Voles in Space: Effects of Predator Odour on Microtus arvalis Breeding Females

Abstract

Voles show an array of adaptations to predation risk. The chance of encountering a specialist, mustelid predator is best minimised by reduced mobility and limited use of space; voles may also shift their activity in time. We inquired whether reproductively active female common voles (Microtus arvalis) employ these adaptations in response to olfactory cues of a ferret. We used capture locations and radio-tracking fixes to examine long-term (home range) and short-term (activity range) space use under odour-simulated mustelid predation risk. Range areas were computed with two methods: minimum convex polygon and local convex hull. Using radio-tracking data, we also measured movement distances and distances to the sources of predator odour. The common vole is predominantly diurnal, with activity peaks at dusk and dawn. Using two indexes of circadian activity, we investigated whether females change their temporal behaviour in response to mustelid odours. Non-predator odours served as controls. We found no effect of mustelid odour on home range or activity range size. Additionally, predator odours did not affect movement distances and temporal behaviour. However, females did avoid areas with mustelid odour. We argue that reproductively active females cannot afford spatial and temporal adaptations, as these limit foraging opportunities, and ultimately, female fecundity. Yet, avoidance of ferret odour confirms its significance for breeding female voles.