Saw a mouse in the house? What to do next

A mouse running across the kitchen floor or along the baseboard is a jolt, especially late at night. The good news is that one sighting, dealt with quickly, is the easiest stage to fix. Here is what to do tonight, how to tell whether it is one mouse or many, the mistakes that make it worse, and when it is time to call for help.

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Saw a mouse in the house: what to do first

Stay calm, note exactly where you saw it and which way it ran, and close off that room if you can. Then, before bed, put away anything a mouse could eat: food on the counter, bread, fruit, pet food and the kitchen garbage. Tomorrow, look for droppings near the spot where you saw it and along the nearest walls. What you find decides your next step.

Mice are timid and want to get out of sight, so the one you saw has almost certainly gone back into a gap behind an appliance, under a cabinet or into a wall. You do not need to chase it. What matters is working out where it lives, how it got in, and how many others are with it.

If you want it handled for you, our mouse and rat control covers the inspection, the treatment and the follow-up visit for one flat price, and you can book a mouse control visit online in about a minute.

Does seeing one mouse mean there are more?

Usually, yes. Mice are most active at night and keep close to walls and dark spaces, so by the time one is seen in the open, others are often living out of sight. Mice also breed quickly: when food and shelter are good, a female can have a new litter every few weeks. A couple of mice in the fall can become a real problem by midwinter.

That does not mean every sighting is an infestation. A single mouse that wandered in through an open garage door, with no droppings anywhere, can be a one-off visitor. The way to tell is to look for the signs below over the next few days, rather than guessing from one glimpse.

• Probably one visitor: no droppings, no noise at night, no chewed packaging, and nothing new after a few days.
• Probably several mice: droppings in more than one room or cupboard, fresh droppings coming back after you clean, scratching in the walls or ceiling at night, or chewed food bags.
• Probably a lot of mice: mice seen during the day, droppings in many places, or a strong musty smell in cupboards.

What to do tonight

You cannot fix the whole problem tonight, but these steps make the house less inviting straight away and give you useful clues for tomorrow:

• Put all food away. Move bread, cereal, snacks, fruit and anything in paper or thin plastic into the fridge or hard containers with lids.
• Pick up pet food and water bowls for the night, and close the bag or bin the pet food is stored in.
• Empty the kitchen garbage and take it outside, or make sure the bin has a tight lid.
• Wipe the counters and stovetop and sweep up crumbs, especially under the toaster and around the stove.
• Close the door of the room where you saw the mouse, and put a rolled towel along the bottom of bedroom doors if it makes you feel better.
• Write down where and when you saw it. Combined with where you find droppings, it tells a technician where mice are travelling.

Can I sleep with a mouse in the house?

Yes. Mice are timid, avoid people and almost never bite unless they are handled. A mouse is far more interested in your pantry than your bed. If you saw it in a bedroom, keep food and snacks out of the room, shake out bedding and clothes left on the floor, and keep the bedroom door closed at night.

The more useful worry is what mice do while you sleep: they contaminate food and surfaces with droppings and urine, chew packaging and wires, and nest in quiet spots. That is why it is worth acting within days rather than waiting to see if it happens again.

Where did the mouse come from?

In Ottawa, most mice move indoors in the fall, as cold nights push them to look for warmth and shelter. Health Canada notes that a mouse can squeeze through a crack about the width of a dime, so most houses have several possible ways in. The most common ones are:

• The garage door, where a worn bottom seal leaves a gap at the corners. From an attached garage, mice follow the shared wall into the house. See mice in the garage in winter.
• Gaps around pipes, cables and vents where the gas line, outdoor tap, air conditioner lines and dryer vent go through the wall.
• The top of the foundation wall, where the wood framing sits on the concrete, often hidden behind shrubs, decks and steps.
• Worn door sweeps on exterior doors, with daylight showing underneath.
• In condos and apartments, the gaps around pipes under the kitchen sink and behind the dishwasher, which connect to other units.

Our guide on how mice get in and how to keep them out shows how to find these gaps yourself and which materials actually keep mice out.

How to check how many mice you have

Give it two or three days and look for these signs. Use a flashlight and check low, dark places first:

• Droppings: small, dark and rice-shaped, about 3 to 6 mm long, along baseboards, in lower cupboards and drawers, behind the stove and under the kitchen sink. Fresh ones are dark and shiny; old ones are grey and crumbly.
• Noise at night: light scratching or scurrying in the ceiling or walls, often near the kitchen, furnace or water heater. Our guide to scratching in the walls at night explains how to tell mice from other animals.
• Chewed packaging: small, rough holes in cereal boxes, flour, rice, birdseed or pet food bags.
• Nests: loose balls of shredded paper, fabric or insulation in quiet corners, stored boxes or the back of a cupboard.
• Greasy smudges along the bottom of walls and around pipes, where mice rub on the same route every night.

A simple test: clean up any droppings you find, then check the same spots two days later. New droppings mean mice are still active there. For a complete list, see our guide to the signs of mice in your house.

Will a mouse leave on its own?

Not usually, and almost never in an Ottawa fall or winter. If a mouse has found warmth, water and something to eat inside, it has every reason to stay, and every reason to breed. Mice can also live on very little food: a few crumbs under the stove and some birdseed in the garage are enough.

Waiting until spring tends to mean more mice, more droppings to clean up and more chewing damage, not fewer. Removing food helps, but it rarely makes mice leave by itself while the way in is still open.

What not to do

• Do not put out loose poison or open bait trays, especially with children or pets in the home. Mice can also carry bait into walls and die out of reach, leaving a smell that can last for weeks. Any product you use should carry a Pest Control Products (PCP) number, which shows it is registered with Health Canada.
• Avoid glue traps. They are inhumane and catch pets, birds and other animals. We do not use glue traps or snap traps on our jobs.
• Do not plug holes with spray foam, caulk, paper or steel wool alone. Mice chew through foam and paper, and steel wool on its own rusts and pulls loose.
• Do not seal every gap while mice are still inside. Trapped mice can die in the walls or chew a new way into the living space. Deal with the mice inside first.
• Do not rely on ultrasonic plug-ins, peppermint oil or dryer sheets. There is little good evidence they keep mice away for long, and they do not close the gap the mice are using.
• Do not sweep or vacuum droppings dry. It throws dust into the air. See the cleanup steps below.

Cleaning up after a mouse safely

Mouse droppings and urine can carry germs. The Public Health Agency of Canada advises cleaning them in a way that does not stir up dust:

• Air out the area first if it is a closed space, such as a cupboard, storage room or cold room.
• Wear rubber or disposable gloves. For a large amount in a small, enclosed space, wear an N95 mask as well.
• Spray droppings and nesting material with a household disinfectant, or 1 part bleach to 9 parts water, and let it soak for about 10 minutes.
• Wipe it up with paper towels, seal everything in a plastic bag, and put that inside a second bag for the outside garbage.
• Throw out any food that mice have chewed or left droppings on, and wash dishes and utensils that were in the cupboard.
• Disinfect the area again, take off your gloves and wash your hands with soap and water.

Mice in Ottawa houses, condos and rentals

Houses and townhouses. Newer subdivisions beside fields, construction and the greenbelt, like those in Kanata and Barrhaven, often see mice in attached garages and along the foundation as the weather turns. Older homes in neighbourhoods like Westboro and Alta Vista tend to have more gaps in older foundations and around pipes.

Semis and row houses. A shared wall means mice can travel between homes. Treating your side still works, but sealing the gaps along the shared wall, and talking to your neighbour, helps keep them from coming back.

Condos and apartments. Tell your property manager, since mice in one unit often mean activity in others. Pipes and wiring that run between units are the usual routes.

Renting? In Ottawa, treating pests in a rental unit is generally the landlord's responsibility, and tenants are expected to prepare the unit and follow the treatment plan. Tell your landlord or property manager in writing as soon as you see a mouse.

When to call a mouse exterminator

Book a technician if any of these apply. They usually mean an established group of mice and at least one open entry point:

• You find droppings in more than one room, or fresh droppings keep coming back after you clean.
• You hear scratching in the walls or ceiling most nights.
• You have seen more than one mouse, or seen one during the day.
• You find chewed wiring, insulation or food in several places.
• Mice came back after you treated or sealed things yourself. See do mice come back after extermination for why that happens.
• You have young children or pets and do not want to handle bait or traps yourself.

In the fall and early winter, sooner is better. Mice are moving indoors and breeding, so a problem caught after the first sighting is smaller and quicker to clear.

How much does it cost to get rid of mice in Ottawa?

Our mouse and rat control in Ottawa is one flat price of $299 plus HST for houses, townhomes and condos. That covers the full inspection, locked bait stations, a photo report of entry points, small gaps sealed with steel mesh on the first visit, a follow-up visit and a six-month guarantee. Rats can need more stations and more follow-up, so if the job is larger than a standard treatment, we confirm the price after the inspection.

If the inspection shows larger gaps, such as a worn garage-door seal, roofline gaps or an older foundation, our rodent proofing service is quoted separately in writing, with a photo of each gap, before any work starts. Every price is listed on our pricing page.

Quick answers about seeing a mouse

Book mouse control online

Pick a day and time window on our booking page and we will email you to confirm. Our mouse and rat control includes a full inspection of the basement, attic access, garage and exterior, tamper-resistant locked bait stations placed away from children and pets (we do not use snap traps or glue traps), a photo report of the entry points we find, small gaps sealed with steel mesh on the first visit, a follow-up visit to check activity and adjust the stations, and a six-month guarantee: if mice or rats return, we re-treat for free.

Have a question before you book? Read our pest control FAQ or contact us.

Book online See mouse & rat control ($299 + HST)

Keep reading

• Signs of mice in your house
• Do mice come back after extermination?

Sources

• Rats and mice, Health Canada
• Hantavirus: spread, prevention and risks, Public Health Agency of Canada

General information for homeowners. Every home is different; your technician will confirm what applies to yours.