ИСТИНА

The arctic fox on Bering Island is one of two ancient subspecies endemic to Commander Islands. This population has been isolated for almost 60 thousand years without natural enemies and mainly depends on marine sources. Despite the fact that there were no reports of population crashes, such as for the neighboring Medny Island, there are similar risks in both populations, and monitoring of the Bering population is necessary. Currently, such monitoring is carried out in two ways: counting individuals in the spring and counting litters in the summer. Spring counting has been carried out more or less regularly since 1995, but the most complete data was collected in 2013–2016, 2018–2019 and 2021. The litters were partially counted in 2009, 2012–2014, 2016, 2018–2019 and 2021. The Island–wide survey was conducted in 2014 with monitoring of reproductive efforts. In the past few years, there was not any trend towards a decline or growth in the population and the total number is estimated at 300–600 adults, with small annual fluctuations. The total number of litters was estimated at 90–100 in 2014, about the same number in other years, also with minor annual fluctuations. Density of dens and frequency of den occupation by foxes depended mainly on local food sources distribution. This is a typical coastal arctic fox population without drastic fluctuations due to abundant and stable food sources. On the other hand, some facts speak in favor of a population decline that could have taken place over the last 25 years. For instance, density of active dens in 1991–1992 was estimated to be twice higher compared to our data. In addition, the number of foxes harvested at the end of the 20th century is comparable to the entire modern population. Therefore, it is necessary to continue annual ecosystem–based monitoring on Bering Island.