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Least Weasel

Mustela nivalis

Mammal · family Mustelidae · order Carnivora

  1. G1
    Critically imperiled
  2. G2
    Imperiled
  3. G3
    Vulnerable
  4. G4
    Apparently secure
  5. G5
    Secure

NatureServe global rank G5: secure[2].

Updated October 30, 2026. Published by Humblebee.

Endangered Species Act
Not listed[1]
NatureServe global rank
G5 Secure[2]
Native in
25 states[3]
Longest recorded life
9.1 years[4]

The Least Weasel (Mustela nivalis) is a small meat-eating mammal in the family Mustelidae[5]. It is ranked Secure worldwide and in the United States, and it is native to 25 US states and territories[2][6][3].

Conservation status

NatureServe gives the Least Weasel a global rank of G5 (Secure) and a US national rank of N5 (Secure)[2][6]. The IUCN Red List category recorded by NatureServe is Least concern[7]. The animal is not listed as endangered or threatened under the US Endangered Species Act in USFWS ECOS data checked on 2026-10-30[1]. State ranks differ across the 25 states, and the full list is in the table on this page[8].

Status Value
Endangered Species Act[1] Not listed
NatureServe global rank[2] G5 (Secure)
NatureServe US rank[6] N5 (Secure)
IUCN Red List (via NatureServe)[7] Least concern

Where Least Weasel lives

NatureServe lists the Least Weasel as native in Alaska, Georgia, Iowa, Illinois, Indiana, Kansas, Kentucky, Maryland, Michigan, Minnesota, Missouri, Montana, North Carolina, North Dakota, Nebraska, New York, Ohio, Pennsylvania, South Carolina, South Dakota, Tennessee, Virginia, Wisconsin, West Virginia and Wyoming[3]. This is where NatureServe records the species, not a promise you will see one there[3]. National Park Service lists record it in 22 park units[9].

Alaska: native, state rank S4AKMaine: not recordedMEWisconsin: native, state rank S4WIVermont: not recordedVTNew Hampshire: not recordedNHWashington: not recordedWAIdaho: not recordedIDMontana: native, state rank S4MTNorth Dakota: native, state rank S4NDMinnesota: native, state rank S3MNIllinois: native, state rank S3ILMichigan: native, state rank S5MINew York: native, state rank S1NYMassachusetts: not recordedMAOregon: not recordedORNevada: not recordedNVWyoming: native, state rank S1WYSouth Dakota: native, state rank S5SDIowa: native, state rank S3IAIndiana: native, state rank S2INOhio: native, state rank SNROHPennsylvania: native, state rank S5PANew Jersey: not recordedNJConnecticut: not recordedCTRhode Island: not recordedRICalifornia: not recordedCAUtah: not recordedUTColorado: not recordedCONebraska: native, state rank S5NEMissouri: native, state rank S3MOKentucky: native, state rank S2KYWest Virginia: native, state rank S3WVVirginia: native, state rank S3VAMaryland: native, state rank S2MDDelaware: not recordedDEArizona: not recordedAZNew Mexico: not recordedNMKansas: native, state rank S4KSArkansas: not recordedARTennessee: native, state rank S2TNNorth Carolina: native, state rank S2NCSouth Carolina: native, state rank S2SCDistrict of Columbia: not recordedDCOklahoma: not recordedOKLouisiana: not recordedLAMississippi: not recordedMSAlabama: not recordedALGeorgia: native, state rank S1GAHawaii: not recordedHITexas: not recordedTXFlorida: not recordedFLPuerto Rico: not recordedPR
State presence as recorded by NatureServe[8].
Show state ranks (25 states)
StateRankMeaning
AlaskaS4Apparently Secure
GeorgiaS1Critically Imperiled
IllinoisS3Vulnerable
IndianaS2Imperiled
IowaS3Vulnerable
KansasS4Apparently Secure
KentuckyS2Imperiled
MarylandS2Imperiled
MichiganS5Secure
MinnesotaS3Vulnerable
MissouriS3Vulnerable
MontanaS4Apparently Secure
NebraskaS5Secure
New YorkS1Critically Imperiled
North CarolinaS2Imperiled
North DakotaS4Apparently Secure
OhioSNRNot Ranked
PennsylvaniaS5Secure
South CarolinaS2Imperiled
South DakotaS5Secure
TennesseeS2Imperiled
VirginiaS3Vulnerable
West VirginiaS3Vulnerable
WisconsinS4Apparently Secure
WyomingS1Critically Imperiled

Habitat

NatureServe records many habitat types for the Least Weasel, including forests, shrubland, grassland, old fields, alpine areas, tundra, cropland and hedgerows, and wetlands and riparian (streamside) areas[10]. Farmland, meadows, scrub and some rural residential areas are also used, and snow cover does not stop it[11]. It tends to stay out of thick forest interiors and sandy deserts[11]. When resting, it uses burrows dug by voles or moles, or nests in places like holes in building walls[11].

Habitat types recorded by NatureServe[10]

Size, diet and lifespan

The Least Weasel is a carnivore that mainly hunts small mammals such as voles, lemmings and mice[12][13]. NatureServe records a typical length of 21 cm (8 in)[14]. Its typical adult weight is 50 g[15]. Gestation is 36 days in AnAge, and a typical litter is 5 young[16][17].

Trait Value
Typical length[14] 21 cm (8 in)
Typical adult weight[15] 50 g (1.8 oz)
Longest recorded lifespan (AnAge)[4] 9.1 years (captivity)
Litter or clutch size[17] 5
Gestation or incubation[16] 36 days
Female maturity[18] 120 days (about 0.3 years)
Food habits[12] Carnivore
Active[19] nocturnal
Migration[20] non-migrant

Estimated diet composition (EltonTraits 1.0)[21]

  • 100% warm-blooded vertebrates

When to look for it

NatureServe describes the Least Weasel as active day or night through the whole year, and it is recorded as a non-migrant, although populations can differ[22][20]. EltonTraits lists it as nocturnal[19]. Breeding can happen in any month, with peaks in spring and again near the end of summer[23]. GBIF records in the United States are highest in January, November and December, which reflects when people look and report and not how many animals there are[24].

January: 130 recordsJanFebruary: 100 recordsFebMarch: 108 recordsMarApril: 84 recordsAprMay: 70 recordsMayJune: 124 recordsJunJuly: 93 recordsJulAugust: 81 recordsAugSeptember: 79 recordsSepOctober: 80 recordsOctNovember: 127 recordsNovDecember: 127 recordsDec
US observation records on GBIF by month, all years. The three months with the most records are highlighted. Records show when people look and report, not how many animals there are[24].
Show records by month
MonthRecords
January130
February100
March108
April84
May70
June124
July93
August81
September79
October80
November127
December127

Where to see it

National Park Service species lists record Least Weasel as present in 22 park units[9]. Present means the park has a confirmed record, not that sightings are common.

States with the most GBIF observation records: Alaska, Ohio, Michigan, Pennsylvania, Minnesota[25]. These counts follow where people look and report, not population size.

Questions people ask

Is the Least Weasel endangered?
No. It is not listed as endangered or threatened under the US Endangered Species Act[1]. NatureServe ranks it G5 (Secure) globally and N5 (Secure) in the United States[2][6].
Where does the Least Weasel live in the US?
NatureServe lists it as native in 25 US states and territories, including Alaska, Michigan, Pennsylvania, Montana and Wyoming[3].
What does the Least Weasel eat?
It is a carnivore that mainly hunts small mammals such as voles, lemmings and mice[12][13]. EltonTraits estimates its diet is 100% warm-blooded vertebrates[21].
How big is a Least Weasel?
NatureServe records a typical length of 21 cm (8 in)[14]. Its typical adult weight is 50 g[15].

Facts and sources

  1. Least Weasel is not listed as endangered or threatened under the US Endangered Species Act in USFWS ECOS data (checked 2026-10-30). USFWS ECOS
  2. NatureServe global conservation status rank for Least Weasel: G5 (Secure). NatureServe Explorer
  3. NatureServe lists Least Weasel as native in 25 US states and territories: Alaska, Georgia, Iowa, Illinois, Indiana, Kansas, Kentucky, Maryland, Michigan, Minnesota, Missouri, Montana, North Carolina, North Dakota, Nebraska, New York, Ohio, Pennsylvania,... NatureServe Explorer
  4. Maximum recorded lifespan in AnAge: 9.1 years in captivity. This is a record, not a typical lifespan. AnAge
  5. Least Weasel (Mustela nivalis) is a mammal in the family Mustelidae, order Carnivora. NatureServe Explorer
  6. NatureServe national rank in the United States: N5 (Secure). NatureServe Explorer
  7. IUCN Red List category as recorded by NatureServe: Least concern. NatureServe Explorer
  8. NatureServe state ranks for Least Weasel (map and table on this page). NatureServe Explorer
  9. NPSpecies park lists recording Least Weasel as present (list on this page). NPS NPSpecies
  10. Habitat types NatureServe records for Least Weasel: Woodland - hardwood, Woodland - conifer, Woodland - mixed, Shrubland/chaparral, Grassland/herbaceous, Old field, Alpine, Tundra, Cropland/hedgerow, Herbaceous wetland, Riparian. NatureServe Explorer
  11. NatureServe notes on habitat for Least Weasel. NatureServe Explorer
  12. Adult food habits recorded by NatureServe: Carnivore. NatureServe Explorer
  13. NatureServe notes on food for Least Weasel. NatureServe Explorer
  14. Typical length recorded by NatureServe: 21 cm (8 in). NatureServe Explorer
  15. Typical adult weight recorded by NatureServe: 50 g (1.8 oz). NatureServe Explorer
  16. Gestation or incubation period in AnAge: 36 days. AnAge
  17. Typical litter or clutch size in AnAge: 5. AnAge
  18. Age at female sexual maturity in AnAge: 120 days (about 0.3 years). AnAge
  19. Activity time in EltonTraits 1.0: nocturnal. EltonTraits 1.0
  20. NatureServe migration category for Least Weasel: non-migrant (populations can differ). NatureServe Explorer
  21. Estimated diet composition in EltonTraits 1.0: 100% warm-blooded vertebrates. EltonTraits 1.0
  22. NatureServe notes on phenology for Least Weasel. NatureServe Explorer
  23. NatureServe notes on reproduction for Least Weasel. NatureServe Explorer
  24. GBIF observation records of Least Weasel in the US by month (chart on this page). GBIF
  25. US states with the most GBIF observation records of Least Weasel: Alaska, Ohio, Michigan, Pennsylvania, Minnesota. Record counts follow observer effort, not population size. GBIF

Status, range and habitat come from NatureServe Explorer (CC BY 4.0) and USFWS ECOS at the snapshot date. Listings change by federal rule. State lists are where NatureServe records the species, not a promise that you will see it there. Never name a place smaller than a state. GBIF and park records count observations and checklists. They show where and when people report the species, not how many animals live there.

NatureServe. 2026. NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org. (Accessed: October 30, 2026). Licensed under CC BY 4.0; SpeciesFacts selected and summarized it.