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The intraspecific relations of two species of the subgenus Sumeriomys have been studied: the social vole Microtus socialis and the paradox vole M. paradoxus. The relationships between animals same-sex individuals in the experimental groups, are generally amicable, but the cohabitation of two or more females suppresses reproduction. Groups formed from unfamiliar individuals were characterized by increased aggressiveness, which led to high mortality. The paradox vole was diffed from social vole by higher motor and social activity and greater aggressiveness towards unfamiliar individuals. The vocal behavior of individuals of both species is similar. 30% of contacts between individuals are accompanied by squeaks; males sing in intersex interactions, but this behavior is rare (less than 1% of contacts).

The results of interspecific crosses of the social vole Microtus socialis with the Altai vole M. obscurus, the East European vole M. rossiaemeridionalis, and the Transcaspian vole M. transcaspicus are presented. The role of the sperm head structure in the reproductive isolation of this species was studied. Hybrids were obtained in five of the six crossing combinations. It is established that significant differences in the sperm head shape in the social vole and in arvalis group species do not prevent fertilization. The sterility of hybrids indicates the existence of postcopulative mechanisms of reproductive isolation.

The botanical composition and the ratio of various plants in the diet of Microtus socialisPall. were determined by microhistological cuticular-coprological analysis of undigested remains. Microtus socialis disappeared from the zonal plain of the Volga-Ural interfluve in the early 1970s and appeared again in 2009. The role of grains in their nutrition became more important, and the ratio of wormwoods sharply decreased. The feeding patterns observed are caused by the long-term absence of these massive phytophages and reflect significant changes in the habitat over the last 40 years.

The social vole (Microtus socialis Pall.) is a landscape species of the Trans-Volga clayey semidesert, which disappeared from the zonal plain in the 1970s but survived in various habitats of lake depressions. In 2009, it settled over the blind plain again. The reasons for the departure and then return of the vole are not known. This phenomenon might be one of the cyclic changes in the specific composition and abundance, which are characteristic of many animals of this region.