The history of golden jackal dispersal in Russia and adjacent countries, as well as in southern, central, eastern and northern Europe, is considered. Data confirming the demographic explosion of this species on the European continent territory are given. Materials on the dispersal of golden jackals in the European Russia are considered in more detail. The main emphasis is made on the study of the process of golden jackal penetration into the territory of Saratov region, from its first sightings in the Saratov Volga region in the late 1980s – early 1990s in the Dyakovsky (Saltovsky) forest to dispersal in adjacent territories. The penetration of the species into the Saratov Right Bank and its further dispersal throughout the region on both banks of the Volga river is described. It is shown that the areas of the modern jackal range are approximately the same both in the Right Volga Bank and Left Volga Bank of the Saratov region. However, the number of jackal is currently higher in the areas of the region located on the right bank of the Volga river. Probably, this is explained by more favorable conditions for the golden jackal habitat in this part of the region, associated with its higher afforestation. Gold en jackals breed in the southern districts of the Saratov region, located on both banks of the Volga river. However, golden jackals are also found in the northernmost parts of the region, and most likely there, as well as in the south of the region, its stable reproductively active groups appear. In the Saratov Volga region, in spite of its very low forest cover, the golden jackal is recorded both in the south-eastern and north-eastern areas, but its numbers are high enough only in the vicinity of the forest on the Prieruslan sands and in areas along the Volga river, where there are areas of floodplain and bairn forests. In the Right Volga Bank of the Saratov region the golden jackal is most abundant in upland oak forests of the Privolzhskaya Upland, occurs in floodplain forests of the Medveditsa river and in the Medveditsa–Khopyor interfluve.

The results of our studies of the great bustard population in the Saratov and Volgograd Trans-Volga regions are presented. For the first time on this territory, censuses of the numbers of bustards were carried out in their lek areas in the spring over a period of three years. This made it possible to obtain more reliable data on the numbers of individuals of this species, as well as on the demographic structure in the model area, and to compare them with those obtained during fall population counts. In our opinion, as a result of intensification of agriculture, the nesting habitats of the bustard have been sharply reduced, which was caused by changes in the structure of crop areas and the massive use of pesticides. In the absence of necessary protective measures, this has led to a reduction in the numbers of birds in the Saratov Trans-Volga region by almost ten times over 20 years. This trend is observed throughout almost the entire world range of the great bustard, where no long-term effective measures aimed at preserving the natural habitats of the species are taken. In the Trans-Volga region, the number of lek areas has decreased by approximately half and the numbers of individuals of the species in the remaining leks have decreased. The demographic structure of the bustard population when studied in lek areas shows a significant predominance of males over females, which contradicts the stability of the population. Due to the reduction in the number of habitats suitable for bustards to nest, the success of their reproduction has decreased significantly. Spring treatment of crop areas with pesticides by ground and aerial methods coincides with the nesting period of birds, which is a powerful factor of disturbance and leads to the loss of clutches. Females the clutches of which have been preserved have the problem of acute food shortage after their chicks hatch, which also leads to elimination of some part of the broods.

The DNA studies of badgers (Meles sp.) from the right-bank and left-bank areas of the Volga River in the Saratov region are described. Asian badgers (Meles leucurus Hodgson, 1847) inhabit the Left Bank of the Volga river in the Saratov region, while European badgers (M. meles Linnaeus, 1758) inhabit the Volga Right-Bank districts of the region; however, Asian badgers have been found in Khvalynsky district of the Saratov region in addition to the European badger. Despite the sufficient number of publications devoted to the Asiatic badger distribution in the Vyatka–Kama region and the Volga region and the studies devoted to the development of systematics of the genus Meles in Russia, the question of the boundaries of the ranges of European and Asiatic badgers and the zones of their sympatry (parapatry) in the Volga–Kama region has not been fully investigated to date. Our work is devoted to the study of this question. The analysis of biological material that we have collected has shown that all five of the studied badger individuals from the Saratov Volga region phenotypically look like Asian badgers; however, DNA analysis showed that only two of them were M. leucurus and other three were heterozygous individuals carrying genes from both species and were identified as hybrids. The remaining 29 individuals were captured in the right-bank areas of the region. Samples were taken from badger individuals from the northern to southern borders of the region in the areas located along the Volga River on the Volga Upland and in the Oka–Don Plain. Among them, one individual from Khvalynsky district turned out to be an Asian badger, one individual from Krasnoarmeysky district was a hybrid of these two species, and three individuals, one from Tatishchevsky, the second from Volsky and the third from Khvalynsky districts showed introgression of Asian badger genes into the genotype of European badger. Thus, we have managed to find out that, at this stage of the development of the climatic cycle phase in the Lower Volga Region characterized by warming winters, the Volga River, with its two reservoirs within the Saratov region, is not an absolute zoogeographical boundary and badgers whose species are characterized by winter sleep can under certain conditions overcome, most likely on ice, both the river itself and the lake parts of the Volgograd and Saratov reservoirs. According to the revealed introgression in some individuals from different areas on the Volga Upland of the right bank of the Saratov region, it can be assumed that such traveling across the Volga River took place earlier, possibly before its flow was regulated by dams.

The paper presents the results of our long-term monitoring of the family of larks (Alauda arvensis L., Melanocorypha calandra L., M. leucoptera Pallas, M. yeltoniensis J. R. Forster and Calandrella rufescens Vieillot) in the semi-desert zone of the Saratov Trans-Volga region. Bird censuses were carried out at 4 key sites on permanent routes during the nesting period, the total length of the census transects was 792 km. Statistical indicators of population dynamics were calculated, namely: the growth rates (Tnp.) and average density values (ind. / 100 ha) of each lark species. A statistical multivariate factor analysis (F-test) was carried out, with the help of which we were able to reveal the influence of a whole range of factors on the lark density dynamics. Changes in habitat conditions at the key areas (Fcrit. = 1.30, p = 0.003), as well as weather factors (Fcrit. = 1.39, p = 0.004) of particular years, have a significant impact on the density dynamics of larks. Evaluation of the variance showed heterogeneity of the sample (St = 0.119, p = 0.006), therefore, the average densities of larks differs significantly from each other. Thus, the structure of the lark community and the annual density of each species are the result of the environmental conditions of the habitats at each key site, and the weather conditions of particular years.

The results of our studies of potential nesting sites for bustards in the Saratov Trans-Volga region are presented. The characteristics of plant communities, as well as the quantitative and qualitative composition of arthropods in these areas, are given. Specific materials obtained in the years 2017–2021 at six plots are given, namely, crops of winter wheat, millet, and sunflower; fallows of various ages: and young (2nd stage) and old, virgin lands. The results obtained are compared with the data of previous years. The results on the state of the forage base of bustards allow us to conclude that loss of nesting habitats by birds of this species has actually occurred. Those areas where, despite the decrease in the abundance of insects, there are still enough of them to feed the chicks, are not used by bustards as nesting habitats. These are fallows of various ages and virgin lands. The lack of a sufficient number of arthropods necessary for feeding chicks in those sites where bustards prefer to nest, namely, cereal crops, leads to catastrophic consequences for reproduction, and, consequently, for the survival of the species. The numbers of large orthoptera and beetles in winter crops, reflecting biomass indices, have decreased by ten times compared to 2000, during the period of extensive agriculture. The intensification of agricultural production, the use of pesticides on various crops, and the change in the structure of crop rotation are the main causes for the insufficient food supply during the period of rearing chicks. The results obtained give grounds to believe that the number of bustards will continue to decline due to their inability to raise their offspring as a result of a shortage in food supply.

This article is devoted to the study of the possibility of determining the ecological density of game animals according to winter route censuses. Determining the density of game animals is a prerequisite for determining their prey quotas. The most valuable parameter characterizing population estimation of specific species of game animals is ecological density. She calculated for the area actually inhabited by a particular animal species. The population density, calculated on the area suitable for the type of land, is widely used in the practice of domestic hunting. Territories with feeding and protective properties for this species are considered suitable sites. The materials of winter route counts confirm that the territories suitable for any animal species are not always completely populated by it, and the territories recognized as unsuitable are visited by these animals. Tracking activity of game animals is recorded both in areas that are considered suitable for the species, and in areas that are not typical for it. The territory of the animal during the day is the area lying inside the minimum convex contour drawn around the daily track of this animal. In this case, as the territory occupied by some animal, we can consider the territory obtained by combining all the minimum convex contours drawn around all daily traces left by this animal for a certain time. The union of the minimum convex contours drawn around all daily traces left by all animals of a given species during the period of accounting work can be considered as the territory inhabited by them at this time of the year. The crossing of a track by a route is a random event. Therefore, to determine the ecological density of a species according to the winter route censuses data, it is necessary to apply the probability theory.

Cytogenetic analysis (routine, G-, C-, AgNOR-chromosome banding) allowed us to obtain new data on chromosomal polymorphism in the population ( n = 13) of the Sicista sp. 1 representative of the Sicista subtilis group from the Saratov region, right bank of Volga River. It was shown that in the studied polymorphic population of a species from the northern part of the species’ range (Voskresenskii district of Saratov region) the diploid number of chromosomes varies from 2 n = 22 to 2 n = 24, and the number of autosome arms ranges from NFa = 39 to NFa = 44, and the sample includes the following six karyotype variants: with 2 n = 24, NFa = 44; 2 n = 24, NFa = 43; 2 n = 23, NFa = 40; 2 n = 23, NFa = 41; 2 n = 22, NFa = 39; 2 n = 22, NFa = 40. Based on the G-banding method, the determined intrapopulation chromosomal polymorphism in Sicista sp. 1 was defined by two chromosomal rearrangements: tandem translocation involving two biarmed autosomes nos. 4 and 10 and a pericentric inversion of pair no. 6. In the studied sample ( n = 13), a stable advantage of heterozygotes was revealed for both structural chromosomal mutations and the chromosomal polymorphism is characterized as balanced or heterozygous. The potential role of the identified polymorphism in chromosomal evolution and the adaptive strategy of the species is discussed.

The present paper is devoted to the study of the possibility of estimating the reproductive potentials of wild ungulate populations, and possibly other large mammals, by the time series of their numbers. We have found out that this is possible, which is confirmed by the high quality of approximation of the time series of abundance by logistic curves, and the corresponding coefficients of their determination for different species ranged from 75 to 96%. For such calculations, one circumstance is necessary, which is that the population of the studied species has been briefly exposed to some unfavorable factor causing a significant reduction in its numbers with subsequent restoration to the previous level, or the time series should contain a well-expressed and extended section of the transition of the population from some lower level to the upper level of the population, passing into a stationary state. The values of the maximum exponential growth rates of ungulate populations that we obtained do not fundamentally differ from the data available in other researchers’ works. In addition, it should be borne in mind that our method for assessing the reproductive potentials of ungulates is statistical, with features accompanying all such methods, for example, in the presence of statistical errors in all determined parameters. However, the evaluation of the magnitude of these errors is a topic for a separate study.

The paper presents the results of our study of ecosystem diversity and the state of split-forest areas located in the Shchuchansky district of the Kurgan region. The species composition of forest stands, the productivity of tree species, the composition of underwood, brushwood and ground cover in plantations were analyzed. Data on the distribution of forest stands of various ages, composition, types of underwood and brushwood, as well as the main dominants of the ground cover are presented. Our studies have shown that forest communities are quite distinctly different in the nature of all storeys. A preliminary assessment of the economic impact on the territory of the site made it possible to identify significant changes in all the components of forest ecosystems, namely, ground cover, the composition and productivity of forest stands. The diversity of forest ecosystems in the study area is due to the ability of many plant species to inhabit a wide range of ecological conditions, as well as the composition, age and crowncontact, which, in turn, determines the nature of the storey of shrubs and ground cover. The volume of the forest type was taken quite large, it combined plantations of all age stages of forest stands development. Features of forest vegetation, typical for split forests of the Southern Trans-Urals, were revealed, namely: mosaic vegetation cover, low crown-contact and the presence of open spaces species in the lower storeys. The materials obtained showed that, despite the significant anthropogenic transformation, the forest ecosystems of the study area retained the main features characteristic of the peculiar vegetation of the forest-steppe of southern Siberia. The research results will make it possible to assess the diversity of forest ecosystems, to give a preliminary forecast of the dynamics of the site's vegetation and can be used in the development of a scientifically grounded strategy for forest management in the region under the conditions of the joint action of many natural and anthropogenic factors.

The dynamics of the density of nesting pairs of five lark species (Alaudidae) living on the territories of the Mezhuzenskii and Uzeno-Dyurinskii Plains, on the northwestern tip of the Caspian Lowland, and in the semi-desert of the Aleksandrovo-Gayskii district of Saratov oblast, and its relationship with Selyaninov’s hydrothermal coefficient (HTC) are considered. This research was carried out annually on 40 fixed routes of 1 km each in the breeding period of the annual lark cycle from 2011 to 2019. It was established that the abundance dynamics trends were negative in four lark species, namely, the Calandra Lark (Melanocorypha calandra), the White-winged Lark (M. leucoptera), the Black Lark (M. yeltoniensis), and the Lesser Short-toed Lark (Calandrella rufescens); and were positive in the Skylark (Alauda arvensis). The calculated trend of HTC indicators for these territories demonstrates a 5.4% annual increase in the moistening of the semi-desert zone of our survey area. To assess the relationship of the density of different lark species to the values of the HTC, we calculated the Spearman correlation coefficients. When analyzing the data obtained, it was found that a high positive correlation of density with the HTC was observed for the Skylark, Calandra Lark, and Black Lark; no such relationship was found in the White-winged Lark, and a high negative correlation of the density of nesting pairs with the HTC was found in the Lesser Short-toed Lark. Based on our research, it can be assumed that moistening of the semi-desert territory is one of the main factors determining the abundance dynamics of larks. The heat–moisture ratio determines the level of vegetation and, accordingly, the quality of habitats for these land-nesting birds.

The Asian badger (Meles leucurus Hodgson 1847) is recorded from the right bank of the Volga River in the Khvalynsky District of the Saratov Region. This is the first report of this species from the Volga region's right bank Volga River beyond the Samara bow. Despite a significant number ofpublications devoted to the distribution of the Asian badger in the Vyatka-Kama and Volga regions, as well as ofstudies on the taxonomy of the genus Meles in Russia, the problem concerning the range limits of the European (Meles metes L. 1758) and Asian (M leucurus) badgers, and the zones of their sympatry in the region in question still remain not fully explored.

The paper considers the fact of the black woodpecker (Dryocopus martius L.) colonization of the Dyakovsky (Saltovsky) forest area, which occupies more than 18,000 hectares on the Yeruslan sands in the Saratov and Volgograd Trans-Volga regions. This forest area is located 25 km from the semi-desert of the Caspian lowland. According to our data, the black woodpecker appeared in the Dyakovsky forest in the winter of 2011–2012 after an extensive fire in the very hot summer of 2010. The mass of dead trees led to an outbreak of xylophagous development, which most likely led to the emergence of a settled population of the black woodpecker in the Dyakovsky forest. For 10 years, we have been conducting observations of the named population. Using the route method, parameters of its density in the winter period were determined, part of the nesting sites was identified, which confirms the year-round habitation and reproduction of the black woodpecker in the Dyakovsky forest. Our observations of the black woodpecker dispersal in the Trans-Volga region are consistent with the data of those authors who established the appearance of this species on the Lower Volga in the Volga-Akhtuba floodplain. In all likelihood, the black woodpecker dispersal in the Trans-Volga region is associated with both some change in the structure of habitats, with some increase in the abundance of this species in the main part of the habitat, and with other factors cited in this work. According to modern concepts, the location of habitats is determined by the “climatic space”, which is potentially suitable for the settlement of a particular species. Other factors interacting with the climate determine the actual development of the territory of this space by the species. Such facts of changes in the boundaries of the habitats of separate species as a result of climate change and factors interacting therewith are widespread in the world.

The paper presents data on the abundance of bobak marmot (Marmota bobak Müller, 1776), obtained from 1987 till 2019. All censuses were performed according to one technique developed by us in the late 1980s. During these long-term investigations, the structure of the bobak marmot areal in the Saratov region was studied. The dynamics of its numbers is described, and its trends for individual groups of districts were revealed, distinguished by trends, the time of the appearance of new settlements as a result of reintroduction after a prolonged depression in the numbers caused by both plowing of the steppes and the well-known events of the 1920s, 1930s and 1940s, when the bobak marmot provided the survival of some part of the population. It has been established that the population peak in the indigenous settlements that have been existing from the end of the Pleistocene–the beginning of the Holocene, was in 1980–1990. New settlements arise in the territories where the marmot was reintroduced, and the species abundance continues to grow. This, first of all, refers to the western slopes of the Volga Upland and the Oka-Don plain, formerly inhabited by marmots. An increase in the numbers of the Kazakhstan subspecies of the bobak is observed at the eastern end of the Syrt plain and on the spurs of the Common Syrt in the Saratov Trans-Volga region. The genetic studies of steppe marmots by R.V. Naumov (2019) on the right Volga bank of the Ulyanovsk region showed that a genetically homogeneous population lives on the vast territory of the Volga region. This casts doubt on the assumption of the existence of the Kozlovi subspecies of the bobak marmot in the local territories of the Voskresensk, Volsk and Khvalynsk districts of the Saratov region, which served as the ground for its inclusion into the new edition of the Red Data Book of the region, which we consider unreasonable (Resolution…, 2019).

The paper presents the results of our study of ecosystem diversity and the state of split-forest areas located in the Shchuchansky district of the Kurgan region. The species composition of forest stands, the productivity of tree species, the composition of underwood, brushwood and ground cover in plantations were analyzed. Data on the distribution of forest stands of various ages, composition, types of underwood and brushwood, as well as the main dominants of the ground cover are presented. Our studies have shown that forest communities are quite distinctly different in the nature of all storeys. A preliminary assessment of the economic impact on the territory of the site made it possible to identify significant changes in all the components of forest ecosystems, namely, ground cover, the composition and productivity of forest stands. The diversity of forest ecosystems in the study area is due to the ability of many plant species to inhabit a wide range of ecological conditions, as well as the composition, age and crowncontact, which, in turn, determines the nature of the storey of shrubs and ground cover. The volume of the forest type was taken quite large, it combined plantations of all age stages of forest stands development. Features of forest vegetation, typical for split forests of the Southern Trans-Urals, were revealed, namely: mosaic vegetation cover, low crown-contact and the presence of open spaces species in the lower storeys. The materials obtained showed that, despite the significant anthropogenic transformation, the forest ecosystems of the study area retained the main features characteristic of the peculiar vegetation of the forest-steppe of southern Siberia. The research results will make it possible to assess the diversity of forest ecosystems, to give a preliminary forecast of the dynamics of the site's vegetation and can be used in the development of a scientifically grounded strategy for forest management in the region under the conditions of the joint action of many natural and anthropogenic factors.

Results of the analysis of IRBP (interphotoreceptor retinoid-binding protein) nuclear DNA gene variability in birch mice of the genus Sicista reflect monophyly of the betulina group and confirm the substantial genetic isolation of the sibling species S. betulina and S. strandi within this group. Using Tamura’s 3‑parameter model T92, it is shown that the mean genetic distances between S. betulina and S. strandi are 0.7%, comparable to the interspecific genetic distances for sibling species from other groups of birch mice. Their intraspecific differentiation, which is particularly well-expressed in S. strandi, is also identified. Differentiation between the northern and southern populations of S. strandi, comparable to the interspecific differences (D = 0.8%), and isolation of the Carpathian specimen of S. betulina from other European and Siberian sample sets (D = 0.2%) are shown.

The dynamics of the numbers of larks inhabiting several areas differing in physical and geographical (landscape) conditions and the level of anthropogenic impact (pasture) on the natural environment is considered. Four key sites (“Akhmat”, “Zhdanov”, “Baiguzha”, and “Vetelki”) are located on the Priuzenskaya plain in the Aleksandrovo-Gaysky district of the Saratov region. The described territory is characterized by a high mosaicity of the facial structure of landscapes and, consequently, plant communities. This habitat diversity forms the structure of the communities as well as the population density of the individual lark species at the key sites surveyed. Our study of the dynamics of the numbers of species inhabiting the named key areas was carried out using calculations of logarithmic trends in the bird densities by the years of our study. In total, there were five species of larks ( Alauda arvensis, Calandrella rufescens, Melanocorypha calandra, M. leucoptera, and M. yeltoniensis ). As a result of our statistical processing of the obtained materials, significant differences were found in the dynamics of the numbers of individual lark species nesting in the key areas differing in landscape-ecological conditions and the level of anthropogenic load on ecosystems. In all likelihood, the dynamics of the density of the nesting lark population in the semi-desert of the Trans-Volga region is associated with both changes in the structure of habitats and, apparently, with the dynamics of the abundance of these species in the main part of their habitats, and with a number of other factors.

V.V. Dokuchaev’s ideas are the foundation of modern ideas about rational nature-usage methods in our steppes in order to ensure productive longevity of agro-ecosystems and agrolandscapes, to obtain high and sustainable yields. Agrolandscape-ecological zoning, analysis and assessment of the areas under study by the natural-economic areas of the southern European part of the Russian Federation (the Central Black-Earth Region, the Northern Caucasus, and the Volga region) were carried out with the aim to develop scientific bases for ensuring productive longevity of agrolandscapes in Russia. Scientific bases for providing the productive longevity of agrolandscapes and a system for assessing the status and management of agroecosystems and agrolandscapes in Russia have been developed. A balanced ratio of productive and protective ecosystems in the infrastructure of the agrolandscape (arable land, meadows, forests, and water bodies), grain, tilled crops and perennial grasses in the structure of sown areas and crop rotations is a prerequisite for creating an effective and sustainable agriculture. Systems of measures for managing agroecosystems and agrolandscapes include improving the structure of land areas, optimizing the structure of crop areas and improving crop rotation, improving farming systems, developing, implementing and optimizing norms for anthropogenic loads upon agrolandscapes in the whole and for individual elements of their spatial structure (arable land, pastures, hayfields, and forests), rational allocation of agricultural crops in the land use area, etc. Perennial grasses are the main source of carbon and nitrogen for replenishing humus reserves, as well as the main factor for protecting the soil from erosion. In the rational structure of the acreage, there must be a necessary and sufficient amount of perennial grasses and legumes (at least 20–25%) and a minimum one of clean fallows and row crops.