Dataset summarising observations of amphibians in estavelles springs

The dataset summarises observations of amphibians performed in springs and estavelles of the Classic Karst region (NE Italy). From June 2020 to January 2025 we performed repeated surveys in all the months of the year, August excluded, both during day and night, in 61 springs sites. We considered springs occurring in the four poljes that were likely to have the typical hydrological regime already described for estavelles. In each site the occurrence and breeding of amphibians was assessed visually by inspecting for at least 10 minutes all the possible shelters including the elements of the substrate. At each survey, for each spring, we recorded abiotic and biotic features that can be important in explaining amphibians’ use of aquatic sites. As abiotic features we recorded the maximum water depth, the intensity of water flow, if the site was emitting or absorbing, the morphology of the spring mouth, diversification of substrate, which can reflect the abundance of shelters. Water flow was differentiated in four categories by the same observer: 1= absent, 2= just occurring, 3= moderate, 4 =strong. Diversification of substrate was based on microhabitat heterogeneity, considering the percent cover of sediments (including organic matter) which was classified as follows: 1, no diversification, one single substrate element covering almost entirely the site; 2, poor diversification, occurrence of two different substrates that added together covered>90% of the spring; 3, quite diversified, at least three elements on the substrate, each of which covering 20-40% of the spring habitat; 4, highly diversified, four or more elements including leaves and branches. As biotic features we recorded the occurrence of aquatic and semi-aquatic macrophytes and the occurrence of individuals (both juveniles and adults) of the pike (Esox cisalpinus) which is the top predator fish of the system investigated.