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The ranges of all three zokor (Myospalax) species, the little-studied burrowing rodent, are described in southeastern Transbaikalia, Russia, based on the results of special expeditions. Myospalax aspalax inhabits only the Onon River basin, M. psilurus populates the forested steppe in the Argun River basin and the upper reaches of the Borzya River (a tributary of the Onon River), while M. armandii is known only from the Klichkinskii Mountain Range. The distribution area of M. armandii is very small (less than 2000 km2) and is isolated from the other parts of the range (in China). The zokor species in the region are shown to be parapatric, with no sympatry being involved. The ranges of M. psilurus and M. armandii are the closest, the distance between the closest settlements being less than 5 km. Reduction in the zokor distributions is observed in Transbaikalia. It is advisable to include M. armandii on the Red Data list of Russia.

Field studies on the distribution and population size of tarbagan (Mongolian marmot) were carried out in 2010–2017 in districts of Zabaikal’skii krai bordering Mongolia and China. The study area constitutes parts of federal-level, strictly protected areas: Daursky State Nature Biosphere Reserve and Dzeren Valley Federal Nature Refuge. It is shown that the tarbagan population in the study area has reached more than 2000 families by 2017. The most active population restoration is observed in habitats historically characterized by the maximum tarbagan population: the Nerchinskii Ridge near the Mongolian border. Engineering structures at the border and the special frontier regime contributed to the preservation of the original marmot settlements. Marmot migration from Mongolia no longer plays an important role in the maintenance of frontier marmot populations in the studied section of the Russian–Mongolian border.

The population and number dynamics of small mammals in the vicinity of the Torey lakes (Southeast Transbaikalia, Russia) were characterized between 2008 and 2017. The monitoring was carried out against the backdrop of the complete drying out of these largest lakes in the region. The stability of the fauna of small mammals was revealed over an 80-year period, although the structure of communities has changed significantly as a result of changes in moistening of the territory. Xerophilous species of mammals had an advantage in the period of studies in the dry climate phase. Correlation analysis showed a possible link between the population dynamics of some common species of small mammals with the precipitation amount of the current and previous years or with the precipitation amount of some spring (in one case, winter) months.

Materials on the new findings of the striped field mouse (Apodemus agrarius) in Transbaikalia, within an earlier disjunction area in the habitat of this species (in the basins of the Onon and Ingoda rivers), are presented. Possible causes of the expansion of the species range are discussed. It is most probable that the species was introduced from the basin of the Argun River with a cargo of agricultural products to the lower reaches of the Onon River or the upper reaches of the Shilka River. Currently, the striped field mouse is a com� mon species inhabiting a floodplain shrub biotope in the lower reaches of the Ingoda and Onon rivers.

It was demonstrated that in Y-maze individuals of the outdoor species Myodes glareolus and the semi-synanthropic species Microtus levis avoided the urine odor of commensal Mus musculus. On the contrary mice stayed longer in the maze compartment with the odor of voles. The level of avoidance of commensal mice odor was higher than the other strange odors (urine of rabbit or outdoor mouse Mus spicilegus). It is assumed that the sharp smell of commensal mice is an adaptation designed to hold and protect a particular ecological niche against other species of rodents, i.e., human buildings.

In the paper the author reports literature data and his own on the shrew fauna and communities of the steppe and forest zones of Eastern Transbaikalia.