Both meadow voles (Microtus pennsylvanicus) and prairie voles (Microtus ochrogaster) prefer habitats with high vegetative cover, but in east-central Illinois, meadow voles tend to be associated with higher cover and prairie voles with lower cover. The competition hypothesis proposes that this pattern of habitat segregation reflects the effects of interspecific competition on habitat selection. To test this hypothesis we conducted field experiments that allowed the two species to select from among several habitats when alone and when together. We expected to find a lower proportion of each species in the habitat most associated with the other species, and a negative correlation between the demography and density of each species and the density of the competing species, but this was not the case. Inter specific competition did affect movement patterns of prairie voles. In the presence of meadow voles, net movement (immigration minus emigration) of prairie voles in high-cover habitats decreased and net dispersal of individuals from high- to low-cover habitats increased. Thus, our results indicated only a weak effect of competition on habitat selection. We suggest that other mechanisms, such as differences in habitat preference (or tolerance), differences in dispersal ability, and the advantage of first residency, need to be considered in conjunction with interspecific competition to explain the habitat segregation observed in these species.
Effects of Vegetative Cover on the Population Dynamics of Meadow Voles