Growth and size of Triturus vulgaris and T. cristatus (Amphibia) in different parts of Norway

The growth and size of the newts, Triturus vulgaris (L.) and T. cristatus (Laurenti) in different parts of Norway (+ Jämtland, Sweden) were studied. Age was estimated from skeletal growth marks, size‐frequency histograms and, for the males, from the number of testis lobes. On average, the T. vulgaris Larvae in central Norway and Jämtland are smaller than those in southeastern Norway, although in good localities, at the same altitude, they are of approximately the same size and complete their development already within 2½–3 months. Larvae living in eutrophic habitats are larger than those in oligotrophic‐dystrophic habitats. In bog habitats at similar times of year the T. cristatus larvae from central Norway are about the same size as those from similar habitats in southwestern and southeastern Norway, but somewhat smaller than those from eutrophic ponds in the Oslofjord area. No significant differences in the mean size of adult T. vulgaris from southeastern Norway and from central Norway were found. The maximum lengths attained were recorded from central Norway, however. In eutrophic habitats T. vulgaris adults BK usually larger than those in oligotrophic/dystrophic habitats. In southeastern Norway, where growth is rapid, T. vulgaris may become sexually mature when 2+ yr‐old, in central Norway usually a year later, in Jämtland. on average, still later, and in their northernmost locality (Vefsn) they probably do not breed until 5+ or 6+ yr‐old. On average, T. cristatus adults from southeastern Norway are slightly larger than those from central Norway, and may become mature at 2+ yr‐old. compared with 4 + yr‐old, at the earliest, in the latter area. The differences in the growth rates of both larvae and metamorphosed stages, of both species, most probably represent a response to climatic differences, although biotope quality is also an important factor.