Фенология начала нерестовых миграций бесхвостых амфибий (Anura, Amphibia) в долинах рек Саратовского Правобережья

Abstract

The intra-century dynamics of the spawning migrations start of the three most numerous species of anuran amphibians (Pelobates vespertinus, Bombina bombina and Pelophylax ridibundus) was analyzed. Local populations of the above anurans in the valley of the middle course of the Medveditsa River (Don Basin, Saratov region) were the object of the study. From 1892 to 2023 the phenological norm of this phase of the annual cycle shifted to earlier dates by an average of 7 days for each species in a climate warming. By 2023, the henological norm of the spawning migration start of P. vespertinus, B. bombina and P. ridibundus was April 14, April 21, and April 22, respectively. In addition, the change rate of this phenological parameter in the model species was similar as well, about 8 days/100 years. The absolute value of the phenological norm change, as well as the rate of its transformation, is comparable among the three species of anuran amphibians, despite any differences in their thermobiological characteristics. The early snow clearence in the Northern Lower Volga region may be one of the reasons for shifting the start dates of amphibian spawning migrations to earlier dates. The continued phenological changes in the spring phase of the annual cycle require continued monitoring of this process. This will allow forming scientifically based forecasts of local population dynamics in the future. Possible consequences of this transformation of the spring phenology of anuran amphibians are increased probability of metamorph survival in low water availability in the floodplain, and spawning migration development in the false spring scenario and susceptibility to return cold weather. This is discussed in relation to the changes identified.