Hearing Mice in the Walls? What It Means and What to Do This Week
Denver Metro & the Front Range
Our phones have been busy with mouse calls this fall, and most of them start the same way. Someone hears scratching in the ceiling or behind the bedroom wall late at night, usually right after the first real cold snap, and wants to know if it's mice.
It usually is. And by the time you can hear them, they've been inside for a while. Here's what that sound means, where mice spend the winter in a Front Range home, and what to do this week.
What the sounds usually mean
- Light scratching or pattering in the ceiling or walls at night. Mice moving through wall voids and between floors, often along pipes and wiring.
- Rustling in the attic. Mice nesting in the insulation, which is warm and easy to tunnel through.
- Gnawing sounds. Mice chew constantly to keep their teeth worn down, on wood, cardboard, plastic and sometimes wiring.
- Heavier thumping or running in the attic. That can be something bigger, like a rat, squirrel or raccoon. Tell us when you call, because the plan is different.
Sounds are a good start, but droppings confirm it. Check along the kitchen baseboards, under the sink, in the back of the pantry, behind the stove and in garage corners. Mouse droppings are small, dark and rod-shaped, about the size of a grain of rice.
One mouse means more
Mice breed fast. A female can have a new litter about every three weeks, and the young are ready to breed themselves within a couple of months. A mouse you see running across the kitchen floor is usually just the one that got bold. The rest are nesting somewhere quiet.
Where mice spend the winter in a Front Range home
- Wall voids, especially around plumbing under kitchens and bathrooms
- Attic insulation, close to the warm ceiling below
- Under and behind the fridge, stove and dishwasher, where motors give off heat
- Basement storage and the space under stairs
- Garages, in stored boxes, bags of seed or pet food, and lawn equipment
- Parked cars and stored vehicles, where engine bays and air filters make warm, sheltered nests
The mistakes that make it worse
- Sealing the hole while mice are still inside. It feels like the right move, but it traps mice in the walls, and they'll chew or find another way into the living space. Trap first, repair after.
- Spreading loose poison. A poisoned mouse can take days to die and often dies inside a wall, where the smell can last for weeks. Loose bait also gets carried off and found by pets and kids.
- Setting one or two traps in the middle of the floor. Mice travel along walls and avoid new objects for a few days. A couple of traps in the open usually catch nothing.
- Waiting for spring. Mice don't move back outside when it warms up. A house with food, water and heat is the best place they've got, and they keep breeding in it.
- Sweeping up droppings. Dry sweeping or vacuuming puts dust in the air. Wet the droppings with disinfectant first, then wipe them up.
What to do this week
- Find the activity. Look for droppings and chewed packaging to see where mice are traveling and feeding.
- Take away the food. Move pet food, bird seed and pantry food into hard containers with lids, and pick up pet bowls at night.
- Trap along the walls. Set traps flat against the wall, along the paths where you found droppings, behind appliances and in cabinets. Use more than you think you need.
- Give it a few nights. Mice are cautious around new objects, so a quiet first night doesn't mean the trap is in the wrong place.
- Check the garage door. Stand inside the closed garage in daylight. If light shows under or around the door, mice can get in there.
- Pop the hood. If your car has been parked for a while, check the engine bay and air filter for nesting material before you drive.
How we handle mice that are already inside
- Active trapping. Traps go along the walls and the paths mice actually use, in the attic, basement, garage and behind appliances, not in the middle of the floor.
- Entry-point repair estimate. At the time of service our exclusion experts will inspect and give you an estimate for any repairs (exclusion) needed to keep mice from getting back in, like gaps around utility lines, garage door seals, dryer vents and foundation gaps.
- Sanitation walk-through. We walk the home with you to find what's feeding them.
- Follow-up visits. If your quote includes a follow-up, we come back to check and reset traps, and it's built into the original price. We always tell you up front whether it does.
Frequently Asked Questions
Is scratching in the walls at night mice?
Usually. Mice are most active at night, and light scratching or pattering in walls, ceilings or the attic after the weather turns cold is the most common sign. Look for droppings along walls, under sinks and in the pantry to confirm it.
If I've seen one mouse, are there more?
Almost always. Mice breed quickly, and by the time one is out in the open there are usually others nesting in the walls, attic or under appliances.
Should I seal the hole where the mice are getting in?
Not while mice are still inside. Trap the ones in the house first, then repair the entry points. Sealing too early traps mice in the walls, where they look for another way into the living space.
Why aren't my mouse traps catching anything?
Mice avoid new objects for a few days, and traps in the open don't get visited. Set more traps than you think you need, along walls and behind appliances, and give them a few nights.
Will mice leave on their own in spring?
No. A house with food, water and warmth is a better home than anything outside, and mice that are nesting indoors will keep breeding there.
Looking for more? Read about rodent control or browse the full pest library.
Free Estimate.
Tell us what you're seeing. We'll diagnose, give you a real quote, and schedule fast.