Effect of protein and birch-bark powder on selection of food by root voles (Microtus oeconomus)

Abstract

We tested the effect of levels of protein and birch-bark powder on selection of food by root voles (Microtus oeconomus). In the first set of cafeteria trials we offered voles pellets containing 3, 6, or 12% protein. Voles having no previous experience with this type of food did not show a preference among levels of protein during the first two trials, but strongly preferred the highest (12%) level of protein in the two subsequent trials. This suggests a learning process based on a physiological feedback mechanism. In the second set of trials, addition of 10% birch-bark powder to the protein pellets did not change the pattern of selection among the three protein levels. In the third cafeteria experiment, voles were offered pellets containing 6% protein and different concentrations (0, 2, 5, 10, and 20%) of birchbark powder. The higher the concentration of birch-bark powder, the less the pellets were eaten. The highest concentration (20% birch-bark powder) was hardly touched by voles. This suggests the presence of olfactory or gustatory cues, immediate physiological discomfort elicited by the secondary compounds in birch-bark powder, or both.