Introduction of muskrat in Omsk oblast.
The muskrat population was formed in Omsk oblast in four stages. The first stage began in 1936 and lasted for 15 years; it was then interrupted by tularemia epizootic. The muskrat number recovered in the next 20 years and was again interrupted by another tularemia epizootic. The recovery of the muskrat population and its introduction throughout Omsk oblast began in 1971. Since 1996, the area has been fully populated by muskrat and changes in the number of the species have assumed the nature of fluctuations with a periodicity of 5 to 6 years. Under conditions of changing moisture content from 1936 to 2015, changes in the muskrat population had a weak direct correlation with the phases of the Bruckner cycle and with the water level in water bodies and a very weak inverse correlation with the solar activity indices (W, Wolf numbers). At the current stage of the formation of the muskrat population in Omsk oblast, the distribution of the indices of its average annual abundance and the average annual density of the population have a medium direct correlation with the area of the water bodies that are available in the area under study.