Montana mammals

Masked Shrew in Montana

Sorex cinereus

Native to Montana S5 Secure in Montana

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

Sorex cinereus, Harwich, Chatham, Ontario, Canada 1Sorex cinereus, Harwich, Chatham, Ontario, Canada 2Sorex cinereus, Harwich, Chatham, Ontario, Canada 3Sorex cinereus, Harwich, Chatham, Ontario, Canada 4Sorex cinereus, Billings National Historical Park, Woodstock, Vermont, USA 1Masked Shrew (Sorex cinereus)
Photo: rpoort · CC BY 4.0Sorex cinereus, Harwich, Chatham, Ontario, Canada 1Photo: rpoort · CC BY 4.0Sorex cinereus, Harwich, Chatham, Ontario, Canada 2Photo: rpoort · CC BY 4.0Sorex cinereus, Harwich, Chatham, Ontario, Canada 3Photo: rpoort · CC BY 4.0Sorex cinereus, Harwich, Chatham, Ontario, Canada 4Photo: er-birds · CC BY 4.0Sorex cinereus, Billings National Historical Park, Woodstock, Vermont, USA 1Photo: Sean Frey · CC BY 4.0Masked Shrew (Sorex cinereus)

Masked Shrew in Montana, by the numbers

Occasional in Montana 43rd most recorded of 122 mammals logged in Montana

962 occurrence records

Records from 2000–2026.

962 total records count every Montana occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 300; the monthly chart covers the 910 records with a full observation date.

When to look for the Masked Shrew in Montana

Most sightings fall in July.

910 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
January9
February7
March7
April26
May41
June172
July335
August190
September35
October58
November21
December9

Monthly masked shrew occurrence records (iNaturalist and GBIF) in Montana, 2000–2026.

Seasonality

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

Occurrence map

Where Masked Shrew has been recorded in Montana

300 records mapped · zoom and drag to explore

300 Montana records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Swan River State Forest 52
Flathead Lake Biological Station 47
Lolo National Forest 22
Glacier National Park 8
Threemile Wildlife Management Area 7
Montana State Trust Lands 6
Warm Springs Wildlife Management Area 5
Sun River Wildlife Management Area 3

Protected places with the most masked shrew 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
Lake County 243
Missoula County 226
Teton County 68
Sanders County 42
Lincoln County 40
Lewis and Clark County 39
Flathead County 35
Deer Lodge County 34
Park County 24
Glacier County 24
Beaverhead County 23
Ravalli County 22
30 other counties 142

The complete county distribution, spread across 42 Montana counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

Cinereus shrews, also called masked shrews, are among the smallest mammals in Montana, and their metabolism runs so fast they have to hunt insects and other invertebrates almost constantly to survive. With 962 records, this is one of the best-documented small mammals in this rank range, concentrated in the moist forest floor of Glacier National Park, the Absaroka-Beartooth Mountains, and Custer-Gallatin National Forest.

Records climb sharply into a July peak, more than 35 times the January low, tracking summer field-survey season and breeding-related movement rather than any true winter absence, since this shrew stays active underground year-round. NatureServe rates it secure (S5) statewide.

Occurrence data from iNaturalist and GBIF.

Sorex cinereus, Harwich, Chatham, Ontario, Canada 1
Full species profile Masked Shrew Sorex cinereus Size 6.9 cm2.7 in Weight 5 g0.2 oz Lifespan Up to 2.5 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
  • NatureServe ExplorerCC-BYthe state conservation rank
  • 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"