Finding a pile of dark droppings in the attic, behind a shutter or along a wall below the eaves can be unsettling. If those droppings are crumbly and collect in heaps, there's a good chance bats are roosting somewhere in your house. Bats play a useful role eating night-flying insects, but their droppings, called guano, are not something you want building up in your Montville home. Below, we'll explain how to recognize bat guano, why it's a health concern, why cleanup needs care and how bat exclusion fits into the solution.
What Bat Guano Looks Like
Bat guano can look a lot like mouse droppings at first glance. A few traits help tell them apart:
- Shape and color. Small, dark brown to black pellets, often a bit lumpy rather than smooth.
- Texture. Dry guano is crumbly and breaks into powder when pressed. Mouse droppings are harder and don't crumble the same way.
- Shiny flecks. Because bats eat insects, guano often has tiny shiny bits of insect wings and shells in it.
- Location. Guano piles up directly below the roost, such as under a rafter, at the base of a wall or below a gap in the siding. Mouse droppings are scattered along travel routes.
- Staining. You may see dark, greasy stains around the gap bats use to get in and out.
Why Bats Roost In Homes
Bats look for warm, sheltered, quiet spaces to rest during the day. Attics, wall voids, gaps behind chimneys, loose soffits and spaces behind shutters can all work. Bats can squeeze through surprisingly small openings, so a gap along the roofline or a loose piece of flashing can be enough. In summer, female bats may gather in groups to raise their young, which is when guano can build up fastest. Because bats come and go at dusk and dawn, many homeowners never see them and only find out from the droppings.
Is Bat Guano Dangerous?
Bat guano is a real health concern, especially once it dries and accumulates. Soil and droppings from bats and birds can contain a fungus that causes histoplasmosis, a lung infection people can get by breathing in spores from disturbed dust. Many people who are exposed have mild or no symptoms, but it can be serious for some, particularly people with weakened immune systems. If you've been around guano and develop flu-like or breathing symptoms, see a doctor and mention the exposure.
Guano can also cause strong odors, stain ceilings and attract insects. Large accumulations can soak into insulation and drywall.
Bats themselves are a separate concern. Never touch a bat with bare hands. A bat that's active during the day, on the ground or unable to fly may be sick. If you or a family member may have had contact with a bat, or you find a bat in a room where someone was sleeping, contact your doctor or local health department for guidance, and call animal control to deal with the bat.
Why You Shouldn't Sweep It Up
The natural reaction is to grab a broom or shop vac. That's the one thing to avoid. Sweeping or vacuuming dry guano with an ordinary vacuum sends fine dust into the air, which is exactly how people end up breathing in fungal spores. Small amounts should be dampened first and handled with gloves and a properly fitted respirator. Larger accumulations, especially in attics, are best handled by professionals with the right protective equipment.
Cleaning up while bats are still using the space also won't solve anything. New guano will keep appearing until the bats are out and their entry points are sealed.
Bats Are Protected In New Jersey
Bats are protected wildlife in New Jersey, and some species are listed as endangered. That means you shouldn't trap, poison or harm them. The accepted approach is exclusion, which lets bats leave on their own and keeps them from getting back in. Timing matters, because sealing a roost while flightless young are inside can trap them. Our guide to bat-proofing an attic explains why the season you choose makes such a difference.
When To Call A Professional
Call for help if you find guano in the attic or walls, see bats flying out of the roofline at dusk or hear scratching and squeaking in the walls in the evening. EcoFusion's NJ DEP-licensed technicians can inspect your home to confirm whether the droppings are from bats or rodents, locate the gaps bats are using and recommend a humane exclusion plan, along with sealing entry points with pest-resistant materials. We'll also let you know what cleanup the space needs once the bats are gone.
Bat guano is a sign to act, not to grab a broom. Identify it carefully, keep your distance from bats and dust and plan exclusion at the right time, and your Montville home can be bat-free without harming the animals.