False spring in the spawning migrations of Spadefoot toads (Pelobates, Anura): Distribution in the European Russia and the phenomenon scale in 2020

Abstract

The 2020 spring processes in the European Russia were developing according to the type of false spring. The absence or weak development of snow cover, as well as its early descent in the last decade of February, determined the rapid warming of the soil profile. A certain complex of meteorological factors led to an abnormally early start of spawning migrations of the common spadefoot toad (Pelobates fuscus (Laurenti, 1768)) and Pallas's spadefoot toad (Pelobates vespertinus (Pallas, 1771)) over a vast territory which included the northwestern, western, central and southeastern parts of the species habitat in the region. Analysis of the snow cover dynamics and the temperature course according to the data of the network of meteorological stations made it possible to assess the phenology of these species of anuran amphibians within this region using the method of reconstructing the reproductive period events of the spadefoot toads. The duration of the period between the start dates of false and true spawning migrations was more than 40 days in the west, in the center and in the south-east of the European Russia. The abnormally early formation of the 2020 false spring phenomenon in the spawning migrations of spadefoot toads is currently registered as a precedent which may have a significant impact on the reproduction success of the species of this genus.