Montana Field Guide

The deer mouse in Montana measures approximately 6 1/2 inches long, including its tail, and weighs under an ounce. Throughout the Intermountain West it varies in color from pale gray to dark reddish brown on its back and upper tail. Its belly, legs and feet, and the underside of its tail are white. Although the upper fur grades to a lighter color along the sides, it is distinguished by the sharp definition between top and underside. In addition, the deer mouse's large, lightly haired ears and big eyes, suited for its nocturnal habits and under-the-snow winter life, help to identify it (Foresman 2001).

Non-migratory.

In virtually all habitats - sagebrush desert, grasslands, riparian areas, montane, subalpine coniferous forests & alpine tundra (Hoffmann and Pattie 1968, Metzgar 1979, Pattie 1967). Usually not seen in wetlands (Jones et al. 1983).

Omnivorous diet although dentition is adapted for seed eating. Invertebrates important in warm months, green plant material a minor but important component. Stores some food in burrow (Jones et al. 1983).

In forest areas densities peak about 2-5 years after clear- cutting, then decline as succession advances. 15 yrs. after cut, uncut & cut densities similar (A81RAM01). On prarie production may be linked to precipitation.

In Beartooths beg. breeding May or June -- 2.3 litters/yr., adults ave. 6.4 young/litter. In Missoula co. breed April - Nov., in Rosebud co. females preg. Mar-Oct & ave. 5.25 young/litter (Metzgar 1979, Pattie 1967).