Estimation of the body condition of European cave salamanders (genus Speleomantes) from digital images
2025
Eleonora Cialente | Ben Oetken | Luca Coppari | Enrico Lunghi
Species monitoring is a key activity for conservation studies. Some of the monitoring methods require individual handling, which may provoke negative effects on animal fitness. We here present a new non-invasive method that allows to estimate the body condition of the European cave salamanders (genus Speleomantes) using the tail area as a proxy, since these species usually accumulate fat tissue in their tail. We selected 915 high-quality images of individuals belonging to the eight Speleomantes species. Using the ImageJ program we calculated the tail measurements (length and area) from which we obtained the Fat Tail Index (FTI). The FTI was then correlated with the Scaled Mass Index (SMI) of individuals. We used GLMM to assess whether SMI is correlated to FTI, individual sex, species identity and the type of inhabited environment. We observed a significant correlation between SMI and FTI (R2 = 0.62). The GLMM analysis showed a significant effect on SMI due to sex, species and the type of environment. Females and individuals from surface environments showed the highest SMI. Among species, we observed a significant variability in their body condition and in the correlation between SMI and FTI. This study provided a reliable and non-invasive method that allows to estimate the body condition for terrestrial salamanders of the genus Speleomantes.
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