Rat Droppings Identification: Roof Rat, Norway Rat or Mouse?

Sizes and shapes at a glance

University of Kentucky pest training lists:

• Norway rat: about 3/4 inch, capsule-shaped, blunt ends
• Roof rat: about 1/2 inch, one pointed end
• House mouse: 1/8 to 1/4 inch, at least one pointed end

A rough rule: if a dropping is about the size of a grain of rice, it is a mouse. If it is closer to a raisin or a large olive pit, it is a rat. A ruler or a coin next to the dropping in a photo helps a technician confirm.

Where you find them tells you a lot

Location narrows it down further:

• Attic insulation, top plates and rafters: usually roof rats
• Crawl space floor, along foundation walls, under the house: usually Norway rats
• Kitchen drawers, cabinets and behind the stove: usually mice, sometimes rats
• Garage floor along walls: mice or Norway rats
• Along fences, on top of the water heater, on shelves: roof rats like high routes

Droppings collect along runways, near food and close to nests. A pile in one spot often marks a feeding or resting area.

Fresh or old?

Fresh droppings are dark, shiny and a bit soft. Within days they dry and harden, and over weeks they turn gray and crumble when pressed with a stick. Finding fresh droppings means the rats are active now.

To check activity, clean an area completely using the CDC's wet method, then look again in a day or two. New droppings mean rats are still using that route. That test is useful after trapping and sealing to confirm the job is done.

Other signs that back up the droppings

Droppings rarely appear alone. University of Kentucky pest training lists other signs:

• Rub marks: dark, greasy smears along walls, beams and pipes where rats brush past
• Gnaw marks: rat holes are about two inches across with rough, torn edges
• Burrows: active ones are smooth and packed at the entrance, free of dust and cobwebs
• Tracks: footprints or tail drag marks in dust or mud

Noise at night, a musky smell, and shredded nesting material round out the picture. See rodent noises at night.

How to clean up rat droppings safely

The CDC's cleanup steps:

1. Wear rubber or plastic gloves.
2. Air out the space for 30 minutes first by opening doors and windows.
3. Use an EPA-registered disinfectant, or a fresh bleach solution of 1 part bleach to 9 parts water.
4. Soak the droppings and urine until thoroughly wet, and let them sit 5 minutes.
5. Wipe up with paper towels and seal them in a covered trash can.
6. Mop or wipe the surface with disinfectant.
7. Disinfect your gloves, take them off and wash your hands.

Do not sweep or vacuum droppings, which can put contaminated particles in the air. For large areas like an attic, see attic cleanup and droppings cleanup.

Counting and mapping droppings

Droppings tell you where to focus. Before you clean, take a few photos and note:

• Where the heaviest piles are; those usually mark feeding or resting spots
• Whether droppings run in a line along a wall, beam or pipe; that is a runway and a good trap spot
• Whether you find them in more than one level of the house, attic and crawl space, which can mean two problems or two species

A technician uses the same map to place traps and to find the entry point, which is often at the end of the runway closest to the outside.

Where Memphis homes tend to collect rat droppings

In older Memphis neighborhoods with tall trees, roof rat droppings pile up in the attic near the eaves, on top of the attic access frame, along the top of interior walls and on HVAC equipment platforms. In homes on crawl spaces, Norway rat droppings collect along the foundation walls, near pipes coming up through the floor and around the access door.

Garages see both. Look along the base of the walls, behind stored boxes, on shelves with seed or pet food, and on top of the water heater.

What to do next

Once you know it is rats, the next step is finding how they get in. Roof rat droppings in the attic point to the roofline. Norway rat droppings under the house point to the foundation. A technician can confirm the species and map the entry points. See rat control.