Do captive male meadow voles experience acute stress in response to weasel odour?

The hormonal stress response is adapted to deal with acute (short-term) stressors; however, chronic (long-term) stressors have negative effects on survival and fitness. Field and laboratory evidence suggests that voles respond behaviourally to predator odours. However, it is unknown whether voles mount an acute hormonal stress response to predator odour. We determined if reproductively active, captive male meadow voles (Microtus pennsylvanicus Ord, 1815) mounted a more pronounced hormonal stress response to weasel odour (ermine; Mustela erminea L., 1758), one of their principal mammalian predators, relative to their response to nonpredator and control odours. We compared the corticosterone response of captive voles to weasel, jumping mouse (Zapus hudsonius Zimmermann, 1780), and control odours following acute (20 min) exposure. The hormonal stress response to the treatment odours did not differ indicating that captive male voles in the reproductive season do not mount an acute stress response to predator odour. We hypothesize that voles do not respond to weasel odour because, independent of other stimuli, olfactory signals are not reliable enough to outweigh the costs, such as suppression of reproduction and of reproductive behaviour, associated with a response