Effect of diet quality on food consumption and body mass in Microtus pennsylvanicus

Small herbivores, such as meadow voles (Microtus pennsylvanicus), have high metabolic requirements but small gut capacities. Therefore, they should prefer food high in macronutrients, like protein, and low in fiber content. Furthermore, protein content affects various reproductive behaviors, including the attractiveness of a vole's scent and maternal behavior. We tested the hypothesis that the protein content of a meadow vole's diet affects both its food intake and subsequent body mass. We predicted that voles fed a low protein diet would consume more food relative to voles fed a high protein diet. Meadow voles were fed either a 9, 13, or 22% protein diet for 4 weeks. We found that male voles fed either a 13 or 22% protein diet consumed more food relative to males fed a 9% protein diet. Protein content of the diet did not affect food intake or body mass of female voles. Such results may be associated with sex differences in the natural history of free-living meadow voles. Consuming more protein may increase the attractiveness of a male vole's scent, thereby increasing his number of mating opportunities.