Family: Muridae, Mice and Rats view all from this family
Description A heavy-bodied mouse. 2 main color phases above: grayish (nearly black in northeastern part of range) and cinnamon-buff; white below. Short, thick, bicolored tail with white tip, usually less than one-third total length. Juvenile dark gray. L 5 1/8–7 1/2" (130–190 mm); T 1 1/8 –2 3/8" (29–62 mm); HF 5/8–1" (17–25 mm); Wt 7/8–1 7/8 oz (27–52 g).
Similar Species Southern Grasshopper Mouse is smaller, with longer tail. Deer mice have longer tails lacking white tip.
Breeding Breeds February–August, peaking June–August; 3–6 litters per year of 1–6 young; gestation 26–37 days in nonlactating females.
Habitat Low valleys; desert; prairies.
Range Much of w North America from se Washington, s Alberta, Saskatchewan, and sw Manitoba south to ne California, e Arizona, and w Texas.
Discussion Grasshopper mice are usually nocturnal and are most active on moonless nights or under heavy cloud cover. As their name suggests, they feed heavily on grasshoppers, but they also eat other insects, especially beetles and their larvae, as well as caterpillars, scorpions, and spiders. They have even been known to kill other species of mice, at least in captivity. Plant material constitutes up to a quarter of their diet—most notably forbs, grasses, sedges, and seeds—with the greatest amounts eaten in midwinter. Grasshopper mice either dig burrows or take over those abandoned by other animals. They maintain a complex system of burrows throughout their rather large territories, including a nest burrow, retreat burrows, cache burrows, defecation burrows, and signpost burrows. The nest burrow, sealed during the day to retain moisture, is the center of activity. Retreat burrows are 8 to 10 inches (200–250 mm) long and extend into the ground at a 45-degree angle to ensure speedy escapes from predators. Cache burrows are used for storing seeds, to be eaten when insects are not available. Signpost burrows are short, usually only 1 to 2 inches (25–50 mm) long. Located at the edge of the territory and marked with glandular secretions, they are used to designate territorial boundaries. The Northern Grasshopper Mouse will actively defend its young, even against humans. It has several calls, one of which is high-pitched and prolonged, and made in a wolf-like fashion with raised nose and open mouth. Another common call is a sharp, bark-like alarm chirp, rapidly repeated. Coyotes, hawks, owls, snakes, and other animals prey on this mouse.
