An understanding of spatial patterns of density requires information on factors that influence habitat selection. This project involves a large experiment designed to test several hypotheses regarding the effects of food availability, risk of predation, interspecific competition, and density on movement and performance of two species of voles in relation to habitat type. Clusters of large experimental pens will be established that differ in plant cover and food availability. Predators will be able to enter and leave the pens at will. Data collected will document movements between pens and the body growth, survival, and reproduction of voles that reside in each pen. Voles play an important role in grassland and tundra ecosystems. They provide a major food source for a wide variety of predatory mammals, birds, and snakes. At high densities voles can have a substantial impact on the structure and composition of vegetation. The results of this experiment will not only provide insight into the link between habitat selection and spatial patterns of density of animals in general, but also produce valuable information for application to issues of conservation and management of grassland ecosystems.
