WARNING AGAINST AN UNSEEN PREDATOR - A FUNCTIONAL ASPECT OF SYNCHRONOUS FEEDING IN THE COMMON VOLE, MICROTUS-ARVALIS

Escape responses of common voles exposed either to a kestrel, Falco tinnunculus, model 'flown' overhead or to neighbouring voles from the same family responding to such a model were investigated. The majority of voles (81%) either froze or ran for cover when exposed to the sight of the kestrel model. Neighbouring conspecifics, who could not see the kestrel model, also responded provided they could see model-exposed voles. A smaller fraction of the neighbouring voles also responded when they could only hear the escape responses of other voles. The fraction of voles responding decreased with increasing distance between the two groups. At short distances visual contact played a major role, and running voles affected neighbours more than freezing animals. At larger distances acoustic contact may prevail. Freezing was as effective a signal as running. It is argued that individual voles may benefit from social synchrony of ultradian feeding rhythms by exchanging warning signals when a predator appears, as well as from possible energy savings and the 'safety in numbers' effect. © 1990 The Association for the Study of Animal Behaviour.