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In the article the chromosomal complement of the social vole (Microtus socialis parvus Satunin, 1906) from five additional points of the North Caucasus is studied in a comparative aspect. Much attention is given to the distribution of this species taking into account the landscape structure and biotopic allocation. It is concluded that the karyotype of the social vole in the analysed area is not susceptible to polymorphism. The chromosomal complement of all studied individuals is identical in the number and morphology of chromosomes.

The features of the spatial distribution of four species of Mouse-Like rodents (Sylvaemus fulvipectus, Cricetulus migratorius, Microtus socialis, and Dryomys nitedula) in the forest associations of the foothill zone of the Republic of Dagestan are analyzed. Sixteen environmental parameters are selected, of which ten significantly showed interspecific differences. The distribution of rodent species is demonstrated relative to the environmental characteristics taken into account in the descriptions; the preferences and requirements for the environment of each species are revealed. Thus, the yellow-bellied mouse and gray hamster were found at all stations, whereas the forest dormouse and social vole were more selective in their choice of stations. As a result, the width of the spatial niches for the yellow-bellied mouse and gray hamster is greater than that of the forest dormouse and social vole. The results of pairwise comparison of the spatial niches of studied rodent species reveal low values of their overlap.

The intraspecific relations of two species of the subgenus Sumeriomys have been studied: the social vole Microtus socialis and the paradox vole M. paradoxus. The relationships between animals same-sex individuals in the experimental groups, are generally amicable, but the cohabitation of two or more females suppresses reproduction. Groups formed from unfamiliar individuals were characterized by increased aggressiveness, which led to high mortality. The paradox vole was diffed from social vole by higher motor and social activity and greater aggressiveness towards unfamiliar individuals. The vocal behavior of individuals of both species is similar. 30% of contacts between individuals are accompanied by squeaks; males sing in intersex interactions, but this behavior is rare (less than 1% of contacts).

A considerable increase in the social vole population distributed in the northwestern Caspian region (Republic of Kalmykia) in 2014–2016 has been recorded. The average long-term dominance index of the rodent cenosis in 2014–2016 was three times as high as in 2002–2010. The rise in the rodent population was caused by an increase in the reproduction rate due to adequate fodder supplies under favorable climatic conditions. In May 2016, social vole mass migration and deaths were registered; it is a rare phenomenon arising in rodents that may be caused by overdensity of their population. All of the males were first involved in the migration process because of increased intraspecific competition, higher aggression levels, and weaker attachment to the habitats as compared to the females. The mass migration and deaths of social voles in the northwestern Caspian region may reflect the unstable equilibrium dynamics caused by changes in the anthropogenic pressure and land-use system, which interacts with the damping effects in the climate.

Entomoparasitic nematodes are the natural regulators of numbers of fleas – plague vectors in natural plague foci. They have an impact on the intensity of epizootic process, progressing in these foci. Objective of the study is to examine entomoparasitic nematodes from fleas of the souslik and vole, collected in the territory of Povolzhsky Region. Materials and methods. Presented are the results of morphological and genetic analysis of entomoparasitic nematodes, flea parasites – Citellophilus tesquorum, Amphipsylla rossica and Ctenophthalmus secundus, collected from the small ground squirrel Spermophilus pygmaeus and social vole Microtus socialis, respectively. Results and conclusions. Established has been morphological identity of nematode parasitic females isolated from all the three species of fleas, and a high degree of similarity to the previously described Rubzovinema ceratophylla, parasitizing on C. tesquorum fleas. Substantiated has been the belonging of parasitic nematodes isolated from fleas C. tesquorum, А. rossica and C. secundus, to one and the same species, specified as Rubzovinema sp., based on the high percentage of the homology of the nucleotide sequences of rRNA genes (99.3–100 %). This species differs from the previously described monoxenous R. ceratophylla in absence of strict host specificity.

The article addresses the interrelationship between different forms of group varia­bility of craniometrical features according to value of their contribution in the overall morphological disparity of individuals in the population Microtus socialis in southern Ukraine. It is shown that most of the variability of traits determined primarily the age animals and less sex, season, number and density of individuals in the population. Obtained results indicate that the age variability is the base for formation of all other forms of group variability. It is proved that the variability of craniometrical traits in young and subadult voles is determined primarily by size and density of individuals in population (cyclic variability). Second largest impact on the variability of craniometrical features includes season, third – sex whose influence on the variability of traits in young voles was statistically proven. In juvenile voles sex and season affect the variability of linear dimensions and proportions of the skull, while in subadult and adults – mostly in the proportions of the skull and almost no influence on the variability of its linear dimensions. Sexual variability of the craniometrical traits increases markedly with the age of voles.

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.

Expression of sexual differences in social vole populations of virgin steppe reserve “Askania Nova” analyzed in the article. It is established that the severity of the sexual differences of value morphological features depending on the age of the animals and to a lesser degree on the season. В статье проанализировано проявление половых различий в популяции общественной полёвки целинной степи заповедника «Аскания-Нова». Установлено, что степень выраженности половых различий величины морфологических признаков изменчива в зависимости от возраста зверьков и в меньшей степени от сезона.

The study reports on chromosomes in several populations of social voles from south-eastern Europe and the Middle East. The standard karyotypes of individuals of Microtus hartingi and Microtus guentheri originating from both south-eastern Europe and Asia Minor comprised 54 mostly acrocentric chromosomes. However, variation between populations was found in the amount and distribution of C-heterochromatin in certain autosomes and the sex chromosomes. Furthermore, a specific pattern of argyrophilic nucleolar organizer region distribution was recorded in different geographic populations. In a population from Asia Minor, a heterozygous centric fusion of two autosomes was found. The G-banded karyotypes of M. guentheri and Microtus socialis were compared, and tandem fusions of autosomes were suggested as possible mechanism of the divergence. The karyotypes of the nine currently recognized species of social voles are reviewed, and implications of chromosomal data for systematics are evaluated.

The botanical composition and the ratio of various plants in the diet of Microtus socialisPall. were determined by microhistological cuticular-coprological analysis of undigested remains. Microtus socialis disappeared from the zonal plain of the Volga-Ural interfluve in the early 1970s and appeared again in 2009. The role of grains in their nutrition became more important, and the ratio of wormwoods sharply decreased. The feeding patterns observed are caused by the long-term absence of these massive phytophages and reflect significant changes in the habitat over the last 40 years.

The social vole (Microtus socialis Pall.) is a landscape species of the Trans-Volga clayey semidesert, which disappeared from the zonal plain in the 1970s but survived in various habitats of lake depressions. In 2009, it settled over the blind plain again. The reasons for the departure and then return of the vole are not known. This phenomenon might be one of the cyclic changes in the specific composition and abundance, which are characteristic of many animals of this region.

In the clay semidesert of the Caspian Lowland, the surface runoff is transformed to soil runoff due to the presence of a system of social vole (Microtus socialis Pall.) passageways in the soils that promotes the retention of soil moisture and prevents the development of soil erosion. A quantitative assessment of this process is given. We describe the mechanism of intense soil erosion arising after the disturbance of vole underground passageways responsible for the formation of specific relief elements and plant communities.

The Social Vole Microtus socialis differs from non-socialis voles from Iran by its smaller size and relatively broader inter-orbital region. Discriminant Function Analysis based on 14 cranial measurements classified all Iranian specimens into their actual group (i.e. socialis or non-socialis). A dotted distribution map of M. socialis is provided for Turkey, Syria, Lebanon, Iraq and Iran. Isolated records from Khorassan and Fars, both in Iran, are discussed. Inter-locality variations were significant in dimensions of the tooth-row, diastema, rostrum, bullae and braincase breadth. The postero-internal loop of the second upper molar was either absent or rare; only in voles from Lebanon and Syria was the incidence of this morphotype observed in about one-third of the specimens. Marginal populations seemed to be morphologically most distant.

In order to ascertain the typical pattern and amount of parental care in the social vole (Microtus socialis guentheri) as well as the individual investment of the female, male, or both parents simultaneously, we studied ten primiparous females and their mates. Results revealed that out of seven parental behaviors, only crouching was correlated with litter size, suggesting that parental care was relatively independent of litter size—that is, duration of time spent with the young, licking them, retrieving them to the nest, having them attached to the female’s nipples, and searching for a nipple on the male were not correlated with litter size. Individual investment of caretakers also varied, with no typical proportion of shared nurturing by the female and male. Accordingly, overall parental investment varied greatly among different sets of parents without correlation to the relative contribution of the female, the male, or both. Finally, duration and frequency of most parental behaviors declined over the course of postnatal development. Altogether, these data suggest a surplus parental investment that was probably not required for survival of offspring but might have evolved either for other purposes such as the formation of social bonds or was selected for in captivity.

Parental care has been categorized into direct and indirect investment. The former includes direct contact with the offspring, as in lactation or huddling with the pups, and the latter includes activities such as nest building or hoarding food for the guarding mate. We report here an unfamiliar type of parental behavior in which one parent aggressively forces its mate to stay in the nest with the pups. In this "forced baby-sitting," one parent grasps the fur of its mate and drags it toward the nest. The behavior was observed in 6 of 10 pairs of the social vole (Microtus socilalis guentheri) and was typically executed by the male. Dragging the mate to the nest was not correlated with other parental behaviors; neither could we explain why/when it occurred. However, this behavioral pattern was eye catching, and its goal was obviously to enforce the mate to stay in the nest with the pups.

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.

Olfactory cues can contain information for discrimination of gender that can affect subsequent social interactions. Social rodents are hypothesized to use more olfactory cues than nonsocial rodents to distinguish males from females. The generality of this hypothesis was tested using the pine vole (Microtus pinetorum), a social vole. We examined nine possible sources of odors. A slide containing an odor from a male and a female was presented to each test subject for 3 min. We recorded the amount of time each test subject spent investigating each odor. Females spent significantly more time investigating male urine and male anogenital odors; however, they did not use any other odor sources to discriminate gender. In contrast, males did not use any odor sources to discriminate gender. Our results do not support the hypothesis that all social rodents use numerous odor sources to discriminate gender. Instead, our results are consistent with the alternative hypothesis that use of odor sources to convey information about gender may differ in rodents that live in different microhabitats.

Human-made agro-ecosystems lack negative feedback controls, which may result in rodent population explosions, causing considerable economic loss and thus increasing human-wildlife conflicts. The traditional solution is the extensive use of rodenticides, which have a negative impact on the environment. In Beit-Sheaan Valley, Israel, which is located on a major route for migrating birds, poisoning of voles may result in the death of birds that prey on the dead voles (e.g. storks and herons). In the present essay we discuss some integrated methods, based on the implementation of ecological principles in agro-ecosystems, that could be used to decrease the use of rodenticides. The first method is light interference during winter (long scotophase), which can result in the death of the social vole Microtus socialis kept in enclosures under natural conditions. Under laboratory conditions such interference causes a decrease in thermoregulatory ability in the cold. As light interference is a source of pollution, only active vole burrows should be illuminated. The second method involves using the mobile irrigation pipelines to flood the vole burrows and force them to escape into the open, where diurnal birds such as storks and herons will prey on them. The third method involves the use of nesting boxes for barn owls and stands for diurnal raptors, both of which prey on voles. The great advantage of using an integrated approach is that voles cannot become adapted to any one of the methods. Such integrated methods, together with appropriate treatment of alfalfa fields by farmers, can provide an efficient and sustainable pest control approach.