Identify Your Pest Wildlife Little brown bat
Little brown bat
Myotis lucifugus · Also called: Little brown myotis
The little brown bat is a small, glossy brown bat and the species most often found roosting in Alberta buildings. It is noticed when a summer colony forms in an attic or wall, leaving droppings, a musty smell and bats streaming out at dusk.
Size 8 to 10 cm long; wingspan 22 to 27 cm
Colour Glossy medium brown back, paler belly, dark wings and ears
Key feature Tiny bat with glossy brown fur and dark wings; weighs about 8 to 9 grams
Season Spring to early fall; summer colonies raise pups June to August
Where Attics, soffits, wall spaces, barns and sheds, often near the roof
What it looks like
This is a tiny bat. Adults weigh about 7 to 9 grams, about as much as two nickels. The silky back fur is usually warm brown, though some southern Alberta bats are sandy pale, and the underside is lighter. Bare skin on the face, ears and wings is blackish, and the ears are short.
In summer, females gather in attics and walls to raise pups, and a large nursery colony can hold hundreds of bats. At dusk they squeeze out of narrow gaps near the roofline one after another and fly in quick, fluttering loops to catch insects. Bat species look alike, so an expert or a clear photo is often needed to confirm which one you have.
Often confused with
Big brown bat
Other myotis bats
Swallows at dusk
Signs to look for
Bats leaving at dusk
Crumbly droppings
Stains near openings
Squeaks and scratching
Musty smell
Risks and damage
Bats in a building are mostly a nuisance. Droppings and urine build up under the roost, stain ceilings and walls and give off a musty smell. Bat droppings crumble into dust, so large piles should not be swept or vacuumed without protection. Rabies in Alberta bats is rare, but a bat bite can be very small. Anyone touched, bitten or scratched by a bat, or who wakes up with a bat in the room, should contact Health Link or a doctor.
In Alberta
The little brown bat is the most common bat in Alberta and the one most often found in buildings. White-nose syndrome, a deadly fungal disease of hibernating bats, is why it is now listed as endangered federally and in Alberta. Colonies raise pups from June to August and leave by fall.
Many Alberta little brown bats spend the winter in caves, not houses. Cadomin Cave, south of Hinton, is a key winter roost, and the province keeps it closed to visitors all year to protect the bats.
How to keep them out
Never block bats in summer
Seal gaps in winter
Screen attic vents
Keep screens in good repair
Put up a bat house
When it is time to bring in a professional
Call a professional if bats are living in your attic or walls, or if droppings are building up. Bats are protected in Alberta, and exclusion must avoid the June to August pup season. Technica’s licensed technicians can find entry points, time one-way exits for the right season and seal the building once bats are out.
Frequently asked questions
Can bats be removed from my attic in summer?
Not in most cases. Alberta law protects this endangered bat’s nursery colonies from June 1 to September 1, and flightless pups would die if the adults were shut out. Wait until fall, let the bats leave through one-way exits, then seal the gaps. If bats are getting into living space, contact a Fish and Wildlife office.
What should I do if a bat is inside my home?
Stay calm and keep children and pets away. Never touch a bat with bare hands. If no one had contact with it, close inside doors and, outside of winter, open a window so it can fly out. In winter, do not put it outside. If anyone was bitten, touched or asleep in the room, contact Health Link or a doctor first.
Why is the little brown bat endangered?
White-nose syndrome, a fungal disease that strikes bats while they hibernate, has killed millions of bats in eastern North America. The threat it poses is why this bat is listed as endangered in Canada and Alberta. It was first confirmed in Alberta bats in 2024, so humane, well-timed exclusion matters.