[Experimental hybridization of voies of the genus Microtus s.l. M. socialis with species of the group arvalis (Mammalia, Rodentia)].

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.

[Dynamics of colonies of the speckled ground squirrel (Spermophilus suslicus Guld., 1770) on the northern boundary of the habitat].

Results of studies in 1999-2009 of the dynamics of five isolated colonies of the speckled ground squirrel (Spermophilus suslicus) at the northern boundary of the habitat of this species (Zaraiskii area, Moscow oblast) are given. An abrupt decrease in the number of this species in colonies was established, as was a multifold decrease (up to 70-90%) in suitable habitats due to the plowing of meadows and build-up of the area. The fragmentation of the optimum habitat of ground squirrels reached a stage where colonies can no longer exist as a stable autonomous system. The process of their extinction unfolds quickly: the number of animals in some colonies decreased five-six times over the last ten years. To preserve this species, it is necessary to create areas of steppefied meadows with regulated agricultural use.