Monitoring amphibians in a changing climate: conservation assessment of Natterjack Toad Epidalea calamita using ecoacoustics

Amphibians are experiencing global population declines, with the Natterjack Toad Epidalea calamita facing significant range contraction and breeding failures across its European range. Effective conservation of this priority species requires robust, long-term monitoring, yet traditional survey methods are often labour-intensive and limited in scope. This study presents the first application of passive acoustic monitoring (PAM) to assess Natterjack Toad breeding activity. Acoustic recorders were deployed at multiple breeding ponds within the Caerlaverock Wetland Centre, Scotland, over three seasons (2022–2024). Acoustic data revealed consistent diel patterns, with peak calling activity around 22:00, and a seasonal peak between late April and mid-May. Interannual variation in calling onset and intensity was observed, likely influenced by temperature and rainfall. Spatial variation in call detections highlighted key breeding sites and local differences in habitat suitability. Due to weather patterns and resourcing limitations, traditional surveys detected minimal evidence of breeding activity, preventing statistical correlation with acoustic data; however, this disparity underscores the value of PAM in detecting presence and breeding behaviour when other methods are constrained. Our findings demonstrate that PAM is a scalable, non-invasive tool capable of capturing fine-scale temporal and spatial patterns in amphibian activity. This approach offers significant potential for long-term monitoring, particularly under changing environmental conditions, and should be integrated into conservation strategies for Natterjack Toad and other threatened amphibians.