The Effects of Winter Climate and Intrinsic Factors on Survival of Cyclic Vole Populations in Southeastern Norway

Abstract

Changes in winter climate is a possible explanation for dampened population cycles in voles. For voles living in the subnivean space for several months of the year, we may expect that winter conditions affect survival. We examined the effect of different winter climate descriptors (snow depth, subnivean temperature, snow crust) and different intrinsic factors (sex, age, physiology, behaviour estimated as the longest distance travelled between traps) on winter survival of bank voles Myodes glareolus in southeastern Norway by live-trapping voles monthly along elevation gradients. We tested whether winter conditions alone (winter hypothesis), intrinsic factors alone (intrinsic hypothesis), or winter conditions in combination with age and sex were more important for winter survival of voles (multiple factor hypothesis). Our results do not support the winter hypothesis as there were no relations between winter survival and snow depth, snow crust and subnivean temperature. We found strongest support for the intrinsic hypothesis, where the distance travelled was positively correlated with survival. We hypothesize that this behavioural descriptor is related to food resources and their importance during winter, where an increased activity range (distance travelled between traps) increase the access to food resources.