Oregon mammals

Big Brown Bat in Oregon

Eptesicus fuscus

Native to Oregon S4 Apparently Secure in Oregon

Not listed as nonindigenous in Oregon by USGS NAS; native to its Oregon 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 Oregon, by the numbers

Occasional in Oregon 89th most recorded of 178 mammals logged in Oregon

320 occurrence records
70 with iNaturalist photos
Jun 25, 2026 Last seen in Oregon

Records from 2000–2026.

320 total records count every Oregon occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 300; the monthly chart covers the 319 records with a full observation date.

When to look for the Big Brown Bat in Oregon

Most sightings fall in July to August.

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

Monthly Oregon records (table)
MonthRecords
January11
February2
March0
April4
May16
June28
July110
August121
September22
October4
November0
December1

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

Seasonality

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

Occurrence map

Where Big Brown Bat has been recorded in Oregon

300 records mapped · zoom and drag to explore

300 Oregon records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Oregon Caves National Monument and Preserve 8
Mt. Hood National Forest 7
Malheur National Forest 3
Eagle Cap Wilderness 3
Newberry National Volcanic Monument 1
Siuslaw National Forest 1
Deschutes National Forest 1
Steens Mountain Wilderness 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 Oregon

CountyRecords
Baker County 40
Lincoln County 35
Jefferson County 32
Wallowa County 25
Harney County 21
Benton County 18
Lane County 14
Deschutes County 14
Jackson County 13
Josephine County 13
Multnomah County 12
Grant County 11
19 other counties 72

The complete county distribution, spread across 31 Oregon counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

Big brown bats are one of the few Oregon bats that regularly roost in buildings alongside natural sites like rock crevices and tree cavities, a flexibility that’s helped the species hold up better than several cave-dependent relatives. Deschutes National Forest carries the strongest record concentration, with four named sightings anchoring the Cascades’ volcanic terrain as core habitat.

Records climb through early summer to a July peak, five times any spring month, tracking the maternity season when females roost together and pups become active fliers. NatureServe ranks the species S4, apparently secure, in Oregon, one of the healthier bat statuses in a state where white-nose syndrome has hit several other species hard.

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 Oregon 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"