Barriers, Traps and Predators – An Integrated Approach to Avoid Vole Damage

Voles (Microtus spp. and Arvicola spp.) are the most abundant rodent species in open European landscapes. Due to their preference for agricultural habitats and their enormous reproductive potential, they are often regarded as pests. Several attempts have been made to reduce vole densities using rodenticide baits, gasses, or traps. No matter what method is used, they all bear the problem of voles reinvading from adjacent habitats. We tested a combination of fence and a new kind of trap that enabled terrestrial vole predators to take the captured prey. The combination of fence and traps was tested in a field trial and compared with mesh wire fences and an obstacle-free control line. This three-line setup was installed at each of three locations in Switzerland. Movement patterns of terrestrial predators were recorded by video observation during a 2-year period. Within this period, we made 1,224 observations of mammals; about ¾ of them, 951, were terrestrial predators and 157 were others like hares or hedgehogs. Due to their smaller size, only 116 voles were observed during the same time. Fences with traps were clearly preferred by predators, and their activity was significantly higher along fences with traps, as compared to the two other types. Predators seemed to check traps actively as they moved significantly more often close and parallel to fences with traps. Voles were not only removed from the traps but also caught while moving in the vicinity of the fences. The observed vole movements were ended by a predator in 11% of all instances. We found that barriers with additional trapping devices attracted predators, which started to patrol these fences regularly. Such a physical barrier in combination with its natural guard is a suitable device to protect high-value crops like orchards. As an integrated tool, it will reduce efforts, costs, and environmental impacts of vole control measures. Subsequent to this study, a new Hshaped double wall fence was constructed. This new type gives additional benefits, as it is easier to maintain and allows both terrestrial and avian predators to take captured voles