Summer foraging patterns and diet selection of muskrats inhabiting a fen wetland

Abstract

Foraging patterns, dietary preference, and diet quality of muskrats (Ondatra zibethicus) were studied at an alkaline fen in northern New York, from May 1985 to August 1986. Cattail (Typha latifolia) was the most prominent plant food item in the diet of muskrats. Feedbed surveys indicated that muskrat foraging bouts decreased from the lakeshore denning area with distance into the fen. This pattern of reduced feeding activity was associated with declines in both open water travel routes (i.e., sluiceways) and cattail biomass. Muskrats preferentially selected the core of the cattails. Tissue assays showed core tissue to contain low amounts of lignin and only moderate levels of cellulose, suggesting that muskrats were selecting the plant part most easily digested. Nitrogen and phosphorus levels in cattail samples from all sampling locations in the fen were similar, suggesting that muskrats concentrated their foraging movements for reasons other than maximizing diet quality. These data suggest that predator avoidance behavior strongly influenced muskrat foraging movements, and that muskrats attempted to maximize feeding efficiency within the constraint of access to available open water escape routes.