Ecology of island muskrats, Ondatra zibethicus, adapted to upland habitat

Abstract

The 85 ha Damariscove Island, Maine, is 4.2 km from the mainland. Its vegetation is mainly coastal shrub and grassland with little freshwater or wetland areas typical of muskrat habitat. The muskrats live underground in burrows and use runways above ground. Their food supply is mainly upland vegetation. Average body weight of 701 animals obtained in fall was 976 g lower than the weight of mainland animals from NE North America. Muskrats have lower litter size (5.4 placental scars per litter) and lower litter frequency (1.4 per adult female) than mainland populations, but because juvenile survival in summer is high (80%), the total production of surviving young per adult female at the end of the breeding season is similar to mainland populations. Sex ratio and age structure in fall are similar to mainland muskrats. -from Author