Montana Field Guide

Muskrats are large voles adapted to aquatic conditions. The name "muskrat" is related to odoriferous secretions from the perineal glands. The long naked tail flattened laterally distinguishes muskrats from other mammals. Webbed hind feet. Fur is dense and rich brown with a coarse guard hair overlay and thick waterproof under-layer. Color varies from dark brown to black. Total length: 16 to 26 inches. Weight: two to four pounds. May be thought of as overgrown sub-aquatic vole. Most active at night but daytime activity is not unusual. Often builds conspicuous dome-shaped houses.

Beaver - has large dorsally flattened scale over tail.

Non-migratory.

The most widespread of North American microtine (a subfamily of mice) rodents. Marshes, edges of ponds, lakes, streams, cattails, and rushes are typical habitats. An essential habitat ingredient is water of sufficient depth or velocity to prevent freezing. The presence of herbaceous vegetation, both aquatic and terrestrial, is another essential ingredient. In general, has very flexible habitat requirements and often coexists in habitats used by beavers (FWP). Lentic or slightly lotic water containing vegetation. Typha spp. (cattails) & Scirpus spp. (bulrushes) usually present. Constructs bank dens, lodges, feeding huts, platforms, pushups & canals (Perry 1982).

Primarily herbivorous and will eat virtually any vegetable matter. Utilizes shoots, roots, bulbs, and leaves of aquatic plants. Cattails and bulrush are preferred foods. Will also consume cultivated crops. On occasion will eat animal matter. Food is stored in the burrow or den and during winter may even eat part of its own lodge (FWP).

Population is cyclic. Wetland habitats important. Over-pop- ulated wetlands may experience an eatout w/ both above ground and below ground emergent vegetation entirely consumed (Perry 1982).

Breeds during spring and summer. Five or six young are born after a 22- to 30-day gestation. May have two or three litters per year (FWP). Polyestrous, promiscuous or loosely monogamous. Breeding parameters vary by geographic area. Prob. 1-3 litters/yr, 5-8 young/litter; probably breeds Mar-Oct with Mar-June peak period (Perry 1982).