[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.

[Biotope distribution of two gerbil species (Meriones meridianus and M. tamariscinus) (Rodentia, Gerbillinae) in southern Kalmykia]. / Biotopicheskoe raspredelenie poludennykh (Meriones meridianus) i tamariskovykh (M. tamariscinus) peschanok (Rodentia, Gerbillinae) na iuge Kalmykii.

Our studies have been conducted in Southern Kalmykia (Black Lands) in 1994-1996. The data obtained on the same territories in 1981-1983, as well as in 1997-1998 were used for comparison. Over the studied period, the size of Meriones tamariscinus population underwent a significant increase. In the early 1980s, the colonies of this species were found only on sandy dunes covered with tamarix. At the present time, M. tamariscinus populations have spread over stabilized sands, abandoned shepherd camps, and riparian thickets of tamarix along the shores of lakes. Both gerbils species (M. meridianus and M. tamariscinus) establish joint colonies in all biotopes, but not in riparian tamarix thickets near lakes, where only Meriones tamariscinus have been found. The abundance of food and favorable conditions for burrowing in stable sands belong to factors, responsible for permanently high numbers of gerbils in these areas.

[Dynamics of rodent community and populations in Kalmyk semideserts under decreasing pasture load and increasing humidity]. / Dinamika soobshchestva i populiatsii gryzunov polupustyn' Kalmykii v usloviiakh snizheniia nagruzki na pastbishcha i uvlazhneniia klimata.

Today, pastural ecosystems of the Kalmyk Republic demonstrate progressive regrowth dynamics, which is explained by a sharp decrease in grazing load and the onset of a new humidification cycle in the Caspian Lowland. By the mid-1990s, the sparse and poor desert vegetation with a significant proportion of ephemerals, characteristic of these ecosystems in the 1980s, had been substituted by highly productive tall-grass communities typical of steppes. Under such conditions, corresponding changes in the distribution and abundance of rodents could be expected. These parameters were assessed in different types of habitats in Chernye Zemli (the Kalmyk Black Lands) from 1980 to 1983 and from 1993 to 1997. Rodents were captured in live traps distributed over permanent test plots and in crush traps arranged in lines. The results showed that the population of midday gerbils did not change significantly during this period, although their favorite open habitats considerably decreased in area. The abundance and range of tamarisk gerbils noticeably increased, whereas those of little sousliks continued to decrease, contrary to our expectations. Thus, a rapid progressive succession in plant communities did not cause the corresponding change (of similar rate and extent) in the structure of rodent community. The difference between the observed and expected results provides evidence that rodent populations are somewhat "inert" in their response to changes in environmental conditions, and their development is relatively independent of these changes, but is contingent upon the state of populations in the past (i.e., the history of colonies).