Basis for Listing

The range of the Northern Grasshopper Mouse (Onychomys leucogaster) extends from south-central Canada through the western and Great Plains states and into northern Mexico. Western Minnesota (Prairie Parkland Province) represents the far northeastern periphery of this species' range. Northern Grasshopper Mice prefer prairie habitat, with gravely soil. Populations in Minnesota are vulnerable to human activity. Agriculture and rock-quarrying activities have disrupted or destroyed much of the habitat this species requires (Minnesota's Remaining Native Prairie). Because they have small populations and are at the edge of their range, they could disappear from Minnesota entirely. The Northern Grasshopper Mouse was listed as a species of special concern in Minnesota in 2013.

  Description

The Northern Grasshopper Mouse is 15.1 cm (5.9 in.) from snout to tip of the tail and weighs, on average, 42.1 g (1.5 oz.) (Hazard 1982). They are gray in color, with white underparts. They can be confused with young White-footed Mice (Peromyscus leucopus), which are a similar gray color. The two species can be differentiated by their size and tail length. Northern Grasshopper Mice weigh almost twice as much as White-footed Mice and have tails less than one third of their body length (Hazard 1982). They are also very muscular compared with other mice, presumably due to their high protein diet. They have unusually long fingers and claws that allow them to grasp and manipulate their prey (Riddle 1999).

  Habitat

In Minnesota, Northern Grasshopper Mice occur on sites with gravelly or coarse soils, including active and inactive quarry sites (Bruns Stockrahm 1991). They occur in a variety of upland prairie habitats, most often in areas with sparse vegetation. They are found in western Minnesota (Prairie Parkland), which is the northeastern limit of their distribution.

  Biology / Life History

Northern Grasshopper Mice are a unique species of rodent for several reasons. Unlike most mice, they are carnivorous. Their diet is mainly grasshoppers, but they also eat beetles and the larvae of grasshoppers, beetles, butterflies, and moths (Hanson 1975). Their molars are high-cusped, providing greater surface area for ripping apart grasshoppers and other large prey. Their jaws also have an enlarged area for muscle attachment, giving them greater strength for biting and chewing animal matter (Riddle 1999). Plant matter that has been found in their gut has been determined to come from the intestines of grasshoppers, rather than being ingested directly by the mice.

This species of mouse is highly aggressive and territorial. Territories are marked with a scent produced by the anal glands, and any intruding rivals of the same sex are run off or attacked. The breeding season lasts from March until August in Colorado, though the season may be different in Minnesota (Hazard 1982). Their courtship behaviors involve a medley of circling, sniffing, and grooming. They form strong mating pair bonds with both parents contributing to the care of the young (rare in mouse species). 

They live in underground burrows that they excavate themselves. Burrows can be identified as having little or no raised area around the hole, since they scatter the substrate as they excavate (Harper et al.1994). Northern Grasshopper Mice prefer sandy and gravelly soil and are often found near quarries, where they can be found living in old spoil piles that have become overgrown with grass.

  Conservation / Management

The habitat of the Northern Grasshopper Mouse often overlaps with human activity. The coarse soils these mice prefer are often excavated for gravel or quarried for stone, which can disturb or destroy their burrows.

  Conservation Efforts in Minnesota

Surveys targeting Northern Grasshopper Mice by the Minnesota DNR’s Minnesota Biological Survey have documented a number of locations for this species. Other research (Bruns Stockrahm 1991; Harper 1994; Bruns Stockrahm et al. 1995) has provided information on local populations, territory size, and movement patterns in Minnesota.

With landowner cooperation, Northern Grasshopper Mice can live in areas with human activities. As long as some areas of refugia are maintained for this species, including old spoils piles, they should be able to avoid excavation activities and relocate (Bruns Stockrahm et al.1995). 

  References and Additional Information

Hansen, R. M. 1975. Plant material in the diet of Onychomys. Journal of Mammalogy 56:530-531.

Harper, E. K., D. E. Welberg Canfield, D. M. Bruns Stockrahm. 1994. Ecology of the Northern Grasshopper Mouse (Onychomys leucogaster) in western Minnesota. Final report submitted to the Division of Ecological Services, Minnesota Department of Natural Resources. 72 pp.

Hazard, E. B. 1982. The mammals of Minnesota. University of Minnesota Press, Minneapolis, Minnesota. 280 pp.

Riddle, B. R. 1999. Northern grasshopper mouse (Onychomys leucogaster). Pages 588-590 in D. E. Wilson and S. Ruff, editors. The Smithsonian book of North American mammals. Smithsonian Institution Press in association with the American Society of Mammalogists, Washington, D.C. 816 pp.

Stockrahm, D. M. B. 1991. Distribution of small mammals in grasslands of western Minnesota with special emphasis on the Prairie Vole (Microtus ochrogaster), the Northern Grasshopper Mouse (Onychomys leucogaster), the Plains Pocket Mouse (Perognathus flavescens), and the Western Harvest Mouse (Reithrodontomys megalotis). Final report submitted to the Minnesota Department of Natural Resources. 53 pp.

Stockrahm, D. M. B. 1995. Ecology of the Northern Grasshopper Mouse (Onychomys leucogaster) and Prairie Vole (Microtus ochrogaster) in Clay County, Minnesota. Final report submitted to the Minnesota Department of Natural Resources. 98 pp.