MIGRATIONS AND SEASONAL PATTERNS OF HABITAT USE IN THE ADDER (VIPERA BERUS): IMPLICATIONS FOR THE CONSERVATION AND MANAGEMENT OF LOCAL POPULATIONS

Adders ( Vrpera berus), ), like many other temperate zone snakes, undertake seasonal migrations between wintering areas and feeding grounds. During a mark-recapture study in a large population in northern Belgium, we obtained detailed information on both habitat types and the migrations between them. Wintering areas were located in heathlands on infertile, sandy soils, which offer suitable locations for hibernation and optimal thermal conditions during specific periods in the active season. Foraging grounds were located outside of heathland areas and encompassed a wide variety of habitats that sustained higher prey densities. Adult males remained in the wintering areas in early spring and then in May migrated toward the foraging grounds, where they resided until the end of September. The breeding females resided in the wintering habitats from May through August, and they were observed in the feeding areas only during the short pre- and post-pregnancy periods. Immature Adders spent a large portion of their time in the feeding grounds. During their seasonal migrations, Adders moved 100-500 m. Adders tended to show fidelity to both hibernation sites and feeding areas. Current efforts to safeguard Adder populations focus almost exclusively on wintering areas. The information we present here highlights the importance of feeding areas as a vital component of Adder habitat. We argue that conservation and management actions will benefit from studying and considering the status of both wintering and feeding grounds and the migration routes between them.