FORAGING AND DIET OF THE RED FOX VULPES-VULPES IN RELATION TO VARIABLE FOOD RESOURCES IN BIALOWIEZA-NATIONAL-PARK, POLAND

Feeding ecology of red fox Vulpes vulpes was studied by scat analysis and snow-tracking in primeval temperate forest and adjacent meadows during four years (1985/86-1988/89). Winters varied from mild to unusually severe. Main food resources for foxes were: rodents of open meadows and river valleys (root vole Microtus oeconomus), forest rodents (bank vole Clethrionomys glareolus and yellow-necked mouse Apodemus flavicollis), hare Lepus europaeus and carcasses of wild boar Sus scrofa and red deer Cervus elaphus either killed by wolves and lynx or that had died from inanition. Composition of fox diet in four cold seasons (autumn-winter) was compared to the abundance of main food resources. Prolonged, sharp decline of Microtus was followed by only a twofold decrease of its share in fox diet. Foxes continued to prey on declining Microtus. The changes in the proportions of forest rodents and hare in fox diet clearly followed the fluctuations in numbers of these two prey. Carcasses were alternative, buffer food to foxes and were taken considerably when Microtus and other prey were in low numbers or poorly accessible. The depth of snow was the most important factor restricting foxes' access to rodents. Snow-tracking revealed that foxes dwelling in the forest widely used adjacent open areas. In open meadows foxes mainly hunted for rodents, while in the forest the most significant foraging activity was scavenging. Seasonal analysis of fox diet revealed that consumption of Microtus by foxes was stable throughout the year (37-47% of biomass consumed). Bank vole significantly contributed to fox diet in autumn, and hare in summer only. Scavenging was most pronounced in winter and spring when carcasses made up 30% of biomass taken.