Does quality of winter food affect spring condition and breeding in female bank voles (Clethrionomys glareolus)?

Abstract

:We studied the effects of food supplementation on 16 bank vole populations in spring. We manipulated food quantity and quality in eight populations that were enclosed and eight other populations that were free-ranging on forest grids. The enclosed populations received large amounts of sunflower seeds, as high-quality food (four enclosures) or barley seeds, as low-quality food (four enclosures). Four of the open populations were supplemented with small amounts of spruce seeds, and four served as non-supplemented controls. Effects of differential food quantity and quality on overwintering weight of individual females and on spring litters were monitored by live-trapping. Pregnant females were removed to the laboratory for parturition and to record pup number and weight. Female body mass at the onset of breeding was highest in enclosures with high-quality food. Females from both enclosure treatments with a large quantity of food were heavier than females from open grids. The litters from enclosures supplemented with high-quality food tended to be one pup larger and grew faster than those from the low-quality food enclosures. Litter size of females of the non-supplemented forest plots did not differ from that of the spruce-seed-supplemented plots or from the enclosure females. In general, quantity of winter food may affect female body weight in spring, but quality of food appeared to have a positive effect on litter size and early growth of pups.