Arctic fox (Alopex lagopus) from the Commander Islands

The Alopex lagopus population was investigated from February 1991 to March 1993 on Bering Island and from July 21 to August 12, 1993 on Mednyi Island. In summer periods, the number of A. lagopus on Bering Island was estimated at 981 +/- 260 in 1991 and 1503 +/- 325 in 1992. The average female fertility determined according to the number of afterbirth spots in uterus was 8.83 +/- 0.39 in 1991 and 8.38 +/- 0.56 in 1992. The average number of the litter was 3.45 +/- 0.67 in 1991 and 5.0 +/- 0.34 in 1992. The difference in the number of the Bering population in different years resulted from the higher survival of cubs during the den period of 1992. The summer distribution of the Bering population over the island was uneven; the zones of the highest concentration were the same in the summer periods of 1991 and 1992. The tagging of cubs and the tags obtained during hunting periods showed that the autumn dispersion of juveniles over Bering Island were determined by the summer density gradient and abundance of food in different sites in winter. On Mednyi Island, 24-26 family territories and 7 litters were registered. In early August, the A. lagopus population included 48-52 adults and 14-33 cubs. Since the catastrophic decrease of the population in the 1970s an exceptionally high level of mortality in juveniles remained in late summer preventing an increase in the numbers of the population.