Little brown bat
A tiny brown flyer that hunts insects over water at dusk and sleeps in caves and barns, eating half its own weight in bugs each night.
Little brown bat at a glance
Myotis lucifugus little brown bat is LIT-tul BROWN bat; Myotis lucifugus is my-OH-tis loo-sih-FYOO-gus
- Type
- Mammal · bat
- Diet
- Insectivore
- Size
- Smaller than a matchbox, with wings spread about as wide as a dollar bill (about 9 to 10 inches). It weighs less than two quarters (5 to 14 grams).
- Lifespan
- Most live 6 to 7 years, but one survived 31 years in Ontario. A female raises just one pup a year.
- Conservation
- Endangered (IUCN, 2021 assessment). U.S. listed status is a proposed endangered rule still under review, not finalized; white-nose syndrome has killed millions of hibernating bats.
Eats midges, mosquitoes, mayflies, caddisflies, moths, beetles
A little brown bat hunts flying insects over ponds and streams, using echolocation, a rapid-fire shout of sound that bounces back to map the night. It eats up to half its own body weight in bugs each night, and a nursing mother eats more than her own weight.
Should you worry?
Very low risk. Bats rarely bite and little brown bats rarely carry rabies, but the rule is real: never touch or pick up a bat, even one that looks dead, and tell an adult if a bat touches you. At Mammoth Cave, stay on the tour path, keep hands off the cave walls, and step on the white-nose cleaning mats, since shoes can carry the fungus that has killed millions of bats.
At dusk by the mouth of Mammoth Cave, a shape half the size of your palm tumbles over the river and catches a moth in midair. To see past the flutter to the animal underneath, hold two things at once. The first is appetite: a little brown bat eats up to half its own weight in insects every night, and a nursing mother eats more than her own weight, which means the mosquito landing on your arm is doing it against fierce competition. The second is family size: out of all that eating, a female raises exactly one pup a year. Huge appetite, tiny birth rate. That mismatch is the whole story.
In 2006 and 2007, a fungus appeared in a New York cave, grew on hibernating bats’ noses and wings, woke them too early, and starved them through the winter. Because bats sleep through winter in big piles, white-nose syndrome spread cave to cave, and some hibernacula lost 90 percent of their bats. It reached Mammoth Cave in 2012, and this species, once the most common bat in eastern North America, is now endangered. The park fights back in small, daily ways: the cleaning mats you step on after a tour, and the caves kept closed so sleeping bats stay asleep.
That is why the little brown bat is on this page and why the rules are gentle. Never touch a bat, even one that looks dead; tell an adult if one touches you; and at Mammoth Cave, step on the white-nose mat, keep your hands off the cave walls, and let the one-pup-a-year survivors have their winter. The mosquito swarm you didn’t notice was quieter because of them.
Did you know?
- White-nose syndrome, first found in New York in 2006 and 2007, has killed millions of hibernating bats; some caves have lost 90 percent of their bats.
- A nursing little brown bat eats more than her own body weight in insects every single night.
- A little brown bat weighs less than two quarters but can snap up moths and mosquitoes over a pond at dusk, mid-flight.
Common questions
Do little brown bats live in Mammoth Cave?
Yes. It is one of 13 bat species confirmed in the park, and one of the cave-dependent species that hibernates there.
Why do bats hang upside down in caves?
Because it helps them launch. Bats can't take off from flat ground easily, but gravity lets them drop straight into flight.
Is a bat flying near me dangerous?
No, it is catching mosquitoes. The one real rule is never to touch or pick up any bat, and to tell an adult if one touches you.
What is white-nose syndrome?
A fungus that grows on hibernating bats' noses and wings, wakes them up early, and starves them through the winter. It reached Mammoth Cave in 2012.