Effect of a predator's visit on the spatial distribution of bank voles: experiments with weasels

Abstract

A series of experiments in seminatural conditions with bank voles Clethrionomys glareolus (Schreber, 1780) and weasels Mustela nivalis Linnaeus, 1766 was designed to show if (i) a short visit by a weasel into an area, and (ii) its scent alone left there, would influence the use of space by bank voles, and whether the age, sex, and reproductive activity of bank voles would differentiate their responses to the risk of predation. Forty-five bank voles were released into an outdoor enclosure (150 m2) divided into three pens of equal size. The risk of predation was manipulated by introducing a weasel into either one or two pens for 24 or 2 h. Changes in the use of space by voles were determined by livetrapping in pens for 11 days after each manipulation. The pens that had been penetrated by weasels were avoided by voles for several days following each introduction of a weasel. The pens where prey had contacted a predator, or where only the odour of a weasel remained, were equally avoided by voles. Sex- and age-related differences in response to risk were noted in bank voles: subadults and nonreproductive adults of both sexes, and reproductively active adult males, shifted their positions significantly after a weasel had penetrated their home pen. Juveniles of both sexes and reproducing females did not abandon their ranges.