Last updated: October 22, 2026
Short answer: Bat guano (bat droppings) can be a health hazard. Built-up guano can grow a fungus that causes histoplasmosis, a lung infection, when the dust is breathed in. Don’t sweep, vacuum or disturb it. Have the bats humanely excluded first, then have the guano removed and the area cleaned with proper protection.
What is bat guano?
Bat guano is the name for bat droppings. Ontario’s house-dwelling bats eat insects, so their droppings are made of tiny insect parts. Guano piles up under roosts in attics, wall voids, soffits and behind shutters or siding. Even a small colony can leave a significant pile over one summer.
What does bat guano look like?
Bat droppings are dark brown to black, about the size of a grain of rice, and dry. They crumble into powder when pressed. Under light they often show shiny flecks, which are insect wings. Mouse droppings look similar but are harder and don’t crumble. Guano usually collects in piles below a roost or streaks down exterior walls.
Where to look: – Attic floors and insulation below the ridge or gable vents – Window sills and decks below a gap in siding or soffits – Stains and droppings stuck to exterior walls below entry points – Behind shutters, chimney flashing and fascia boards
Not sure if it’s bats or mice? See What to Do If You Find Rodent Droppings.
Is bat guano dangerous?
It can be. Accumulated bat and bird droppings can support the fungus Histoplasma capsulatum. Disturbing dry guano releases spores that cause histoplasmosis when breathed in. Many people have mild or no symptoms, but it can be serious for infants, older adults and people with weakened immune systems. Guano also smells, stains drywall and attracts insects.
Can I clean up bat guano myself?
Small amounts outside, such as a few droppings on a deck, can be wetted down and wiped up with gloves and a mask. Guano in an attic or insulation is a different job. It means disturbing large amounts of dust in a confined space. That should be done by trained technicians with respirators, containment and proper disposal, and only after the bats are out.
What should I do if I find bat guano?
- Don’t touch or disturb it. No sweeping, vacuuming or pulling out insulation.
- Don’t seal holes yet. Sealing with bats inside can trap them, and in summer it can trap flightless pups.
- Call a wildlife professional to find the entry points and confirm whether bats are active.
- Humane exclusion. One-way doors let bats leave and stop them getting back in.
- Seal and clean. After the bats are gone, entry points are sealed and the guano is removed.
Why does the time of year matter?
In Ontario, bats raise their young in summer maternity colonies, and the pups can’t fly for several weeks. Excluding bats at the wrong time traps the young inside, where they die. That’s inhumane and creates odour problems. Some Ontario bats, including the little brown myotis, are protected as endangered, so timing and method matter. See Why You Shouldn’t Seal Entry Points During Bat Maternity Season.
What if a bat gets into the living area?
If a bat is in a room where someone was sleeping, or it had contact with a child, pet or someone who can’t say whether they were bitten, contact your local public health unit. Bats can carry rabies and bites can be tiny. If it’s safe, confine the bat to one room and close the door. See What to Do If You Find a Bat in Your House.
How Elite Pest & Wildlife handles bats and guano
- Inspection of the roofline, soffits, vents and attic to find active entry points and guano build-up. Wildlife inspections cost $75 to $100 plus HST, and the fee is credited toward the work.
- Humane exclusion with one-way doors, timed around bat maternity season
- Sealing of entry points with durable, animal-proof materials, backed by a 5-year warranty on sealed areas, according to the terms of the completed work
- Price: every home is different, so bat exclusion is quoted after the inspection. See our price guide.
Serving Hamilton, Stoney Creek, Ancaster, Dundas, Waterdown, Burlington, Oakville and the Niagara Region. See bat removal services or call (289) 799-8718.
FAQ
What is bat poop called?
Bat poop is called guano. The word is also used for seabird droppings. In Ontario homes, bat guano is usually found under attic roosts and below gaps in soffits, siding or vents.
Is bat guano dangerous to breathe?
It can be. Disturbing dry, accumulated guano can release spores of the fungus that causes histoplasmosis. Avoid sweeping or vacuuming it, and leave attic cleanups to trained professionals with respiratory protection.
How do I tell bat droppings from mouse droppings?
Bat droppings crumble into powder when pressed and often sparkle with insect wing fragments. Mouse droppings are harder, smoother and don’t crumble. Bat droppings also collect in piles under a roost rather than scattered along walls.
How much does bat removal cost?
Bat removal starts with a wildlife inspection, which costs $75 to $100 plus HST and is credited toward the work. Exclusion is quoted after the inspection, because the price depends on how many entry points there are, roof height and access. It includes one-way doors and sealing, backed by a 5-year warranty on sealed areas.
Should I seal holes as soon as I find bats?
No. Sealing with bats inside traps them, and in summer it can trap pups that can’t yet fly. Bats should be humanely excluded with one-way doors first. Holes are sealed only after the bats have left.