Bats in the house in Ottawa: what the law allows, maternity season, and how exclusion is done

Updated 2026-09-16

Some bats that roost in Ottawa homes are endangered species. What the law allows in 2026, why summer is the wrong time to seal them out, how a proper exclusion works, and what to do if a bat gets into the living space.

Why bats use houses

Attics, wall cavities and the space behind siding stay warm and sheltered. That makes them good places for female bats to gather in summer and raise their young.

The Government of Ontario notes that the little brown myotis most regularly uses buildings for maternity colonies. That matters, because the little brown myotis is an endangered species.

What the law says in 2026

White-nose syndrome, a disease caused by an invasive fungus, reached Canada in 2010. According to the Government of Ontario, it has caused a 94% overall decline in known numbers of hibernating myotis bats in Nova Scotia, New Brunswick, Ontario and Quebec.

The little brown myotis, northern myotis and tri-coloured bat were added to the federal Species at Risk Act list as endangered in 2014. Environment and Climate Change Canada advises against disturbing areas bats occupy at times of year when they are present.

In Ontario, the Species Conservation Act, 2025 replaced the Endangered Species Act on March 30, 2026. The little brown myotis was listed as endangered under the old Act. The new Protected Species in Ontario List (O. Reg. 60/26) carried over the species classified as extirpated, endangered or threatened, other than aquatic species and migratory birds, so the little brown myotis remains protected. Ontario's rules on nuisance wildlife say listed species at risk need a permit before they are captured or harmed.

The practical result: bats are not trapped, killed, poisoned or relocated. They are excluded, at the right time of year, so they leave on their own.

Maternity season and the exclusion window

In summer, mothers leave to feed at night and return to pups that cannot yet fly. Seal the building then and the pups are trapped inside. The Government of Ontario warns that work on a building while bats are in it can trap them and separate mothers from dependent young.

The Canadian Wildlife Federation says evictions are best done in March and April or from September to November, and only in winter if you are sure the bats are not overwintering in the building.

For most Ottawa homeowners that means using the summer to plan and book, and doing the exclusion in early fall once the young are flying.

How exclusion is done

First, someone watches the house at dusk to see exactly where the bats come out. Bats can use very small gaps, so the inspection covers the whole outside: roof edges, soffits, flashing, chimney, siding joints and vents.

Signs that bats are the problem include small dark droppings piled below a gap or on an attic floor, dark stains around an opening, and squeaking or scratching in a wall around dusk.

Second, every gap that is not an active exit is sealed.

Third, one-way devices, usually netting or tubes, go over the active exits. Bats can crawl out and fly off, but cannot find the way back in.

Foam, caulk or screening should never go over an active exit while bats are still using it. That traps them inside, where they die or find their way into the living space.

Fourth, the devices stay up for several nights of mild weather. Once no bats are seen leaving, the devices come off and those openings are sealed for good.

Environment and Climate Change Canada suggests putting up bat boxes as a place for the colony to go. Guano in the attic should be cleaned up with proper protective equipment once the bats are out.

If a bat gets into the living space

Rabies is the real concern. The Public Health Agency of Canada lists any exposure to bats as a rabies risk, and a bat bite may not be noticed. If there is any chance of contact, wash the area, get medical advice promptly and contact Ottawa Public Health. Rabies is almost always fatal once symptoms start, and treatment has to begin before that.

If no one has touched the bat, close interior doors, open a window to the outside and turn off the lights. Never handle a bat with bare hands.

Cost and timing

Indicative 2026 range from the price guide on this site, before HST: a whole-house bat exclusion runs about $500 to $1,500 or more, depending on the house height and how many gaps need sealing. Book the inspection in summer so the work can be done as soon as the window opens in fall.