MICROHABITAT USE AND BEHAVIOR OF VOLES UNDER WEASEL AND RAPTOR PREDATION RISK - PREDATOR FACILITATION

An example of predator facilitation is that a microhabitat shift in a prey species induced by one predator increases the probability of the prey falling victim to other predators. Least weasels (Mustela nivalis ) hunt in dense plant cover, whereas kestrels (Falco tinnunculus) hunt in habitats with sparse plant cover. Field voles (Microtus agrestis), the main food of weasels and kestrels, prefer open country with a hig h grass layer. We simulated a multipredator environment in an aviary ( 3.0 x 4.8 x 2.2 m) to find out whether predator facilitation plays a r ole in the interactions between voles, small mustelids, and raptors. I n each replicate, we placed a field vole in a pen including sides of h igh and low grass layers (cover and open). In a predator-free situatio n, voles preferred cover but shifted to open when a weasel was introdu ced to cover. In the presence of a kestrel, voles occupied cover and d ecreased their mobility In the presence of a kestrel plus a kestrel, v oles behaved as under the kestrel risk alone. Therefore, in these avia ry circumstances, voles perceived the kestrel risk as greater than the weasel risk. Predator facilitation in the assemblage of predators sub sisting on rodent prey may contribute to the crash of the four-year vo le cycle: microhabitat shift due to an avoidance of weasel jaws may dr ive voles to raptor talons.