Abstract (eng)
Four out of eight amphibian species inhabiting the Exelberg-ponds on the outskirts of Vienna are listed as “near threatened” (Bufo bufo, Rana dalmatina, Rana temporaria and Ichthyosaura alpestris). Hyla arborea, Pelophylax ridibundus, Triturus carnifex and Lissotriton vulgaris are categorized as “vulnerable” (Austrian Red List 2007). The time of migration at the Exelbergstraße was correlated with the first sightings of clutches in the ponds on March 13th 2012. All 14 ponds were used as oviposition sites and successful reproduction was recorded in all of them. The agile frog (Rana dalmatina) bred in 13 of 14 ponds (except pond 1). The most clutches were laid by the common frog (Rana temporaria). When Rana dalmatina and Rana temporaria were breeding in the same pond, one of the two species gained dominance over the other, varying from pond to pond. Most of the egg strings of the common toad (Bufo bufo) and clutches of Rana temporaria were found at pond number 2, which was the largest and deepest of the water bodies located in the south of the area. It was the only pond in which Bufo bufo tadpoles successfully underwent metamorphosis. The rarest amphibian species in the area was Hyla arborea, the European tree frog. Compared to the study of SCHEDL & PINTAR (2008), this vulnerable species has declined. The most significant predators of amphibian larvae in the ponds were dragonfly nymphs (Anisoptera). They highly influenced the survivorship of the tadpoles and newt larvae. Ideal breeding ponds were warm, exposed to the sun, rich in vegetation and located at the “Lange Wiese”. Tadpoles in these kinds of ponds were larger and heavier than tadpoles in shadier ponds and showed significant higher scaled mass indices than tadpoles in ponds 3 and 4 (Mann-Whitney U; p<0.001). Breeding ponds at the Lange Wiese were preferred by most of the species. Possible explanations for this are higher water temperatures, higher oxygen levels and the greater variety of food sources. The newts Lissotriton vulgaris, Ichthyosaura alpestris and Triturus carnifex were unable to reproduce in any of the shady, temporary ponds (3, 4, 5).