Voles competing with mice: differentiating exploitative, interference and apparent competition using patch use theory

We derived unique sets of predictions from patch use theory to differentiate apparent, exploitative and interference competition. Armed with these predictions, we used field enclosures to determine whether white-footed juice (Peromyscus leucopus) perceived meadow voles (Microtus pennsylvanicus) as apparent competitors. The enclosures were sited at forest-field ecotones. Within them, we manipulated vole density, food patch microhabitat (i.e. predation risk) and distance from the forest edge. We studied the effect of these variables on giving-up densities of white-footed mice. Giving-up densities increased in response to higher Vole activity. Under higher vole activity, mice increased foraging costs associated with risky. open microhabitats. These results were consistent only with apparent competition. Thus shared predators may be contributing to the pattern of habitat selection between mice and voles along forest-field ecotones.