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

Abstract

Predators may control the impact of herbivores on their plant resources by 1) decreasing herbivore numbers, 2) imposing predation risk affecting foraging behavior. The goal of the present study was to examine the effects of a predator and auditory cues indicating its presence on the rate of tree seedling (Acer rubrum, Betula lenta) consumption by meadow voles (Microtus pennsylvanicus). The first of our experiments involved introduction of a stoat (Mustela erminea) into an enclosed vole population and the second a playback of recordings of vole distress calls, movements of a stoat and its vocalizations. In both experiments we manipulated vegetation cover and the availability of food next to the experimental seedlings to assess the effects of microhabitat under the different risk situations. The results of the first unreplicated experiment suggested an increased rate of seedling predation in the presence of the stoat. Consistent with these results, the playback of predator sounds in the second replicated experiment caused an increased rate of seedling predation compared to control plots with no recordings. A mowed circle around a seedling station, representing increased risk of predation on the voles, decreased seedling consumption. This effect was modest in the playback treatment. We suggest the results to be due to displacement behavior by the 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 voles to decrease their levels of vigilance during low‐risk playback breaks. The modest inhibitory effect of cover removal on seedling predation in the playback treatment is consistent with this interpretation. The results confirm recent evidence for trophic cascades mediated by behavioral interactions between predator and prey. They are novel in suggesting that the presence of predation risk can increase the inhibitory effects of consumers on their resources.