Mus musculus

House Mouse

Family: Muridae · Class: Mammalia · Order: Rodentia

The house mouse is a small rodent measuring 65 to 95 mm (2.6 to 3.7 inches) in body length, with a tail of similar length ranging from 60 to 105 mm. Adult weight typically ranges from 12 to 30 grams (0.4 to 1.1 ounces). The pelage is generally grayish-brown on the dorsal surface, transitioning to lighter gray or buff on the ventral side. The ears are large relative to body size, measuring 12 to 20 mm in length, and the eyes are small and dark. The tail is nearly hairless with visible scale rings and is typically darker on the dorsal surface. Originally native to the Indian subcontinent, the house mouse has achieved a nearly cosmopolitan distribution through human-mediated dispersal. In California, the species is established throughout the state from sea level to montane elevations, occurring in all 58 counties. Populations are present on offshore islands including the Channel Islands, where they were introduced by human activity. The species has been documented at elevations exceeding 4,300 meters (14,100 feet) in the Sierra Nevada, though populations are most dense in lowland areas with human habitation. House mice occupy diverse habitats but show strong association with human-modified environments. The species thrives in agricultural areas, urban settings, residential structures, warehouses, and food storage facilities. In natural habitats, populations occur in grasslands, scrublands, and forest edges, typically in areas with adequate shelter and food resources. Mice construct nests from available materials including paper, fabric, plant matter, and other fibrous substances, typically in concealed locations within 3 meters of food sources. House mice are primarily nocturnal and highly social, living in territorial groups with complex dominance hierarchies. Reproduction occurs year-round under favorable conditions, with females producing 5 to 10 litters annually. Gestation period is 18 to 21 days, and litter size ranges from 3 to 12 offspring, with an average of 6. Sexual maturity is reached at 5 to 7 weeks of age. The diet is omnivorous but consists primarily of seeds, grains, and other plant matter, supplemented with insects and other protein sources when available. Daily food consumption is approximately 3 grams, though mice can survive extended periods without water by metabolizing moisture from food. As a non-native species in California, the house mouse is not afforded conservation protection and is not listed under state or federal endangered species legislation. Population trends indicate stable or increasing numbers throughout most of the state. The species is considered a significant agricultural pest, causing damage to stored grains and other crops, with estimated annual losses exceeding millions of dollars. In natural ecosystems, house mice may compete with native rodent species for resources and serve as prey for various predators including owls, snakes, and carnivorous mammals. Control efforts focus primarily on exclusion, trapping, and rodenticide application in agricultural and residential settings.

Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, and more.