Study of the Ecology of the Eurasian Pygmy Shrew (Sorex minutus L.) in the European Part of Its Range: Note III. Ecological Population Structure, Molting, Population Numbers, and Variety

A summary of an analysis of the population ecological characteristics of the Eurasian pygmy shrew in the European part of its range, including the results of the ecological structure of the population, molting, and population dynamics of the shrew, is presented. The ecological structure of the population is characterized by a faster increase in juveniles, the proportion of which reaches more than 72% in September. Every year the age structure of the population changes, which correlates to the intensity of reproduction and the total amount of individuals in the population. The sex ratio depends on the age of the individuals, the season of the year, and the condition of the population. As compared to the numbers of the Siberian population, we established a relatively low density of the population in the study area (0.3 individuals per 100 trap-nights or 2.2 individuals per ten trench-days). The number changes noticeably from year to year, but without any sharp periodicity, and in general it is not synchronous with the dominant species Sorex araneus. Nevertheless, over more than 60 years of studies of the population of Sorex minutus, only four unclear rises emerged. These increases in numbers occur under the influence of a rather complex combination of exogenous factors.