Onychomys torridus
southern grasshopper mouse

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

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.

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.

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.

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.

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.

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

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.