Energy storage in salamanders' tails: the role of sex and ecology.

In vertebrates, the main tissue devoted to energy storage is the adipose tissue. In salamanders, energy reserves can also be stored in the adipose tissues of the tail. Therefore, we evaluated if energy storage in salamanders' tails is related to individual body condition, life cycle and environmental constraints. We calculated a scaled measure of tail width for 345 salamanders belonging to six Mediterranean taxa exhibiting wide phylogenetic, behavioural and ecological variation. We related this measure to the Scaled Mass Index (SMI), a body condition index which reliably predicts body fat. We found significant relationships between the SMI and scaled tail width in the terrestrial Spectacled salamander and Alpine salamanders, independently of sex. At the same time, we found that energy storage in the tail is maximum in Alpine Salamanders, which experience reduced activity periods and restricted access to resources. Conversely, we found a significant effect of sex in Imperial cave salamanders, where females store reserves in the tail to counterbalance resource investment in parental care, and in Corsican Brook Newts, where the reproductive function of males' tails may imply a greater tail width. Finally, in the biphasic Great Crested Newt, tail width was not related to SMI in both sexes.