Can water voles be controlled with vole fences?

Fossorial water voles are the major grassland pest north of the Alps. Highly prolific, they are able to spread rapidly across the countryside. Although migration barriers or so-called ’water-vole fences’ can be built to prevent their expansion, the farm area under grassland is usually far too large to be fully fenced with such barriers. Between 2009 and 2014, we monitored water-vole population trends on two grassland- dominated sites in the Lucerne Midlands in the vicinity of linear water-vole fence systems that did not fully fence the target area (open systems). One of these open-fence systems was combined with natural migration obstacles ( forest and lakeshore), while the other was not. It was found that an open-fence system located between natural migration obstacles and combined with direct control measures kept the water-vole population low in the target area, even in times of severe watervole infestation in the surroundings. Nevertheless, the open-fence system proved ineffective when not used in conjunction with direct vole-control measures and natural migration obstacles.