Montana mammals

American Ermine in Montana

Mustela erminea

Native to Montana

Not listed as nonindigenous in Montana by USGS NAS; treated as native to its mapped Montana range.

IUCN Red List status

  1. LC
  2. NT
  3. VU
  4. EN
  5. CR
  6. EW
  7. EX

LC – Least Concern

Widespread and abundant; not at risk.

Mustela Erminea headMustela erminea hibernicaMustela erminea uprightAmerican ermine standing alert on a wooden beamAmerican ermine peering from a mossy den entranceAmerican ermine in white winter coat crossing an alpine talus slope
Photo: Keven Law from Los Angeles, USA · CC BY-SA 2.0Mustela Erminea headPhoto: Alastair Rae from London, United Kingdom · CC BY-SA 2.0Mustela erminea hibernicaPhoto: Steve Hillebrand, USFWS · Public domainMustela erminea uprightPhoto: Robbie Hannawacker · CC0American ermine standing alert on a wooden beamPhoto: miaow7477 · CC0American ermine peering from a mossy den entrancePhoto: Игорь Загребин · CC0American ermine in white winter coat crossing an alpine talus slope

American Ermine in Montana, by the numbers

Occasional in Montana 59th most recorded of 122 mammals logged in Montana

37 occurrence records
31 with iNaturalist photos

Records from 2000–2026.

37 total records count every Montana occurrence from GBIF and iNaturalist; the monthly chart covers the 36 records with a full observation date.

When to look for the American Ermine in Montana

Most sightings fall in August to September.

36 Montana occurrence records (iNaturalist and GBIF) by month of year, 2000–2026. Shows when the species is recorded, not a guarantee of presence.

Monthly Montana records (table)
MonthRecords
January1
February0
March2
April0
May1
June2
July4
August12
September8
October3
November1
December2

Monthly american ermine occurrence records (iNaturalist and GBIF) in Montana, 2000–2026.

Seasonality

Year-round in Montana, with recorded sightings peaking in August–September.

Occurrence map

Where American Ermine has been recorded in Montana

37 records mapped · zoom and drag to explore

37 Montana records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Glacier National Park 7
Lolo National Forest 1
Council Grove State Park 1
Flathead National Forest 1

Protected places with the most american ermine sightings, from the USGS Protected Areas Database plus named mountain ranges, good spots to look, not a full breakdown, so they don't sum to the total.

Where it's recorded in Montana

CountyRecords
Missoula County 6
Glacier County 6
Lake County 4
Mineral County 4
Ravalli County 4
Sanders County 4
Flathead County 3
Beaverhead County 2
Lincoln County 1
Meagher County 1
Park County 1
Gallatin County 1

The complete county distribution, spread across 12 Montana counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

American ermine records in Montana come mostly from the west side of the state: Missoula and Glacier counties hold 6 each, and Glacier National Park, with 7, is the named place that holds the most. This small weasel hunts voles and other small rodents along brushy edges in that mountain country. Most of the 37 records, 31 in all, came through iNaturalist.

Reports peak in August and September, a crest that likely tracks when observers are out as much as any seasonal change in the weasel. NatureServe treats the species as native to its mapped Montana range.

Occurrence data from iNaturalist and GBIF.

American Ermine in other states

Mustela Erminea head
Full species profile American Ermine Mustela erminea Size 17–33 cm6.7–13 in Weight 70–260 g2.5–9.2 oz Lifespan Up to 12.5 yr View the full profile

More mammals in Montana in the atlas

Data & sources

The data and visualizations on this page draw on these open sources:

  • GBIFCC-BY 4.0occurrence records behind the range map, elevation, and record counts
  • iNaturalistCC0 / CC-BY / CC-BY-SAobservations, photos, and audio recordings
  • IUCN Red Listattributed factthe global conservation status
  • USGS NASpublic domainnative / introduced status
  • Natural Earthpublic domainthe relief basemap
  • USFSpublic domainnational-forest boundaries
  • USGS Protected Areas Databasepublic domainthe named parks, forests, and refuges behind "notable places to look"