Importance of Spring Habitats for Amphibians: The Case of Estavelle Ecotones in the Classical Karst Region

Springs are ecotones between groundwater and surface water, important for a variety of both surficial and subterranean organisms. However, their use by amphibians has been poorly assessed. This is evident considering estavelles, typical ecotones functioning not only as spring but also as sinkholes. Here we aim to assess the use of estavelles by amphibians in the Classical Karst Region. From June 2020 to January 2025, we surveyed 61 springs, both during day and night. We visually recorded the occurrence of amphibians, along with abiotic and biotic features-including the presence of pikes (Esox cisalpinus), water flow level, drying events, and substratum heterogeneity. Forty-three springs exhibited estavelle-like hydrological behavior at least once. We identified five amphibian species. The use of springs was frequent for Proteus anguinus, Rana latastei, and Pelophylax sp. Amphibians' occurrence was significantly linked to non-perennial estavelles characterized by low water flow, habitat heterogeneity, and absence of pike. Overall, reproductive activity in estavelles was limited; breeding likely occurs in nearby damp lentic habitats connected to the springs. Our results provide the first herpetological assessment of estavelle spring habitats in the Classical Karst Region, emphasizing their role as shelters for epigean species and feeding patches for stygobionts.