Maryland mammals

Big Brown Bat in Maryland

Eptesicus fuscus

Native to Maryland S4 Apparently Secure in Maryland

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

Occasional in Maryland 25th most recorded of 57 mammals logged in Maryland

164 occurrence records
164 with iNaturalist photos

Records from 2000–2026.

164 total records count every Maryland occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 154; the monthly chart covers the 154 records with a full observation date.

When to look for the Big Brown Bat in Maryland

Most sightings fall in August.

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

Monthly Maryland records (table)
MonthRecords
January5
February6
March11
April7
May18
June14
July18
August31
September18
October14
November7
December5

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

Seasonality

Year-round in Maryland, with recorded sightings peaking in August.

Occurrence map

Where Big Brown Bat has been recorded in Maryland

154 records mapped · zoom and drag to explore

154 Maryland records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Chesapeake and Ohio Canal National Historical Park 4
Martinak State Park 3
Milburn Landing State Park 1
Kings Landing Natural Resource Management Area 1
Catoctin Mountain Park 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 Maryland

CountyRecords
Baltimore County 32
Montgomery County 26
Allegany County 11
Howard County 9
Frederick County 9
Garrett County 8
Prince George's County 8
Washington County 7
Calvert County 7
Anne Arundel County 7
St. Mary's County 5
Carroll County 5
8 other counties 30

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

Big brown bat carries one of the stronger records among Maryland’s bats, with sightings logged across Savage River and Green Ridge state forests and around Deep Creek Lake in the state’s western mountains. This species tolerates cold well, often roosting in buildings and rock crevices through much of the year instead of migrating far.

Records climb steadily from spring into summer and peak in August, tracking the season when young bats are flying and foraging alongside adults. NatureServe ranks the species S4, Apparently Secure, in Maryland.

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 Maryland 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"