Nutritional Ecology of Microtine Rodents: Digestibility of Forage

Three species of microtine rodents had different digestive capabilities when fed similar food. The prairie vole, which in natural habitats eats primarily forbs, digested rabbit pellets (made from alfalfa and grain) significantly better than California voles and brown lemmings, which eat primarily grasses and sedges. Prairie voles digested grasses as well as California voles (∼50% of energy), but prairie voles lost weight and died when fed a grass diet, whereas California voles maintained their weight. Brown lemmings digested grasses and sedges poorly compared to voles (35% of energy) but maintained their weight. Inefficient use of energy by lemmings was interpreted as an adaptation for subsistence on forage with low concentrations of minerals. Comparison of data from previous studies of microtine rodents confirmed the general differences in digestibility of food types reported in this study: seeds and garden vegetables were highly digestible (89% of energy), dicotyledon leaves and stems were less so (74%), and monocotyledon shoots were least digestible (54%). These differences among herbivores and forage types should be considered when calculating energy and nutrient budgets.