Demographic Structure of the Volga-Ural Population of Saiga Antelopes (Saiga tatarica (Linnaeus, 1766)) (Bovidae, Mammalia) Migrating to the Saratov Trans-Volga Region

The demographic structure of the Volga–Ural population of saigas migrating to the Saratov Trans-Volga region is shown. It was established that animals from the West Kazakhstan region (Republic of Kazakhstan) appear in the border areas of the Saratov Trans-Volga region in the second and third ten-day periods of April, depending on the weather conditions of specific years. At the end of May, migration mainly ends, and the animals split into groups and spread across a number of areas in the Saratov Trans-Volga region. According to our observations and survey data, between 2011 and the early 2020s, the number of saigas entering the Saratov Trans-Volga region in spring ranged from several thousand to tens of thousands. In recent years, as the entire population has grown, this figure has increased to several hundred, and in 2025, to many hundreds of thousands of individuals. According to our observations, both females with calves born in Kazakhstan and pregnant and barren females migrate to the region. The number of males migrating together with herds of females is small. At the beginning of migration in 2025, the number of yearlings per adult female was 0.9 individuals, but this reproductive rate increased to 1.6 individuals in the third ten-day period of June. This fact indicates the calving of female saigas in the Saratov Trans-Volga region, which is confirmed by our survey data. In the last ten-day period of July, when the entire territory of saiga distribution in the Saratov Trans-Volga region was surveyed, this index was 1.5 individuals. Most likely, this fact could be explained by mortality of yearlings. The number of adult males increases from 2.3% in the first ten days of May to 6.7% in the third ten days of June and to 8.3% in the third ten days of July. From these data, we can conclude that the migration of males is spread out over time, but most of them remain in Kazakhstan, which is confirmed by our observations during expedition trips to the West Kazakhstan region in 2011–2019 along the Zhanybek–Aral-Sor and then Zhanybek–Borsy routes.