Decrease in the Population of the Small Ground Squirrel Spermophilus pygmaeus Pallas, 1779 (Rodentia, Sciuromorpha, Sciuridae) in the Volga–Ural Steppe Natural Focus of Plague

The results of our study of a small ground squirrel (Spermophilus pygmaeus Pallas, 1779) population on the territory of the Volga–Ural interfluve between 1940 and 2023 are presented. The influence of global warming on the population dynamics of this species in the Volga–Ural steppe natural plague focus is considered. Data from the annual censuses of the small ground squirrel abundance (number of individuals per hectare), indicators of reproduction intensity, and the average monthly air temperature indicators at weather stations in the town of Kharabali for the period of 1940–2023 were statistically processed and analyzed. It is emphasized that the population dynamics of this species is determined by a whole complex of natural and anthropogenic factors. Meanwhile, in semi-desert conditions, the limiting factor for the small ground squirrel population is the distribution of air temperature and precipitation over seasons and years. This study assesses the influence of temperature in January–February, which provokes emergence to the surface when small ground squirrels awaken from hibernation. The main mechanism determining the negative impact of modern climate warming on the small ground squirrel population in the Northern Caspian Sea region has been established.