Vole diet on experimentally managed reforestation areas in northern Sweden

In northern Sweden two field experiments with the reforestation techniques soil scarification, ploughing, burning and grass herbicidal treatment were performed. Small rodents were trapped regularly on the managed plots and their stomachs were examined microscopically for diet composition. Both bank voles Clethrionomys glareolus and field voles Microtus agrestis were common on the reforestation areas while only a small number of grey-sided voles Clethrionomys rufocanus were taken. All three species underwent a population cycle during the studies. The management techniques generally resulted in small and irregular effects on the food selection. The most pronounced changes were lower intake of grasses by M. agrestis after herbicidal treatment and of filamentous tree lichens by C. glareolus after most treatments.
Both bank voles and field voles ate predominantly forbs in the summer half of the year, whereas the field voles took also a considerable amount of grass. As a complement to green vegetable-matter bank voles ate berries and fungi in summer-autumn and tree lichens at other times of the year, but seeds and animals food only in very small amounts. Ail three species consumed large quantities of dwarf-shrubs in autumn and especially in winter. Considerable amounts of bark were eaten by field voles and a smaller proportion by bank voles in autumn-winter.
Both for bank and field voles there were indications of worsening food conditions as the population cycle went on, There were, for example, an increase in grass and bark intake in field voles and a decrease in seeds and berries for the hank vole.