Species

Little brown bat

Myotis lucifugus

Once one of the commonest bats in North America, now among the hardest hit by white-nose syndrome.

Photo LeeAnn Latremouille (opens in a new tab) / iNaturalist, CC BY 4.0 (opens in a new tab)

At a glance

Size: Body about 8 to 10 cm; wingspan about 22 to 27 cm
Weight: About 5 to 14 g
Habitat: Forests and towns near water
Diet: Aquatic insects such as midges, mayflies and caddisflies, plus moths, beetles and some mosquitoes
Active: Night, from dusk
Roost: Buildings, tree cavities and bat houses in summer; caves and mines in winter
Young: One pup a year
Rabies vector: Yes

Identification

Key marks: Glossy, sleek brown fur; darker wings and ears; short, blunt tragus; long hairs on the toes reaching past the claws
Told apart from: Big brown bat, which is larger with a heavier head
Told apart from: Indiana bat, which is duller, pinkish-lipped and has short toe hairs
Told apart from: Northern long-eared bat, which has much longer ears
Where to look: Emerging from barns, attics and bat houses at dusk; hunting over ponds and streams

Behaviour

Little brown bats hunt over water and along forest edges, catching insects in the air and sometimes skimming them from the surface. Females gather in summer maternity colonies in attics, barns and bat houses, often in the hundreds.

In winter they hibernate in caves and mines, where their body temperature drops close to that of the cave and they can go weeks without waking.

In Georgia they are uncommon and found mainly in the mountains and hills of the north.

Why they matter

Little brown bats are among the longest-lived small mammals known: one banded bat was recaptured more than 30 years later. Few animals of their size come close.

They are also a measure of loss. White-nose syndrome, first found in New York in 2006, has killed the great majority of little brown bats in parts of the Northeast, turning a species that was once everywhere into one that many people will never see.

Reproduction and lifecycle

Mating — late summer and autumn at cave entrances; sperm is stored until spring
Gestation — about 50 to 60 days after fertilisation
Birth — June and early July, a single pup
Flight — at about three weeks old
Independence — by late summer
Lifespan — often several years; more than 30 has been recorded

Living around people

A colony in a barn or attic should never be excluded between May and August, when pups cannot yet fly.
Bat houses mounted in the sun near water can give colonies a safe alternative.
Keep out of caves and mines where bats hibernate, and clean gear to slow white-nose syndrome.
Never handle a bat with bare hands; bats are rabies vector species.

Misconceptions

A little brown bat eats a thousand mosquitoes an hour. That figure came from a laboratory experiment; wild bats eat a mixture of insects, of which mosquitoes are only a part — though the total they eat is still very large.
Bats are blind. They see well; echolocation adds to their vision rather than replacing it.
Excluding bats in summer is harmless. Pups left inside die.

Related species

Seasonal activity

When this species is breeding, and when there are nests on the ground. Mowing during the shaded months is how most nests are found.

Breeding and active nests by month for this species
	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Breeding	Jan: no	Feb: no	Mar: no	Apr: no	May: no	Jun: no	Jul: no	Aug: no	Sep: no	Oct: no	Nov: no	Dec: no
Active nests	Jan: no	Feb: no	Mar: no	Apr: no	May: no	Jun: no	Jul: no	Aug: no	Sep: no	Oct: no	Nov: no	Dec: no
Notes	Hibernating in caves and mines	Hibernation continues	Emerging from hibernation, earlier in the South	Females move to summer maternity colonies	Colonies gather in buildings and bat houses	Pups are born, one per female	Young begin to fly at about three weeks old	Young are independent; colonies disperse	Swarming and mating at caves and mines	Hibernation begins	Hibernating	Hibernating

Where it lives

Recorded in 56 states and provinces. Each one links to the other animals there, and to the rehabilitators licensed for them.

Treated as a rabies-vector species in Alabama, Alaska, Arkansas, California, Colorado, Connecticut, Delaware, District of Columbia, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, Wyoming, Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, Northwest Territories, Nova Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan and Yukon. There, only a certified rehabilitator may take one.

Canada

If you found one

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