Habitat preference of Clethrionomys rufocanus in boreal Sweden

• A long-term decline of vole populations in boreal Sweden, especially of the grey-sided vole (Clethrionomysrufocanus Sund.), has been revealed by snap-trapping in 1971–2004. We identified important habitats forthe grey-sided vole by mapping the distribution of cumulated number of reproductive females in 1971–1978, prior to the major decline in the 1980s. Mean abundance of C. rufocanus was higher in the western(inland) than eastern (coastland) part of the study area. As the inland appeared to represent the most, as faras we know, pristine, abundant part of the population, we based identification of high quality habitats oninland data only. Four habitats were more important than others and yielded nearly 86% of the reproductivefemales in spring: (1) forests of dry, (2) moist and (3) wet/hydric dwarf-shrub type, in addition to (4)forest/swamp complexes rich in dwarf-shrubs. The latter three habitats were used more frequently thanexpected from their occurrence in the landscape. Still, the variation in density of reproductive femaleswithin patches of the same habitat was frequently high. This suggested that habitat composition in thesurrounding landscape, perhaps may have affected local vole density at the patch scale. Clear-cut samplingplots appeared to be low-frequently used by reproductive females, but also by males and immatures. Inconclusion, our study indicated the importance of also studying habitat at a larger scale than that of thepatch to get a deeper understanding on how habitat influences local and regional densities and populationdynamics of C. rufocanus.

Nyckelord

habitat patches

habitat quality

immatures

landscape design

local habitat

reproductive females

reproductive males

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