As temperatures drop, rodents begin searching for warm, sheltered places to escape the harsh outdoor conditions. Homes across Ontario become prime targets for mice, rats, and squirrels the moment the cold weather arrives. Once indoors, rodents reproduce quickly, contaminate surfaces, chew wiring, damage insulation, and turn quiet spaces into noisy, stressful areas. Preventing them from entering in the first place is far easier, and far less expensive, than removing them after they’ve established nests.

Rodent-proofing is the process of securing the home against any entry points, attractants, and structural weaknesses that give rodents access. With a strategic approach, homeowners can protect their living space long before winter takes hold. This guide explains how rodents get in, what attracts them, and the steps required to keep them out all season long.

Why Rodents Move Indoors When Winter Approaches

Rodents are opportunistic animals. In mild weather, they thrive outdoors by foraging, nesting, and travelling in predictable patterns. As conditions shift, so does their behaviour.

They Seek Warmth and Shelter

Dropping temperatures force rodents to find consistent heat sources. Homes provide warmth, insulation, and protection from the wind. Basements, attics, crawl spaces, and wall voids feel safe and secure, especially for rodents preparing to overwinter.

They Need Reliable Food Sources

Winter reduces access to seeds, vegetation, and insects. If food becomes scarce outdoors, rodents search for new sources. Kitchens, pantries, garbage bins, and pet food become highly attractive.

They Look for Nesting Materials

Rodents use insulation, cardboard, fabric, and debris to build nests. Attics and storage areas supply everything they need to raise offspring, even in the coldest months.

They Want Protection From Predators

Cats, owls, foxes, and larger wildlife remain active year-round. Rodents instinctively choose hidden areas inside walls or ceilings because predators cannot reach them once they settle inside.

How Rodents Enter the Home

Rodents squeeze, chew, and claw their way through surprisingly small openings. Understanding these access points is the foundation of proper winter rodent-proofing.

Gaps in the Foundation

Small cracks in foundation walls allow mice to enter at ground level. Even a gap the width of a pencil can serve as an entryway. These are among the most common points of intrusion.

Openings Around Utility Lines

Wiring, plumbing, gas lines, and air conditioning conduits create natural openings. If the surrounding sealant wears away, rodents use the space to slip inside.

Damaged Door and Window Frames

Worn weatherstripping, warped frames, or loose thresholds create gaps big enough for mice and sometimes even rats. Garages are especially vulnerable.

Roofline Weaknesses

Squirrels and rats often enter through damaged soffits, loose fascia boards, and unprotected roof intersections. Once in the attic, they can travel freely through the home.

Vents Without Protective Screening

Kitchen vents, attic vents, dryer vents, and gable vents can all become rodent pathways. Screens deteriorate with time or weather exposure, making them easy to chew through.

Holes Created by Other Wildlife

Raccoons, woodpeckers, and birds sometimes create openings that rodents later exploit. Once a hole exists, mice quickly spread through it and establish nests.

Signs Rodents Are Already Investigating Your Home

Rodents rarely enter without leaving clues. These early signs often appear before a full infestation develops:

• Droppings in kitchen drawers, cupboards, basements, or attics
• Scratching noises in walls or ceilings, especially at night
• Chewed cereal boxes, pet food bags, or stored items
• Shredded insulation or nesting material in corners
• Musty or ammonia-like odours in confined spaces
• Grease marks or rub lines along walls
• Holes in baseboards or gaps behind appliances
  
  

Identifying these signs early helps prevent a minor issue from becoming severe.