Norway Rat - Rattus norvegicus
State Rank Reason (see State Rank above)
Species is nonnative/ introduced
The Norway Rat, an unwelcome species that introduces itself along with human migrations, is known mainly for its habits carried to extremes - digging and gnawing through huge food stockpiles, electrical wires, and pipes - and the disease epidemics it has caused. It measures from 12 to 18 inches and weighs from 6 3/4 to 17 ounces in Montana. It is a thickset rodent, with grayish brown coarse fur above and a gray underside. Black hairs sprinkled throughout its upper coat make it look grizzled (Foresman 2012). It has large bare ears and a round, scaly tail.
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(Observations spanning multiple months or years are excluded from time charts)
Non-migratory. Innate movement. Dispersal characteristics unclear. Hitches rides in grain cars, etc.
Probably restricted to human habitation, dumps, feed lots, haystacks, feed mills, and grain storage elevators (mostly in valley bottoms). Cities, perhaps farms and ranches.
Excellent burrower. Often digs extensive tunnel systems with nexting cavities. Also builds nests of twigs, leaves, and scraps. Chewing activities may destroy properties other than food. Carries diseases.
Prolific. High reproduction rate. Breeds year-round.
- Additional ReferencesLegend: View Online Publication
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- Foresman, K.R. 2001. The wild mammals of Montana. American Society of Mammalogists, Special Publication Number 12. Lawrence, KS. 278 pp.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hoffmann, R.S. and D.L. Pattie. 1968. A guide to Montana mammals: identification, habitat, distribution, and abundance. Missoula, MT: University of Montana. 133 p.
- Kritzman, E.B. 1977. Little mammals of the Pacific Northwest. Pacific Search Press, Seattle, WA.
- Reid, F. 2006. Peterson Field Guide to Mammals of North America, 4th Edition. Houghton Mifflin Company: Boston and New York, 608 pp.
- Rust, H. J. 1946. Mammals of northern Idaho. J. Mammal. 27(4): 308-327.
- Tryon, C. A. 1947. Entrance and migration of the Norway rat into Montana. Journal of Mammology 28(2):188-189.
- Additional Sources of Information Related to "Mammals"