| Summary: | International audience For nearly a hundred years, a mass of attempts has been made to understand the causes of multi-annual fluctuations of rodents. Approaches that seek to isolate one factor among possibly dozens have all led to a long list of conclusions, all correct, about "what does not explain…". Approaches assuming multifactor explanations face the major difficulty of considering the complexity of systems where the importance of each of the multiple factors can vary in space and time. They need to be evaluated by long-term and large-scale observations and experimental manipulations, options that hardly get long-term human involvement and financial support. Meanwhile, some rodent populations can still have a devastating impact on agriculture, food, health and other species and little has been provided from ecological sciences to improve control operations. This leaves the field open to intensive usage of rodenticides, often too late or for too long and with adverse effects, and farmers poorly armed to protect their crop.The montane water vole, Arvicola amphibius and the common vole, Microtus arvalis, can reach densities of several thousand per hectare, in the grasslands of mid-altitude mountains of Europe. The multiannual fluctuations of those species, studied since the late 1970s in the Jura massif, are the results of a shift in farming practices in the 1960s, themselves determined by socio-economic constraints. The importance of specific drivers on each scale (from local to regional) has been evidenced by multidisciplinary and multisectoral partnerships. Regional partnerships with agricultural organizations in particular have made it possible to set up long-term monitoring operations (voles, predators, pathogens, etc.) and quasi-experiments to measure the effects of habitat modifications and interventions at low population density in parallel with more basic works carried out by researchers. This led to design a toolbox making farmers able to control small mammal populations at a lesser environmental ...
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