The post hoc measurement as a safe and reliable method to age and size plethodontid salamanders.

Enrico Lunghi,Raoul Manenti,Gentile Francesco Ficetola,Claudia Corti,Joseph Gavin Bradley,Yahui Zhao,Simone Giachello

doi:10.1002/ece3.6748

Abstract

The worldwide biodiversity crisis with the resulting need to increase species protection has led researchers to pursue and select survey methods that guarantee the best quality of data and produce the least negative effects on wild animals. Plethodontids are the most diverse family of salamanders; all species are very sensitive to human handling and noninvasive, but accurate, measurement methods are needed to reduce researchers’ impact. Here, we tested the reliability of a noninvasive post hoc method in estimating the snout–vent length (SVL) from photographs showing salamanders’ dorsal view. The correlation between the estimated snout–vent length (SVLe) and the conventional SVL was high (R 2 m = .81), and no significant difference occurred between operators with different experience. Finally, we list the numerous advantages for the use of SVLe in terms of data quality and in reducing the stress caused to wild animals.

Highlights

Earth is experiencing the sixth mass extinction (Barnosky et al, 2011), an event widely exacerbated by human actions (Ceballos et al, 2015)
We tested the reliability of a noninvasive post hoc method in estimating the snout–vent length (SVL) from photographs showing salamanders’ dorsal view
We list the numerous advantages for the use of snout–vent length (SVLe) in terms of data quality and in reducing the stress caused to wild animals

Summary

| INTRODUCTION

Earth is experiencing the sixth mass extinction (Barnosky et al, 2011), an event widely exacerbated by human actions (Ceballos et al, 2015). The most common method used to measure salamanders is snout–vent length (SVL), a method that requires handling individuals. SVL aids in distinguishing life stage and size in salamanders; SVL can be used to differentiate adults from juveniles by using the smallest sexually mature adult as a reference (Lanza, Pastorelli, Laghi, & Cimmaruta, 2006) This method is useful for differentiating between life stages of plethodontid salamanders with direct development because adults and juveniles exhibit few other morphological differences (Wells, 2007). Each survey can last only for a defined time and there are limited chances to spot errors accrued during data collection This increases the risk of obtaining inaccurate or even useless data (Brown, Kaiser, & Allison, 2018; Lunghi, Romeo, et al, 2019; Margenau, Crayton, Rucker, Jacobsen, & Brown, 2018). We provide an estimation of the errors occurring among and within individuals’ measurements

| MATERIALS AND METHODS

| DISCUSSION

Findings

| CONCLUSIONS