Home/Species/ American Ermine

Mustela richardsonii

Bonaparte, 1838

American Ermine

G5Secure Found in 36 roadless areas NatureServe Explorer →

G5SecureGlobal Rank

Identity

Unique IDELEMENT_GLOBAL.2.1223017

Element CodeAMAJF02070

Record TypeSPECIES

ClassificationSpecies

Classification StatusStandard

Name CategoryVertebrate Animal

Endemicoccurs (regularly, as a native taxon) in multiple nations

KingdomAnimalia

PhylumCraniata

ClassMammalia

OrderCarnivora

FamilyMustelidae

GenusMustela

COSEWICPS:T

Synonyms

Mustela ermineaLinnaeus, 1758

Other Common Names

ermine (EN) Hermine (FR) Short-tailed Weasel (EN) Stoat (EN)

Concept Reference

Colella, J.P., L.M. Frederick, S.L. Talbot and J.A. Cook. 2021. Extrinsically reinforced hybrid speciation within Holarctic ermine (Mustela spp.) produces an insular endemic. Diversity and Distributions 27: 747-762.

Taxonomic Comments

Split from Mustela erminea by Colella et al. (2021). Morphological and genetic analyses by Colella et al. (2021) support the recognition of at least three species within the Mustela erminea complex (M. erminea, M. richardsonii, and M. haidarum), coincident with three of four genetic clades, tied to diversification in separate glacial refugia. They found substantial geographic variation within each species, with generic morphometric results largely consistent with historical infraspecific taxonomy.

Conservation Status

Rank MethodExpertise without calculation

Review Date2016-04-04

Change Date1996-11-18

Edition Date2008-01-04

Range Extent>2,500,000 square km (greater than 1,000,000 square miles)

Number of Occurrences> 300

Rank Reasons

Widespread and secure.

Range Extent Comments

This species is a widespread continental North American species, ranging across Canada south through most of the northern United States to central California, northern Arizona (Berna 1991), northern New Mexico, Iowa, the Great Lakes region, Pennsylvania, and northern Virginia (Fagerstone 1987) (Colella et al. 2021). The species in most of Alaska now refers to the Beringian species, Mustela erminea.

Occurrences Comments

This species is represented by a large number of occurrences (subpopulations).

Threat Impact Comments

On a range-wide scale, no major threats are known. Locally the species may be threatened by unrestricted trapping and habitat loss due to timber harvest or natural disturbance (Fagerstone 1987).

Ecology & Habitat

Habitat

Prefers wooded areas with thick understory near watercourses. Rarely occurs in heavily forested regions. Has adapted to a wide variety of habitats. Dens in hollow log or under log, stump, roots, brushpile, or rocks. In winter in southern Ontario, usually stayed beneath snow surface (Simms 1979).

Ecology

Home range averages 12-16 ha (Jackson 1961). In southern Ontario, density over 95 ha averaged 6 per sq km; home range averaged 20-25 ha for males, smaller for females; most individuals remained on study site less than 1 year (Simms 1979).

Reproduction

Breeds July-August. Gestation lasts 255 days. Litter of 4-9 (average 6-7) is born mid-April to early May. Females are sexually mature in 3-4 months, males in 12 months (probably). Delayed implantation.

Terrestrial Habitats

Forest - HardwoodForest - ConiferForest - MixedWoodland - HardwoodWoodland - ConiferWoodland - MixedShrubland/chaparralGrassland/herbaceousOld fieldAlpineCropland/hedgerow

Palustrine Habitats

HERBACEOUS WETLANDFORESTED WETLANDRiparian

Other Nations (2)

CanadaN5

Province	Rank	Native
Alberta	S5	Yes
Northwest Territories	S5	Yes
Yukon Territory	S5	Yes
Manitoba	S5	Yes
Saskatchewan	S5	Yes
British Columbia	S5	Yes
Nova Scotia	S5	Yes
Quebec	S5	Yes
Island of Newfoundland	S4	Yes
Ontario	S5	Yes
New Brunswick	S5	Yes
Prince Edward Island	S5	Yes
Nunavut	S5	Yes
Labrador	S5	Yes

United StatesN5

Province	Rank	Native
Rhode Island	SH	Yes
Vermont	S5	Yes
Washington	S5	Yes
Wyoming	S5	Yes
Alaska	S5	Yes
Maine	S5	Yes
Ohio	S3	Yes
New Hampshire	S5	Yes
Wisconsin	S4	Yes
Michigan	S5	Yes
Pennsylvania	S5	Yes
Massachusetts	S5	Yes
New Jersey	SNR	Yes
California	SNR	Yes
Nevada	S3	Yes
Idaho	S4	Yes
Montana	S5	Yes
New Mexico	S3	Yes
Iowa	S4	Yes
North Dakota	S3	Yes
Connecticut	S5	Yes
South Dakota	S4	Yes
Oregon	S5	Yes
Utah	S3	Yes
Minnesota	SNR	Yes
Arizona	S1	Yes
New York	S5	Yes
Colorado	S4	Yes

Roadless Areas (36)

Alaska (10)

Area	Forest	Acres
Douglas Island	Tongass National Forest	28,065
Game Creek	Tongass National Forest	54,469
Juneau Urban	Tongass National Forest	101,581
Juneau-Skagway Icefield	Tongass National Forest	1,187,268
Madan	Tongass National Forest	68,553
Mansfield Peninsula	Tongass National Forest	54,991
North Wrangell	Tongass National Forest	8,091
Rhine	Tongass National Forest	23,010
Sitka Sound	Tongass National Forest	13,459
Taku-Snettisham	Tongass National Forest	664,928

California (2)

Area	Forest	Acres
Jennie Lake	Sequoia National Forest	2,388
Pilot Creek	Six Rivers National Forest	9,192

Colorado (3)

Area	Forest	Acres
Bristol Head	Rio Grande NF	46,087
Pole Mountain / Finger Mesa	Rio Grande NF	43,863
Storm Peak	San Juan NF	57,617

Idaho (1)

Area	Forest	Acres
Needles	Payette National Forest	131,279

Montana (7)

Area	Forest	Acres
Evans Gulch	Lolo National Forest	8,059
Freezeout Mountain	Beaverhead-Deerlodge National Forest	97,305
Hoodoo	Lolo National Forest	105,162
Maple Peak	Lolo National Forest	6,469
North Siegel	Lolo National Forest	9,208
South Siegel - South Cutoff	Lolo National Forest	13,474
Tash Peak	Beaverhead-Deerlodge National Forest	61,312

Nevada (3)

Area	Forest	Acres
Ruby - Marsh	Humboldt-Toiyabe National Forest	10,164
Snake - Chokecherry	Humboldt-Toiyabe National Forest	30,845
Snake - Murphy	Humboldt-Toiyabe National Forest	27,064

New Hampshire (2)

Area	Forest	Acres
Jobildunk	White Mountain National Forest	3,660
Pemigewasset	White Mountain National Forest	32,255

Oregon (1)

Area	Forest	Acres
Hebo 1a	Siuslaw National Forest	13,930

Utah (3)

Area	Forest	Acres
418012	Uinta National Forest	25,758
Fishhook	Dixie National Forest	12,959
Hogsback	Wasatch-Cache National Forest	7,936

Washington (1)

Area	Forest	Acres
Pasayten Rim	Okanogan National Forest	17,074

Wyoming (3)

Area	Forest	Acres
Gros Ventre Mountains	Bridger-Teton National Forest	106,418
Spread Creek - Gros Ventre River	Bridger-Teton National Forest	166,097
Teton Corridor Trailheads	Bridger-Teton National Forest	286

References (12)

American Society of Mammalogists (ASM). 2025. Mammal Diversity Database (Version 1.13) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.10595931. Online. Available: https://www.mammaldiversity.org/
Bradley, R.D., L.K. Ammerman, R.J. Baker, L.C. Bradley, J.A. Cook. R.C. Dowler, C. Jones, D.J. Schmidly, F.B. Stangl Jr., R.A. Van den Bussche and B. Würsig. 2014. Revised checklist of North American mammals north of Mexico, 2014. Museum of Texas Tech University Occasional Papers 327:1-28. Available at: http://www.nsrl.ttu.edu/publications/opapers/ops/OP327.pdf
Colella, J.P., L.M. Frederick, S.L. Talbot and J.A. Cook. 2021. Extrinsically reinforced hybrid speciation within Holarctic ermine (Mustela spp.) produces an insular endemic. Diversity and Distributions 27: 747-762.
Colella, J.P., T. Lan, S.C. Schuster, S.L. Talbot, J.A. Cook, and C. Lindqvist. 2018. Whole-genome analysis of Mustela erminea finds that pulsed hybridization impacts evolution at high latitudes. Communications Biology 1(51):1-10.
Committee on the Status of Endangered Wildlife in Canada (COSEWIC). 2005. Species Database: Ermine haidarum subspecies. Available online at: https://species-registry.canada.ca/index-en.html#/documents?documentTypeId=18&sortBy=documentTypeSort&sortDirection=asc&pageSize=10. Accessed 12Aug2005.
Cook, J. A., A. L. Bidlack, C. J. Conroy, J. R. Demboski, M. A. Fleming, A. M Runck, K. D. Stone, and S. O. MacDonald. 2001. A phylogeographic perspective on endemism in the Alexander Archipelago of southeast Alaska. Biological Conservation 97: 215-227.
Fagerstone, K.A. 1987. Black-footed ferret, long-tailed weasel, short-tailed weasel, and least weasel. Pages 549-573 in: M. Novak, J.A. Baker, M.E. Obbard, and B. Malloch, eds. Wild Furbearer Management and Conservation in North America. Ont. Minist. Nat. Resour., Toronto.
Fleming, M.A., and J.A. Cook. 2002. Phylogeography of endemic ermine (Mustela erminea) in southeast Alaska. Mol. Ecol. 11:795-807.
Hebda, A.J. 2011. List of mammals of Nova Scotia (including synonyms used in the literature relating to Nova Scotia) (revision 2) 24 July 2011. Nova Scotia Museum Collections Unit, Halifax, Nova Scotia. 24 pp. Online. Available: https://naturalhistory.novascotia.ca/sites/default/files/inline/images/names_and_synonyms_ver3.pdf
MacDonald, S.O. and J.A. Cook. 1996. The land mammal fauna of Southeast Alaska. The Canadian Field-Naturalist 110(4):571-598.
MacDonald, S.O. and J.A. Cook. 2005. Proposed additions to the U.S. Forest Service, Alaska Region, Sensitive Species List. Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM.
Wilson, D. E., and D. M. Reeder (editors). 1993. Mammal species of the world: a taxonomic and geographic reference. Second edition. Smithsonian Institution Press, Washington, DC. xviii + 1206 pp. Available online at: http://www.nmnh.si.edu/msw/.