Synthetic mustelid semiochemicals depress survival of long-tailed vole (Microtus longicaudus) populations and feeding damage

Abstract

Microtus and Myodes continue to be major pests in agricultural and forest production in many temperate and boreal ecosystems of North America and Eurasia. However, voles may also be keystone species because of their predator-prey dynamics and feeding linkages in many networks. As an alternative to rodenticides, exploration continues for a suitable fear-based method to reduce vole damage to crops. This study tested the hypotheses (H) that a “neat” formulation of synthetic anal-gland compounds of the short-tailed weasel (Mustela erminea L.) would reduce (H1) abundance, reproduction, survival, body mass, and movement of long-tailed vole (Microtus longicaudus Merriam) populations; and (H2) feeding damage to coniferous seedlings by voles in forest plantations. Vole populations were live-trapped on replicate sites from May 2005 to June 2006 during a peak year in abundance near Golden, British Columbia, Canada. Synthetic weasel odour was continually present on treatment sites from June 2005 to June 2006. Overwinter mortality to planted coniferous seedlings from vole feeding was measured on all sites in May–June 2006.Synthetic weasel odour compounds did not reduce mean abundance of M. longicaudus but, in fact, resulted in significantly higher numbers of voles in the treatment sites owing to a major pulse of transient (single capture) animals. Mean number of successful pregnancies and total recruits were also higher in treatment than control sites, but early juvenile survival, movements, and body mass were all similar between control and weasel-odour sites. However, mean Jolly-Seber 28-day total survival rates were higher (2.9–3.9 times) on control than treatment sites for both male and female voles during the overwinter-spring 2005–06 period. Much of the reduced survival was due to transient animals which tended to have a higher proportion of adults to juveniles in treatment than control sites. Some degree of disruption presumably occurred on the treatment sites perhaps owing to increased breeding intensity by females in the face of perceived predation or the presence of various mammalian predators attracted to the weasel odour and preying upon voles. This disruption may be linked to the use of synthetic weasel odour in suitable release devices that maintain the odour even in high quality habitats for voles. Despite the difference in abundance, voles seemed to feed less on plantation trees in the treatment than control sites. If this population disruption is real, we suggest that large-scale (e.g., 10+ ha) application of synthetic weasel odour in areas requiring crop protection from voles would be a worthwhile endeavour. This prediction is particularly germane for M. longicaudus where weasel odour treatment might be able to disrupt substantially their one population fluctuation on newly clearcut sites.