Regulrities and factors of the numbers dynamics of the bank vole (Myodes glareolus Schr.) in the protected territories of Eastern Fennoscandia

Based on the materials obtained in the protected areas of Eastern Fennoscandia, we analyzed the course and factors of the long-term population dynamics (1958-2018) of the bank vole (Myodes glareolus Schr.) in the conditions of the northern border region of its distribution. It was established that the studied species is characterized here by a low number compared to the optimum of the area: 1.9 specimens for 100 traps per day, 1.7 - for 10 grooves per day. However, it continues to maintain a leading position in the total population of small mammals, accounting for 50.5% in catches by trap lines and about 10% in catches by grooves, where it is second only to the common shrew in number. Pronounced long-term population changes characterized by a significant amplitude of fluctuations and irregular alternation of short-term relatively high rises with very long and deep depressions were revealed. It was found that in contrast to the central optimal zone, where intrapopulation compensatory mechanisms play a significant regulatory role, on its northern periphery this function is performed by external, mainly weather-phenological factors, which differ in the conditions of the northern limits of the area by utmost extremity and non-rhythmic manifestation. The analysis of the obtained materials allows us to conclude that among all the significant factors determining the environmental situation of the year, the timing of the onset of spring, the temperature and the amount of precipitation in late spring and early summer, as well as the yield of coniferous seeds largely determining the feeding conditions of overwintering for the forest rodents are the most considerable.