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Validation of the post-hoc method to estimate snout-vent length in the order Caudata

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  • Simone Marzocca,
  • Eleonora Cialente,
  • Maria Rachele Pierorazio,
  • Luca Coppari,
  • María Torres-Sánchez,
  • David A. Beamer,
  • Enrico Lunghi
Simone Marzocca
Dipartimento di Medicina clinica, sanità pubblica, scienze della vita e dell'ambiente, Università dell’Aquila, Piazzale Salvatore Tommasi 1, 67010, Coppito, L’Aquila, Italia.
Eleonora Cialente
Dipartimento di Medicina clinica, sanità pubblica, scienze della vita e dell'ambiente, Università dell’Aquila, Piazzale Salvatore Tommasi 1, 67010, Coppito, L’Aquila, Italia.
Maria Rachele Pierorazio
Dipartimento di Medicina clinica, sanità pubblica, scienze della vita e dell'ambiente, Università dell’Aquila, Piazzale Salvatore Tommasi 1, 67010, Coppito, L’Aquila, Italia.
Luca Coppari
Dipartimento di Medicina clinica, sanità pubblica, scienze della vita e dell'ambiente, Università dell’Aquila, Piazzale Salvatore Tommasi 1, 67010, Coppito, L’Aquila, Italia.
María Torres-Sánchez
Dipartimento di Medicina clinica, sanità pubblica, scienze della vita e dell'ambiente, Università dell’Aquila, Piazzale Salvatore Tommasi 1, 67010, Coppito, L’Aquila, Italia.
David A. Beamer
Graduate School of Human and Environmental Studies, Kyoto University, Yoshida Nihonmatsu-cho, Sakyo, Kyoto, Japan
Enrico Lunghi
Dipartimento di Medicina clinica, sanità pubblica, scienze della vita e dell'ambiente, Università dell’Aquila, Piazzale Salvatore Tommasi 1, 67010, Coppito, L’Aquila, Italia.
DOI: https://doi.org/10.36253/a_h-18890

Published 2026-01-16

Keywords

  • SVL,
  • measure,
  • post-hoc method,
  • salamander,
  • Urodela,
  • photograph,
  • dorsal
    • ...More
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How to Cite

Marzocca, S., Cialente, E., Pierorazio, M. R., Coppari, L., Torres-Sánchez, M., Beamer, D. A., & Lunghi, E. (2026). Validation of the post-hoc method to estimate snout-vent length in the order Caudata. Acta Herpetologica. https://doi.org/10.36253/a_h-18890

Copyright (c) 2026 Simone Marzocca, Eleonora Cialente, Maria Rachele Pierorazio, Luca Coppari, María Torres-Sánchez, David A. Beamer, Enrico Lunghi

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

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Abstract

Validation of the post-hoc method to estimate snout-vent length in the order Caudata

Abstract. Amphibians are the most endangered class of vertebrates, with a high rate of decline recorded since the 20th century. Even activities related to the study of these animals for informing conservation actions, for instance by handling them to collect biometric individual parameters, can have negative effects on the amphibians’ health. A post-hoc method that estimates snout-vent length from dorsal photographs has been developed to reduce handling time and stress to individuals, providing additional advantages in precision and repeatability of measurements taken. However, at present, this methodology has been tested only on approximately 1% of the known salamanders, thereby limiting its broad application. Here, we tested this method on a diverse sample of Caudata that includes 25 species across 5 families and characterized by different morphologies. The correlation between predicted SVL (estimated from dorsal photographs) and observed SVL (measured directly from ventral photographs) values was assessed using Linear Mixed Models. The results showed a significant correlation between observed and predicted SVL, with an average and constant discrepancy of about 1.6 mm. When considering the increase of SVL, there was a slight tendency to underestimate SVLe in newts, plethodontids, and proteids. Estimation errors slightly increased with the SVL. The error increased in larger newts, while decreased in larger plethodontids. Our study highlighted the reliability and applicability of adopting this methodology for data collection in all Caudata species.

 

Keywords. SVL, measure, post-hoc method, salamander, Urodela, photograph, dorsal.

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