Search Field Guide
Advanced Search
Montana Animal Field Guide

Montana Field Guides

Muskrat - Ondatra zibethicus

Global Rank: G5
State Rank: S5

Agency Status


External Links

Listen to an Audio Sample

Copyright Jeff Rice, all rights reserved. Audio file courtesy of the Acoustic Atlas at Montana State University (
General Description
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.

Diagnostic Characteristics
Beaver has large dorsally flattened scale over tail.

Species Range
Montana Range

Click the legend blocks above to view individual ranges.

Western Hemisphere Range


Summary of Observations Submitted for Montana
Number of Observations: 352

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(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 (high, medium, or low) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. 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 2001, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point database associated with each ecological system;
    4. 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 associated as using 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 associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the 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 assignments of habitat quality.  If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at or (406) 444-3655.

    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.

    Literature Cited
    • 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.  2001.  The wild mammals of Montana.  Special Publication No. 12.  Lawrence, KS: The American Society of Mammalogists.  278 p.
    • 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.

Food Habits
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).

Reproductive Characteristics
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 AboveLegend:   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 ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • 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.
    • Bauer, Delane, 2002, 2002 Four Seasons Wildlife Study. Savage Mine Report, Richland County, Montana.
    • Caire, W., J.D. Tyler, and B.P Glass. 1989. Mammals of Oklahoma. University of Oklahoma Press, Norman. xiii + 567 pp.
    • Camp Dresser & McKee, Inc., Wheat Ridge, CO., 1981, Anaconda Stillwater Project 6-month environmental baseline report. CDM Project No. 3139. Vol. I Appendix. Jan. 15, 1981.
    • Carlsen, Tom, and Rick Northrup, 1992, Canyon Ferry Wildlife Management Area Final Draft Management Plan. March 1992.
    • Clark, W. R. 1994. Habitat selection by muskrats in experimental marshes undergoing succession. Can. J. Zool. 72:675-680.
    • Clough, G. C. 1987. Ecology of island muskrats, ONDATRA ZIBETHICUS, adapted to upland habitat. Can. Field-Nat. 101:63-69.
    • Cross, James, and Richard P. Weckwerth, 1977, Upland Game Bird (and Fur Survey) Inventory. Wildlife Investigations, Region One. W-130- R-8, Job No. II-1, July 1, 1976 - June 30, 1977.
    • Cross, James, and Richard P. Weckwerth, 1978, Upland Game Bird (and Fur Survey) Inventory. Wildlife Investigations, Region One. W-130- R-9, Job No. II-1, July 1, 1977 - June 30, 1978.
    • Cross, James, and Richard P. Weckwerth, 1980, Upland Game Bird (and Fur Survey) Inventory. 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.
    • Dice, L.R. 1923. Mammal associations and habitats of the Flathead Lake Region, Montana. Ecology 4(3):247-260.
    • 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.
    • Fliger, R. 1963. Montana's muskrats. Montana Wildlife. April.
    • Foresman, K.R. 2001. The wild mammals of Montana. American Society of Mammologists, Special Publication Number 12. Lawrence, KS. 278 pp.
    • Harris, Robert S., Turnstone Biology, 1996, Batavia Waterfowl Production Area, Kalispell, MT. Project No. NH-STPX-STPS 0002(269) CN 3221. October 25, 1996.
    • Hoffmann, R.S. and D.L. Pattie. 1968. A guide to Montana mammals: identification, habitat, distribution, and abundance. University of Montana, Missoula. 133 pp.
    • 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.
    • Maxim Technologies, Inc., 2002, Western Energy Company Rosebud Mine, Colstrip, Montana: 2002 Annual Wildlife Monitoring Report; December 1, 2001 - November 30, 2002. Febr. 24, 2002.
    • Maxim Technologies, Inc., Helena, MT., 1999, Wetlands Study Report Dry Prairie Rural Water. November 1999.
    • Messier, F., J. A. Virgl, and L. Marinelli. 1990. Density-dependent habitat selection in muskrats: a test of the ideal free distribution model. Oecol. 84:380-385.
    • Montana Dept. of Transportation., 200?, Montana Dept. of Transportation Biological Resources Report: Wetland mitigation east of Browning. Montana Wetland ?? Proj. No. NH 0002(232) CN 0703. In Perry Ranch - East of Browning Wetland Mitigation Site, Glacier County. US#3. Man.? Fin Dist3 Admin.Dist3
    • Morrison-Maierle Env. Corp., Helena, MT., 1993, Biological assessment and wildlife reconnaissance, Holnam Cement Plant, Trident, Montana. In Application to Amend Operating Permit 00004 for Trident Quarries, Three Forks, Montana. Exhibit DD: Wildlife Reconnaisance Study. June 28, 1996.
    • Nadeau, S., R. DeCarie, and M. St. Georges. 1995. Nonlinear modeling of muskrat use of habitat. J. Wildl. Manage. 59(1):110-117.
    • Parker, R. R., E. A. Steinhaus, G. M. Kohls, and W. L. Jellison. 1951. Contamination of natural waters and mud with Pasteurella tularemsis and tularemia in beavers and muskrats in the northwestern United States. National Inst. of Health Bull. No. 193. 61 pp.
    • Peterson, Joel, and Michael R. Frisina, 1987, II Upland Game Bird and Inventory, Region Three, Game Birds and Fur (Small Game) Survey and Inventory. Statewide Wildlife Survey and Inventory. W-130- R-18, Job No. II-3, July 1, 1986 - June 30, 1987.
    • Powder River Eagle Studies, Inc., Gillette, WY., 2000, Spring Creek Mine 1999 Wildlife Monitoring. March 2000.
    • Reeves, H.M. and R.M. Williams. 1956. Reproduction, size, and mortality in the Rocky Mountain muskrat. J. Mammal. 37(4): 494-500.
    • 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.
    • Schladweiler, Philip, and John P. Weigand., 1983, Relationships of endrin and other chlorinated hydrocarbon compounds to wildlife in Montana, 1981-1982. September 1983.
    • 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. 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"
Login Logout
Citation for data on this website:
Muskrat — Ondatra zibethicus.  Montana Field Guide.  Montana Natural Heritage Program and Montana Fish, Wildlife and Parks.  Retrieved on May 24, 2016, from