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Native Species Global Rank
State Rank Reason below)
Agency Status USFWS
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State Rank Reason (see State Rank above)
Species is relatively common within suitable habitat and widely distributed across portions of the state
Details on Status Ranking and Review
Muskrat ( Ondatra zibethicus) Conservation Status Review
Review Date = 05/03/2018
Score G - 200,000-2,500,000 km squared (about 80,000-1,000,000 square miles)
Comment380,531 square Kilometers from Natural Heritage Program range maps Long-term Trend
Score E - Relatively Stable (±25% change)
CommentHabitat is likely stable within +/- 25% since European settlement Short-term Trend
Score U - Unknown. Short-term trend in population, range, area occupied, and number and condition of occurrences unknown.
CommentNo data on trends available Threats
Score H - Unthreatened. Threats if any, when considered in comparison with natural fluctuation and change, are minimal or very localized, not leading to significant loss or degradation of populations or area even over a few decades’ time. (Severity, scope, and/or immediacy of threat considered Insignificant.)
CommentNo operational threats in the next 15-20 years identified
Score C - Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance; or species has high dispersal capability such that extirpated populations soon become reestablished through natural recolonization (unaided by humans).
CommentNot Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has a high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance. Species has good dispersal capabilities such that e Environmental Specificity
Score D - Broad. Generalist. Broad-scale or diverse (general) habitat(s) or abiotic and/or biotic factors are used or required by the species, with all key requirements common in the generalized range of the species in the area of interest. If the preferred food(s) or breeding/nonbreeding microhabitat(s) become unavailable, the species switches to an alternative with no resulting decline in numbers of individuals or number of breeding attempts.
CommentFound in lentic and lotic waterbodies across a diversity habitats Raw Conservation Status Score
3.5 + 0 (geographic distribution) + 0.5 (environmental specificity) + 0 (long-term trend) + 1 (threats) = 5
Muskrats are large voles adapted to aquatic conditions. The name "Muskrat" is related to odoriferous secretions from the perineal glands. The long naked tail flattened laterally distinguishes Muskrats from other mammals. Webbed hind feet. Fur is dense and rich brown with a coarse guard hair overlay and thick waterproof under-layer. Color varies from dark brown to black. Total length: 16 to 26 inches. Weight: two to four pounds. Most active at night but daytime activity is not unusual. Often builds conspicuous dome-shaped houses.
Beaver has large dorsally flattened scale over tail.
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
The most widespread of North American microtine (a subfamily of mice) rodents. Marshes, edges of ponds, lakes, streams, cattails, and rushes are typical habitats. An essential habitat ingredient is water of sufficient depth or velocity to prevent freezing. The presence of herbaceous vegetation, both aquatic and terrestrial, is another essential ingredient. In general, has very flexible habitat requirements and often coexists in habitats used by Beavers. Lentic or slightly lotic water containing vegetation.
Typha spp. (cattails) and Scirpus spp. (bulrushes) usually present. Constructs bank dens, lodges, feeding huts, platforms, pushups and canals (Perry 1982).
Ecological Systems Associated with this Species
Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system,
point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at:
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
Primarily herbivorous and will eat virtually any vegetable matter. Utilizes shoots, roots, bulbs, and leaves of aquatic plants. Cattails and bulrush are preferred foods. Will also consume cultivated crops. On occasion will eat animal matter. Food is stored in the burrow or den and during winter may even eat part of its own lodge.
Population is cyclic. Wetland habitats important. Over-populated wetlands may experience an eatout with both above ground and below ground emergent vegetation entirely consumed (Perry 1982).
Breeds during spring and summer. Five or six young are born after a 22- to 30-day gestation. May have two or three litters per year. Polyestrous, promiscuous or loosely monogamous. Breeding parameters vary by geographic area. Probably 1 to 3 litters/yr, 5 to 8 young/litter; probably breeds March to October with March to June peak period (Perry 1982).
Literature Cited Above
Legend: View Online Publication Perry, H.R. 1982. Muskrats. Pp. 282-325 in: Chapman, J.A. and G.A. Feldhamer (eds). Wild mammals of North America. John Hopkins University Press, Baltimore. 1147 pp. Additional References
Legend: View Online Publication Do you know of a citation we're missing? Adelman, E.B. 1979. A survey of the nongame mammals in the Upper Rattlesnake Creek drainage of western Montana. M.S. thesis. University of Montana, Missoula. 129 pp. Allen, A. W. and R. D. Hoffmann. 1984. Habitat suitability index models: muskrat. U.S. Fish and Wildlife Service. FWS/OBS-82/10.46 27pp. Allen, A.W. 1987. The relationship between habitat and furbearers. Pages 164-179 in M. Novak, J.A. Baker, M.E. Obbard, and B. Malloch, eds. Wild Furbearer Management and Conservation in North America. Ontario Trappers Assn. and Ontario Ministry Nat. Res., Toronto, Ontario. Anaconda Minerals Company, and Camp, Dresser & McKee. 1981. Anaconda Stillwater Project 6-month environmental baseline report. CDM Project No. 3139. Vol. I Appendix. Jan. 15, 1981. Anderson, M.E. 1977. Aspects of the ecology of two sympatric species of Thamnophis and heavy metal accumulation with the species. 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Wildlife Investigations, Region One. W-130-R-11, Job No. II-1, July 1, 1979 - June 30, 1980. Cross, James, and Richard P. Weckwerth, 1981, Upland Game Bird (and Fur Survey) Inventory. Wildlife Investigations, Region One. W-130-R-12, Job No. II-1, July 1, 1980 - June 30, 1981. Cross, James, and Richard P. Weckwerth, 1982, Upland Game Bird (and Fur Survey) Inventory. Wildlife Investigations, Region One. W-130-R-13, Job No. II-1, July 1, 1981 - June 30, 1982. Cross, James, and Richard P. Weckwerth, 1983, Upland Game Bird (and Fur Survey) Inventory. Wildlife Investigations, Region One. W-130-R-14, Job No. II-1, July 1, 1982 - June 30, 1983. Dames & Moore. 1975. Interim report environmental baseline studies for Crow Indian coal leases: known as Tract II and Tract III, Westmoreland Resources, Sarpy Creek Basin, Big Horn County, Montana. Billings, Mont. Deems, E.F., Jr. and D. Pursley (eds). 1978. North American furbearers: their management, research and harvest status in 1976. Int. Assoc. Fish and Wildlife Agencies and University of Maryland. 171 p. Dice, L.R. 1923. Mammal associations and habitats of the Flathead Lake Region, Montana. Ecology 4(3): 247-260. Dood, A.R. 1980. Terry Badlands nongame survey and inventory final report. Montana Department of Fish, Wildlife, and Parks and Bureau of Land Management, Helena, MT. 70 pp. ECON, Inc. (Ecological Consulting Service), Helena, MT., 1976, Colstrip 10 x 20 Area wildlife and wildlife habitat annual monitoring report, 1976. Proj. 135-85-A. December 31, 1976. Errington, P. L. 1961. Muskrats and marsh management. Stackpole Co., Harrisburg, PA. 183 pp. Errington, P. L. 1963. Muskrat populations. Iowa State Univ. Press, Ames. 665 pp. Feigley, H.P. 1981. Studies on native small mammals as intermediate hosts of Echinococcus multilocularis. M.Sc. Thesis. Bozeman, Montana: Montana State University. 50 p. Fliger, R. 1963. Montana's muskrats. Montana Wildlife. April. 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. Haight, C.P. 1937. Some observations on the predator-prey complex in the Gallatin Valley. M.Sc. Thesis. Bozeman, Montana: Montana State University. 58 p. Hale, K.M. 2007. Investigations of the West Nile virus transmission cycle at Medicine Lake National Wildlife Refuge, Montana, 2005-2006. M.Sc. Thesis. Bozeman, MT: Montana State University. 74 p. Hand, R. L., 1952. Unusual Behavior of Muskrats and Wild Ducks. The Murrelet 33(1):14 Harris, Robert S., Turnstone Biology, 1996, Batavia Waterfowl Production Area, Kalispell, MT. Project No. NH-STPX-STPS 0002(269) CN 3221. October 25, 1996. Hatier, K.G. 1995. Effects of helping behaviors on Coyote packs in Yellowstone National Park, Wyoming. M Sc. Thesis. Bozeman, MT: Montana State University. 78 p. Hendricks, P., S. Lenard, D.M. Stagliano, and B.A. Maxell. 2013. Baseline nongame wildlife surveys on the Fort Peck Indian Reservation. Report to the Assiniboine and Sioux Tribes of the Fort Peck Indian Reservation. Montana Natural Heritage Program, Helena, MT. 83 p. 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. Johnson, L.J. 1960. Mammal studies on the Lubrecht Forest, Montana: a preliminary report. Proc. Mont. Acad. Sci. 20: 40-47. Joslin, Gayle, and Heidi B. Youmans. 1999. Effects of recreation on Rocky Mountain wildlife: a review for Montana. [Montana]: Montana Chapter of the Wildlife Society. Krear, H.R. 1953. An ecological study of the muskrat in the Laramie area. M.S. thesis. Univ. Wyoming. 173 pp. Land & Water Consulting, Inc., Missoula, MT., 2002, Montana Dept. of Transportation Wetland Mitigation Monitoring Report, Year 2001: Lawrence Park, Kalispell, Montana. Proj. No. 130091.008. July 2002. In 2001 Wetland Mitigation Monitoring Reports, Vol. I. Land & Water Consulting, Inc., Missoula, MT., 2002, Montana Dept. of Transportation Wetland Mitigation Monitoring Report, Year 2002: Big Spring Creek, Lewistown, Montana. Proj. No. 130091.029. February 2003. In 2002 Wetland Mitigation Monitoring Reports, Vol. I. Land & Water Consulting, Inc., Missoula, MT., 2002, Montana Dept. of Transportation Wetland Mitigation Monitoring Report, Year 2002: Creston Site, Creston, Montana. Proj. No. 130091.007. February 2003. In 2002 Wetland Mitigation Monitoring Reports, Vol. I. Marinelli, L., and F. Messier. 1993. Space use and the social system of muskrats. Can. J. Zool. 71:869-875. Martin, P.R., K. Dubois and H.B. Youmans. 1981. Terrestrial wildlife inventory in selected coal areas, Powder River resources area final report. Montana Department of Fish, Wildlife and Parks and Bureau of Land Management, Helena, MT. No. YA-553-CTO- 24. 288 p. Matthews, W.L. 1981. 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Grizzly bear habitat use on cutthroat trout spawning streams in tributaries of Yellowstone Lake. M.Sc. Thesis. Bozeman, MT: Montana State University. 128 p. Rust, H. J. 1946. Mammals of northern Idaho. J. Mammal. 27(4): 308-327. Sawyer, H. E. 1935. Studies on the rodents of Montana. M.A. thesis. University of Montana, Missoula. 111 pp. Schladweiler, Philip, and John P. Weigand., 1983, Relationships of endrin and other chlorinated hydrocarbon compounds to wildlife in Montana, 1981-1982. September 1983. Stetson, E. 1976. Aspects of the diving physiology of muskrats (Ondatra zibethica): post-dive oxygen consumption and lactic acid levels. M.A. thesis. University of Montana, Missoula 45 pp. Stewart, R.W. and J.R. Boder. 1977. Summer activity of muskrats in relation to weather. J. Wildl. Manage. 41:487-499. Thompson, L.S. 1981. Circle West wildlife monitoring study: Third annual report. Technical report No. 8. Montana Department of Natural Resources and Conservation. Helena, Montana. Thompson, L.S. 1982. Distribution of Montana amphibians, reptiles, and mammals. Bozeman: Montana Audubon Council. 24 pp. Thompson, Richard W., Western Resource Dev. Corp., Boulder, CO., 1996, Wildlife baseline report for the Montana [Montanore] Project, Lincoln and Sanders counties, Montana. In Application for a Hard Rock Operating Permit and Proposed Plan of Operation, Montanore Project, Lincoln and Sanders Counties, Montana. Vol. 5. Stroiazzo, John. Noranda Minerals Corp., Libby, MT. Revised September 1996. VTN Colorado, Inc. Decker Coal Company., 1975, Draft environmental impact assessment for the proposed North Extension of the West Decker Mine. Waage, Bruce C., 1999, Western Energy Company Rosebud Mine, Colstrip, Montana: 1998 Annual Wildlife Monitoring Report; December 1, 1997 - November 30, 1998 Survey Period. February 24, 1999. Western EcoTech, Helena, MT., 1999, Wetland delineation report for the Haskins Landing Proposed Wetland Mitigation Area. MWFE? June 2, 1999. Western Technology and Engineering, Inc. (WESTECH)., 1994, Wildlife Monitoring Absaloka Mine Area Annual Report, 1994. Montana SMP 85005. OSMP Montana 0007D. Febr. 24, 1994. Western Technology and Engineering, Inc. (WESTECH)., 1996, Wildlife Monitoring Absaloka Mine Area Annual Report, 1995. Montana SMP 85005. OSMP Montana 0007D. Febr. 23, 1996. Westmoreland Resources, Inc., Hardin, MT., 1983, 1980 Wildlife Monitoring Report. 12/21/79-12/20-80. Willner, G.R., G.A. Feldhammer, E.E. Zocker, and J.A. Chapman. 1980. Ondatra zibethicus. Mamm. Species No. 141. 8 pp. Web Search Engines for Articles on "Muskrat"
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