Hearing Mice in the Walls but No Droppings? What It Could Be and How to Check

This page walks through how to tell which it is without cutting open drywall.

Graphic: summary of this guide, made by our team from the cited sources.

Why there may be no droppings where you look

• They stay in the wall. House mice nest in sheltered spots, including wall voids, and rarely travel more than 30 feet from the nest and food (UC IPM Pest Notes: House Mouse). If their food is in the garage or a crawl space, they may never come out into your living space.
• It is early. One or two mice that just moved in for the fall leave few droppings at first. UC IPM says house mice often enter homes in autumn.
• You are looking in the wrong place. Droppings collect along travel routes: on top of the sill plate in the basement, behind the stove's kick plate, in the back of the cabinet under the sink, in the attic along the top plates.

Signs of mice besides droppings

Droppings are the easiest sign, but not the only one. If you hear something but find no pellets, look for these:

Sign	What it looks like	Where to look
Gnaw marks	Two parallel tooth marks about 1/16 inch across; bits of chewed wood, paper or packaging	Baseboards, cabinet backs, food boxes
Rub marks	Dark, greasy smudges from oil and dirt on the fur	Along pipes, beams and wall edges they travel
Nests	Shredded paper, insulation, fabric or cardboard	Boxes in storage, behind appliances, wall cavities
Smell	A musty or musky odor from urine	Closets, cabinets, near the wall where you hear noise
Chewed food	Many small nibbles from several packages	Pantry, pet food, birdseed

Sources: gnaw marks and rub marks from Utah State; nests and musty smell from NC State Extension; musky odor in large or long-term infestations and nibbling from UC IPM.

Utah State says shredded paper or insulation that does not yet look like a nest usually means a nest is nearby.

Some "droppings" are not from mice. Bat droppings look similar, but when crushed they show shiny insect fragments under a magnifying glass, according to Utah State. If you find dark pellets with lengthwise ridges, they may be cockroach droppings. Utah State says rodent droppings are smooth.

How fresh is the evidence?

Old signs can mislead you. A previous owner's mice may have left droppings in the attic years ago. Utah State gives these clues:

• Fresh droppings are moist, soft and black, and look shiny.
• After a few days to a week they dry out, harden and turn dull.
• After a few weeks mouse droppings are hard, dry, and dull or whitish.
• An intact dead mouse means an active problem. An old dried body may only mean a past one.

Utah State suggests removing what you find so new droppings stand out on your next check. Use the CDC method: gloves, spray with disinfectant until wet, wait 5 minutes, wipe with paper towels. Do not sweep or vacuum (CDC rodent cleanup steps).

Match the noise to the animal

Clue	Mice	Rats	Tree squirrels
When you hear it	Night	Night, often louder	Early morning and late afternoon
What it sounds like	Light scurrying and skittering	Gnawing, clawing, fighting, scrambling	Daytime activity, mostly in the attic
Where	Low walls, under cabinets, ceilings	Basements and ground floors (Norway rats), upper floors and attics (roof rats)	Attic and upper walls

Sources: mice and rat sounds from Utah State; rat locations from UC IPM Pest Notes: Rats; squirrel timing from UC IPM Pest Notes: Tree Squirrels.

Utah State notes that a stethoscope can help pinpoint rodent activity inside a wall.

Five checks before you treat

1. Write down when you hear it. Night points to rodents. Sunrise and late afternoon in the attic points to squirrels.
2. Look in the hidden spots listed above with a flashlight. The National Park Service describes mouse droppings as about 1/8 to 1/4 inch, like small dark grains of rice (NPS Conserve O Gram on mouse and rat damage). The same guide suggests an ultraviolet (UV) flashlight, because mouse urine glows under UV. Many substances glow, though, so treat a glow as a clue only when other signs are nearby.
3. Check outside. Look for chewed vents, gaps at the roofline, and tree branches touching the roof. UC IPM says squirrels often get into attics through gaps or broken vents and use overhanging trees and utility lines.
4. Set a tracking test. Dust a thin line of flour or talc where pipes enter the wall under a sink. Footprints by morning confirm traffic; Utah State notes mouse tracks are 3/8 to 3/4 inch long and rat tracks 3/4 to 1¼ inch.
5. Set snap traps as monitors. A few mouse traps along walls near the noise tell you quickly if mice are present.

Does one mouse mean more?

Often, yes, if it stays. A female house mouse can have 5 to 10 litters a year of about 5 or 6 pups each, and young mice can breed at 5 to 6 weeks old, according to UC IPM. Mice also leave a lot of evidence once settled. NC State says one mouse can produce 50 to 75 droppings a day. So if weeks pass with steady noise and still no droppings anywhere in the house, the animal may not be a mouse at all, or it lives entirely inside the wall and feeds somewhere hidden, such as a garage or crawl space.

Where mice get into walls

Mice squeeze under gaps 1/4 inch tall and through openings 3/8 inch wide. They can run up rough vertical surfaces and jump up to 12 inches onto a flat surface, according to UC IPM. Check these spots from outside and inside:

• Where pipes, wires and dryer vents pass through walls
• Gaps around the garage door and utility doors
• The sill plate along the top of the foundation in a basement or crawl space
• Openings under sinks where plumbing enters the wall
• Gaps at the roofline and torn vent screens

If it is mice

If you find pellets but aren't sure they're from mice, compare them with our guide to what mouse poop looks like.

Trap where they leave the wall, then seal the gaps once activity stops. Our step-by-step guide to a mouse in the wall covers trap placement and sealing. NC State describes compressing metal lath screen into holes and expanding its edges with a screwdriver so it fills the gap. Avoid poison in walls. UC IPM notes that mice usually stay within 30 feet of the nest, so poisoned mice often die inside the structure and cause an odor problem. Trapping avoids that.

For bait, NC State says peanut butter or honey can hold other foods on the trigger, and baiting a few traps with a cotton ball or string can catch females looking for nest material. It also says to check traps daily.

If it is squirrels or something else

UC IPM says tree squirrels are most active in early morning and late afternoon. That timing is the easiest way to tell them from mice. One exception: UC IPM describes the flying squirrel as small and nocturnal, so night noise high in the house is not proof of mice. UC IPM recommends sheet metal or 1/4-inch hardware cloth to close their entry holes, and says to make sure no animal is inside before you seal it.

Squirrels in an attic need a different plan: exclusion after the animals are out, and possibly a licensed wildlife control operator. Local laws on trapping squirrels vary, so check with your state wildlife agency first. If weeks of checks turn up no tracks, no catches and no other signs, ask a pest professional for a non-invasive inspection before anyone opens the wall.