Scientific publications

Long-term (1958–2012) materials on the reproduction and ecological (sex and age) structure of the field vole (Microtus agrestis L.) population in Northwest Russia are analysed. The breeding season in this species in the region begins early in April and lasts until September. During this time, the over-wintered females produce two or three litters, and the young from the early litters produce up to two or even three litters. The field vole population comprises several seasonal generations of the young, differing in the rates of growth and development, and the scope of participation in breeding. Juveniles from early litters of the year are noted for rapid growth and development, and almost all of them breed in the year of birth. The young born in June or later mainly mature only after a winter. The former ensure the population growth in the current year, and the latter are the basis for the late summer and autumn population of the next year. Litter size is 2 to 10 (with an average of 5.7 ± 0.2), which is slightly higher than the values in southerner areas. Embryonic mortality is about 2 %, postembryonic – around 20 %. The intensity and timing of breeding vary among years depending on the environmental conditions and the consolidated population abundances. The population age polymorphism contributes to its stability, and acts as a mechanism of the population self-regulation.