Body size, population structure and fecundity traits of a Salamandra atra atra (Amphibia, Urodela, Salamandridae) population from the northeastern Italian Alps

The ecology and population structure of Salamandra atra atra was analysed i n 1996 in a mountainous area (1100 m a.s.l.) in the Alps of NE Italy (Sella Nevea, Friuli). A total of 148 salamanders was found, males and females re presenting 51.7% and 48.3%, respectively of the adult population, and thus not differing respectively from the expected 1:1 sex-ratio. The final ratio between juveniles and adults was 0.25. Snout-vent length +/- SD of adult m ales was 74.9 +/-7.5 mm, and that of adult females was 76.0 +/-7.7 mm. Sixt een females considered to be pregnant were taken into captivity. Of these o nly four were non-gravid. All the other females gave birth to a single juve nile after a mean period of 7.5 months. This result deserves particular att ention, since until now S. atra was said to give birth almost invariably to two young. There was no significant relationship between maternal and off- spring snout-vent length. The presented data are discussed in the light of adaptation to Alpine environments and compared to those obtained from other population of S. atra and from S.a. aurorae and S. lanzai.