Facilitative interactions between the Eurasian badger (Meles meles), the red fox (Vulpes vulpes), and the invasive raccoon dog (Nyctereutes procyonoides) in Bialowieza Primeval Forest, Poland

Based on radio-tracking of Eurasian badgers (Meles meles (L., 1758)), red foxes (Vulpes vulpes (L., 1758)), and raccoon dogs (Nyctereutes procyonoides (Gray, 1834)) and observations at burrows conducted in Bialowieza Primeval Forest (eastern Poland) in 1996-2002, we addressed the hypothesis that facilitative interactions between a native (badger) and an alien (raccoon dog) species contributed to the invasion success of the latter. In winter, 88% of badger setts were occupied by both badgers and raccoon dogs, 4% by badgers and red foxes, and 4% by all three species. In summer, only 20% of badger setts were cohabited by other carnivore species (10% by raccoon dogs and 10% by foxes). Duration of occupation of badger setts by raccoon dogs averaged 117 days (SE = 21 days). Seasonal variation in raccoon dog use of badger setts was explained by changes in ambient temperature: the lower was the temperature, the higher was the rate of sett occupation by raccoon dogs. When wintering in the same sett, badgers and raccoon dogs used different parts of the sett. We conclude that facilitation by badgers (through habitat amelioration and refuge from cold and predation) makes the realized niche of raccoon dogs larger than predicted from their fundamental niche. The facilitating role of badger is stronger in winter, which is a critical period for raccoon dog survival in the temperate and boreal zone.