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Montana Animal Field Guide

Montana Field Guides

American Mink - Mustela vison

Global Rank: G5
State Rank: S5

Agency Status


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General Description
This medium-sized, semi-aquatic carnivore has a long, thin body; short, sturdy legs; short, pointed nose; short, rounded ears, and a dorsoventrally flattened head. Thickly furred tail. Usually rich dark brown in color with a white chin patch. Sometimes white spots on belly. Fur is soft and lustrous with long, glossy guard hairs. Dense pelage is its only obvious aquatic adaptation. Total length: 19 to 28 inches. Weight: 1.5 to two pounds. A medium-sized mammal with an elongate body, a long tail, small rounded ears, and relatively short legs; pelage is soft, luxurious, and generally rich brown to almost black dorsally; the underparts are paler, sometimes with a whitish chin patch and whitish spotting elsewhere; five digits on each foot; head to body 330 to 430 mm in males, 300 to 400 mm in females; tail 158 to 230 mm in males, 128 to 200 mm in females; mass 681 to 2310 g in males, 790 to 1089 g in females; basilar length of skull 58 to 69 mm (Burt and Grossenheider 1964, Hall 1981, and Nowak 1991).

Diagnostic Characteristics
Differs from weasels in having brown rather than white or yellowish underparts. Differs from Marten in having a white chin patch (Marten has pale buff patch on throat and breast), generally darker pelage (Marten's pelage generally is yellowish brown except on the feet and end of the tail), and 4 rather than 5 upper postcanine teeth. Differs from the Fisher in having 4 rather than 5 upper postcanine teeth, a white chin patch, and smaller size. River Otter is much larger (up to 130 cm total length and 11 kg).

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: 202

(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)

Non-migratory. Males make extensive movements and juveniles disperse.

Usually found along streams and lakes. Commonly occurs in marshes and beaver ponds. Permanence of water and dependable source of food are most important habitat components. Often uses den sites of other animals and is commonly found in association with Muskrats. Semi-aquatic forager. Can kill prey larger than itself. Chiefly nocturnal, territorial, and secretive. Dens underneath piles of brush or driftwood, under rocks, in hollow logs, and in houses or dens abandoned by Beavers or Muskrats. Very aggressive mating behavior. Wetland habitats - riverine, palustrine, lacustrine.
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
Preys primarily on small mammals, birds, eggs, frogs, and fish. Its diet is almost entirely animal. During summer preys on waterfowl. Aquatic and terrestrial prey. Order of importance varies. Lacustrine: fish, mammals, invertebrates, birds, reptiles and amphibians. Palustrine: birds, invertebrates, mammals, reptiles and amphibians. Opportunistic.

Almost complete population turnover within 3 years. Diameter of movements for males usually not greater than 3 miles. Two adjacent females had home ranges of 19.3 and 50.4 acres.

Reproductive Characteristics
Mates from January through March; 40- to 79-day gestation; delayed implantation; young born during April or May; averages four or five per litter. Apparently breed in March, perhaps earlier. Average 4 young per litter. Born in April or May. By 8 weeks of age, the young may accompany female on hunting trips.

  • Literature Cited AboveLegend:   View Online Publication
    • Burt, W.H. and R.P. Grossenheider. 1964. A field guide to the mammals. Houghton Mifflin Co.
    • Hall, E.R. 1981. The mammals of North America, volumes I and II. John Wiley & Sons, New York, NY. 1181 pp.
    • Nowak, R.M. 1991. Walker's mammals of the world. Fifth edition. Volumes I and II. Johns Hopkins University Press, Baltimore. 1629 pp.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Allen, A. W. 1983. Habitat suitability index models: mink. U.S. Fish and Wildlife Service. FWS/OBS-82/10.61 19 pp.
    • Arnold, T. W. and E. K. Fritzell. 1990. Habitat use by male mink in relation to wetland characteristics and avian prey abundance. Can. J. Zool. 68:2205-2208.
    • Bauer, Delane, 2002, 2002 Four Seasons Wildlife Study. Savage Mine Report, Richland County, Montana.
    • Bell, J. F., K. Farrell and J. R. Gorham. 1957. A polyvalent toxoid for botulism in mink. Am. J. Vet. Res. 18(66):167-170.
    • Butts, Thomas W., Western Technology and Eng., Helena, MT., 1993, Continental Lime Indian Creek Mine, Townsend, MT. 1993 Life of Mine Wildlife Reconnaissance. June 1993. In Life-of-Mine Amendment. Continental Lime, Inc., Indian Creek Mine & Plant. Vol. 2. October 13, 1992.
    • 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.
    • Chapman, J. A., and G. A. Feldhamer, editors. 1982. Wild mammals of North America: biology, management, and economics. Johns Hopkins University Press, Baltimore, Maryland.
    • 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.
    • Flath, D. L. 1984. Vertebrate species of special interest or concern. Mammals, birds, reptiles, amphibians, fishes. Spec. Publ. Montana Department of Fish, Wildlife, and Parks, Helena. 76 pp.
    • Foresman, K.R. 2001. The wild mammals of Montana. American Society of Mammologists, Special Publication Number 12. Lawrence, KS. 278 pp.
    • Greer, K. R. 1957. Some osteological character of known-age ranch minks. J. Mammal. 38:319-330.
    • Hjelle, B.T. 1948. The mink in North Dakota. North Dakota Outdoors, 10(9):12-14.
    • Hoffmann, R.S. and D.L. Pattie. 1968. A guide to Montana mammals: identification, habitat, distribution, and abundance. University of Montana, Missoula. 133 pp.
    • Keith, L. B. and J. R. Cary 1991. Mustelid, squirrel and porcupine population trends during a snowshoe hare cycle. J. Mammal. 72(2):373-378.
    • Lariviere, S.. 1999. Mustela vison. American Society of Mammalogists, Lawrence, KS. Mammalian Species No. 608:1-9.
    • Lechleitner, R. R. 1953. An analysis of some age criteria in a domestic and a wild population of mink (MUSTELA VISON). M.S. thesis. University of Montana, Missoula. 54 pp.
    • Mitchell, J. L. 1958. Mink age and sex ratios. Montana Fish and Game Dept. P-R Job Compl. Rep. Proj. W-49-R-7:8-15.
    • Mitchell, J.L. 1961. Mink movements and a population on a Montana river. J. Wildl. Manage. 25(1):48-54.
    • Mitchell, James L. 1957. A Study of Mink Movements and Populations on the Lower Madison River, Montana. M. S. thesis.
    • Montana Dept. of Fish, Wildlife & Parks, 1985, Upland Game Bird and Furbearer Survey and Inventory. Wildlife Investigations, Region One. W-130- R-16, Job No. II-1, July 1, 1984 - June 30, 1985.
    • Montana Dept. of Fish, Wildlife & Parks, 1986, Upland Game Bird and Furbearer Survey and Inventory. Wildlife Investigations, Region One. W-130- R-17, Job No. II-1, July 1, 1985 - June 30, 1986.
    • Montana Dept. of Fish, Wildlife & Parks, 1987, Upland Game Bird and Furbearer Survey and Inventory. Wildlife Investigations, Region One. W-130- R-18, Job No. II-1, July 1, 1986 - June 30, 1987.
    • 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.
    • 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.
    • Racey, G. D. and D. L. Euler. 1983. Changes in mink habitat and food selection as influenced by cottage development in central Ontario. J. Anim. Ecol. 20:387-402.
    • 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.
    • Stoddart, D. M. 1983. Some factors influencing the distribution of mink. J. Zool. 200:281-302.
    • 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.
    • Thunderbird Wildlife Consulting, Inc., Gillette, WY., 2003, Spring Creek Mine 2002 Wildlife Monitoring. March 2003.
    • Urban, Larry, 2002, Biological Resources Report: Wagner Pit Wetland Restoration Site. Proj. No. STPX 56(50) CN 4645. February 23, 2002. In Wgner Pit WS#13 Upper Yellowstone, Yellowstone County. Fin. Dist. 5 AdminDist 5.
    • USDI Fish and Wildlife Service., 1961, A Detailed report on fish and wildlife resources affected by McNamara Dam and Reservoir, Blackfoot River Project, Montana. June 1961.
    • Waage, Bruce C., 2002, Western Energy Company Rosebud Mine, Colstrip, Montana. 2001 Annual Wildlife Monitoring Report; December 1, 2000 - November 30, 2001. Febr. 26, 2002.
    • WESTECH Env. Services, Inc., Helena, MT., 2000, Reconnaissance of wildlife and fisheries resources at the Ruby Garnet Alder Gulch property. May 24, 2000. In Application for an Operating Permit and Proposed Plan of Operations, Alder Gulch Mine Project, Madison County, Montana. Appendix J: Wildlife Reconnaissance. Cominco American Resources, Inc. Assisted by Hydrometrics, Inc. Prepared for Montana Dept. of State Lands. [June 6, 2000].
    • Western Energy Co., Colstrip, MT., 1982, Western Energy Company Rosebud Mine, Colstrip, Montana: Annual Wildlife Report, 1982.
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Citation for data on this website:
American Mink — Mustela vison.  Montana Field Guide.  Montana Natural Heritage Program and Montana Fish, Wildlife and Parks.  Retrieved on May 26, 2016, from