European plethodontid salamanders on the forest floor: Local abundance is related to fine-scale environmental factors

Understanding habitat selection by animal populations is one of the most relevant topics in ecology. In this study, we analyzed fine-scale habitat selection in a population of the salamander Speleomantes strinatii living in a Mediterranean forest environment. We used repeated surveys to estimate salamander abundance on 40 plots (12 m2) by applying hierarchical models to repeated count data. In addition, we estimated seven habitat variables for each plot to infer the relationships between local factors and salamander abundance. The salamander population showed a patchy distribution; higher abundances were found in plots with a prevalent North aspect and with a high number of rocks lying on the forest floor. Conversely, there was a negative influence of superficial water runoff on salamander abundance. Our results demonstrate that fine-scale environmental factors, mainly related to the physiological constraints of the salamanders, shape local abundance even in apparently suitable environments. Finally, the overall estimate of 0.86 individuals/m2 (95% CI 0.34-1.08) was similar to one obtained in a similar environment with removal sampling, suggesting efficiency of N-mixture modelling to estimate abundance of European plethodontids.