Onychomys leucogaster
(Northern Grasshopper Mouse)

Order: Rodentia
Order Description:Rodents
Family: Cricetidae
Family Description:
Mice and Rats

This species has at least two color phases: grayish above, or cinnamon-buffClick word for definition to reddish brown, they are white underneath. As juveniles, they are dark gray. Their tail is shorter, less than half their body length, but it is bicolored with a white tip. Total length is 5 1/8 to 7 ˝ inches (130-190 mm), tail length is 1 1/8 to 2 3/8 inches (29-61 mm), and they weigh about 1 to nearly 2 ounces (27-52 g). They have noticeably long front claws and large front feet.

From south-central Canada, south through Great Plains to northern Mexico. Extends west through Great Basin and southwestern deserts of Arizona and New Mexico, and also occurs in Rocky Mountains.

They occur, in areas with sandy, diggable soil and sparse vegetation, in grasslands, shrub steppeClick word for definition, overgrazed pastures, weedy roadside ditches, and semi-stabilized sand dunes. In Idaho, species is most numerous in sagebrush areas, but usually in fine sandy or silty soils.

Eats 70-90% animal material, primarily arthropods (grasshoppers, beetles, spiders, larval LepidopteraClick word for definition), but will also eat plant material and small rodents, especially in winter.

Grasshopper mice are active throughout the year, although their activity is greatly reduced during the full moon or heavy, prolonged rainfall. They are nocturnalClick word for definition but their activity seems influences by lunar phases. They occupy underground burrows when inactive which they plug for moisture retention and temperature regulation. They also dig small "retreat burrows" when away from their nest burrow. They may store seeds. They usually occur at relatively low densities, but may become a controlling factor for prey items. Their predatory behavior is well known. They are active predators killing prey as formidable as scorpions. They kill other rodents by gripping them with their long, front claws and biting the prey. They appear to be territorial and actually mark their territory with scent glands. They also emit shrill whistles that seem to function in advertising their presence, much like larger predators like coyotes. They are aggressive toward others of their species, which may be associated with their territorial behavior. They maintain an unusually large home range (or territory) for a small mammals; up to 5.8 acres (2.3 ha).

Breeding occurs from late spring to early fall, and GestationClick word for definition lasts about 32 to 38 days. litterClick word for definition size is typically 3 to 4 young, but ranges from 1 to 6. Males assist in caring for the young by bringing insects in to the young. This is very different from typical rodent behavior where males rarely help care for young. Young develop rapidly, and seem to act like young dogs or coyotes by fighting and seeming preparing for their predatory life style. Young reach sexual maturity at 3-4 mo.

Status: Unprotected nongame species

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Important State References:
Reynolds. T.D. 1980. Effects of some different land management practices on small mammal populations. J. Mammal. 61:558-561.

Information written by Donald Streubel,© 2000
Photos by James Moodie, © Feb 1998.
Map image provided by Stephen Burton,© 2000
Design by Ean Harker©1999, 2000.