On seasonal and age dependent weight changes in bank vole (Clethrionomys glareolus Schreb)

A long-term research of the bank vole inhabiting Karelia revealed two characteristic trends corresponding to the two critical life periods of the rodent in focus. The weight index of more than 1200 species of the bank vole was studied. The first season - the autumn one (the second half of October - the beginning of November), when the snow cover is not deep yet, requires a lot of energy for survival. The second season - the winter one (December - January) is characterized by low temperatures and deep snow cover. During the second season, the thermal regulation of the rodents’ body adapts to low temperatures and is well protected by deep snow cover. The bank voles born in spring and in the beginning of summer grow and develop during a more favorable period and, therefore, demonstrate higher growth rate and maturation speed. The bank voles born much later grow and develop in less favorable conditions and, therefore, demonstrate lower growth rate. However, the effect of these dependences can be diminished under the influence of both exogenous (bad weather, low level of fodder yield and etc.) and endogenous factors.