Montana mammals

Big Brown Bat in Montana

Eptesicus fuscus

Native to Montana S4 Apparently 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.

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 Montana, by the numbers

Occasional in Montana 78th most recorded of 122 mammals logged in Montana

162 occurrence records

Records from 2000–2026.

162 total records count every Montana occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 161; the monthly chart covers the 146 records with a full observation date.

When to look for the Big Brown Bat in Montana

Most sightings fall in July.

146 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
January2
February0
March1
April1
May6
June24
July81
August15
September13
October2
November0
December1

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

Seasonality

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

Occurrence map

Where Big Brown Bat has been recorded in Montana

161 records mapped · zoom and drag to explore

161 Montana records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Giant Springs State Park 1
Lewis and Clark Caverns State Park 1
Kaniksu National Forest 1
Upper Missouri River Breaks National Monument 1
Montana State Trust Lands 1
Lubrecht State Experimental Forest 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 Montana

CountyRecords
Carter County 71
Missoula County 23
Ravalli County 22
Yellowstone County 7
Fergus County 6
Rosebud County 6
Carbon County 4
Prairie County 3
Powder River County 3
Cascade County 2
Lake County 2
Valley County 1
11 other counties 12

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

Big brown bat records in Montana reach from Red Rock Lakes to Flathead Lake and the Missouri River corridor, reflecting a bat that roosts as readily in buildings and bridges as in natural rock crevices. With 162 total records, all from GBIF, it’s one of the more thoroughly documented bats in this rank band.

Reports climb sharply to 81 in July, when maternity colonies are most active and young bats begin flying, then fall off fast by fall. NatureServe ranks the species S4, Apparently Secure, in Montana.

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 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"