House mice follow warmth and food. From September to November, when overnight temperatures in York Region and Toronto drop, they come in through gaps around pipes, vents, garage doors and the sill where the house sits on its foundation. Inside, walls, ceilings and the space behind kitchen cabinets give them a warm route to food. They breed quickly, so a few mice in October can be a larger problem by January.
How do I know if I have mice in my walls?
| What you notice | Likely cause | DIY safe? | Who to call |
|---|---|---|---|
| Light scratching or scurrying at night, inside walls or ceilings | Mice | Yes: traps and sealing | Licensed exterminator if it continues |
| Droppings about the size of a grain of rice along walls, in drawers or under the sink | Mice | Yes, with safe clean-up | Exterminator for heavy activity |
| Heavier thumping or gnawing, droppings about 1 to 2 cm | Rats | Traps only with care | Licensed exterminator |
| Noise in the attic early morning and dusk, not all night | Squirrels or other wildlife | No: do not block them in | Wildlife removal (a different job from mouse control) |
| Musty smell, shredded paper or insulation in a corner | A mouse nest | Yes, with gloves and disinfectant | Exterminator if droppings are widespread |
| Lights flicker or a breaker trips, with mouse signs nearby | Possible chewed wiring | No | Electrician and exterminator |
Health Canada lists the signs of rats and mice as scratching sounds in walls at night, gnawing marks, damaged food packages, droppings, urine and tracks on dusty surfaces. Pets often find them first: a cat or dog staring at one spot on a wall is worth noting.
How do mice get into the house?
Mice can squeeze through an opening about the size of a dime, according to Health Canada, and rats through one the size of a quarter. Walk around the outside of the house with a flashlight and look for:
- Gaps where pipes, cables, the gas line and the air conditioner lines enter the house.
- Dryer, bathroom and kitchen vents without screens or with damaged flaps.
- Worn weather stripping at the bottom of the garage door and exterior doors.
- Cracks in the foundation, and the gap between the foundation and the siding or brick.
- Openings where the roof meets the soffit, and gaps around window wells.
Seal gaps with steel wool or copper mesh packed tight, then caulk over it, or use metal flashing, hardware cloth or cement for larger holes. Mice chew through foam, plastic and caulk on its own. Keep firewood, compost and clutter away from the walls of the house, and cut back plants touching the siding.
How do I get rid of mice in the walls myself?
- Set snap traps or electronic traps along walls, behind appliances and near droppings, with the trigger end against the wall. Mice run along edges, not across open floors. Use several traps, not one.
- Bait with a small amount of peanut butter or another sticky food. Wear gloves when handling traps and dead mice.
- Store food, pet food and birdseed in glass, metal or thick plastic containers with tight lids, and keep counters and floors clear of crumbs.
- Seal entry points at the same time. Trapping without sealing means new mice replace the ones you catch.
- Check traps daily and keep going until you have caught nothing for a week or two.
Health Canada advises that poison baits should not be the only method, and that any bait used where children or pets can reach it must be in a tamper-proof bait station. Poisoned mice often die inside walls, where the smell can last for weeks. Ultrasonic repellers are widely sold, but Ontario homeowners on RedFlagDeals mostly report they did nothing; traps and sealing are what the government guidance relies on.
When should I call an exterminator for mice?
Call a licensed exterminator if you are still catching mice or finding fresh droppings after one to two weeks of trapping and sealing, if you hear activity in several parts of the house, if there are signs of rats, or if you have young children or pets and do not want to handle bait yourself. In Ontario, applying pesticides as a paid service requires a structural exterminator licence from the Ministry of the Environment, Conservation and Parks. A good exterminator does more than set bait: they find the entry points and tell you which ones to close.
If lights flicker or a breaker starts tripping in the same area where you hear mice, have an electrician check the wiring. Mice gnaw on wire insulation, and chewed wiring inside a wall is a fire risk.
What does rodent control cost on Doyo?
On Doyo, Rodent Control is $531, the full price with Doyo's fee included. It covers a licensed exterminator, entry points found and reported, traps and bait stations set, and one follow-up visit. Pest control pros on Doyo hold an Ontario Structural Exterminator licence, which Doyo checks before they are offered the work. Tell the pro about children and pets when you book, so they choose the treatment with that in mind. If you want help closing the gaps the exterminator reports and they can be reached from the ground, Doyo's handyman General Repairs job is $59 an hour.