Rat droppings vs mouse droppings: how to tell them apart

Mouse droppings are small, about the size of a grain of rice, with pointed ends, and you usually find dozens scattered along walls and in cabinets. Rat droppings are larger, closer to a raisin, and blunter. Fresh droppings of either kind are dark and soft. Older droppings are gray, dry and crumbly. Where you find them, and what else is nearby, narrows it down further.

Do not sweep or vacuum droppings while you investigate. The CDC warns that stirring them up can put virus particles in the air, and deer mice, common around El Paso, are the main US hantavirus carrier.

Mouse droppings

Mouse droppings are tiny and plentiful. A single mouse leaves a lot of them, so a few nights of activity can produce a scattering along a baseboard, in a utensil drawer or under the sink. They are dark, narrow and pointed at one or both ends.

House mice and deer mice leave droppings that look alike to most people. Location is a better clue. Droppings in a kitchen usually mean house mice. Droppings in a garage, shed, cabin or stored boxes near open desert, along with grass nests, could be deer mice. Treat both with care. Our deer mouse vs house mouse article shows how to tell the animals apart.

Rat droppings

Rat droppings are bigger, thicker and fewer than mouse droppings for the same amount of activity. You find them along runways, in attics along beams, behind appliances and in garages. Roof rats tend to leave them up high: attics, the tops of cabinets, along pipes. Norway rats leave them low, near the floor and around burrows.

Woodrat signs

Woodrats, the native pack rats, leave droppings too, but the bigger giveaway is the nest. Texas Tech's Mammals of Texas describes the woodrat midden as a crude cone of sticks, cactus joints and other rubbish around the nest. Droppings and urine stains collect in and around it. If you find droppings next to a pile of twigs and cactus pieces in a garage corner or under a shed, you have a woodrat.

Fresh or old?

Age tells you whether the problem is current.

• Fresh droppings are dark, shiny and soft enough to smear.
• Droppings a few days old darken further and harden.
• Old droppings turn dull gray and crumble when pressed.
• To test activity, clean an area properly, then check it a day or two later for new droppings.

Other things that look like droppings

A few things get mistaken for rodent droppings. Cockroach droppings are much smaller, like coffee grounds or pepper, and often smear. Bat droppings crumble into shiny specks when pressed and pile up under a roost. Lizard droppings usually have a white tip. If you are unsure, a technician can tell during a rodent inspection.

What the amount and pattern tell you

A few droppings in one spot suggest a mouse passing through. Droppings in several rooms, or fresh ones every day after cleaning, suggest an established population. Droppings concentrated along one wall show a runway, which is the best place to set traps. Droppings mixed with shredded paper or insulation point to a nest nearby.

In attics, droppings along beams and near the hatch, combined with noise overhead, point toward rats. In a garage, droppings in stored boxes and along the base of walls are common with mice. Droppings around a pile of sticks and cactus are a woodrat.

When to call for help

Call a provider if you find droppings in several rooms, in the attic, or in a closed shed or cabin, or if fresh droppings keep appearing after a week of trapping. A rodent inspection will confirm the animal and find the entry points.

Droppings and urine stains

Rodent urine often leaves faint stains and a musty, ammonia-like smell, especially in closed spaces. Under a black light, urine stains may glow, which some technicians use to trace runways. Clean urine spots the same way as droppings: soak with disinfectant, wait, then wipe.

How to clean droppings safely

The CDC method works for both mice and rats.

• Air out the space for 30 minutes with doors and windows open.
• Wear rubber or plastic gloves.
• Spray droppings with a fresh mix of 1.5 cups of bleach per gallon of water, or a disinfectant, and let it soak 5 minutes.
• Pick up with paper towels and bag them. Seal the bag, put it in a second bag and into a covered trash can.
• Disinfect the surface again, then wash gloved hands, remove gloves and wash your hands.

For heavy messes, closed sheds or attics, consider professional droppings cleanup.

Frequently asked questions

Sources

1. CDC: How to clean up after rodents
2. CDC: About hantavirus
3. Texas Tech University, Mammals of Texas: White-toothed woodrat
4. Texas Tech University, Mammals of Texas: Black rat

Related reading

• Signs of rodents in your home, and what each one tells you
• Rodent Droppings Cleanup and Sanitizing in El Paso
• Hantavirus and other rodent diseases: what El Paso residents should know
• Deer mice vs house mice: how to tell them apart in El Paso