Sexual dimorphism in body size and life-history traits in a population of Triturus alpestris alpestris

Although female urodeles are normally larger than males, mechanisms causing sexual dimorphism in body size are not yet extensively documented. In the Trituruus alpestris alpestris population of Hocmolbing, located at high altitude in the northeastern calcareous Alps of Austria, females are significantly longer and heavier than males. To elucidate proximate determinants of size differences in this population, newts that had died of a sudden frost at the beginning of the 2001 breeding season, were collected and the adults' age and growth patterns were evaluated by skeletochronology. Females proved significantly older than males, attaining sexual maturity one year later, but they did not differ in adult growth rate. The results showed that in this population of T. alpestris, sexual size dimorphism is due to differences both in age structure and the timing of sexual maturation.