Winter’s Unwanted Guests: A Guide to Rodent Infestations in the GTA & Southwestern Ontario

Winter in Ontario brings beautiful snowfall, cozy nights indoors — and unfortunately, an annual rise in rodent activity. As temperatures drop, mice, rats, and other small pests look for warmth and shelter, turning homes across the GTA, Peel Region, Halton Region, Hamilton, Kitchener-Waterloo, Cambridge, Guelph, London, Woodstock, Ingersoll, and surrounding Southwestern Ontario communities into prime targets.

If you’re hearing scratching sounds in your walls, tapping noises in the attic, or noticing droppings under the kitchen sink, there’s a good chance you’ve become part of Ontario’s seasonal surge in rodent invasions.

This guide explains why winter rodent infestations happen, the health risks, how to protect your home, and what homeowners across the GTA & Southwestern Ontario should do when signs of activity appear. High-authority government links are included to support public safety and improve your website’s credibility and SEO.

Why Winter is Peak Rodent Season in Ontario

Rodents don’t hibernate. As soon as temperatures fall below freezing, they begin seeking indoor shelter where they can:

• Stay warm
• Find access to food
• Build safe nesting sites
• Hide from predators

Ontario’s Public Health agencies confirm that rodents reproduce year-round indoors, meaning a small winter intrusion can turn into a full infestation within weeks.

Official guidance on rodent-borne disease risks:
Public Health Ontario — Rodent-borne diseases
https://www.publichealthontario.ca/en/diseases-and-conditions/infectious-diseases/vector-borne-zoonotic-diseases/hantavirus

Common Rodents Invading GTA & Southwestern Ontario Homes

House Mice (Most Common)

• Can squeeze through gaps as small as a dime
• Excellent climbers; often heard in attic spaces and wall voids
• Rapid reproduction: 10–12 litters per year

Norway Rats

• Enter basements, garages, crawlspaces, and foundations
• Large body size makes scratching and chewing noises louder
• Known to chew on electrical wiring, risking fires

Roof Rats (Increasing in GTA)

• More common in warmer climates but steadily increasing in cities like Toronto, Mississauga, and Brampton
• Frequently invade attics
• Require different exclusion techniques than Norway rats

Public Health Ontario also provides detailed descriptions of rodents and diseases associated with them:
https://www.publichealthontario.ca/en

Signs of Rodent Activity Inside Your Home

Homeowners usually discover infestations because they hear unusual noises — especially at night.

1. Scratching in walls

Often heard behind kitchen cabinets, bathroom walls, and basement utility rooms.

2. Noises in the attic at night

Rodents are nocturnal, so nighttime activity is usually more noticeable.

3. Droppings

Mouse droppings: small, black, rice-shaped
Rat droppings: larger, blunt ends

4. Chewed food packaging or gnaw marks

5. Grease marks along walls or baseboards

6. Nesting materials

Insulation, paper, cardboard, or shredded fabric.

If you notice any of these, immediate action reduces the risks of property damage and disease.

Cities & Communities in the GTA & Southwestern Ontario Most Affected

This blog focuses only on the regions Vanish Canada Pest Control serves.

Rodent activity is highest in:

Greater Toronto Area & Peel

• Toronto
• Mississauga
• Brampton

Halton & Hamilton Region

• Oakville
• Burlington
• Milton
• Hamilton
• Ancaster
• Stoney Creek

Kitchener–Waterloo–Cambridge–Guelph Corridor

• Kitchener
• Waterloo
• Cambridge
• Guelph

Southwestern Ontario

• London
• St. Thomas
• Woodstock
• Ingersoll
• Tillsonburg
• Stratford
• Brantford

Population density, older homes, urban waste systems, and commercial buildings all contribute to higher rodent pressure in these regions.

Top Health Risks Caused by Rodents

Rodents inside the home aren’t just annoying — they pose real health dangers.

1. Hantavirus

Found in rodent droppings, urine, and saliva. It can become airborne during cleaning.
Ontario guidance:
https://www.ontario.ca/page/animal-health-hantavirus

2. Salmonella

Rodents frequently contaminate food or surfaces.

3. Leptospirosis

Spread through rodent urine, especially in basements or garages.

4. Asthma & breathing issues

Rodent dander and droppings can trigger respiratory reactions.

5. Parasites

Rodents bring mites, fleas, and ticks into homes.

6. Rabies (indirect wildlife interactions)

While rodents rarely carry rabies, homeowners responding to noises sometimes encounter wildlife like bats or raccoons, which can be rabies carriers.

Provincial rabies guidelines:
https://www.publichealthontario.ca/en/diseases-and-conditions/infectious-diseases/vector-borne-zoonotic-diseases/rabies

How Rodents Enter Homes in the GTA & Southwestern Ontario

Most winter infestations happen through small but overlooked gaps around the home.

Typical entry points include:

• Gaps in door frames or weather stripping
• Holes around utility lines
• Cracks in foundation walls
• Damaged soffits, fascia, or roofline
• Dryer-vent openings
• Basement windows
• Garage doors that don’t fully seal
• Openings behind kitchen cabinets

The Ministry of Ontario advises homeowners to secure outdoor structures and seal all potential access points:
https://www.ontario.ca/page/preventing-and-managing-conflicts-small-animals

How to Protect Your Home: A Three-Part Winter Strategy

1. Seal Entry Points (The Most Important Step)

Rodent exclusion requires durable materials, including:

• Steel mesh
• Hardware cloth
• Metal flashing
• Professional-grade sealants

Avoid relying on DIY foam alone — rodents can chew through it in minutes.

For best results, a technician inspects:

• The entire foundation
• Roof edges
• Attic and vent openings
• Garage edges
• Gaps around pipes
• Basement windows

2. Remove Food & Water Sources

Inside:

• Store pantry items in sealed containers
• Clean crumbs and grease immediately
• Keep pet food stored in sealed bins
• Empty trash daily and clean garbage bins regularly

Outside:

• Secure garbage & compost
• Remove birdseed spills
• Store firewood away from the house
• Clean up fallen fruit
• Fix leaky hoses or exterior taps

The City of Toronto provides additional rodent prevention guidelines:
https://www.toronto.ca/city-government/public-notices-bylaws/bylaw-enforcement/property-standards-keep/rodent-control/

3. Monitor & Respond Quickly

Early detection is crucial.

Professionals use:

• Bait stations around the exterior
• Snap traps (placed safely away from children & pets)
• Thermal & moisture-detection tools
• Rodent-proofing inspections

Homeowners should not use banned rodenticides or unsafe DIY methods. Response must follow Ontario laws.

Why Winter Rodent Infestations Are More Common in Your Region

GTA (Toronto, Mississauga, Brampton)

• High density, older buildings, overflowing waste systems
• Construction vibrations disturb underground burrows
• Cold wind tunnels push rodents indoors

Hamilton, Burlington, Oakville

• Waterfront climate pushes rodents inland
• Large network of older homes
• Squirrel and raccoon populations create openings that rodents exploit

Kitchener, Waterloo, Cambridge, Guelph

• University and downtown housing increases rodent spread
• Older basements and additions create easy access points

London, Woodstock, Ingersoll, St. Thomas

• Heavy suburban development disrupts natural habitats
• Agricultural-urban mix increases mouse populations

Safe Cleaning and Handling Procedures

When dealing with rodent droppings indoors, safety is essential.

What to do:

✔ Wear gloves and a mask
✔ Open windows 30 minutes before cleaning
✔ Spray droppings with disinfectant
✔ Never vacuum dry droppings
✔ Double-bag trash
✔ Wash hands thoroughly

Official safety guidance from Public Health Ontario:
https://www.publichealthontario.ca/en/diseases-and-conditions/infectious-diseases/vector-borne-zoonotic-diseases/hantavirus

When to Call a Professional Immediately

You should contact a licensed pest control provider right away if you notice:

• Nighttime scratching
• Activity in the attic or walls
• Continuous droppings
• Chewed wiring
• Damaged insulation
• Strong smell from dead rodents
• Repeated entry even after DIY attempts

Professionals ensure:

• Full inspection
• Identification of entry points
• Trapping/removal
• Long-term exclusion
• Cleanup recommendations

In Ontario, wildlife and rodent control must follow safety and legal standards described by the Ministry of Natural Resources and Forestry:
https://www.ontario.ca/page/wild-animal-control-information-for-municipalities

Your Winter Home Protection Checklist

Here is a simple checklist you can offer clients or publish separately:

Outside:

• Seal gaps
• Install door sweeps
• Clean gutters
• Trim trees
• Secure garbage

Inside:

• Store food properly
• Clean kitchen nightly
• Check the attic monthly
• Monitor basement
• Inspect around appliances

Final Thoughts

Rodent infestations in the GTA and Southwestern Ontario are a yearly winter challenge — but they are entirely preventable. With proper exclusion, sanitation, and monitoring, homeowners can protect their properties and families from damage, contamination, and disease.