Twenty years’ monitoring of a population of Italian crested newts Triturus carnifex: strong site fidelity and shifting population structure in response to restoration

Abstract

Human-induced environmental alterations, e.g. the introduction of alien species and the application of management practices, together with climatic change, represent the main threat to worldwide amphibian conservation. Long-term monitoring programmes are mandatory to monitor the status of amphibian populations in changing landscapes and climatic conditions. In this study, we showed the population dynamic of the Italian crested newts Triturus carnifex living in four artificial ponds in Central Italy over a 20-year period. Adult newts were recognised through a capture-mark-recapture protocol, involving the analysis of belly patterns. The first best population model showed a constant newt survival among years and a complete recapture rate; the second supported model showed a sex-dependent survival, with slightly higher values for males with respect to females, and corroborated a complete recapture rate. A high philopatry occurred: we observed less than 10% of individuals dispersing from a birth site to other ponds. In 20 years of continuous monitoring, the population of Italian crested newt increased. The removal of goldfish Carassius auratus from one of the ponds in 2010 allowed adult newts to overwinter within the pond and to have two reproductive periods, with overwintering larvae after the second spawning.

KEY WORDS:

• alien species impacts
• amphibian decline
• belly pattern
• capture-mark-recapture
• Carassius auratus
• long term monitoring

Acknowledgements

Newts were captured with permissions by the Ministry of the Environment (prot. 0006222) and the Province of Grosseto (prot. 0030326), as well as the agreement by the National Institute for Environmental Research (ISPRA, prot. 0048780) and the Societas Herpetologica Italica (SHI, prot. 0047321). The authors thank Alice Giovani, Mattia Ricci, Lee Kats, Andrea Vannini and Michele Zago for their valuable help in the collection and analysis of data. Jan Willem Arntzen and Leonardo Ancillotto kindly provided us with useful suggestions and comments on the first draft of this manuscript. Vasco Sfondrini kindly took the time to read and correct English grammar and syntax, markedly improving the readability and the fluency of the manuscript. To finish, the comments of two anonymous referees improved greatly our manuscript. This work is dedicated to the bright memory of Enrico Romanazzi, who spent his research life to promote the conservation of amphibians in north-eastern Italy.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed at https://doi.org/10.1080/03949370.2016.1236040