Once one of North America's most common bats, the little brown bat has been devastated by white-nose syndrome — a fungal disease that has killed an estimated 90% of populations in affected regions since 2006.

Also called: Little Brown Myotis

Native status: Native; under emergency consideration for federal listing due to white-nose syndrome

§ Quick facts

SizeBody 6–10 cm (2.4–4 in); wingspan 22–27 cm
Weight5–14 g (0.18–0.49 oz)
LifespanWild typically 6–7 years; oldest documented 34
OrderChiroptera
FamilyVespertilionidae

§ Encyclopedia

The little brown bat or little brown myotis is an endangered species of mouse-eared microbat found in North America. It has a small body size and glossy brown fur. It is similar in appearance to several other mouse-eared bats, including the Indiana bat, northern long-eared bat, and Arizona myotis, to which it is closely related. Despite its name, the little brown bat is not closely related to the big brown bat, which belongs to a different genus.

Source: Wikipedia — Little brown bat Licensed under CC BY-SA 4.0

§ Identification

Field marks. Small chocolate-brown bat with glossy fur and pale belly. No keeled calcar (vs. Indiana Bat). Round to slightly pointed ears.

Similar species. Indiana Bat (keeled calcar). Northern Long-eared Bat (longer ears). Big Brown Bat (significantly larger).

Voice. Ultrasonic echolocation calls peaking 40–80 kHz.

§ Diet & behavior

Diet. Flying insects — mosquitoes, midges, mayflies, moths, caddisflies. A single bat can eat 1,000+ mosquito-sized insects per hour.

Behavior. Once one of the most abundant US mammals; populations crashed 90%+ since white-nose syndrome arrived in 2006. Maternity colonies of 100s–1000s of females in attics, barns, and tree cavities. Hibernates in caves and mines at 35–45°F.

§ Range

Throughout North America from Alaska to Mexico

§ Habitat

Caves and mines (winter); buildings, trees, bridges (summer)

§ Threats

White-nose syndrome (Pseudogymnoascus destructans), wind turbine strikes, habitat loss, pesticides.

§ Conservation status

According to the IUCN Red List, the little brown bat is currently classified as Endangered.

§ What helps

Don't enter caves with hibernating bats (you can spread the fungus). Install bat houses. Support White-Nose Syndrome Response Team research.

Support our work More ways to help

§ Further reading

§ Sources cited

  • USGS National Wildlife Health Center
  • Bat Conservation International
  • USFWS
  • IUCN Red List 2018