The populations of field voles (Microtus arvalis) are greatly fluctuating. At the field scale, they vary a lot from one plot to another. We compared in this study various types of pastures : permanent pastures, grazed, mown and grazed, or only mown, and leys with legumes, mainly with lucerne (Medicago sativa). The meadows (i.e. the pastures, permanent or not, that are only mown) have the highest densities of voles, due to the nature of the sward (height and density, presence of legumes) and to the kind of management. The habitat is more favourable to the voles there : greater quietness and prolificity, better protection against the predators. To maintain the vole population densities at a level not harmful to the production of forage, some measures are described. They regard the management of the land (upkeep of the fields, duration of the rotations), land-use planning (form and distribution of the fields, creation of hedges, connection with wooded areas), and the protection of the predators.