Response of gray-tailed voles to odours of a mustelid predator: A field test

We conducted a field study to lest the hypothesis that gray-tailed voles Microtus canicaudus would move from preferred tall-grass habitat into open, short-grass habitat after exposure to the odours of a mustelid predator in their preferred tall-grass habitat. We also tested the hypothesis that if voles did not avoid the odours of a mustelid predator, they would exhibit suppressed reproduction, delayed sexual maturation, and decreased activity. The experiment was conducted from May to August 1996 in 0.2-ha enclosures in which one-half of each enclosure contained tall grass and in the other one-half the grass was mowed to a height of 5-20 cm. The proportion of voles living in the preferred tall-grass habitat averaged > 0.9 and did not differ significantly before, during, or after voles were exposed to faeces and urine of mink Mustela vison (a mustelid predator), or rabbit Oryctolagus cuniculus (a nonpredator, control). We observed no significant differences between treatments in reproductive rates, time to sexual maturation, juvenile recruitment, or activity. We conclude that in a field situation, gray-tailed voles do not exhibit a behavioural or demographic response to simulated predation risk by a mustelid predator (odours of faeces and urine). The disagreement between our results and those obtained from laboratory studies is discussed.