Modified live traps increase capture success of semifossorial voles in Alpine meadows

Live-trapping of rodents is facilitated by their thigmotaxis (i.e. the tendency to walk along linear structures of the habitat). However, in open habitats, such as meadows and prairies, where linear structures (e.g. rocks and fallen branches) are generally absent and where densities are likely to be low, capturing rodents is often very demanding or ineffective. This applies especially to semifossorial small mammals. Therefore, we developed a technique to increase the capture success of these rodents in Alpine meadows. We applied a box in Tetrapak (R) with the perforated floor at the opening of Sherman traps. Semifossorial voles (Microtus spp.), leaving their burrows, would remain in a confined status, in the dark within the Tetrapak (R), being forced to enter the trap or to go back in the tunnel. Sherman traps modified with Tetrapak (R) were positioned immediately upon active burrows, alternating with the same number of unmodified traps. Then, we compared the number of captures with and without this modification. Two trapping sessions were carried out, for 3 days/site each, in eight sites (totally 2784 trap-days). Overall, 55 semifossorial voles were trapped; 41 (74.6%) were caught in modified traps, showing that they increase the capture success of semifossorial voles in Alpine meadows.