Field Guide/Mammals/Western Harvest Mouse

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Reithrodontomys megalotis (Western Harvest Mouse)
Family: Cricetidae
Size: 2.3-3.0 in (59-77 mm) in length, 0.21-0.38 oz (6-11 g) in weight
Description: The Western Harvest Mouse is a small, long-tailed rodent that has prominent, orange-tipped ears.[1][2] It is among the smallest rodents in Minnesota with a brown back and whitish belly.[3] Its tail is bi-color, with a scaly appearance covered by hair.
Similar Species: It is difficult to distinguish the Western Harvest Mouse from similar species, but it is slightly larger than the Plains Harvest Mouse, the Sonoran Harvest Mouse, and the Eastern Harvest Mouse. Also, its hair is shorter and its tail is more distinctly bi-color than the Salt Marsh Harvest Mouse.[1]

Range: The Western Harvest Mouse is commonly found in southwestern Canada, southward to southern Mexico, western United States, the central Rockies, and central and upper Midwest.[1][4] Although rare in Minnesota, it is commonly found in the southern region.[3]
Habitat: Old fields, meadows, weedy roadsides, agricultural areas, grassy situations within pine-oak forests, and near the banks of rivers. It prefers dense vegetative cover, and may also be found in shrubby arid regions. The Western Harvest Mouse builds spherical nests that are usually located on the ground under heavy grass, bushes, weeds, or fallen logs.[4][5]
Diet: It is a granivore and herbivore. It mainly eats seeds, but it also eats some herbaceous material and insects.[2][4]
Activity: It is primarily a nocturnal and non-hibernating species, and is most active on moonless, rainy nights.[1]

Reproduction: The Western Harvest Mouse breeds year round, but mostly during the early spring to late autumn with a reduced midsummer activity. Its gestation period lasts 23-24 days, with an average litter size of 6, and it is able to produce multiple litters annually. The young sexually mature in 2-4 months.[1][5]
Lifespan: Few reach the age of 12 months.[1]
Western Harvest Mouse, Reithrodontomys megalotis

  1. a b c d e f Webster, W. D.; Jones, J. K. Jr. (1982), "Reithrodontomys megalotis", Mammalian Species (167): 1–5,, retrieved September 23, 2012 
  2. a b Reid, F. A. (2006), Mammals of North America, Boston, NY: Houghton Mifflin Company, pp. 289–290 
  3. a b Hazard, E. B. (1982), The Mammals of Minnesota, Minneapolis, MN: The University of Minnesota Press, p. 83 
  4. a b c Linzey, A. V.; Matson, J. (2008), "Reithrodontomys megalotis", IUCN Red List of Threatened Species (Version 2012.1),, retrieved September 28, 2012 
  5. a b NatureServe (2012), "Reithrodontomys megalotis", NatureServe Explorer: An online encyclopedia of life (Version 7.1),, retrieved September 28, 2012