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Mustela nivalis

Linnaeus, 1766

Least Weasel

G5Secure Found in 1 roadless area NatureServe Explorer →
G5SecureGlobal Rank
Least concernIUCN
Identity
Unique IDELEMENT_GLOBAL.2.102930
Element CodeAMAJF02020
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVertebrate Animal
IUCNLeast concern
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomAnimalia
PhylumCraniata
ClassMammalia
OrderCarnivora
FamilyMustelidae
GenusMustela
Synonyms
Mustela rixosa
Other Common Names
Belette pygmée (FR) least weasel (EN)
Concept Reference
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/
Taxonomic Comments
Following ASM (2025), this species includes subpalmata and previously included M. aistoodonnivalis. The Chinese and South East Asian forms tonkinensis, formosana, russelliana, and aistoodonnivalis have variously been considered distinct species (either closer to M. nivalis or M. kathiah) or as subspecies or synonyms of M. nivalis; these are all tentatively retained under M. nivalis, with the exception of M. aistoodonnivalis, which is recognized as a distinct species. The other named forms (tonkinensis and russelliana) may represent this species as well, which would make russelliana the oldest name available, although further research is needed.
Conservation Status
Rank MethodExpertise without calculation
Review Date2016-04-04
Change Date1996-11-18
Range Extent Comments
Circumboreal, Holarctic distribution. Western Hemisphere: most of Canada and Alaska south to British Columbia, Montana, Wyoming, Oklahoma, Missouri, Ohio, Virginia, and along the Appalachians to the Great Smoky Mountains (North Carolina, Tennessee). Range has expanded southward in the Great Plains since the mid-1960s as the climate has become cooler and more mesic (Frey 1992). Thought to be rare (though sometimes locally fairly common) throughout the range in the southeastern U.S., but actual status is uncertain (Handley 1991). Introduced in New Zealand, Malta, Crete, the Azore Islands, and apparently also Sao Tome off west Africa (Sheffield and King 1994). Ranges to 3660 m in mountains of Eurasia.
Ecology & Habitat

Habitat

Habitat varies geographically and includes open forests, farmlands and cultivated areas, grassy fields and meadows, riparian woodlands, hedgerows, alpine meadows, scrub, steppe and semi-deserts, prairies, coastal dunes, and sometimes rural residential areas; snow cover is not an obstacle; generally avoids deep dense forest and sandy desert. When inactive, occupies burrow made by vole or mole, or rests in nest in hole in wall of building or under corn shock or similar site. Den site may change often. Young are born in abandoned underground burrows made by other mammals (or similar secluded sites).

Ecology

Home range size varies with conditions; up to 26 ha in males, up to 7 ha in females; in England, average home range was 7-15 ha for males, 1-4 ha for females (King 1975). Basically solitary, except during breeding season and when females have young. High dispersal rate, good ability to colonize vacant habitat when rodent populations increase.

Density fluctuates with rodent populations; 0.2-1.0/ha in favorable conditions, average as low as 1-7/100 ha over wider areas (Erlinger 1974, Golley 1960, Sheffield and King 1994).

Mortality rate is high (overall annual rate is 75-90%); average age at death is less than one year. Predators include various Carnovora, raptors, and possibly snakes.

Reproduction

May breed throughout the year but mainly in spring and late summer. When rodents are plentiful, may breed in winter under snow. Gestation lasts 34-37 days, including the 10-12 days between fertilization and implantation. Litter size averages 4-5 in temperate zone, higher in arctic latitudes. Commonly two litters/year. Young are tended by both parents, weaned by 6-7 weeks. Family groups break up when young are about 9-12 weeks old. Spring-born females are sexually mature in 3-4 months (may produce a litter in their first summer), males in 8 months. Reproductive output increases when food is abundant (more young are born, greater survivorship).
Terrestrial Habitats
Woodland - HardwoodWoodland - ConiferWoodland - MixedShrubland/chaparralGrassland/herbaceousOld fieldAlpineTundraCropland/hedgerow
Palustrine Habitats
HERBACEOUS WETLANDRiparian
Other Nations (2)
CanadaN5
ProvinceRankNative
QuebecS2Yes
OntarioSUYes
NunavutS5Yes
LabradorS2Yes
British ColumbiaS4Yes
Yukon TerritoryS4Yes
Northwest TerritoriesS5Yes
AlbertaS5Yes
ManitobaS3Yes
SaskatchewanS5Yes
United StatesN5
ProvinceRankNative
MontanaS4Yes
MarylandS2Yes
AlaskaS4Yes
NebraskaS5Yes
MichiganS5Yes
West VirginiaS3Yes
North CarolinaS2Yes
PennsylvaniaS5Yes
VirginiaS3Yes
KansasS4Yes
IndianaS2Yes
New YorkS1Yes
MissouriS3Yes
South DakotaS5Yes
MinnesotaS3Yes
South CarolinaS2Yes
WisconsinSUYes
OhioSNRYes
North DakotaS4Yes
KentuckyS2Yes
TennesseeS2Yes
IowaS3Yes
WyomingS1Yes
IllinoisS3Yes
GeorgiaS1Yes
Threat Assessments
ThreatScopeSeverityTiming
2 - Agriculture & aquaculture——High (continuing)
2.1 - Annual & perennial non-timber crops——High (continuing)
5 - Biological resource use——High (continuing)
5.1 - Hunting & collecting terrestrial animals——High (continuing)
7 - Natural system modifications——High (continuing)
7.3 - Other ecosystem modifications——High (continuing)

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Roadless Areas (1)
Minnesota (1)
AreaForestAcres
Baker - Homer - Brule LakesSuperior National Forest6,712
References (28)
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  2. Abramov, A. V., and G. F. Baryshnikov. 2000. Geographical variation and intraspecific taxonomy of weasel <i>Mustela nivalis</i> (Carnivora, Mustelidae). Zoosystematica Rossica 8:365-402.
  3. 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/
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  7. Erlinger, S. 1974. Distribution, territoriality, and numbers of the weasel Mustela nivalis in relation to prey abundance. Oikos 25(3):308-314.
  8. Frey, J. K. 1992. Response of a mammalian faunal element to climatic changes. J. Mamm. 73:43-50.
  9. Golley, F.B. 1960. Energy dynamics of a food chain of an old-field community. Ecol. Manag. 30(2):187-206.
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  19. Lin, L. K., M. Motokawa, and M. Harada. 2010. A new subspecies of the least weasel <i>Mustela nivalis</i> (Mammalia, Carnivora) from Taiwan. Mammal Study 35(3):191-200.
  20. Linzey, D.W. 2016. Mammals of Great Smoky Mountains National Park: 2016 revision. Southeastern Naturalist 15(Monograph 8):1–93.
  21. Liu, Y., Y. Pu, S. Chen, X. Wang, R. W. Murphy, X. Wang, R. Liao, K. Tang, B. Yue, and S. Liu. 2023. Revalidation and expanded description of <i>Mustela aistoodonnivalis</i> (Mustelidae: Carnivora) based on a multigene phylogeny and morphology. Ecology and Evolution 13(4):e9944.
  22. Reig, S. 1997. Biogeographic and evolutionary implications of size variation in North Amnerican least weasels (MUSTELA NIVALIS). Canadian Journal of Zoology 75:2036-2049.
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  24. Schwartz, C. W., and E. R. Schwartz. 1981. The wild mammals of Missouri. University of Missouri Press, Columbia. 356 pp.
  25. Sheffield, S. R., and C. M. King. 1994. Mustela nivalis. Am. Soc. Mamm., Mammalian Species No. 454:1-10.
  26. van Zyll de Jong, C. G. 1992. A morphometric analysis of cranial variation in Holarctic weasels (MUSTELA NIVALIS). Zeitschrift fur Saugetierkunde 57:77-93.
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  28. Wilson, D. E., and D. M. Reeder (editors). 2005. Mammal species of the world: a taxonomic and geographic reference. Third edition. The Johns Hopkins University Press, Baltimore. Two volumes. 2,142 pp. [As modified by ASM the Mammal Diversity Database (MDD) at https://www.mammaldiversity.org/index.html]