Are Climate Change and Introduced Fish Altering Demography and Reproductive Phenology of the Italian Smooth Newt?

Abstract Amphibians are a highly threatened vertebrate group, facing a global decline driven by habitat degradation, increasing droughts, and climate change. Long-term monitoring studies are essential for assessing population responses to these pressures, although these data are rare in Mediterranean contexts. In this study, we present the results of a 25-year capture-mark-recapture monitoring program of the Italian smooth newt Lissotriton vulgaris meridionalis population at four artificial ponds within a Natura2000 site in central Italy. We aimed to determine the long-term demographic trends and to assess the influence of an invasive predator removal and local environmental changes on demography and breeding phenology. Our findings revealed positive and sustained population growth over the monitoring period, which was particularly evident following the eradication of the invasive goldfish Carassius auratus from one of the ponds in 2010. Survival rates were consistently high for both males and females, and all tracked individuals exhibited strong site fidelity. While a slight trend towards an earlier breeding phenology was observed in the second decade of monitoring, the change was not statistically significant. This suggests that while the population shows resilience to direct threats and benefits from active habitat management, it may be beginning to show subtle responses to long-term climate-related pressures. This study highlights the effectiveness of targeted conservation interventions and underscores the importance of continued, long-term monitoring to detect population shifts facing a changing environment.