Bat Droppings vs. Mouse Droppings in Utah
Bat guano and mouse droppings are about the same size, and both turn up in Utah attics, garages and wall voids. Telling them apart decides everything that comes next: how to clean up safely, which health risk you are dealing with, and whether the fix is trapping mice or a DWR-timed bat exclusion. Here is how USU Extension, the CDC, Utah DHHS and wildlife damage specialists say to tell the difference.
The short version
Bat and mouse droppings are about the same size, so size alone won't tell you much. What separates them is texture and location. Bat droppings are made of insects: they are dry and segmented, and they crumble into a powder full of shiny bits of wings and shells. Mouse droppings are smooth, hard and pointed, and they stay in one piece. Bats leave piles under the spot where they hang; mice scatter droppings along walls and near food. Getting it right matters, because the cleanup rules and health risks are different, and because the fix for bats (a timed exclusion) is nothing like the fix for mice (trapping and sealing).
Bat, mouse, rat or bird? A side-by-side guide
| Animal | Size and shape | Texture | Where you find it |
|---|---|---|---|
| Bats | About the size of mouse droppings, elongated and segmented | Dry and crumbly; crushes to powder with shiny bits of insect wings and shells | In piles under the roost (often near the roof peak), stuck to rafters and beams, on the siding or ground below an entry gap |
| Mice | 1/8 to 1/4 inch, like a small dark grain of rice, with at least one pointed end | Smooth, hard and fibrous; does not crumble unless very old | Scattered along the base of walls, in drawers and cupboards, near food and nesting material; one house mouse leaves 50 to 75 a day |
| Rats | 1/2 to 3/4 inch, wider than mouse droppings and blunt at the ends | Hard, not segmented | Along runways, near food and stored items |
| Birds | Variable | Includes white, chalky material | Under nests, perches and vents; bat droppings never contain this white material |
Sources: ICWDM bat damage identification; USU Extension; National Park Service Conserve O Gram 3/12.
What bat droppings look like
The Internet Center for Wildlife Damage Management describes bat droppings as segmented, elongated and friable. When crushed they become powdery and reveal shiny, undigested insect remains, while droppings from mice and rats taper, aren't segmented, are harder and more fibrous, and don't turn powdery unless they are very old. Utah State University Extension says the same thing from the other direction: bat droppings are solid brown and crumble easily because they contain insect fragments, while rodent droppings contain plant fiber and don't crush easily. In Utah, bats eat only insects, so this test holds for every species you are likely to find in a house.
Where you find them is the biggest clue
USU Extension notes that roosting bats cluster near roof peaks, so their guano collects in piles beneath those high points and can also be found clinging to rafters and roof beams. Rodent droppings won't be in piles or on rafters and are more common along the base of walls. Outside, ICWDM says bats urinate and defecate as they leave a roost, leaving spots and stains on siding, windows and anything parked beneath the exit, and a small scatter of guano on the ground can point to an entrance you can't see from below. Look above the droppings for dark, slightly sticky rub marks around a gap, which ICWDM says form where many bats pass the same spot over a long period.
Mice leave a different pattern. The National Park Service's guide to rodent signs says mouse droppings are usually dark, 1/8 to 1/4 inch long and similar to small grains of rice, with at least one pointed end, and that a single house mouse can produce 50 to 75 pellets a day. You will usually find them along runways, in drawers and cupboards, and near food, often with shredded nesting material or gnawed edges nearby. Rat droppings are larger (1/2 to 3/4 inch), wider and blunt at the ends. Bird droppings are easy to rule out: ICWDM notes that bat droppings never contain the white, chalky material found in bird droppings. Larger droppings in a garage, shed or cabin can also come from pack rats (see our pack rat guide).
Testing a dropping without putting yourself at risk
The crush test is useful, but only if it doesn't stir up dust. If there is any chance the droppings are from mice, treat them as rodent droppings first. The CDC says not to sweep or vacuum rodent urine, droppings or nesting material, because that can put virus particles into the air. Instead, put on rubber or plastic gloves, spray the droppings with a household disinfectant or a fresh bleach solution (1.5 cups of bleach per gallon of water) until they are very wet, let them soak 5 minutes, then wipe them up with paper towels and throw the towels away in a covered can. For a closed-up shed, garage or cabin, open the doors and windows and stay out for 30 minutes before you start.
To check whether a pellet is from a bat, wear gloves, pick up a single dry pellet with a tool, take it outside and press it on a paper towel. If it powders and glitters, it is almost certainly a bat. If it holds together or smears, assume mice. A clear photo next to a coin is often enough for a professional to tell you which you have.
Why it matters: different animals, different risks
Mouse droppings and hantavirus
Utah DHHS says the deer mouse is the most common source of hantavirus in North America. The virus is shed in droppings, urine and saliva, and people are usually infected by breathing dust that contains dried, contaminated material, often while opening or cleaning buildings that have been closed up. The disease is rare in Utah. In an April 2025 warning, DHHS said Utah typically has one or two reported cases a year but that it is fatal in about 60% of reported cases, and its fact sheet says symptoms are thought to appear one to five weeks after exposure. See our deer mice and hantavirus guide for more on Utah homes.
Bat guano and histoplasmosis
Histoplasmosis is a lung infection from breathing spores of the fungus Histoplasma, which the CDC says lives in soil and spreads in bird and bat droppings that mix into soil. The CDC says the fungus mainly lives in the central and eastern United States, so the risk in Utah is lower than in the Ohio and Mississippi river valleys, but a large, old guano pile in a closed attic is still a dust hazard. USU Extension says anyone cleaning guano should wear a mask that blocks particles as small as 2 microns and should moisten and ventilate the area while working. Our histoplasmosis guide covers symptoms and who is most at risk.
Rabies: the droppings aren't the danger, the bat is
CDC rabies recommendations (ACIP) say that contact with an animal's blood, urine or feces does not count as a rabies exposure. Bats themselves are a different matter. Utah DHHS reports that every animal that tested positive for rabies in Utah in 2025 was a bat, 24 in all, exposing at least 19 people and 26 pets. If you find a bat in a room where someone was sleeping, or anyone may have touched it, don't release it; contain it and call your local health department so it can be tested. Our bat rabies exposure guide walks through those steps.
What to do once you know
- If it's mice: clean up with the CDC wet method, trap the mice already inside and seal the gaps they use. The National Park Service notes mice can fit through openings as small as 1/4 inch. See our rodent exclusion service.
- If it's bats: don't seal the holes yet. USU Extension says entrances should not be sealed while flightless young are present, and Utah DWR advises against sealing from May through August and doesn't permit colony removal from June through August unless bats are in close contact with people. A permitted wildlife control company sets up one-way exclusion in the open window, then seals the building.
- Either way, clean up after the animals are out. Guano and rodent waste left in insulation keep smelling and can attract insects. ICWDM notes the odor of decomposing bat guano draws arthropods that can later move into the house, and our bat bugs guide covers the parasites that can follow a colony. See bat guano cleanup in Utah for how a professional attic cleanup works.
Related guides: signs of bats in the attic, the fall bat exclusion window and bats in winter in Utah. You can also browse our service area.
Common questions
How can I tell bat droppings from mouse droppings?
Bat droppings are about the same size as mouse droppings but are segmented and dry, and they crumble into powder with shiny insect fragments when crushed. Mouse droppings are smooth, hard and pointed at one or both ends and don't crumble. Location helps too: bat droppings pile up under a roost or stick to rafters and siding, while mouse droppings are scattered along walls and near food.
Is it safe to crush a dropping to test it?
Not with bare hands, and not indoors over dry droppings. If the droppings might be from mice, the CDC says to spray them with disinfectant or a bleach solution and let them soak for 5 minutes before wiping them up, because stirring up dry rodent droppings can put hantavirus into the air. Wear gloves, test one pellet with a tool outdoors, or have a professional identify it.
Can I get rabies from bat droppings?
No. CDC rabies guidance says contact with an animal's blood, urine or feces is not a rabies exposure. The risk comes from the bat itself: in Utah, every animal that tested positive for rabies in 2025 was a bat. Never touch a bat with bare skin.
Can I vacuum or sweep up bat or mouse droppings?
Not mouse droppings. The CDC says not to sweep or vacuum rodent droppings, urine or nesting material, and to wet them with disinfectant first. For bat guano, USU Extension says to wear a mask that blocks dust particles as small as 2 microns and to moisten and ventilate the area while working. Large attic accumulations are a job for a professional with proper protective equipment.
I found bat droppings in November. Are the bats gone?
Not necessarily. USU Extension says most Utah bats leave their roosts in the fall, which makes fall the best time to seal openings, but Utah DWR says hibernating Utah bats tend to spread out in crevices and that the winter locations of most western bat populations are unknown, so a building roost can't be ruled out. Fresh droppings, rub marks or noise mean bats may still be using the space. An inspection can confirm whether the roost is active and where the entry points are.
Sources
- Utah State University Extension: Bats (Wildlife Damage Management Series, PDF)
- Internet Center for Wildlife Damage Management: Bat damage identification
- National Park Service Conserve O Gram 3/12: Identifying mouse and rat damage (droppings)
- CDC: How to clean up after rodents
- Utah DHHS: Hantavirus
- Utah DHHS: Hantavirus fact sheet (PDF)
- KSL.com: Utah health officials urge caution when cleaning up after rodents this spring (Apr. 28, 2025, quoting Utah DHHS)
- CDC: About histoplasmosis
- CDC MMWR: Human Rabies Prevention, United States, 2008 (ACIP recommendations)
- Utah DHHS: Rabies Annual Report 2025
- Utah DWR: What to know about bats in Utah (July 14, 2026)
- Utah DWR: White-nose syndrome (hibernating bats in Utah)
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