The structure of two northern mole vole colonies from northern Chelyabinsk oblast (the Kunashak colony, 1981–1983) and southern Kurgan oblast (the Kurtamysh colony, 1985–1999) has been analyzed with respect to the number and composition of families, seasonal and annual population dynamics, age and sex composition and sex ratio, individual life span, migrations, breeding, and reproductive potential. The Kunashak colony is at the northwestern boundary of the species range, and its population is monomorphic (all animals are of the black color morph). The Kurtamysh colony is located in an optimal habitat, and its population is polymorphic, consisting of animals of three color morphs (black, brown, and transitional). Consideration is given to certain specific features of northern mole voles belonging to different color morphs.