STRUCTURE AND KINETICS OF RODENT POPULATIONS, IN A REGION UNDER AGRICULTURAL LAND ABANDONMENT

In the Jura mountains (France), the conversion of cultivated land into permanent grassland has led to an increase in the frequency of grassl and rodents (Common Vole, Microtus arvalis, and Ground Vole Arvicola t errestris) pullulations (1). Permanent grassland is now gained by coni ferous plantations, more rarely by natural colonization, as agricultur al land abandonment is continuing. The analysis of the consequences of this evolution of the landscape on the structure and kinetics of rode nt populations could enable us to prevent the risks of damage caused b y these different species. Therefore, information has been gathered on rodent communities in every habitat and on two levels of perception - that of the station (some thousand square metres) and that of the sit e (some 1400 hectares) - between 1982 and 1990. Processes which determ ine the way rodent populations are functioning depend on the variation s of the distribution and the density of the dominant species - the Co mmon Vole (M. arvalis) - and on the structure of the landscape. The fa ct that several species, which are living in very different habitats, have synchronous kinetics gives an indirect proof of the role of non-c limatic external factors (predation, parasitism, diseases), through th e structure of the landscape. Different perpectives for the control of rodent populations are given according to the evolution of agricultur al land abandonment.