On the study of the equal-toothed shrew (Sorex isodon Turov) in the north-western periphery of its range

The article is based on long-term (1958–2017) expedition and stationary research in the Kivach, Kostomuksha and Lapland nature reserves and Karelian field stations – Priladozhsky, Kaskesnavoloksky and Gomselsky covering a vast part of taiga of the North-West of Russia. The article analyzes the population and ecological features of the equal -toothed shrew (Sorex isodon Turov) associated with its habitat near the North- Western borders of its range. It was found that in these conditions, the species was characterized by a generally low level of abundance compared to the optimal for the range (an average, 0.02 per 100 trap days and 0.1 per 10 trench days), distinct transition to stenotopy and obvious fixation on elements of the anthropogenic landscape. It is also characterized by the peculiarity of the territorial structure, the shift of reproduction to a later date and its general extension until mid –September. During the reproduction season, wintering adult females bring two litters: the first – in late May-early June, the second – in July. The litter size ranges from 2 to 11 per adult female (an average, 7.7 + 0.3). The share of mature and offspring-bearing profitable animals in general is small (up to 5-8 %) and varies by year depending on the state of the population and weather conditions.