Mouse in the Wall? How to Confirm It and Get It Out Without Opening the Wall

Graphic: the four steps in this guide, made by our team from the UC IPM, Utah State and New York State Department of Health sources cited below.

Step 1: Confirm it is a mouse

Noise alone isn't proof. Utah State's school IPM manual says mice are harder to hear than rats, but you can sometimes hear them scurrying and skittering, and that squirrels and other animals make similar noises, so you should confirm with other signs (USU).

What you notice	Points to
Light scratching and skittering at night, low in the wall or under cabinets	Mice
Louder gnawing, clawing and scrambling at night	Rats
Noise in the attic or upper walls mostly early morning and late afternoon	Tree squirrels
Droppings about 1/4 inch long in drawers and along baseboards	Mice

Sources: mouse and rat noises and dropping size from USU; squirrel activity times from UC IPM Tree Squirrels.

Then look for the evidence UC IPM lists for house mice: droppings, gnaw marks, tracks, a musky odor in long-term infestations, and nests of finely shredded paper (UC IPM). Check under the kitchen sink, behind the stove and fridge, and in the cabinet nearest the noise. Our guide to what mouse poop looks like helps you rule out roaches and bats.

If you hear noise but find no droppings anywhere, read why you may hear mice in the walls but see no droppings before you buy traps.

Step 2: Find where it gets in and out

Mice come out of walls through gaps where pipes, wires and ducts pass through: under sinks, behind the dishwasher and fridge, around heating pipes and at the gap under baseboards. UC IPM says a house mouse can squeeze under a gap 1/4 inch tall and through an opening 3/8 inch wide (UC IPM). Look for:

• Dark rub marks along an edge
• Droppings collected in one spot
• Fresh gnaw marks or chewed insulation near a pipe

Step 3: Trap at the exits, not inside the wall

UC IPM's trapping guidance works well here (UC IPM):

1. Use plenty of snap traps. Mice rarely go more than 30 feet from their nest and food, so space traps no more than about 10 feet apart where you see activity.
2. Set them close to the wall so mice pass directly over the trigger.
3. Try pairs of traps set 1 to 2 inches apart to catch mice that jump over one.
4. Put them behind objects and in dark corners near the exit points you found, out of reach of children and pets.

Check traps every day. UC IPM advises using enough traps to make the trapping period short and decisive; if a trap catches nothing for several nights, move it closer to fresh droppings.

Why not poison? Bait doesn't stay with the mouse. UC IPM notes that because house mice stay within about 30 feet of their nest, rodenticide will often leave mice dying inside the structure (UC IPM). For a mouse nesting in a wall, that can mean inside the wall cavity. If that already happened, see our guide on how long a dead mouse smell lasts and how to get rid of it.

What about ultrasonic plug-ins? UC IPM says ultrasonic sound is directional, doesn't reach behind objects, and that there is little evidence any sound, magnetic or vibration device drives established mice out (UC IPM).

Step 4: Seal the gaps after the noise stops

Once you have gone several nights without noise or new droppings, seal the holes. New York State recommends sheet metal, concrete or knitted copper mesh for cracks and gaps around vents, wires and pipes, 1/4-inch wire mesh over necessary openings, and tight door sweeps on exterior doors (NY DOH). Sealing before the mice are gone can trap one inside the wall.

When to open the wall or call someone

Call a pest professional if you hear noise in several rooms, keep catching mice for more than two or three weeks, or suspect rats. Opening drywall is a last resort, usually only to remove a dead animal that has a smell you can pin to one spot. Clean droppings and nests with the CDC method: wet them with disinfectant first and never sweep or vacuum them dry (CDC).