Sustainable control of grassland small mammals

International audienceSmall mammals such as the European rabbits, the plateau pikas, the prairie dogs have been traditionally perceived as pests and targeted for control on a large scale despite their importance as key-stone species in their native ecosystem. This is also the case for the fossorial form of the water vole (Arvicola terrestris). This species can reach large population densities and causes heavy damage to grassland with subsequent economic losses for farmers (9,000 to 25,000 € for a 70 ha farm during an outbreak year in Franche-Comté, France). However, higher population densities of A. terrestris and also of Microtus arvalis, help maintaining a large and rich community of vole predators. Such non-target species (red kite, common buzzard, wild boar, red fox, etc.) are impacted, some of them heavily, by the unconditional use of rodenticides (e.g. bromadiolone). In order to minimize the use of rodenticides in controlling A. terrestris populations, a long term research program has been undertaken since the late 80s, aiming at identifying the key-parameters of such regional systems. Based on a systems approach, this collaborative research network involves academic researchers, farmer, game, conservationist organizations and governmental and local administrations together. On a regional scale (area of about 2500 km2), Delattre et al. (1992), Giraudoux et al. (1997), Fichet et al. (2000) provided evidence that M. arvalis and A. terrestris population dynamic patterns correlate with land composition. On a sectorial scale (area of about 25 km2), Delattre et al. (1996), Delattre et al. (1999) showed for M. arvalis that landscape heterogeneity dampen population fluctuations and may modulate prey/predator relationships; Duhamel et al. (2000) that A. terrestris outbreak epicentres occur in homogeneous grassland and Foltete et al. (2008) that hedgerow networks slow down the propagation of travelling waves. On a local scale (area of about 0.01 km2), Delattre et al. (2006), Morilhat et al. (2007, 2008) showed that A. terrestris population growth was enhanced by larger gallery networks of Talpa europea, was slowed down by ploughing and cattle tramping and was modified by neighbouring landscape (10 - 100 ha). This led to a number of recommendations, now implemented for a more sustainable control of A. terrestris (Delattre and Giraudoux 2009) with substantial decrease in rodenticide utilization and lesser impact on non-target species. Poster downloadable at: http://pagesperso-orange.fr/giraudoux/PosterSETAC_120416_1200.pd