Rat and mouse articles · Updated
Rat vs. mouse droppings: how to tell them apart
Mouse droppings are about a quarter inch or less and pointed. Roof rat droppings are about half an inch, slim and pointed. Norway rat droppings are about three-quarters of an inch and blunt. Never sweep or vacuum them dry; wet them with disinfectant first.
Droppings are the best clue you have, and you can read them without ever seeing the animal. Size and shape tell you what left them. Where they are tells you how it's getting around. Freshness tells you whether it's still there. Here's how to read them, and how to clean them up without making yourself sick.
Size and shape
Put a coin next to them and take a photo before you do anything else.
- House mouse: about an eighth to a quarter inch, thin, pointed at one or both ends. Often scattered along a wall or in a drawer.
- Roof rat: about half an inch, slim, pointed at the ends, a little curved. Often in small piles along a runway in the attic or on top of cabinets.
- Norway rat: about three-quarters of an inch, thick, blunt at the ends. Usually at ground level: garage, shed, along the slab.
Where you find them
Location tells you as much as size. Droppings in the silverware drawer, under the kitchen sink or behind the stove are almost always mice. Droppings in the attic along the top plates, on the insulation near the hatch or on top of the water heater point to roof rats. Droppings in the garage can be either. Droppings outside near burrows are Norway rats.
Lines of droppings along a wall or a beam mark a runway, and that's where traps go. The roof rats vs. mice article covers the other clues.
Something in the attic or the garage?
Want a local rodent technician to look at it? Same-day appointments are often available. (972) 325-9652
Fresh or old?
Fresh droppings are dark, a little shiny and soft. Within a few days they dry out, turn dull and get harder. Old droppings are gray and crumble when you press them with a stick. A mix of old and fresh means rodents have been around a while and are still active. Only old droppings, and no new ones after a week, suggests the rodents have moved on, though the gap they used is probably still open.
Things that look like droppings
Cockroach droppings are smaller than mouse droppings and look more like coffee grounds or pepper, often in corners and cabinet hinges. Bat guano crumbles into shiny bits when crushed and collects under a roost. Squirrel droppings are a bit larger than rat droppings and more rounded. If you're not sure, a technician can tell at a glance.
How to clean them up safely
The CDC's hantavirus guidance lays out the steps. Wear rubber or plastic gloves. Spray the droppings and any urine with a disinfectant or a bleach solution until they're very wet, and let them soak for five minutes. The CDC's mix is one part bleach to nine parts water, about one and a half cups of bleach per gallon. Wipe them up with paper towels and throw them in the trash. Then mop or sponge the area with disinfectant, wash your gloved hands, take the gloves off and wash your hands with soap and warm water.
Don't sweep or vacuum droppings. That can send particles into the air. For a shed, cabin or other closed building, the CDC says to air it out for 30 minutes first.
Who carries what
The CDC names the deer mouse, white-footed mouse, rice rat and cotton rat as the rodents in North America that can carry the hantaviruses that cause hantavirus pulmonary syndrome. Those are mostly field rodents, but they do turn up in garages and sheds near open land. House mice and roof rats carry their own risks. The rodent diseases article covers them.
Urine stains and smell
Droppings usually come with urine. In an attic you may see yellowish stains on the insulation or the ceiling drywall below, and smell a sharp, musky odor near the hatch. Mice leave tiny urine pillars, small mounds of dirt and grease, along their runs in places they use heavily. A black light can make urine stains easier to see on hard surfaces. Treat stained areas the same way you treat droppings: wet them with disinfectant before wiping.
Photos help the technician
Before you clean anything, take a few clear photos with a coin or a ruler next to the droppings, and note where each photo was taken. A technician can often tell from the photos what you have and roughly how long it's been there. It also helps you see later whether new droppings are showing up after trapping and sealing.
When the droppings are everywhere
A few droppings in a drawer is a quick cleanup. Droppings scattered across an attic, tunnels in the insulation or a strong smell is a bigger job that usually means removing insulation. That's attic cleanup, and it should come after the rodents are trapped and the gaps are sealed. If you're finding fresh droppings every week, start with mouse control or rat control first.
Something in the attic or the garage?
Ready to have the gaps found and closed? Call and describe what you're hearing or finding. (972) 325-9652
Common questions
How many droppings does a mouse leave?
A lot. Even a few droppings usually means mice have been around for a while.
Can I vacuum droppings with a HEPA vacuum?
The CDC advises against sweeping or vacuuming. Wet them down and wipe them up instead.
Do I need to wear a mask?
For a few droppings, gloves and the wet-wipe method are the main precautions. For a heavy mess in an attic or shed, wear a respirator or hire a professional.
Are rat droppings more dangerous than mouse droppings?
Both can carry germs. Treat all rodent droppings the same way: wet them, wipe them up and disinfect.
Should I keep a dropping to show the technician?
A clear photo with a coin for scale works better. If you want to save one, pick it up with a gloved hand into a sealed plastic bag, then clean the spot.