Onychomys torridussouthern grasshopper mouse

Last updated:

Geographic Range

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

Habitat

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.

Physical Description

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
    0.78 oz
    AnAge
  • Average basal metabolic rate
    0.165 W
    AnAge

Reproduction

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.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    3.7
    AnAge
  • Average gestation period
    30 days
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    41 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    41 days
    AnAge

Lifespan/Longevity

Behavior

Grasshopper mice are extremely aggressive predators. They are largely nocturnal, good climbers, and active year round. They hunt their prey like most sophisticated predators. After stalking their potential kill, they seize the animal with a rush, killing with a bite to the head. While overpowering their prey, O torridus closes its eyes and lays its ears back. Grasshopper mice are solitary animals, guarding their large territory fiercely against all intruders. They may, however, live in male-female pairs year round, although this seems to shorten the life span, as one of the two partners inevitably kills the other. Grasshopper mice often commit acts of cannibalism, killing and eating other members of their species if they are threatened or in need of food. Perhaps the most unusual thing about the grasshopper mouse is its trademark "howl". Onychomys can produce a loud, piercing, pure tone, which lasts between 0.7 and 1.2 seconds, and is audible to the human ear up to100 meters away. Standing on their hind legs with their noses pointed upwards, they give this call when faced with an adversary, including other grasshopper mice, or prior to making a kill. This shrill warning, often repeated, is compared to a miniature wolf call, due to its smoothness and prolongation, and to the animal's wolf-like posture.

Communication and Perception

Food Habits

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.

Economic Importance for Humans: Positive

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.

Economic Importance for Humans: Negative

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.

Conservation Status

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

Other Comments

As with all predators, the grasshopper mouse requires a large territory in order to find the amount of food it requires to survive. In Nevada, the number of grasshopper mice average about 1.83 per hectare.

Contributors

Denis Kester (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

The Encyclopedia of Mammals. MacDonald, Dr. David. Facts on File Publications. New York.1984. pg. 644.

Grzimek's Encyclopedia of Mammals, Volume 3. Grzimek, Dr, Bernhard. McGraw-Hill Publishing Company. New York. 1990. pgs. 216-217.

Walker's Mammals of the World, 4th Edition, Volume II. Nowak, Ronald M., Paradiso, John L. The John Hopkins University Press. Baltimore and London. 1983. pgs. 589-590.