Can we relate common vole abundance variations to crop damage?

Abstract

Ever since the common vole (Microtus arvalis Pallas) started to colonize the lowland farmland areas of Castilla y León (NW Spain) in the 70´s, recurrent population outbreaks have occurred leading at times to important crop damage. For ecologically based management to be effective, it is necessary to act preventively and design strategies adapted to different contexts. With this aim, the Regional Government in Castilla y León started in 2007 a protocol of continuous monitoring of the vole populations throughout the region. Nevertheless, not enough information currently exists to relate vole abundance changes to the damages that finally occur. Determining the relationship between vole abundance and crop damage would help predicting damage from population changes, and hence defining threshold levels upon where to act to reduce economic impacts, optimizing management processes. We analyse the geographical distribution of damage caused by common voles in the agricultural campaign 2013/2014 (during which a vole population outbreak occurred in different areas of the Region), and relate it to vole abundance estimates based on activity signs. Vole abundance estimates were gathered regularly throughout the region from November 2013 (winter crop seeding) until August 2014 (harvest of those crops), both within crop fields, in reservoir areas (alfalfas and meadows), and in dispersion lines (tracks and grassy field edges). Crop damage was assessed in 2895 fields throughout Castilla y León, of 19 different crop types. With this approach, we aim to identify factors predicting damage in different crop types, and vole abundance threshold levels for early management action.