Wyoming mammals

Big Brown Bat in Wyoming

Eptesicus fuscus

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

LC – Least Concern

Widespread and abundant; not at risk.

Big Brown Bats (Eptesicus fuscus)Big brown bat flying in daylight with wings spreadBig brown bat flying at night with wings spreadBig brown bat roosting on lichen-covered tree barkBig brown bat roosting on a wooden structure
Photo: Connor Long · CC BY-SA 4.0Big Brown Bats (Eptesicus fuscus)Photo: rhododendrites · CC-BY-SABig brown bat flying in daylight with wings spreadPhoto: Dan Riskin · CC-BYBig brown bat flying at night with wings spreadPhoto: Rita Clare · CC0Big brown bat roosting on lichen-covered tree barkPhoto: Bonnie Isaac · CC0Big brown bat roosting on a wooden structure

Big Brown Bat in Wyoming, by the numbers

Rare in Wyoming 95th most recorded of 126 mammals logged in Wyoming

153 occurrence records
10 with iNaturalist photos
Feb 1, 2025 Last seen in Wyoming

Records from 2000–2026.

153 total records count every Wyoming occurrence from GBIF and iNaturalist; the monthly chart covers the 149 records with a full observation date.

When to look for the Big Brown Bat in Wyoming

Most sightings fall in July to August.

149 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
January3
February1
March1
April0
May12
June22
July55
August45
September10
October0
November0
December0

Monthly big brown bat occurrence records (iNaturalist and GBIF) in Wyoming, 2000–2026.

Seasonality

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

Occurrence map

Where Big Brown Bat has been recorded in Wyoming

153 records mapped · zoom and drag to explore

153 Wyoming records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Fort Laramie National Historic Site 4
Grand Teton National Park 4
Devils Tower National Monument 1
Bridger National Forest 1
Bighorn Canyon National Recreation Area 1

Protected places with the most big brown bat 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
Laramie County 40
Big Horn County 26
Sweetwater County 15
Campbell County 12
Sheridan County 10
Natrona County 10
Goshen County 8
Fremont County 4
Washakie County 4
Teton County 4
Converse County 3
Platte County 3
8 other counties 14

The complete county distribution, spread across 20 Wyoming counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

Big brown bat’s 153 Wyoming records lean heavily toward GBIF (148 of 153), consistent with acoustic and capture-survey data around Medicine Bow National Forest and nearby high-plains stream corridors rather than casual sightings of a bat that forages well after dark. This is one of the most cold-tolerant North American bats, able to roost in buildings and rock crevices through much of the year rather than migrating long distances.

Reports rise through late spring and peak at 55 in July, tracking peak summer insect-foraging activity along stream corridors. NatureServe ranks the species S5, Secure, in Wyoming.

Occurrence data from iNaturalist and GBIF.

Big Brown Bats (Eptesicus fuscus)
Full species profile Big Brown Bat Eptesicus fuscus Size 7.5 cm3 in Weight 17 g0.6 oz Lifespan 19 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"