Individual and seasonal differences in antipredatory behaviour of root voles - a field experiment

The response of root vole (Microtus oeconomus) to least weasel (Mustela nivalis) odours during breeding (August) and nonbreeding seasons (November) was studied in the root voles' natural habitat. The aim of this study was to determine if antipredator behaviour of the root vole changed between breeding and nonbreeding seasons and if this change was closely related to individual environmental cues, e.g., weasel odours. It was found that when bait and weasel odour was used, trappability was greater in breeding season than in nonbreeding season. Moreover, in the breeding season, heavier (i.e., older) voles were more frequently captured than lighter (i.e., younger) ones. Results show that voles' antipredator behaviour of weasel avoidance changes seasonally and that during the breeding season voles display a trade-off conflict between predator risk and foraging, if predator risk is high. It is possible that older voles are driven to reproduce in the current breeding season and thus display less weasel avoidance than do younger voles, which have higher probability of surviving to the next breeding season. Results indicate that indirect (nonlethal) effects of mammalian predators on voles' behaviour strongly depend on age, sexual activity, and season.