Regional variation in the size of the common shrew Sorex araneus in Norway

Abstract

We analyzed variation related to region, age, and sex in the length and height of the mandible of the common shrew Sorex araneus in Norway (n = 261), with some notes on the length of the tail and on the body weight. Specimens were classified by four age groups according to their date of capture, tooth wear, and reproductive status. Shrews from Finnmark (northernmost Norway) were about 3 % smaller in the two mandible dimensions than shrews from Hordaland (southern Norway), while only minor or no differences were found between the two major samples from Hordaland. Juveniles were, on average, 2 - 3 % smaller than overwintered adults. In no measurements were males larger than females, but statistical significant sexual dimorphism was found only in body weight. A general deterioration of the climate and habitat quality may be found with increasing latitude, but local gradients (e.g. lowland towards alpine regions) could be equally important for the size of the common shrew.