Common vole (Microtus arvalis) fluctuations in agricultural landscapes of southern Europe: population patterns and enemy dynamics

Abstract

Common voles (Microtus arvalis) can be abundant in agricultural landscapes of Europe and their numbers can strongly fluctuate through time, which confers them a key ecological role for the structure and dynamics of local communities. Also, they are often declared and controlled as agricultural pests as can cause significant socio-economical and health impacts during outbreaks. Contrary to expectations from climate warming, the species has colonized the large semi-arid agricultural plains of NW Spain largely facilitated by a synchronous and rapid increase of farming surfaces with hitherto uncommon favourable habitats (alfalfa crops) and production regimes (irrigation). Ecological knowledge of the populations recently established in farmland is scarce, so quantifying the demographic impact of specific factors (environmental and intrinsic) in the temporal and spatial variation of vole abundance is paramount in order to progress with: (1) a general understanding of the causation of rodent fluctuations and (2) the practical knowledge that can be used in the management of their impacts. Here we present novel data from seasonally monitored populations regarding vole dynamics and that of their natural enemies, including aerial (raptors) and terrestrial (weasels) predators, as well as parasites (fleas). We describe how extrinsic factors involved in trophic interactions with voles (predation and parasitism) show different (direct or delay) patterns of density-dependence during the course of population fluctuations, and tentatively discuss their impact on local vole population growth.