Wyoming mammals

Western Little Brown Myotis in Wyoming

Myotis lucifugus

Native to Wyoming S5 Secure in Wyoming

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

IUCN Red List status

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

EN – Endangered

Very high risk of extinction in the wild.

Little brown myotis roosting alertly on a wooden beamLittle brown myotis roosting in the corner of an attic beamLittle brown myotis roosting on painted wood sidingLittle brown myotis resting among blue spruce branches
Photo: Steph Brulot-Sawchyn · CC0Little brown myotis roosting alertly on a wooden beamPhoto: LeeAnn Latremouille · CC BY 4.0Little brown myotis roosting in the corner of an attic beamPhoto: Tom Romeo · CC BY 4.0Little brown myotis roosting on painted wood sidingPhoto: Patrick Jackson · CC BY 4.0Little brown myotis resting among blue spruce branches

Western Little Brown Myotis in Wyoming, by the numbers

Rare in Wyoming 90th most recorded of 126 mammals logged in Wyoming

435 occurrence records
12 with iNaturalist photos
Aug 19, 2025 Last seen in Wyoming

Records from 2000–2026.

435 total records count every Wyoming occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 300; the monthly chart covers the 433 records with a full observation date.

When to look for the Western Little Brown Myotis in Wyoming

Most sightings fall in July to August.

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

Monthly Wyoming records (table)
MonthRecords
January5
February1
March1
April1
May31
June72
July125
August151
September39
October7
November0
December0

Monthly western little brown myotis occurrence records (iNaturalist and GBIF) in Wyoming, 2000–2026.

Seasonality

Year-round in Wyoming, with recorded sightings peaking in July–August.

Occurrence map

Where Western Little Brown Myotis has been recorded in Wyoming

300 records mapped · zoom and drag to explore

300 Wyoming records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Yellowstone National Park 44
Fort Laramie National Historic Site 32
Bighorn Canyon National Recreation Area 24
Grand Teton National Park 20
Fossil Butte National Monument 4
Devils Tower National Monument 1

Protected places with the most western little brown myotis 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 Wyoming

CountyRecords
Teton County 108
Big Horn County 50
Sheridan County 38
Goshen County 33
Sublette County 30
Park County 23
Sweetwater County 22
Laramie County 21
Fremont County 17
Albany County 15
Natrona County 14
Lincoln County 11
11 other counties 53

The complete county distribution, spread across 23 Wyoming counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

Western little brown myotis carries a strong Wyoming record, 435 total sightings clustered around Yellowstone National Park, though the IUCN lists the species globally Endangered due to white-nose syndrome, a fungal disease that has collapsed brown bat colonies across much of North America since the mid-2000s. The heavy GBIF weighting, 427 of 435 records, points to acoustic and capture-survey data rather than casual photographs of this small, fast-flying bat.

Records climb sharply from May onward and peak at 151 in August, tracking the active summer foraging season before bats disperse to winter hibernacula. NatureServe still lists the species S5, Secure, in Wyoming, a reminder that state-level abundance and the global disease threat are two different pictures.

Occurrence data from iNaturalist and GBIF.

Little brown myotis roosting alertly on a wooden beam
Full species profile Western Little Brown Myotis Myotis lucifugus Size 8–9.5 cm3.1–3.7 in Weight 6–13 g0.2–0.5 oz Lifespan 35 yr View the full profile

More mammals in Wyoming 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"