A bounding flash through dense streamside grass is the only glimpse most naturalists ever get of these beautiful mice. Two species occur in Colorado, the western jumping mouse and the meadow jumping mouse. These are stunning, yellowish brown mice with pure white bellies and a prominent buff stripe on the side. The species are difficult to distinguish in the field except by geography. The animals are about ten inches long, of which more than half is the thin, nearly naked tail. Weights are about an ounce.
Range: Western jumping mouse occurs in the mountains; the meadow jumping mouse at the edge of the Great Plains up against the Rockies.
Habitat: Jumping mice live in vegetation near ponds and streams. Willow thickets or grassy aspen forests are prime habitat for the western jumping mouse. The habitat of the meadow jumping mouse probably has been greatly restricted by converting prairie potholes and other wetlands to irrigation reservoirs.
Diet: Their diet is mostly grass seeds, spiced with occasional insects. Jumping mice are the smallest of our true hibernators. In late summer they store fat for fuel before retiring for the long winter (September to May) to a burrow in a well-drained site above the spring flood-line and below the winter frost-line.
Reproduction: Jumping mice produce a single litter of four to eight young each summer; young of additional litters probably would not have time to fatten for hibernation. Gestation takes about 18 days, and the young are weaned at one month of age. For small mammals, jumping mice are long-lived, commonly living four years or more. (A vole twice the size of a jumping mouse would be in advanced old age at less than one year.) Perhaps their life span, like that of bats, is related to hibernation: they can live a long time because "they don't live very often."
By David M. Armstrong
Department of Ecology & Evolutionary Biology
Environmental Studies Program, University Museum of Natural History
University of Colorado-Bouldermausmann@aol.com