New Jersey mammals

Big Brown Bat in New Jersey

Eptesicus fuscus

Native to New Jersey S3 Vulnerable in New Jersey

Not listed as nonindigenous in New Jersey by USGS NAS; native to its New Jersey 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 Bat in New Jersey, by the numbers

Common in New Jersey 26th most recorded of 94 mammals logged in New Jersey

109 occurrence records
109 with iNaturalist photos
May 27, 2026 Last seen in New Jersey

Records from 2000–2026.

109 total records count every New Jersey occurrence from GBIF and iNaturalist; the map plots a georeferenced sample of 105; the monthly chart covers the 105 records with a full observation date.

When to look for the Big Brown Bat in New Jersey

Most sightings fall in May.

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

Monthly New Jersey records (table)
MonthRecords
January2
February2
March6
April4
May23
June12
July20
August16
September5
October5
November4
December6

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

Seasonality

Year-round in New Jersey, with recorded sightings peaking in May, with a smaller rise in July–August.

Occurrence map

Where Big Brown Bat has been recorded in New Jersey

105 records mapped · zoom and drag to explore

100 New Jersey records mapped

Notable places to look

Park, forest, or monumentiNaturalist records
Cape May Point State Park 2
Brendan T. Byrne State Forest 1
Washington Crossing State Park 1
Stokes State Forest 1
Pequest Wildlife Management Area 1
Delaware Water Gap 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 New Jersey

CountyRecords
Somerset County 10
Hunterdon County 9
Monmouth County 8
Warren County 7
Sussex County 7
Gloucester County 7
Mercer County 6
Burlington County 6
Middlesex County 5
Bergen County 5
Ocean County 5
Essex County 4
7 other counties 30

The complete county distribution, spread across 19 New Jersey 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 spread wider across New Jersey than any single hotspot suggests, 109 records reaching 19 of the state’s 21 counties, from Somerset and Hunterdon through Warren and Sussex down to Cape May Point State Park. No named site stands out: Cape May Point, at the coastal wetlands of the state’s southern tip, has just 2 records, and Stokes State Forest and the Delaware Water Gap add one apiece.

Beetles over the treetops

A big brown bat is built heavier than most of New Jersey’s bats, with broad wings that let it fly steady, unhurried circuits over forest openings, ponds, and streetlit neighborhoods. Beetles make up much of its diet, and a single bat can work through heavy numbers of them on a summer night. It roosts where people live as readily as in trees, tucking into barns, attics, and bridges, which is why records turn up in the state’s most developed counties as well as its forested parks.

Summer skies, winter walls

Reports climb from May through August, when flying insects are thickest and the year’s young bats join their mothers on the wing. Unlike the tree bats that leave New Jersey each fall, big brown bats winter in place, hibernating in caves, mines, and the sheltered crevices of buildings. An occasional midwinter record usually means a warm spell has roused one from its roost for a brief flight.

Status in New Jersey

NatureServe ranks the big brown bat S3, Vulnerable, in New Jersey, even though the species remains G5, secure, across its full range. It is native to the state, and USGS NAS does not list it as nonindigenous.

Occurrence data from iNaturalist and GBIF.

More mammals in New Jersey in the atlas

Data & sources

The data and visualizations on this page draw on these open sources: