Rodent articles · Updated
Rat droppings vs mouse droppings: how to tell them apart
Mouse droppings are small, about a quarter inch, like dark grains of rice. Rat droppings are about half an inch or more. Roof rat droppings tend to have pointed ends, Norway rat droppings blunt ones. Clean them wet, never dry.
Size tells you most of what you need. Mouse droppings are about a quarter inch long, thin, and look like dark grains of rice. Rat droppings are about half an inch or longer and thicker, closer to a raisin. Shape and location narrow it down from there: roof rat droppings tend to have pointed ends and show up in attics, while Norway rat droppings have blunt ends and turn up low, in garages and crawl spaces.
Whatever you find, don't sweep it or vacuum it dry. The CDC's guidance is to soak droppings with disinfectant first, then wipe them up.
Mouse droppings
House mouse droppings are small and scattered. Mice don't use one spot. They leave droppings as they travel, so you find a few here and a few there, along the back of a drawer, under the sink, behind the stove, along the garage wall. Lots of droppings spread through a pantry usually means mice have been there a while.
- About a quarter inch long, thin, with pointed ends
- Dark when fresh
- Scattered along walls, in drawers and cabinets
- Often with shredded paper or fabric nearby
Roof rat droppings
Roof rats are San Antonio's attic rat. Their droppings are about half an inch long, slimmer than a Norway rat's, and usually pointed at the ends. You'll find them along the top plates of the attic, on ductwork, on top of the insulation and on rafters where rats travel. In the yard, look under fruit trees and along the top of fences.
Norway rat droppings
Norway rats leave the biggest droppings, thicker than a roof rat's with blunt ends, often in clusters. They show up low: along garage walls, under the house in a crawl space, near burrows by the slab and around trash cans and compost. If you're finding them and burrows together, see Norway rat control.
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Fresh or old?
Fresh droppings are dark and a little shiny or soft. Old ones turn gray, dry and crumbly. That matters because old droppings in an attic can be left over from a problem that's already gone, while fresh ones mean rodents are still active. One trick: clean an area completely, then check it again in a few days. New droppings mean they're still around.
Things that look like rodent droppings
A few look-alikes cause false alarms. Cockroach droppings are smaller than mouse droppings and look more like ground pepper or coffee grounds. Bat guano crumbles into shiny bits when you press it, because it's full of insect parts, and it piles up under a roost. Squirrel droppings are larger and rounder than rat droppings. If you're seeing large, rounded droppings in the attic and hearing noise at dawn, read rat or squirrel in the attic. This line handles rats and mice only.
Where to look in a San Antonio house
Droppings collect where rodents travel and eat. Check these spots with a flashlight before you call anyone:
- The attic along the top plates, on the ductwork and around the air handler
- Garage walls behind stored boxes and around pet food or bird seed
- Under the kitchen sink and behind the stove and refrigerator
- The back corners of drawers and pantry shelves
- The water heater closet and the laundry area
- Under the house, if it sits on piers with a crawl space
Ready to have the gaps found and sealed? Call and describe what you're seeing.
Call (210) 955-2948
What droppings tell a technician
Droppings are a map. Where they're thickest shows where rodents spend time, and a line of them along a wall shows the route between a nest and food. Droppings clustered near a gap in the soffit or a pipe hole under a sink often point to the way in. Fresh droppings in one area and old ones elsewhere can show that activity has moved.
That's why it helps to leave droppings in place until a technician has looked, if you're having someone out soon. Take photos, then clean up with the wet method once they've seen it.
How to clean droppings safely
The CDC's hantavirus guidance gives the steps. Ventilate a closed space like a shed or storage room for 30 minutes before you start. Wear gloves. Don't sweep or vacuum droppings, urine or nests. Soak them with a disinfectant or a bleach solution, the CDC's mix being 1 part bleach to 9 parts water, and let it sit 5 minutes. Then wipe up with paper towels, bag it all and throw it away. Our droppings cleanup page covers bigger jobs.
Questions from callers
How many droppings does one mouse leave?
Enough that a single mouse can make a drawer look infested in a few days. Count isn't a reliable way to judge how many mice you have.
Can I tell roof rat from Norway rat droppings for sure?
Not always. Location helps most: up high usually means roof rats, down low usually means Norway rats or mice.
Do droppings mean I need an exterminator?
Not necessarily. A few mouse droppings in the garage might be handled with traps and a door seal. Droppings that keep coming back, or droppings in the attic, usually need a closer look.
Should I wear a mask?
The CDC's steps center on gloves, ventilation and soaking so dust doesn't rise. For a big or dusty mess, or if you have breathing problems, hire it out.