Grasshopper Mouse

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.

Southern grasshopper mouse

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.

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.

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.

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. In captivity they should be offered a complete diet of rodent lab blocks, and rat or mouse mix, with bits of fruit or veggies regularly. Cheerios or wheat bread are great treats, in small quantities. Do NOT feed chocolate, fried foods, salted foods, candy or junk food! They may enjoy crickets and mealworms if they are captive bred, never feed wild insects as they may carry parasites. Vitamins, like Nutri-Cal are a good addition to their diet, and added calcium during nursing and growth due to demands on their systems at those times, but take care not to overdo it. Water bottles should be used to proved constant, clean water. Ceramic or stoneware food dishes work well for keeping seeds or fresh foods off the floor, and a wire mesh hopper that allows them to eat the lab blocks through without extra waste.

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