RESUMO
BACKGROUND: Pelobates fuscus is an anuran amphibian that overwinters on land deep in soil, including regions with low sub-zero temperatures. It is not yet known if such behaviour can be explained by low cold-hardiness of the species. OBJECTIVE: To measure cold-hardiness of P. fuscus and compare the results with data about its location in winter in nature. METHODS: Lower lethal temperatures and supercooling points (SCP) were measured in specimens collected near the Saratov city in south-eastern European Russia. RESULTS: SCP of P. fuscus range from -1.7 to -2.7°C. All individuals withstood exposure of 1°Ð¡ for 20 days; but freezing is lethal to animals: one individual out of five withstood exposure of -1°Ð¡ for 3 days, and -2°Ð¡ is lethal to all animals. The condition of supercooling is unstable. CONCLUSION: The lower tolerable temperature is probably about 0°Ð¡. Low cold hardiness determines overwintering deep in substrates, which allowed the species to disperse over a large geographical range, which also includes cold regions with little snow in winter.
