It starts after the house goes quiet. A light scratching inside the bedroom wall, a faint scurry behind the drywall, then silence — until it starts again an hour later. In Oakville homes in late October, that sound is usually mice in the walls: animals that moved in for warmth as the nights turned cold, now travelling inside your house without ever crossing an open floor. Here's how to tell, why walls suit them, and what actually fixes it.
What mice in the walls sound like — and when
Mice are nocturnal, and wall sounds follow their clock. Health Canada lists scampering and scratching in the walls at night as a warning sign of mice, and that timing is your first clue.
Listen for:
Light scratching and scuffling after dark, often in the same stretch of wall night after night — that's a travel route, not a one-off visit
Quick, light scurrying that moves along the wall or up toward the ceiling, never heavy and never slow
Faint squeaking near a nesting spot, where mice are gathered rather than travelling
Soft gnawing in a quiet corner of the wall — mice chew constantly to keep their teeth worn down
Timing and weight separate mice from everything else. Squirrels are daytime animals — noise in the morning and late afternoon, with louder chewing, is a squirrel in the attic, not mice in a wall. Raccoons are heavier still: slow thumping after dark that you feel as much as hear. If it's light, quick, and only at night, think mice first.
The other signs to check outside the wall
You will almost never see the mice themselves. Check for the sign they leave where the walls open into your rooms:
Droppings the size of a grain of rice — small, dark, about 3 to 6 mm long, pointed at one end. Look along baseboards, at the back of kitchen cupboards, under sinks, and behind appliances.
Grease or rub marks — dark smudges along baseboards, pipes, and the edges of small holes. Mice use the same routes over and over, close to the wall, and their fur leaves those marks where they brush past.
Gnaw marks and chewed packaging — fine teeth marks on food packets, cardboard, wood and wiring where they come out to feed.
Shredded nesting material — paper, fabric or insulation torn up and tucked behind appliances, in cupboards, or at the top of a wall.
A stale, musky or ammonia-like smell in enclosed spaces — cupboards, closets and utility rooms — that gets stronger the longer mice have been nesting nearby.
Your pet fixating on one wall — a dog or cat staring or pawing at the same spot is not proof, but it is a good reason to check the signs above.
One sign can be a maybe. Scratching at night plus fresh droppings along the same wall is mice until proven otherwise — fresh droppings are dark and shiny, old ones grey and crumbly.
Why walls, and how mice travel inside them
A wall cavity gives a mouse everything it needs in one hidden package: warmth, darkness, protection, and insulation it can nest in. The hollow spaces between studs also work as private hallways. Mice travel up and down and between rooms following pipes, wiring and the tops of walls, then slip out through tiny gaps where pipes and cables pass through — behind the stove, under the sink, at the back of a cupboard — to reach food and water, and back again before morning.
That is why a wall problem rarely stays in one wall. The route that passes your bedroom also connects the kitchen below and the attic above, which is why our mice removal work starts with mapping routes and entry points, not just listening at the loudest spot.
And getting in was easy. A mouse can fit through a hole the size of a dime — roughly a quarter-inch gap, about the width of a pencil. The usual Oakville entry points are unsealed holes around pipes, cables and vents, gaps at the foundation and garage, damaged trim, and openings where the roofline meets the walls. One unsealed utility opening is usually enough.
Why you shouldn’t just live with it — or bait it
Mice stay active all winter and can breed year-round indoors, so a small fall problem does not shrink while you wait — it grows, inside the structure. Constant gnawing can damage wiring inside the wall, where you cannot see it, and droppings and urine build up along the travel routes and in the nesting insulation.
This is also where baiting falls short. A bait program does not close a single hole and has to be topped up forever — a band-aid you keep paying for while new mice use the same dime-sized gaps. Worse, a mouse that dies inside a wall cavity announces itself for weeks, in a place you cannot reach. Our position is the opposite: find every entry point and seal the home permanently. No subscription, no repeat cycle — the house gets closed, and it stays closed.
A safety note: don't sweep or vacuum droppings dry — that puts dust you'd rather not breathe into the air. A few droppings are one thing; a heavily fouled wall or attic is a job to have assessed first, and we'll tell you straight which one yours is.
What we do about mice in the walls
Sean Thornton — owner-operator, 20+ years at this — inspects the home inside and out: he reads the sounds and sign to confirm it's mice (and only mice), checks the attic, basement, kitchen and garage for routes, and maps every entry point around pipes, vents, the foundation and the roofline. Then the home is sealed — gaps closed with materials mice can't chew through, vents screened, every opening gone over end to end — so the hallway system inside your walls has no doors left. That's the work behind our wildlife removal in Oakville mice calls, and it’s a one-time fix, not a program you rent.
Frequently asked questions
How can I be sure the scratching in my wall is mice and not a squirrel?
Check the clock and the weight. Mice are light, quick and active only at night. Squirrels are heavier, louder, and active in the morning and late afternoon — and they're usually in the attic, not inside a wall. An inspection settles it for certain before any work starts.
How small a gap can a mouse really get through?
About the size of a dime — roughly a quarter inch. Any gap you could push a pencil through, especially around a pipe, cable or vent, is worth treating as a door. That's why the entry-point audit matters more than any single trap.
Will mice in the walls damage my house?
They can. Mice gnaw constantly, and inside a wall that can mean chewed wiring and insulation, on top of droppings and urine along their routes. The damage is hidden, which is why dealing with the entry points early costs less than dealing with it later.
Why not just use bait or traps from the hardware store?
Traps can catch the mice you have; neither traps nor bait close the gaps letting the next ones in, and bait can leave a dead mouse inside a wall you can't reach. Sealing the entry points is the step that ends the cycle instead of repeating it.
Will the mice leave on their own in spring?
A colony nesting and breeding inside your walls, with food routes through your kitchen, has no reason to move out — and the gaps they use only get bigger. Houses don't grow out of a mouse problem.
Hearing scratching in the wall tonight?
Call Regional Wildlife Services at 905-320-8984. We take phone calls and bookings 7 days a week; service appointments run Monday to Friday typically, and weekend calls book jobs in for the following week. We serve Oakville, Burlington, Milton, Hamilton, Stoney Creek, Georgetown and the Niagara region. Tell us where the sound is and when you hear it — that alone tells us a lot about who's travelling in your walls. Ready when you are: contact us.
