ИСТИНА

Arctic foxes are critically endangered in subarctic Fennoscandia, where a fading out of the characteristic lemming cycles and competition with abundant red foxes have been identified as main threats. We studied an arctic fox population at the Erkuta Tundra Monitoring site in low arctic Yamal (Russia) in order to determine which resources support breeding activity in this population. At Erkuta, lemmings have been rare during the last 15 years and red foxes are nearly absent, creating an interesting contrast to the situation in Fennoscandia. Arctic foxes were breeding in nine of the ten years of the study. The number of active dens was on average 2.6 (range: 0 -- 6) per 100 km2 and increased with small rodent abundance. It was also higher after winters with many reindeer carcasses, which occurred when mortality was unusually high due to icy pastures following rain-on-snow events. Average litter size was 5.2 (SD = 2.1). Scat dissection suggested that small rodents (mostly Microtus spp.) were the most important prey category. Prey remains at dens show that birds, notably waterfowl, were also an important resource in summer. The arctic fox in southern Yamal, which is part of a species-rich low arctic food web, seems at present able to cope with a state shift of the small rodent community from high amplitude cyclicity with lemming dominated peaks, to a vole community with low amplitude fluctuations. Only continued ecosystem-based monitoring will reveal their fate in a changing tundra ecosystem.