[Effect of habitat type and population density on the stress level of midday gerbils (Meriones meridianus Pall.) in free-living populations]. / Viianie tipa mestoobitaniia i plotnosti naseleniia na stressirovannost' peschanok (Meriones meridianus Pall.) v svobodnozhivushchikh populiatsiiakh.

New methods of noninvasive evaluation of the endocrine status of animals by the content of hormones in feces were used to study the relationship between the stress level and social (population density) and ecological (habitat integrity) indices in natural populations of midday gerbil in the Southern Kalmykia in 2000. Stress level proved to increase with habitat disturbance but did not depend on population density of animals. The obtained data are discussed in the context of species-specific ecology and social behavior of midday gerbils.

[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).

[The use of radioisotope labelling for studying the feeding of sandflies (Phlebotominae) and their move into colonies of the greater gerbil (Rhombomys opimus Licht.)]. / Ispol'zovanie radioizotopnogo mecheniia dlia izucheniia prokormleniia moskitov (Phlebotominae) i ikh peremeshchenii v poseleniiakh bol'shoi peschanki (Rhombomys opimus Licht.).

The fly off and distribution of sandflies, vectors of zoonotic cutaneous leishmaniasis after meal on great gerbils were studied by means of radioisotope techniques. The experiments were carried out near the town of Mubarek (Uzbekistan). Three Rhombomys opimus were marked by intraperitoneal injection of 14C-glycine solution. Then they were allowed to come back to their burrows. The sandflies were radioactively labelled during bloodsucking on the rodents. Fifty-seven labeled female sandflies were caught on the surface of burrows with the marked R. opimus and on 5 colony burrows at a distance of 70-280 m from it for 6 nights. Seventeen females were Phlebotomus papatasi (0.9% of all the caught females of this species) and 40 females belonged to the Paraphlebotomus subgenus (7.0%). The fly off occurred both before and against the wind. The labeled females were found on all burrows where sticky papers were placed, but their density was 16 times lower at a distance of 280 m than in the burrow colony of their release.

[The sociality syndrome. A comparative study of the behavior of gerbils]. / Sindrom sotsial'nosti. Sravnitel'noe issledovanie povedeniia peschanok.

To explain the evolution of sociality the authors propose the hypothesis that every social interaction is based on the contest. The synergetic nature of any interaction determines the permanent involving partners in the contests and leads to increasing social pressure within community. The contestants' interactions inhibit an activity in one of the partners. Two possible evolutionary strategies of adaptation to increasing social density are: 1) an increase in resistance to the activity inhibition; 2) a retaining in memory the results of inhibition, i.e. reducing of ability to restore inhibited activity. Three species of gerbils (Gerbillidae): Mongolian (Meriones unguiculatus), Libyan (M. libycus), and midday gerbil (M. meridianus) were compared. Being similar in their ecology and behavioural repertoire three species differ strongly in extent of sociality: the highest in Mongolian gerbil and the lowest in midday one. The duration of social acts in laboratory groups of gerbils as well as frequency of acts delaying conflicts under natural conditions were assumed to correlate with increase in resistance to social pressure. Both parameters were higher in mongolian and libyan gerbils. The data on dynamics, asymmetry, and stability of social relations indicates more stable retaining in memory the results of interactions in Mongolian and Libyan gerbils than in midday ones but the latter restore inhibited activity more quickly. In the laboratory groups where the available space is compressed the midday gerbils maintain population at a level not lower than Mongolian ones and much higher than M. libycus. Moreover aggression within the group of midday gerbils doesn't result in rapid population decrease as in other two species.