Distributional ecology in the shrews Sorex araneus L. and Sorex minutus L. in western Norway

Abstract

Relative abundance and distribution of Common and Pygmy Shrews in Hordaland county, western Norway, were studied at a number of sites along a coast-inland gradient by examining museum collections, and by trapping. Pygmy Shrews were found at all sites except one inland, while Common Shrews were lacking at two of the most western sites. A dramatic reduction in the percentage of Pygmy Shrews was found towards the interior, ranging from 80.9% on the outermost islands, 42.0% along the coast, and 2.2% inland. Pygmy Shrews were most abundant in poor habitat (habitat quality was subjectively evaluated from the diversity and richness of vegetation). A shift in body length between sympatry and allopatry was found in both species, increasing the difference between them in sympatry. At one site where they coexisted or were caught in about the same numbers, habitat segregation between the two was not very apparent. Habitat quality influenced the weight, but not size, of Common Shrews along an altitudinal gradient. Habitat type and quality probably control the distribution of the Common Shrew, but the abundance of Pygmy Shrews may be controlled by Common Shrews.