Montana Field Guide

Olive-backed Pocket Mouse - Perognathus fasciatus

The olive-backed pocket mouse (Wyoming pocket mouse) measures at most 5 5/8 inches as an adult, with its tail being half or more of that length. It weighs under 1/2 ounce. Its silky fur is olive-gray, with a top band of black and olive (Zeveloff 1988). A yellowish-buff line marks its sides and the patches of fur behind its ears are light yellow. It is buffy to pure white below. Like all the members of its biological family, it has fur-lined cheek pockets for storing food, which open on each side of its mouth. The well-developed legs and 3/4-inch-long hind feet enable it to hop and jump. Active at night, the olive-backed mouse's eyes appear to glow with a faded amber light. It has 20 teeth, the upper incisors having grooved faces. (Burt and Grossenheider 1964).

Montana Range

Non-migratory.

A wide variety of grassland and soil types. Grazed and ungrazed meadows on sandy soils, shortgrass and sage near sandy draw. Sage-grassland, creek and grassland types.

Can obtain metabolic water from digestion of dry seeds.

An actibe burrower. Usually plugs entrances in daytime. Locomotion is by quadrupedal hopping, sometimes by walking. Rests on hind feet and tail when gathering food. Harvests with forepaws.

Bimodal peaks in production during parturition period sug- gests the possibility of two litters/year, but still unclear. Breeding season begins in April.