Changes of the population dynamics of Sorex araneus and Myodes glareolus in South Karelia

Abstract

The paper examines the population dynamics of common species of small mammals in southern Karelia (Sorex araneus L., 1758 and Myodes glareolus Scherber, 1780) based on the results of long-term stationary studies. Small mammals in the study area were captured in the summer and autumn of the period 1966–2014 using standard snap trap lines. At each trapping session, all habitat types were sampled. The dominant species in the small mammal population, like anywhere in Eastern Fennoscandia, were Sorex araneus and Myodes glareolus. Both dominant species live here at the edge of their ranges. As a result of the data analysis of the long-term abundance of these small mammal species, the presence of two time periods (1966–1990 and 1991–2014) was established, differing for each of the species under consideration in the nature of changes in abundance. For both the common shrew and the bank vole in the second period, a change in the nature of population cyclicity was noted, expressed by a change from a tendency toward 3–4-year cycles to chaotic fluctuations. Also, a decrease in the amplitude of population fluctuations was observed for both species. For the bank vole, there was also a decrease in the population level. A discrepancy was noted in the previously existing correlation of the long-term abundance of the background species. The probable reason for such changes is the warming of the climate observed in the north of Eurasia in the 21st century. For peripheral populations of small mammals, endogenous factors regulating numbers come to the fore. This influence is indirect, as warmer winters and springs create more favorable living conditions for animals.