EFFECTS OF AVAILABILITY OF FOOD AND INTERSPECIFIC COMPETITION ON DIETS OF PRAIRIE VOLES (MICROTUS-OCHROGASTER)

Analysis of fecal samples from experimental populations of prairie vol es (Microtus ochrogaster) and meadow voles (Microtus pennsylvanicus) r evealed that their diets strongly overlapped. Both species preferred d icots, but meadow voles ate significantly more monocots than did prair ie voles. To test the hypothesis that interspecific competition for fo od influenced the diet of prairie voles, we examined the diets of prai rie voles with and without meadow voles present. We found significantl y more monocots in the diet of prairie voles when meadow voles were pr esent, but only in early autumn when availability of high-quality food items was lower and densities of voles were higher. We conclude that variability in diets of voles can occur as a response to changes in av ailability of food, quality of food, and interspecific competition, th e latter particularly when availability of high-quality food is relati vely low and densities of voles are relatively high.