In short. A mouse gets through a 6 mm opening, a rat through roughly two and a half centimetres, and both come back the same way if it is not closed. That is why traps alone almost always disappoint. The first useful question is not which poison to buy, but where they are getting in.

Mouse or rat? How to tell the difference

The house mouse measures 6-10 cm (without the tail), leaves rice-grain droppings and slips through a 6 mm hole. The Norway rat is much larger, its droppings are 1-2 cm, it burrows and runs along foundations. Treatment differs by species.

A female mouse can have 5 to 10 litters a year. A few individuals become an infestation in one quarter.

The 5 signs of an infestation

  • Droppings along walls, under the sink, in drawers.
  • Running or scratching noises in walls and ceilings at night.
  • Chewed food packaging, wires or insulation.
  • Grease marks and runways along baseboards.
  • Persistent ammonia-like urine smell.

Why traps alone are never enough

Store traps and poisons kill a few rodents but don't close the access points: the colony rebuilds through the same holes. Worse, a poisoned rat dying inside a wall creates odours and flies for weeks. The key is sealing the entry points, which DIY solutions ignore.

What a professional protocol does

Full inspection, locked bait stations (child/pet-safe), targeted traps, then systematic sealing of conduits, cracks and door gaps, plus a follow-up visit. It's the elimination + exclusion combo that solves it for good, with a written guarantee.

A pest problem at your place?

Clear diagnosis, quote from $99, written guarantee. Service within 24h across the Greater Montreal area.

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What falls to you, and what falls to the City

The split often surprises people. On its rodent control page, the City of Montreal states that a problem in a public space, a park or an alley is reported to 311, but that the owner of a private home must call a qualified exterminator and carry out the necessary corrections. A tenant reports to the landlord without delay.

On where Montreal rats actually come from, between damaged sewers, excavation work and openings in the building itself, we covered both routes in this article.

Frequently asked questions

Are rodents dangerous to health?

Yes: they contaminate food and surfaces (salmonella, hantavirus), and their droppings are allergens. Chewed wires are also a real fire hazard.

How long to eliminate an infestation?

Usually 2 to 4 weeks depending on extent: active elimination then sealing and a follow-up visit to confirm no return.

How much is rodent control?

From about $99 depending on the species, area and number of access points to seal. Detailed quote after inspection, no commitment.

Are baits safe with kids or a dog?

Yes: we use locked stations and Health Canada-approved products placed out of reach. Household safety is part of the protocol.