Differential behavioural and hormonal responses of voles and spiny mice toowl calls

Rodents usually respond to the presence of owls by reducing overall activit y, in particular foraging. In this study, a playback of recorded tawny owl, Strix aluco, calls was sufficient to induce a marked: effect in the social (Gunther's) vole, Microtus socialis. Some of the voles exposed to owl call s reduced their activity ('freeze' pattern) unlike control voles exposed to a human voice, Other voles, however, dashed around the cage ('flee' patter n). Owl calls also increase corticosterone levels in the voles, showing tha t the calls induced stress. We suggest that the behavioural dichotomy to fr eeze or flee in voles is a result of differences in individual normal behav iour and/or in stimulus interpretation In the common spiny mouse, Acomys ca hirinus, no behavioural changes were detected after exposure to owl calls, despite increased cortisol levels which are indicative of stress. Differenc es in the habitats of voles and spiny mice may explain the apparent lack of behavioural response in the latter. They are rock-dwelling rodents prefere ntially foraging between boulders and in rock crevices, where they are rela tively protected from aerial predation, whereas voles forage in relatively open spaces. (C) 1999 The Association for the Study of Animal Behaviour.