Bat Droppings: How to Identify Them and Tell Them From Other Pellets

If you found small dark pellets in your attic, garage, basement, or anywhere else in your home, here is how to figure out what they are from — and what to do next. This guide covers what bat droppings actually look like, how they differ from mouse, squirrel, and raccoon droppings, where you typically find them, the real health risks, and the right next steps.

What bat droppings look like

Bat droppings — also called guano — are small, rice-grain-shaped pellets, typically about a quarter inch long (around 6 millimetres). They are dark brown to black in colour, dry, and noticeably crumbly. The crumbly texture is the single most useful identification feature: bats eat insects almost exclusively, and their droppings are mostly insect chitin (the hard outer shell of beetles, moths, and mosquitoes), which crushes into a dry powder rather than a smear.

Fresh guano often has a faint sheen or sparkle when you look closely under good light. Those tiny reflective points are undigested wing fragments and beetle shell pieces. As the droppings age, the shine fades and the colour deepens toward a dull dark grey-black.

The other reliable tell is how guano accumulates. Bats are roost-loyal — they hang from the same handful of spots night after night. Their droppings fall straight down, building a tight, concentrated pile directly underneath the roost. You will not find bat guano scattered across an entire attic floor; you will find it heaped under a specific beam, vent, or rafter, often with a clean perimeter around the pile.

If you see a small mound of dark, dry, rice-shaped pellets that crumble when pressed, you are almost certainly looking at bat droppings.

Bat droppings vs mouse droppings

This is the most common identification question we hear, and the answer is straightforward once you know the test.

Size. Bat guano and mouse droppings are nearly identical in size and shape — both about the length of a rice grain, both dark brown to black. Size alone will not tell you which animal you are dealing with.

The crush test. Take a single dropping and press it gently between two pieces of paper or two gloved fingers. Bat guano crumbles cleanly into a dry powder — that is the insect chitin breaking apart. Mouse droppings smear and stay intact when crushed, because the diet is grain-based and oilier. This single test is nearly always definitive. If it powders, it is bat. If it smears, it is mouse.

Location pattern. Bat droppings collect in piles directly below entry points and roosting spots — under the soffit corner, on the attic floor below where bats squeeze in, on a deck beneath a vent. Mouse droppings are scattered along travel paths beside walls, behind appliances, near food storage, and inside cupboards. A concentrated mound under one specific spot points strongly toward bats; a trail of pellets along a baseboard points toward mice.

Smell. Bat guano develops a strong ammonia odour as urine soaks into the pile and the colony grows. The smell is distinctive — sharp, eye-watering, and noticeably worse on warm humid days. Mouse droppings carry a musty, more generic rodent smell rather than the ammonia bite.

If you are still unsure after the crush test, take a clear close-up photo with a coin or ruler for scale and send it during your free inspection. Our team identifies it on site.

Bat droppings vs squirrel and raccoon droppings

Other wildlife leave droppings in attics too, and the differences are easy to spot once you know what to look for.

Squirrel droppings are larger than bat or mouse droppings — roughly half an inch long, more cylindrical and rounded at the ends, often a lighter reddish-brown that lightens further as it dries. They are firmer than bat guano, do not crumble into powder, and tend to be scattered across attic insulation rather than piled in one spot. Squirrels run across beams, gnaw wires, and hide nuts, so their droppings spread across a wide area instead of accumulating below a single roost.

Raccoon droppings are in a different size class entirely. They are large, tubular, and resemble dog feces — typically one to two inches long and as thick as a thumb. They often contain visible undigested berry seeds, corn kernels, or insect parts. Raccoons are latrine animals: they return to the same spot repeatedly, building large piles in attic corners, on flat roof sections, or on garage floors. If you find a heavy pile of large tubular scat, see our wildlife removal service — that is a raccoon problem, not a bat problem.

The easiest tell across all four animals: bat droppings are smaller than squirrel and raccoon droppings, and crumble where mouse droppings smear. Size and the crush test together solve almost every identification question.

Where you will typically find bat droppings

Knowing where to look — and where you find them — gives you another strong identification signal.

The most common location is the attic floor directly below the soffit-fascia gap. The soffit-fascia junction is the most common bat entry point on Ontario homes, and droppings accumulate in a tight pile just inside the attic at that spot.

Other typical spots include:

• On insulation in the attic, in a dense cluster directly below the roost — usually under a specific rafter, ridge beam, or peak.
• On window sills, decks, or porches directly below an exterior entry point. Bats often pause briefly on the siding before squeezing through, leaving a trail of droppings on whatever surface is below.
• Inside or at the base of chimneys, especially older masonry chimneys without proper caps. Less common than soffit entries, but it does happen.
• Inside wall cavities. You will not see these directly, but you may hear scratching or chittering at dusk and dawn — and the ammonia smell will eventually bleed through into upstairs rooms.

If you are seeing droppings in multiple locations on the exterior of the home, you likely have multiple entry points. Most homes we inspect have six to fourteen active or potential entry points, which is why a forensic-level inspection of the entire envelope matters.

Why bat droppings matter for your health

Here is the honest risk picture, without the scare tactics.

Dried bat guano releases Histoplasma capsulatum spores when disturbed. Inhaling those spores can cause histoplasmosis, a fungal respiratory infection. Most healthy adults experience mild flu-like symptoms or none at all. The infection is more serious for the elderly, young children, and people with compromised immune systems, where it can progress to severe respiratory illness.

The danger is not the presence of guano in a sealed attic — it is disturbance. Spores stay locked in the pile until something stirs them into the air. That means:

• Do not sweep bat guano. Sweeping launches spores into the breathing zone immediately.
• Do not vacuum it with a household vacuum. Standard vacuums are not HEPA-rated for fungal spores, and the exhaust spreads the spores across the whole house and into the HVAC system. This is one of the worst things you can do.
• Do not handle it without proper PPE. Cleanup requires a P100 respirator, Tyvek coveralls, gloves, and eye protection at minimum.

Treat bat guano the same way you would treat asbestos or lead paint: leave it alone until someone with the right gear handles it.

Professional cleanup uses negative-pressure HEPA containment that captures spores before they enter the breathing zone, removes contaminated insulation, treats framing and surfaces with antimicrobial solution, and restores the attic to a safe baseline. Our attic cleanup and decontamination service covers the full process.

What to do once you have identified bat droppings

You have done the identification work — now here is the practical action plan.

1. Do not disturb the droppings. No sweeping, no vacuuming, no kicking the pile, no curious poking with a stick. Leave them exactly where they are until trained cleanup happens.
2. Do not seal the entry points yet. This is the mistake homeowners make most often. Sealing entry points while bats are inside traps the colony — they cannot get out, they perish in the walls, and the resulting smell and structural damage are far worse than what you started with. Sealing without proper one-way valve exclusion is also illegal under Ontario’s Fish and Wildlife Conservation Act.
3. Schedule a free inspection. Our specialists walk the entire envelope, identify every entry point, plan the exclusion, and quote the work. The difference between bat removal and bat exclusion matters here — see our bat exclusion vs bat removal post for the full breakdown.
4. If you rent or live in a multi-unit building, notify your property manager. They will need to authorize exclusion and cleanup work, and the sooner that conversation starts, the sooner the problem is solved.

Every job we do is backed by our Lifetime Warranty.

If a bat re-enters through any point we sealed, we come back and do all the work necessary — at no extra cost. Forever.

The warranty is transferable to new owners if you sell the home.

When to call us

If you have identified bat droppings in your home — or want a second set of eyes — book a free inspection. Every home is different. Get a free, no-obligation quote after a brief inspection. Our team has refined the process across hundreds of homes and thousands of entry points across Grey Bruce Simcoe. Visit our home page or learn more about our bat removal and exclusion service.