Southern Grasshopper Mice are also known as scorpion Mice: they are able to kill (and then eat) scorpions, by first immobilizing the venomous tail and then biting the head. They also prey on beetles that secrete defensive chemicals from the tip of the abdomen, by jamming the pointed barb into the ground and then striking a deathblow to the head. Of the three species of grasshopper mice, the southern Grasshopper Mouse inhabits the driest regions. Although it does not have the physiological adaptations of some other desert rodents, such as kangaroo rats or pocket mice, it may be able to get enough water from the bodies of its prey - arthropods and small mammals - to live without drinking water.

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Southwestern United States and adjacent northwest Mexico; from western Nevada, southern California, and southern Arizona (United States), south to northern Baja California, Sonora, and northern Sinaloa (Mexico).

Found mainly in western and southwestern United States, and in Northern Mexico.

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Central California, southern Nevada, and extreme southwestern Utah south to northern Baja California, western Sonora, and northernmost Sinaloa, Mexico (Musser and Carleton, in Wilson and Reeder 1993).

Body size averages between 9-13 cm for the head and body, and 3-6 cm for the tail. Covered with fine, dense fur. The upper body is a grayish or pinkish-cinnamon color. The basal two-thirds of the tail are colored like the upper body. The underside and terminal tip are both white. The tail of O. torridus is longer than half the length of its head and body.

Average mass: 22 g.

Average basal metabolic rate: 0.165 W.

Length: 16 cm

Weight: 30 grams

Sexual Dimorphism: None

Length:
Average: 143.9 mm
Range: 130-160 mm

Weight:
Range: 20-40 g

Habitat and Ecology

Systems

• Terrestrial

Onychomys torridus nest in small burrows dug into the ground. Often these burrows have been deserted by other rodents, or were taken by the grasshopper mouse through force. Grasshopper mice are found in shortgrass prairies, and desert scrub. Most prefer xeric areas at low elevations. They have a home range of two-three hectares, and are found in low densities.

Terrestrial Biomes: desert or dune ; savanna or grassland

Comments: Hot, arid valleys and scrub deserts of Lower Sonoran life zone, with sparse and scattered vegetation such as mesquite, huisache, creosote bush, cholla, yucca, and various short grasses. Also found in blackbush zones on alluvial fans. Young are born in nest in underground burrow system that may have been abandoned by another small mammal.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

10-25% of the diet of O. torridus consists of seeds, plants, and vegetables. The remainder includes mainly scorpions, but also grasshoppers, beetles, and small vertebrates, including other rodents, such as Peromyscus, Perognathus, and Microtus.

Comments: Primarily insect prey (scorpions, spiders, ants, beetles), but small vertebrates also consumed. Also eats some vegetable matter (seeds, green vegetation).

Both sexes (more frequently the male) emit shrill calls which are apparently used as territorial or spacing mechanisms. Probably usually lives less than 12 months in the wild. In Arizona, home range averaged 2.6 ha (nonbreeding) and 3.7 ha (breeding) for males, 1.7 ha for females; home ranges of males overlapped with those of males and females; home ranges of breeding females overlapped only slightly, overlapped more during nonbreeding period (Frank and Heske 1992).

Comments: Primarily nocturnal; rarely seen during the day. Apparently active throughout the winter.

Average lifespan

Status: captivity: 4.6 years.

Maximum longevity: 4.6 years (captivity) Observations: Females seldom breed for more than 2 years. Sexual maturity is reached as early as 6 weeks after birth (Ronald Nowak 1999). As juveniles, females have on average 3.8 litters per year with a total of 9.8 young. As adults, the litter number decreases to 1.6 litters per year for a total of 4 young per year.

Grasshopper mice are capable of breeding year-round, but most reproductive activity occurs during the late spring and the summer. Gestation lasts 26-35 days. Females born as early as April may produce two or three litters before year's end. Females born in late summer may have as many as six litters during the following breeding season. Litter size ranges from one to six young. Young weigh approximately 2.6 grams. They open their eyes at two weeks of age, immediately begin nursing from their mother, and are weaned at three weeks of age. Females seldom breed after two years of sexual maturity.

Average birth mass: 2.6 g.

Average gestation period: 30 days.

Average number of offspring: 3.7.

Average age at sexual or reproductive maturity (male)

Sex: male: 41 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 41 days.

First litters are born to females at 4-5 months of age, litter size is 1-5. Sperm production in males is reduced in summer. Reproductive senescence occurs in both sexes after about 12 months of age. Apparently, males compete among themselves for reproductive females (Frank and Heske 1992).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Species: 3
Species With Barcodes: 1

As with many rodents, grasshopper mice are extremely fertile. They are difficult to wipe out, even by man.

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Population

Population Trend

Major Threats

Conservation Actions

Although grasshopper mice are mainly carnivorous, they do eat the same crops they normally help defend if their usual prey, insects and small vertebrates, become scarce.

Largely due to their ferocity and appetite, grasshopper mice help farmers by eating a large number of insects and rodents that would otherwise destroy crops.

Comments: O. arenicola formerly was included in this species but was elevated to species status by Hinesley (1979). Onychomys mtDNA-haplotypes define at least five discrete geographical subsets (Wyoming Basin/Interior Plains/Colorado Plateau, Columbia Basin/Great Basin, Gulf Coastal Plain, Chihuahuan Desert, and Western Deserts), corresponding with five inferred areas of endemism for biota restricted to arid and semiarid habitats in North America (Riddle and Honeycutt 1990).