Do prey densities determine preferences of mammalian predators for habitat edges in an agricultural landscape?

Increased predation pressure along habitat edges is often associated with increased predator activity. However, factors affecting predator affinity for habitat edges remain largely untested. Here, we tested the hypothesis that the high prevalence of mammalian predators along habitat edges arises due to increased abundance of their principal prey – small mammals. Gradients in the abundance of carnivores and small mammals across a habitat edge gradient (secondary mixed forest interior vs. secondary mixed forest interior/grassland edge vs. grassland interior) were monitored during a 2-year survey performed in a fragmented central European landscape. Our data provide support for the hypothesis that a high abundance of carnivores in habitat edges was associated with increased numbers of small mammals. The abundance of mammalian predators and small mammals consistently increased in habitat edges. Moreover, prey densities tended to explain carnivore patch preferences even when statistically controlling for the effect of habitat type (edge vs. interior habitats), suggesting a direct causality between carnivore habitat preferences and actual prey density. Interestingly the small mustelids (least weasel, Mustela nivalis, and ermine stoat, Mustela erminea) exhibited lower flexibility in adjustment of their spatial activity according to prey densities, in contrast to remaining carnivores. We suppose that this pattern may be caused by differences in agility/home-range size or performance intraguild competition between small mustelids and remaining carnivore species.