Habitat destruction and fragmentation present serious problems for many animal species. This report deals with habitat fragmentation, and puts forward proposals for solutions. First, the spatial requirements and migration distances of various animal species are described. Then, the systems of biotope networks, and the most important problems are described, using real examples, for the regions of the Jura, the Central Plateau, the Pre-Alps, and the Alps. The central part of the report is the map of the large-scale network and the wildlife corridors (map 2). Each interregional wildlife corridor is briefly described in Annex 3, together with its general conditions, and possibilities for its improvement. Finally, chapter 8 describes how the report can be implemented.