RESPONSE OF GRAY-TAILED VOLES TO ODORS OF A MUSTELID PREDATOR - A FIELD-TEST

We conducted a field study to lest the hypothesis that gray-tailed vol es Microtus canicaudus would move from preferred tall-grass habitat in to open, short-grass habitat after exposure to the odours of a musteli d predator in their preferred tall-grass habitat. We also tested the h ypothesis that if voles did not avoid the odours of a mustelid predato r, they would exhibit suppressed reproduction, delayed sexual maturati on, and decreased activity. The experiment was conducted from May to A ugust 1996 in 0.2-ha enclosures in which one-half of each enclosure co ntained 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 tal l-grass habitat averaged > 0.9 and did not differ significantly before , during, or after voles were exposed to faeces and urine of mink Must ela vison (a mustelid predator), or rabbit Oryctolagus cuniculus (a no npredator, control). We observed no significant differences between tr eatments in reproductive rates, time to sexual maturation, juvenile re cruitment, or activity. We conclude that in a field situation, gray-ta iled voles do not exhibit a behavioural or demographic response to sim ulated predation risk by a mustelid predator (odours of faeces and uri ne). The disagreement between our results and those obtained from labo ratory studies is discussed.