Washington mammals

Big Brown Bat in Washington

Eptesicus fuscus

Native to Washington S4 Apparently Secure in Washington

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

Occasional in Washington 63rd most recorded of 145 mammals logged in Washington

301 occurrence records
35 with iNaturalist photos
Jul 7, 2026 Last seen in Washington

Records from 2000–2026.

301 total records count every Washington occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 296; the monthly chart covers the 294 records with a full observation date.

When to look for the Big Brown Bat in Washington

Most sightings fall in July to August.

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

Monthly Washington records (table)
MonthRecords
January2
February21
March2
April9
May20
June43
July60
August85
September34
October10
November4
December4

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

Seasonality

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

Occurrence map

Where Big Brown Bat has been recorded in Washington

296 records mapped · zoom and drag to explore

294 Washington records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
San Juan Islands National Monument 3
Lake Roosevelt National Recreation Area 2
Wenas Wildlife Area Complex 1
Washington State Department of Natural Resources (WADNR) State Resource Management Area 1
Gifford Pinchot National Forest 1
Steamboat Rock 1
Skagit-Snoqualmie Wildlife Area Complex 1
Lake Chelan 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 Washington

CountyRecords
King County 52
Thurston County 37
Pierce County 31
Yakima County 15
Klickitat County 13
Lewis County 11
Snohomish County 11
Chelan County 10
Douglas County 9
Spokane County 8
Walla Walla County 8
Columbia County 8
23 other counties 88

The complete county distribution, spread across 35 Washington counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

For Washington, big brown bat has a 301-record occurrence file covering 2000–2026. The overlay pairs 35 iNaturalist records with 291 GBIF records, a source mix that matters when interpreting the map. Measured strictly by submitted records, it sits 57 in the 126-species state list.

The monthly series reaches its high point in August (85 records), compared with 2 in January. The named-site evidence is anchored by Okanogan-Wenatchee National Forest and its 1 record. This is documented occurrence, with no basis for converting record totals into animal numbers.

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 Washington 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"