“Living on the edge”: The role of field margins for common vole (Microtus arvalis) populations in recently colonised Mediterranean farmland

Ruth Rodríguez-Pastor,Juan José Luque-Larena,Xavier Lambin,François Mougeot

doi:10.1016/j.agee.2016.06.041

Abstract

Small rodents are common inhabitants of farmlands where they play key ecosystem roles but can also be major pests when overabundant, causing crop damages and significant economic losses. Agricultural landscapes are characterised by high fragmentation with remnant semi-natural habitats being typically restricted to narrow field margins. These linear habitats are key to maintaining local biodiversity, but can also harbour “irruptive pest” species, such as voles. The common vole Microtus arvalis, is a main vertebrate pest in continental European farmlands, and recently invaded the inland Mediterranean agricultural landscapes of NW Spain, where regular crop-damaging outbreaks now occur. Knowing how reliant common voles are on field margins in Mediterranean agricultural landscapes would be an important step forward for more targeted management. Here we report on common vole habitat use in Mediterranean European farmland and compare them with those found in northern latitudes, thus seeking for both general patterns as well as geographical differences. We conducted seasonal trappings over 6-years in the main habitats (cereal and alfalfa crops, fallows, and their margins). We show a strong edge effect, in the form of an exponential decay in vole abundance from the margin towards the inside of fields, and vole abundances 2.3 times higher in margins that inside fields. The magnitude of this edge effect varied depending on crop type, season and vole abundance (density-dependence). Cereal crops were characterised by a stronger edge effect than alfalfas or fallows (with abundance 8–10 times higher in margins than in fields during spring and autumn). Cereals appeared as the least optimal habitat for common voles, with important spill-over of voles inside the fields in summer when densities increased. Field margins, where vegetation characteristics hardly change seasonally, provide a limited (5% of the agricultural surface) but stable habitat and key refuge for common voles in Mediterranean farmlands. Our results suggest that targeting management actions in the field margins of cereal crops during spring and autumn and inside alfalfa fields during population increases should be considered in integrated control schemes of crop-damaging common vole outbreaks.

Highlights

Current agricultural landscapes result from the removal, fragmentation and reduction of original natural habitats, leading to heterogeneous mosaics made up of large expanses of monoculture with scattered uncultivated areas of varying sizes and shapes
Vole abundance was higher in field margins than in cereals in all seasons (45%, 23% and 46% higher in spring, summer and autumn, respectively)
The recent occurrence of common vole populations in Mediterranean agricultural landscapes of SW Europe, where severe water deficit periods could seasonally limit the species distribution comparing with northern European latitudes, implies understanding how the species is distributed and its population dynamics

Summary

Introduction

Current agricultural landscapes result from the removal, fragmentation and reduction of original natural habitats, leading to heterogeneous mosaics made up of large expanses of monoculture with scattered uncultivated areas of varying sizes and shapes (i.e., semi-natural habitats). These semi-natural habitats are often reduced to linear features, such as hedges, field margins or grassy strips along watercourses, woods or roads (Tattersall et al, 2002) and nonlinear habitats, such as set-asides, stubbles or fallows. Wild animals typically inhabit these uncultivated areas such that their conservation is crucial for maintaining habitat heterogeneity and biodiversity (Benton et al, 2003; Tscharntke et al, 2005).

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