Home range probably is less than 2.5 acres. Can become very abundant. May displace muskrat populations, though the two species may coexist where conditions are "good" (Jackson 1990). In Maryland, population density was estimated at 3-16 per ha; trapper harvest, and in one year, freezing, accounted for most mortality (Willner et al. 1979). Commonly preyed on by alligators. Lifespan generally is 2-3 years or less.