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

LC – Least Concern

Widespread and abundant; not at risk.

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

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 79th most recorded of 178 mammals logged in Oregon

80 occurrence records

74 with iNaturalist photos

Jun 25, 2026 Last seen in Oregon

Records from 2000–2026.

80 total records count every Oregon occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 76; the monthly chart covers the 76 records with a full observation date.

When to look for the Big Brown Bat in Oregon

Most sightings fall in July to August.

76 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)

Month	Records
January	3
February	0
March	0
April	2
May	3
June	12
July	21
August	20
September	10
October	4
November	0
December	1

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

76 records mapped · zoom and drag to explore

76 Oregon records mapped

Notable places to look

Park, forest, or monument	iNaturalist records
Oregon Caves National Monument and Preserve	8
Deschutes National Forest	1
Siuslaw National Forest	1
Newberry National Volcanic Monument	1
Sauvie Island Wildlife 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

County	Records
Deschutes County	10
Josephine County	9
Lane County	6
Lake County	5
Washington County	5
Jackson County	5
Jefferson County	4
Columbia County	3
Douglas County	3
Benton County	3
Clatsop County	3
Klamath County	3
11 other counties	21

The complete county distribution, spread across 23 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 County leads a thin, scattered county list with 10 records, and Oregon Caves National Monument and Preserve in the Siskiyous is the busiest named place, with 8.

Records climb through early summer to a July peak, several 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.

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"