Muskrat - Ondatra zibethicus
FWP Conservation Tier
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.
Summary of Observations Submitted for Montana
Number of Observations:
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Map Help and Descriptions
(Records associated with a range of dates 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:
- 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);
- 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 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 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 email@example.com
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: http://mtnhp.org/requests/default.asp
) 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.
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- 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.
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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).
- Additional ReferencesLegend: View WorldCat Record View Online Publication
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R-8, Job No. II-1, July 1, 1976 - June 30, 1977.
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R-9, Job No. II-1, July 1, 1977 - June 30, 1978.
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R-11, Job No. II-1, July 1, 1979 - June 30, 1980.
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R-12, Job No. II-1, July 1, 1980 - June 30, 1981.
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R-13, Job No. II-1, July 1, 1981 - June 30, 1982.
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R-14, Job No. II-1, July 1, 1982 - June 30, 1983.
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- 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.
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- Marinelli, L., and F. Messier. 1993. Space use and the social system of muskrats. Can. J. Zool. 71:869-875.
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- Maxim Technologies, Inc., Helena, MT., 1999, Wetlands Study Report Dry Prairie Rural Water. November 1999.
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- 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.
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- Schladweiler, Philip, and John P. Weigand., 1983, Relationships of endrin and other chlorinated hydrocarbon compounds to wildlife in Montana, 1981-1982. September 1983.
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- 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.
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- Willner, G.R., G.A. Feldhammer, E.E. Zocker, and J.A. Chapman. 1980. Ondatra zibethicus. Mamm. Species No. 141. 8 pp.
- Additional Sources of Information Related to "Mammals"