Refuge sites of voles under owl predation risk: priority of dominant individuals?

Abstract

In an aviary experiment, we studied whether body size or habitat familiarity of field voles (Microtus agrestis) affected predation risk by Tengmalm's owls (Aegolius funnrus). In the field, we compared die body size of field voles snap-trapped in good (covered) and poor (open) habitats in 1992 and 1994 to determine whether there were habitat-related differences in the body size of voles. In the aviary, large individuals occupied the good habitat significantly more than small individuals both in the control (owl not present) and experimental treatments (owl present). Furthermore, habitat-familiar voles inhabited die good habitat more than habitat-unfamiliar voles did when an owl was present. Our field data were consistent with our aviary data: larger field voles were more frequently found in good habitats than in poor habitats. In the aviary, Tengmalm's owl predation risk was higher for small and habitat-unfamiliar voles. This suggests that large field voles may have priority to sheltered habitats. Furthermore, habitat familiarity may play a central role in avoiding risky habitats.