The comparative analysis of the yellow souslik population status in Yeruslan Sands of Transvolga region in the early twentieth and twenty-first centuries revealed that the general pattern of the species distribution, habitat preferences and abundance have not mainly changed over 80-year period. During the last 80 years, yellow souslik has maintained the stable population number and lives in dispersed colonies at the low density (<10 ind./ha after the emergence of young). Yellow sousliks show a strong preference for less disturbed and non-transformed virgin steppe-like habitats on sandy soils. The variation of abundance in time and space is determined by the variation in habitat distribution and heterogeneity, weather conditions and grazing impact, but does not outranges the typical for the species low population densities. During the last decades, significant changes were observed in interspecific interactions with other ground squirrel species. At present, yellow sousliks form mixed hybridized colonies with Spermophillus major, which may threaten the preservation of "pure" settlement of the species at the northern border of the yellow souslik range. The stable long-term population dynamics of yellow souslik in Yeruslan Sands show the importance of the preservation of natural habitats favorable for the species existence.

Measures to control populations of small mammals in natural ecosystems are taken because of their involvement in plague epizootics and probable competition for food with livestock in pastures. These measures are aimed at the keystone species of biocenosis, whose removal leads to breakage of biocenotic connections and reduction of species diversity. Moreover, available data show that these measures fail to restrain the development of epizootics in natural plague foci and do not bring expectable economic profit when applied in pastures. This is evidence that the practice of small mammal population control is inexpedient.

Приведены данные о современном распространении, биотопическом распределении и динамике численности желтого суслика в Приерусланских песках Заволжья в сравнении с данными Орлова (Орлов, 1925, 1927, 1929; Орлов, Кайзер, 1933), полученными на той же территории в начале 20 века. Сравнительный анализ состояния популяции желтого суслика в Приерусланских песках в начале 20 и 21 вв. показал, что общие характеристики распространения, биотопического распределения и численности за этот срок принципиально не изменились. На протяжении последних 80 лет желтый суслик поддерживает относительно стабильную численность в разреженных поселениях с невысокой плотностью, приуроченных к сохранившимся целинным участкам на песчаных и супесчаных почвах. Колебания плотности во времени или пространстве определяются биотопической разнородностью, погодными условиями и условиями выпаса скота, но не выходят за рамки общей, свойственной виду в целом, низкой плотности населения. Существенные изменения произошли лишь в сфере межвидовых отношений: в настоящее время желтый суслик образует смешанные гибридные поселения с большим сусликом, что может в определенной степени угрожать сохранению “чистых поселений” вида на северной границе его ареала. Относительно стабильное состояние популяции желтого суслика по сравнению с другими видами сусликов Заволжья определяется тем, что массив Приерусланских песков подвергся минимальному антропогенному воздействию. Популяция желтого суслика в Приерусланских песках рассмотрена как модель, которая демонстрирует, что сохранение естественных местообитаний – наиболее важный фактор, обеспечивающий выживание и устойчивое существование этого вида.

Data on the influence of a summer drought on the state of vegetation and the period of activity of the yellow ground squirrel in colonies of the Saratov Trans-Volga Yeruslan sands are presented. During the 2009 drought, the flora virtually ceased vegetating and was characterized by low rates of species diversity, projective cover, and height of herbage. Ground squirrels entered hibernation two weeks earlier than in previous years (with normal humidity). The only colony with a long period of activity in that year was near a meadow-reed estuary. The presence of green vegetation in small meadows contributed to a prolongation of the activity of ground squirrels and the usual date of the start of hibernation.

There are nine species of sousliks from the Spermophilus genus in Russia (Latin and Russian names of sousliks are taken from the work of Pavlinov et al., 2002). Representatives of this group are considered agricultural pests and hosts of agents of zoogenous infections. For these reasons, people have been struggling against them for 200 years. Modern methodologies for plague disinfestation recommend that four species of sousliks (Spermophilus musicus, S. dauricus, S. pygemaeus, and S. undulatus) be exterminated. The redcheeked souslik (S. erythrogenys) is exterminated as a pest. Taking into consideration the general trend toward conserving species diversity of living organisms, whether they have a negative impact on humans or not, it is necessary to reconsider our treatment of sousliks as pests and encourage a more intensive conservation of these rodents, which are biocenotically significant for arid and semiarid ecosystems. Four out of nine species of sousliks in Russia are registered as having a permanent decrease in their number (the red-cheeked souslik, spotted souslik, little souslik, and Daurian souslik). Two species of sousliks (the Caucasian suslik and the Daurian souslik) occupy restricted natural habitats, which increases their risk of becoming extinct. Measures on the conservation of sousliks in Russia should be coordinated with organizations that control their abundance.

The progression of tall-grass steppes has caused a consequent reduction in the abundance of the little ground squirrel. By the beginning of this century, its population had fallen to zero and was not compensated by other rodent species’ biomass. The little ground squirrel is a biocenotically valuable species for a semidesert terrain, since it participates in the latter’s pedogenesis and is a food source for the steppe eagle. Thus, its disappearance would threaten to significantly disturb the structure of the biocenosis.

Purposeful measures for population control of major rodent pests are taken throughout the world in view of great epidemiological and economic significance of this animal group, but such measures disagree with present-day requirements for the conservation of biological diversity. It appears expedient to develop a new concept of rodent pest control that stipulates a reduction in the amount of applied rodenticides. The coordinated efforts of specialists in nature conservation and agencies responsible for pest control are necessary for this purpose.

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.

We summarize theoretical approaches and practice of rodent pest control in Russia and former USSR during last 50 years. We review literature as well as original data to understand mechanisms of rodent populations recovery after chemical control campaigns in urban areas,agricultural lands and natural foci of plague. Laboratory and field experiments indicate that inherent individual variation in behavioural,physiological and life-history traits provides survival of heterogeneous mix of individuals in residual population with increased resistance to poisonous baits and high reproductive potential that leads to fast recovery of a population. In a series of field experiments with various rodent and lagomorph species （Mus musculus,Rattus norvegicus,Meriones unguiculatus,M.meridianus,M.tamariscinus,Ochotona pallasii） we have shown that patterns of recolonization of depopulated area and mechanisms of population recovery vary among species and depend on species-specific social organization. After control territorial and group-living species demonstrated an increase in mobility and affiliative and marking behaviour and a decrease in intraspecific aggression. The rate of recolonization of treated areas was high due to redistribution of survived individuals and immigration by neighbors. Population recovered to original level due to increased breeding performance and fecundity of both survived residents and immigrants. In contrast,socially-independent species exhibited minor changes in behaviour. Recolonization was mainly due to better survival and recruitment of youngs,so the rate of recolonization was low. Species-specificity of behavioural compensation mechanisms to control should be considered when developing ecologically based rodent management strategies

Studies performed in the southern Kalmyk Republic from 1993 to 2005 have shown that the midday and tamarisk gerbils are similar in their biotopic distribution and that their preferences for certain habitats depend on specific features of feeding. Individual home ranges of both species overlap, and the patterns of their daily activity are synchronous. These facts suggest that there is no interference competition between the midday and tamarisk gerbils in pastures of the southern Kalmyk Republic.

Indices of abundance and reproduction rate are considered in some groups of aquatic and terrestrial vertebrates from the zones of technogenic disasters. Upon a critical population decline caused by external destructive factors, such as emissions of acute ecotoxicants, the ecophysiological and behavioral compensatory mechanisms are activated, which provide for restoration of the total population size to the optimum within a short period of time. Environmental pollution with substances disturbing the reproductive function has the gravest consequences for animals. In this case, population size may remain fairly high, and, therefore, the effect of enhanced reproduction as a response to population decline does not take place, which eventually leads to a gradual but irreversible destruction of the population. Pathologies of reproduction should be used as a criterion for assessing the state of animals in the zones of technogenic disasters.

In a social vacuum following a catastrophic decline in population density of small mammals, species-specific adaptive behavioral mechanisms optimizing reconstitution of the spatial and social structure are manifested to a different extent in different species. At the same time, the rate of structure and population recovery depends on specific social organization of a species. The field observation data on the behavior of three species, Pallas' pika as well as Mongolian and midday gerbils, in an experimentally depleted population are presented. Mongolian gerbil living in family groups demonstrated developed adaptive mechanisms of this kind in contrast to two other species with pronounced individual territorialism.

A comparative analysis of the spatial-ethological structure of social vole (Microtus socialis Pall.) colonies was made on the basis of studies performed in Dagestan (1987–1991) and the southern Kalmyk Republic (1993–1998). Notwithstanding differences in environmental conditions and the extent and forms of anthropogenic impact, the population structure of the species proved to be similar and stable. Irrespective of population density, its core consists of family groups. Specific features of social behavior (aggressiveness toward unfamiliar animals) provide for the protection of home ranges and help to maintain a stable population structure.