Every September, our phones start ringing with the same story: scratching in the walls at night, droppings behind the stove, a mouse darting across the kitchen floor. It isn’t a coincidence. As the first cold nights arrive across Simcoe County, mice that spent the summer outdoors begin looking for somewhere warm to wait out the winter — and your home is the most appealing option on the block.
Why fall is rodent season in central Ontario
Mice don’t hibernate. When overnight temperatures drop, they need a heated, sheltered space with access to food, and the transition from warm summer nights to frosty fall ones is the trigger that pushes them indoors. In Barrie, with its hard winters, this happens fast — often over a single cold snap in late September or October.
A single female mouse can produce five to ten litters a year, with up to half a dozen young each time. That’s why “just one mouse” is almost never just one mouse a few weeks later. Catching the problem early, before a breeding population establishes inside a warm wall void, makes all the difference.
Where mice actually get in
Mice can squeeze through a gap the width of a pencil — about 6 mm. The entry points we find most often on Barrie-area homes are:
- Gaps around plumbing, gas lines, and dryer vents
- Spaces under and beside garage doors
- Weep holes in brick veneer
- Where the foundation meets the siding
- Worn or missing door sweeps
Older homes in neighbourhoods like Allandale and Letitia Heights tend to have more of these gaps, but new builds backing onto green space such as the Ardagh Bluffs trails or the Bear Creek wetlands aren’t immune either.
Early warning signs
- Small, dark, rice-grain-sized droppings, especially behind appliances and in cupboards
- Light scratching or scurrying sounds in walls and ceilings at night
- Gnaw marks on food packaging or baseboards
- A faint musky, ammonia-like smell in concentrated areas
How to keep them out
The most effective long-term fix is exclusion — sealing the gaps mice use before they get in. We pair professional mice and rodent control with exclusion and proofing so the current population is removed and the entry points are closed with rodent-proof materials.
The single highest-value step you can take is to seal up before the first hard frost. If you’re already hearing activity, don’t wait — book an inspection. For homeowners across Barrie and beyond, every job is backed by our Zero Pest Guarantee.