Vole fluctuations, red fox responses, predation on fawns, and roe deer dynamics in a temperate latitude

Abstract

The alternative prey hypothesis predicts that predators respond both functionally and numerically (with a time lag) to fluctuations in the main prey abundance, which affects the survival of alternative prey. This pattern was found in northern Europe in the community formed by voles (Microtidae), red foxes (Vulpes vulpes) and roe deer (Capreolus capreolus). We studied the same predator—prey community in a temperate latitude where, according to the predation hypothesis, only the functional response of predators to changes in main prey availability should occur. In the years 1997–2007, in western Poland, we estimated the index of common vole (Microtus arvalis) abundance (burrow counts), the density of foxes (spotlight counts), the young production in foxes (young/adult ratio), the index of fox predation on fawns (prey remains near dens) as well as the reproduction index (fawn/female ratio) and density of roe deer (total counts). The vole abundance fluctuated considerably, the young production in foxes did not correlate with the main prey availability, but the density of foxes showed direct numerical response. The index of fox predation on fawns decreased with the vole abundance and negatively affected the fawn/female ratio in roe deer. Thus, the relationships between voles and foxes were not fully consistent with the predation hypothesis. The direct numerical response of foxes should tend to stabilize this predator—prey community. It is suggested, however, that responses showed by vole-eating predators in temperate latitudes may sometimes affect their alternative prey, including animals with unfavourable conservation status.