Exposure to Chemical Cues from Predator-Exposed Conspecifics Increases Reproduction in a Wild Rodent

Predation involves more than just predators consuming prey. Indirect efects, such as fear responses caused by predator presence, can have consequences for prey life history. Laboratory experiments have shown that some rodents can recognize fear in conspecifcs via alarm pheromones. Individuals exposed to alarm pheromones can exhibit behavioural alterations that are similar to those displayed by predator-exposed individuals. Yet the ecological and evolutionary signifcance of alarm pheromones in wild mammals remains unclear. We investigated how alarm pheromones afect the behaviour and ftness of wild bank voles (Myodes glareolus) in outdoor enclosures. Specifcally, we compared the efects of exposure of voles living in a natural environment to a second-hand fear cue, bedding material used by predator-exposed voles. Control animals were exposed to bedding used by voles with no predator experience. We found a ca. 50% increase in litter size in the group exposed to the predator cue. Furthermore, female voles were attracted to and males were repelled by trap-associated bedding that had been used by predator-exposed voles. Movement and foraging were not signifcantly afected by the treatment. Our results suggest that predation risk can exert population-level efects through alarm pheromones on prey individuals that did not encounter a direct predator cue.