Ermine was once an important fur resource in Russia, too. Russian scientists concerned with managing the fur harvest invested years of work in the study of population variation in stoats and other mustelids (King 1975b, 1980d; Pod-dubnaya 1992; Polkanov 2000). They calculated the relationship between the number of ermine skins harvested each year and the fluctuations in the local populations of small rodents and water voles. The pattern was quite clear, even from the somewhat rough and ready density indices they used and the considerable number of complicating factors.

For example, over the whole Kamchatka region, the yield of stoat skins from 1937-1938 to 1963-1964 varied from 4,000 to 12,000 per year. The peak years came about every 3 to 4 years, usually lagging a little behind a peak in the numbers of small rodents. In some local districts within the region, the most productive years exceeded the worst by 15 times, even up to 50 times in others. The best years for stoats and sables (another important fur-bearing mustelid) usually coincided (Vershinin 1972).

On the wide flat floodplains of the Volga and Kama Rivers in central European Russia, the main prey for stoats are water voles, plus a variety of smaller rodents. In this region, the correlation between the numbers of water voles and stoats caught was so close that the yield of ermine pelts each winter could be forecast merely from the number of water voles collected in the previous June (Aspisov & Popov 1940). Only when a low population of water voles coincided with a peak in numbers of smaller rodents was the forecast wrong.

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