Montana Field Guide

Northern Grasshopper Mouse - Onychomys leucogaster

In Montana the female northern grasshopper mouse averages significantly larger and heavier than the male. It will be approximately 5 3/4 inches in total length and 1 3/10 ounces in weight (Foresman 2001). The northern grasshopper mouse changes upper fur color throughout its life history: grayish as a juvenile, buffy to reddish brown as an adult, and back to grayish in old age (Zeveloff 1988). It is white on the belly, legs and feet, and underside of the short, thick, blunt tail. It is a stocky but efficient miniature predator which makes a long, high-pitched call similar to a wolf or coyote howl (Zeveloff 1988 and Kritzman 1977). Long curved claws on large front feet capture and hold insects, other rodents, birds, and reptiles. All of this mouse's feet have furry soles. (Foresman 2001).

Montana Range

No migration.

Found in a wide variety of open habitats, grassland to sagebrush desert . Sandy, silty soils may con- struct its own burrows or usurp others. 3 types of burrows: nest, retreat & defecation.

A carnivorous rodent, animal matter is up to 80% of diet in spring, 60% of diet in midwinter. Cannibalism not rare. Large intestine shorter than that of most rodents. Primarily eats arthropods.

Highly territorial. Boundaries are scent marked. Occurs at low densities intraspecific interactions aggressive. May deposit feces in shallow pits to mark territory. Males emit high pitched whistle (at night).

Young are weaned w/in about 3 weeks. Male helps raise the young. The young play like puppies. First litter of yr. gestation period 26-37 days, later litters 32- 47 days.