining omnivory in nature are not well-understood. This research examines how the combination of food availability and population density may regulate omnivory in the white-footed mouse (Peromyscus leucopus). We predict that as food abundance increases, the white-footed mouse will become more specialized in its diet. However, population density of the mice will increase as well, which may result in decreased food availability at a later time. As food availability decreases, we predict that the mice will become more generalized in its diet. We have used observational and experimental approaches, based on isotopic analysis of marked individuals, to examine dietary patterns among different populations. Here, two additional projects are proposed: 1) an experiment that simultaneously increases food abundance at two trophic levels to distinguish between how overall and relative food abundance affects omnivory; 2) a survey on background isotopic signals in local food webs to provide high-quality estimates of omnivory. This research will contribute to our understanding of mechanisms driving omnivory, with the potential to help us predict whether omnivory will increase or decrease when natural habitats experience fluctuations in available resources. The broader impacts of this research include the training of graduate and undergraduate students, the potential of the results to be incorporated in local educational programs, and the stimulation of interdisciplinary approaches in scientific studies.
