Family: Dipodidae, Jumping Mice view all from this family
Description Yellow sides; dark band down middle of back; belly white, sometimes tinged yellow. Long tail darker above, whitish below. Very large hindfeet. 4 upper molariform teeth on each side, the first reduced in size. L 8 1/2–10 1/4” (215–260 mm); T 5–6 3/8” (126–160 mm); HF 1 1/8–1 3/8” (28–34 mm); Wt 1/2–1 3/8 oz (15–38 g).
Similar Species Meadow Jumping Mouse is smaller and occurs farther north and east. Pacific Jumping Mouse generally occurs to the west of this species.
Breeding Mates soon after emergence from hibernation; probably 2 or 3 litters per year, each of 3–9 young, born June–July, sometimes much later. Newborn weighs less than 1/16 oz (1 g).
Habitat Variable: primarily moist fields, thickets, and woodlands, especially where grasses, sedges, or other green plant cover is dense; grassy edges of streams, ponds, and lakes.
Range Western North America from s Yukon, all of British Columbia, s Alberta, s Saskatchewan, and extreme sw Manitoba south through w and ne Montana, ne South Dakota, w Oregon, w California, n Nevada, Utah, ec Arizona, and c New Mexico.
Discussion Although it often runs on all four feet, the Western Jumping Mouse may make a series of jumps 3 to 5 feet (90–150 cm) long when startled from its hiding place, then “disappear” by remaining motionless in a new one. It can swim and climb. Between August and October, the mouse fattens, then retires to a winter burrow to hibernate, curled into a ball with its long tail wrapped around its body. It lives in burrows that it digs itself or in those of other animals. While it does not make runways, it will use those of other animals. Although primarily nocturnal, like other jumping mice, this species has been observed in the daytime foraging in salal thickets 1 foot (30 cm) or more off the ground. The seeds of grass, dock, and many other green plants, strawberries, blueberries, blackberries, and subterranean fungi are its chief foods. Young are born in a spherical nest of interwoven, broad-leaved grasses or, if in a bog, of sphagnum moss, constructed in a depression in the ground. Those young born too late in the year to acquire sufficient fat reserves probably perish during hibernation. When alarmed, this species may drum on the ground with its tail. Owls and Bobcats are its chief predators.
