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

TL;DR

This study shows that estavelle springs in the Classical Karst Region are important habitats for amphibians, especially for shelter and feeding.

Contribution

The paper provides the first detailed assessment of amphibian use of estavelle springs in the Classical Karst Region.

Findings

Over two-thirds of surveyed springs exhibited estavelle behavior at least once.

Amphibian presence was linked to low water flow, habitat complexity, and absence of predators like pike.

Estavelles serve as shelters for surface-dwelling amphibians and feeding sites for subterranean species.

Abstract

This study explores how amphibians use springs, especially estavelles, in the Classical Karst Region. Estavelles are springs that can also act as sinkholes or ponors when water levels drop. Despite their importance, little is known about amphibian use of these habitats. The research surveyed 61 springs from June 2020 to January 2025, recording amphibian presence, breeding stages, and environmental factors such as water flow, habitat features, and predators. Results showed that over two-thirds of springs exhibited estavelle behavior at least once. Five amphibian species were identified, with some regularly found in springs for movement and breeding, while others used them temporarily. Amphibian presence was strongly linked to springs with low water flow, habitat complexity, and absence of predators like pike. The findings suggest that estavelles and surrounding areas serve as important shelters and feeding sites, especially for frogs. Overall, the study highlights the ecological importance of estavelles for amphibian survival, providing valuable insights for the study and conservation of neglected animals in karst landscapes.

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.

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