Effective citizen science implementation reveals ecological and conservation insights for two amphibian species

Amphibians are the most endangered group of vertebrates, facing numerous threats, and detailed data are required to identify stressors and prioritize conservation efforts. While these data exist for many species, gaps remain, especially in understudied regions. Citizen science is an approach that can vastly increase the available data for informed decision-making. This study aims to use such an approach to investigate the population dynamics of two amphibian species in urban environments. We used the program MARK to perform a capture-mark-recapture analysis on two datasets: a large dataset collected in a multiyear citizen-science program, focused on two urban near eastern fire salamander (Salamandra infraimmaculata) populations, both found within a large city; and a second dataset, collected in a 1-year survey, focused on two green toad (Bufotes sitibundus) populations in an urban park and in a nearby nature reserve. Individuals of both species have unique patterns of dorsal spots, allowing for noninvasive recapture identification. Using repeated measurements of recaptured salamanders, we derived a species-specific growth curve that converts body length into an age estimate. Combined with a survival analysis of the capture–recapture dataset, this age estimate revealed a prolonged period of increased vulnerability during the salamanders' terrestrial phase, from metamorphosis until they reach full size. Additionally, the two case studies suggest that exotic fish introduction can have highly detrimental impacts on these amphibian species and should be the focus of future studies.