Pennsylvania mammals

Western Little Brown Myotis in Pennsylvania

Myotis lucifugus

Native to Pennsylvania S1 Critically Imperiled in Pennsylvania

Not listed as nonindigenous in Pennsylvania by USGS NAS; native to its Pennsylvania range.

IUCN Red List status

  1. LC
  2. NT
  3. VU
  4. EN
  5. CR
  6. EW
  7. EX

EN – Endangered

Very high risk of extinction in the wild.

Little brown myotis roosting alertly on a wooden beamLittle brown myotis roosting in the corner of an attic beamLittle brown myotis roosting on painted wood sidingLittle brown myotis resting among blue spruce branches
Photo: Steph Brulot-Sawchyn · CC0Little brown myotis roosting alertly on a wooden beamPhoto: LeeAnn Latremouille · CC BY 4.0Little brown myotis roosting in the corner of an attic beamPhoto: Tom Romeo · CC BY 4.0Little brown myotis roosting on painted wood sidingPhoto: Patrick Jackson · CC BY 4.0Little brown myotis resting among blue spruce branches

Western Little Brown Myotis in Pennsylvania, by the numbers

Occasional in Pennsylvania 38th most recorded of 77 mammals logged in Pennsylvania

284 occurrence records
21 with iNaturalist photos

Records from 2000–2026.

284 total records count every Pennsylvania occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 283; the monthly chart covers the 282 records with a full observation date.

When to look for the Western Little Brown Myotis in Pennsylvania

Most sightings fall in June to August.

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

Monthly Pennsylvania records (table)
MonthRecords
January34
February16
March14
April13
May6
June40
July44
August52
September9
October5
November32
December17

Monthly western little brown myotis occurrence records (iNaturalist and GBIF) in Pennsylvania, 2000–2026.

Seasonality

Year-round in Pennsylvania, with recorded sightings peaking in June–August, with a smaller rise in November and January.

Occurrence map

Where Western Little Brown Myotis has been recorded in Pennsylvania

283 records mapped · zoom and drag to explore

283 Pennsylvania records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Forbes State Forest 13
Quebec Run Wild Area 5
Thickhead Wild Area 3
State Game Land #101 2
Moraine State Park 2
Delaware Water Gap National Recreation Area 1

Protected places with the most western little brown myotis 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 Pennsylvania

CountyRecords
Bedford County 53
Westmoreland County 51
Mifflin County 33
Centre County 30
Erie County 25
Fayette County 18
Lawrence County 16
Berks County 15
Bucks County 11
Luzerne County 5
Crawford County 4
Sullivan County 4
13 other counties 19

The complete county distribution, spread across 25 Pennsylvania counties. Every occurrence record falls in one county, so these sum to the total. Counties from GBIF and US Census boundaries.

Despite the site’s “western” slug, this overlay contains Pennsylvania-scoped little brown bat records. Pymatuning and Presque Isle offer open insect-hunting water, while Delaware Water Gap adds wooded tributaries, cliffs, and buildings that may provide shelter.

Records peak in January and again in October and November. Finds at winter shelters or around structures can dominate cold-season data, so the pattern describes reporting circumstances, not the number of bats flying outdoors.

Occurrence data from iNaturalist and GBIF.

Little brown myotis roosting alertly on a wooden beam
Full species profile Western Little Brown Myotis Myotis lucifugus Size 8–9.5 cm3.1–3.7 in Weight 6–13 g0.2–0.5 oz Lifespan 35 yr View the full profile

More mammals in Pennsylvania 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"