Interspecific Interactions and Habitat Use by Prairie Voles (Microtus ochrogaster) and Meadow Voles (M. pennsylvanicus)

Interspecific competition can influence patterns of habitat use by small mammals. We examined the effects of interspecific interactions on habitat use by prairie voles (Microtus ochrogaster) and meadow voles (M. pennsylvanicus), two species that co- occur in grass habitats in east-central Illinois, but differ in their tolerance of sparse cover (prairie voles are more tolerant than meadow voles of sparse cover). We conducted a species-removal study in open populations, a species-addition study with enclosed populations, and dyadic encounters in the field, using mown and unmown grass areas, and in the laboratory. In the species-removal study, we found a positive response of prairie voles to removal of meadow voles from unmown grass habitat, and of meadow voles to removal of prairie voles from mown grass habitat. Additionally, when both species were present in control sites, prairie voles were most abundant in mown grass and meadow voles in unmown grass. In enclosures we confirmed greater tolerance of sparse cover by prairie voles (similar numbers of individuals in mown and unmown sites) than meadow voles (more individuals in unmown than mown sites), and these patterns were unaffected by addition of the other species. In dyadic encounters conducted in the field, male prairie voles were dominant over male and female meadow voles in mown grass habitat, whereas female meadow voles were dominant over male and female prairie voles in unmown grass habitat. These dominance relationships, which are consistent with the known social systems of the two species, were not observed when dyadic encounters were conducted in the laboratory in a neutral arena that lacked structural habitat cues. Taken together, our data confirm differences between prairie voles and meadow voles in tolerance for sparse cover and indicate a role, though limited, for interspecific competition in reinforcing patterns of habitat use by each species.