California mammals

American Ermine in California

Mustela erminea

Native to California

Not listed as nonindigenous in California by USGS NAS; treated as native to its mapped California 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 California, by the numbers

Occasional in California 140th most recorded of 233 mammals logged in California

76 occurrence records
55 with iNaturalist photos

Records from 2000–2026.

76 total records count every California occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 75; the monthly chart covers the 75 records with a full observation date.

When to look for the American Ermine in California

Most sightings fall in July.

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

Monthly California records (table)
MonthRecords
January3
February0
March3
April4
May6
June8
July26
August15
September7
October2
November1
December0

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

Seasonality

Year-round in California, with recorded sightings peaking in July.

Occurrence map

Where American Ermine has been recorded in California

75 records mapped · zoom and drag to explore

75 California records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Yosemite National Park 8
Inyo National Forest 3
John Muir Wilderness 3
Kings Canyon National Park 3
Redwood National Park 3
Phillip Burton Wilderness Area 2
Lassen Volcanic National Park 2
Desolation Wilderness 2

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 California

CountyRecords
Mono County 13
El Dorado County 7
Humboldt County 6
Mariposa County 6
Marin County 5
Tuolumne County 5
Inyo County 4
Fresno County 3
Sonoma County 3
Mendocino County 2
Tehama County 2
Shasta County 2
9 other counties 18

The complete county distribution, spread across 21 California 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 California fit cool conifer forest, rocky slopes, and mountain meadows.

Most of the state’s 76 records come from the Sierra Nevada, led by Mono County with 13 and Yosemite National Park with 8, while a smaller set turns up along the cool north coast in Humboldt County, Redwood National Park and the Point Reyes wilderness in Marin. Those sites mark where people happened to photograph or collect an ermine, not where its best habitat lies.

Reports climb to a July high of 26 and stay busy into August before tapering off. Snow cover, summer trail traffic and the weasel’s own movements all shape that curve, so it isn’t a population count.

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 California 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"