The first sign is usually a sound. Somewhere around one in the morning there’s a scrabble in the wall behind the headboard, heavier than a mouse would make, then nothing, then the same scrabble going back the other way about twenty minutes later. Most people lie there for a while trying to decide whether they imagined it.
You didn’t imagine it. And that out-and-back trip is good news of a sort, because a rat will use one path night after night (same baseboard, same pipe chase, same hole) until something forces it to change. Follow the droppings and the grubby marks backwards along that path and you’ll usually end up within a metre or two of the way in.
It also makes the slippers-and-flashlight question easier, the one everybody ends up asking themselves in the basement at 1 a.m.: drive to Home Depot for another box of snap traps, or phone pest control in the morning?
Brown rats, properly called Norway rats, are what you’ll almost certainly find in a GTA basement, so they’re who this is about.
Why rats keep to the walls
Rats see badly. They get around mostly by nose and by touch, whiskers brushing along a surface as they go, and open floor makes them uneasy. So in a basement they take the long way round, tight to the foundation wall, squeezing behind the furnace and the old paint cans nobody has touched since 2015.
Look along the base of the walls rather than the middle of the floor. Droppings pile up there. On concrete block, or on a copper pipe running along a joist, you might also find a dark, slightly shiny smear a few centimetres up, and if you rub it with a gloved finger it feels greasy. That’s body oil and grime off their coats, laid down one trip at a time.
They don’t commute far, either. Give a rat reliable food and it rarely ranges beyond 30 to 50 metres, so droppings in your garage generally mean a nest under your own deck or in your own woodpile, not at the neighbours’ place three doors down, much as you’d like it to be.
Rat or mouse?
Size, mostly. An adult Norway rat is chunky, 20 to 25 cm of body plus a scaly tail that’s a bit shorter again, with a blunt snout and small furry ears, while a house mouse would fit in your palm with room to spare. Through the ceiling you’ll hear mice as a quick pitter-patter, whereas a rat is heavier and more of a scuffle, sometimes with a thump when it drops off a joist.
Droppings settle it. Rat droppings run about 12 to 20 mm long with blunt ends, while mouse droppings are only 3 to 6 mm and pointed, closer to a grain of rice. Roof rats, the kind that climb into attics, do turn up in Canada but they’re rare this far north, so thumping in a Toronto attic is far more likely to be a squirrel.
What the signs are telling you
| What you find | What it usually means |
|---|---|
| Shiny, dark, soft droppings by the baseboard | Fresh, so the route is in use now |
| Grey droppings that crumble when touched | Old, and possibly abandoned |
| Greasy smudges on block walls or pipes | A runway they use every night |
| Pale, fresh chew marks on wood or plastic | Active gnawing |
| Holes 6 to 9 cm wide by the foundation or deck | An outdoor burrow |
| Shredded insulation or paper in a corner | A nest close by |
| Sharp ammonia smell in a closed room | Weeks of urine, not days |
If you can’t tell whether the droppings are new, clean the area properly and check the same spot two nights later. Anything there now was left after you cleaned.
When and where you notice them
Hearing them after midnight is normal, since rats are mostly nocturnal, and on its own it says very little about numbers. Seeing one cross the driveway at three in the afternoon is a different situation. It can mean there are enough rats that the weaker ones are being pushed out to feed in daylight, or that something disturbed the nest, and either way I wouldn’t wait on it.
The spread matters as well. A single spot by the furnace with a clear line to one gap in the foundation points to a small problem, whereas droppings in the garage, the basement storage room and behind the kitchen stove all in the same week point to several routes and more animals.
Watch the dog. If he’s taken to parking himself in front of one stretch of baseboard every evening, head cocked, or the cat has started sitting outside the basement door like she’s waiting for a bus, there’s something on the other side of that drywall they can hear or smell and you can’t.
How fast the numbers climb
Faster than most people would guess. Females can produce several litters a year at six to twelve pups a time, and the young are breeding at around three months old. Do the arithmetic on a pair that moved into a warm crawl space in spring and by Thanksgiving you aren’t dealing with two rats anymore. The one you saw by the recycling bin in May almost certainly had company.
How they got in, and why your house
Rats would rather not chew if they don’t have to, and older houses give them plenty of options. The usual ones are gaps where the gas line, water service or cable comes through the foundation, a dryer or furnace vent with the cover missing, cracked parging below grade, the bottom corner of a garage door that no longer meets the slab, and old clay drain tile or a sewer connection that was abandoned during a renovation and never capped. An adult can get through a hole about 2 cm across, and if the edge is soft, like old caulk, vinyl or rotted wood, it’ll gnaw it wider.
As for why they chose you, it’s usually food plus somewhere to hide. A green bin lid that doesn’t latch, sunflower seed under the feeder and a bag of dog food on the garage floor will all do it, and so will a compost bin with a gap at the bottom or apples left to rot on the lawn. Clutter under the deck or in the shed gives them cover. Road and sewer work on the street can also push rats out of their old burrows, which is why some people first notice them a few weeks after the city digs up the road.
Why the trap hasn’t caught anything
Rats are wary of anything new in their path, and a trap set on Tuesday may get walked around until Friday. Some technicians put traps out unset for a few days so the rats get used to them first.
Placement does most of the work. The trap should sit flat against the wall with the trigger end facing the wall, right across the route they use, which you can find by following the smudges and droppings. One set in the middle of the basement floor is sitting where a rat never walks.
Mistakes that make it worse
A few things people do in a hurry tend to backfire.
- Poison put out and forgotten. Rats die in the walls, and owls, hawks or a neighbour’s dog can be poisoned eating them.
- Holes sealed before the rats are gone. They’ll chew a new way out.
- Spray foam on its own. Rats go through it, so use steel wool or copper mesh with sealant, sheet metal or mortar.
- Droppings swept up dry. Wet them with disinfectant first, wear gloves and a mask, and bag it all.
What to do tonight
- Put away pet food and bird seed, and check that bin lids latch.
- Write down where and when you saw signs. Take photos.
- Sprinkle flour along the route you suspect. Check it for tracks at breakfast.
- Do a flashlight lap of the outside, looking for burrows and chewed gaps.
- Leave the holes open until you know whether they’re inside or out.
When to call someone
One rat and one trap in the garage is something plenty of people handle themselves. Droppings in more than one room, scratching most nights or a fresh burrow beside the foundation is a bigger job, because the fix means finding every way in, closing each one with something rats can’t chew, and coming back to make sure nothing is still moving.
There’s a safety side as well. Rats chew wiring, and chewed wiring inside a wall is a fire risk, while a gnawed supply line can leak behind the drywall for months before a stain shows on the ceiling below.
North York has plenty of what rats like, including older foundations, ravine edges and sewer connections that go back decades, so a company that does a lot of pest control in North York will have seen most of what’s under your deck already. When you call, get them to explain how they’ll close up the holes, not just what they’ll put down for bait, and ask when the follow-up visit is.
If it were my house, I’d make that call this week rather than next.
