Effects of stoat's presence and auditory cues indicating its presence on tree seedling predation by meadow voles

Predators may control the impact of herbivores on their plant resources by 1) decreasing herbivore numbers, 2) imposing predation risk affecting forag ing behavior. The goal of the present study was to examine the effects of a predator and auditory cues indicating its presence on the rare of tree see dling (Acer rubrum, Betula lenta) consumption bq meadow voles (Microtus pen nsylvanicus). The first of our experiments involved introduction of a stoat (Microtus pennsylvanicus) into an enclosed vole population and the second a playback of recordings of vole distress calls, movements of a stoat and i ts. vocalizations. In both experiments we manipulated vegetation cover and the availability of Food next to the experimental seedlings to assess the e ffects of microhabitat under the different risk situations. The results of the first unreplicated experiment suggested an increased rate of seedling p redation in the presence of the stoat. Consistent with these results, the p layback of predator sounds in the second replicated experiment caused an in creased rate of seedling predation compared to control plots with no record ings. A mon ed circle around a seedling station, representing increased ris k of predation on the voles. decreased seedling consumption. This effect wa s modest in the playback treatment. We suggest the results to be due to dis placement behavior by time voles exposed to prolonged risk and conflicting demands of foraging and avoiding predators. Alternatively. as suggested by the model of Lima and Bednekoff, prolonged risk of predation forced the vol es to decrease their levels of vigilance during low-risk playback breaks. T he modest inhibitory effect of cover removal on seedling predation in time playback treatment is consistent with this interpretation. The results conf irm recent evidence for trophic cascades mediated by behavioral interaction s between predator and prey. They are novel in suggesting that the presence of predation risk can increase the inhibitory effects of consumers on thei r resources.