Squirrels in Ontario

Overview

Squirrels are the busiest and most persistent attic invaders in Ontario. The eastern grey squirrel — which includes the familiar black colour phase common across the GTA — plus the smaller, more vocal red squirrel, spend their days looking for exactly what your attic offers: a warm, dry, elevated nest site safe from predators. Lighter and more agile than raccoons, squirrels travel the tree canopy and utility lines straight onto rooflines, then exploit or gnaw open any weak point. The tell-tale sign is quick, light scurrying overhead during the day, often loudest at dawn. Left alone, a pair becomes a nesting family, and constant gnawing on wiring turns a noise problem into a fire risk.

Identification

Most homeowners identify squirrels by sound and damage rather than sight. When you do see one, the two Ontario species are easy to tell apart, and both are easy to distinguish from a raccoon by size.

Against a raccoon, the distinction is straightforward: squirrels are a fraction of the weight, active in daylight, and produce fast scurrying rather than heavy thumps. Their entry holes are small and cleanly gnawed — around 40 mm — where a raccoon leaves torn, forced damage.

Life Cycle

Grey squirrels typically produce two litters a year, one in late winter or spring and another in mid-to-late summer, with usually three to four young per litter after roughly six weeks’ gestation. The young are blind and helpless at birth and remain dependent on the mother in the nest for several weeks before they’re weaned and begin to venture out. This twice-yearly breeding cycle means an attic can shelter dependent babies through much of the warm season — the key reason removal has to check for young before an adult is pulled.

Habitat & Behaviour

Squirrels are diurnal and territorial, building leafy nests (dreys) in tree forks and, when they can get in, in attics, soffit cavities, and wall voids. They are relentless chewers: their incisors grow continuously, so they gnaw on wood, plastic, and wiring both to access spaces and to keep their teeth worn down. Red squirrels are especially bold and vocal, often the noisier attic tenant. Squirrels are excellent jumpers and climbers, using branches, fences, and hydro lines as highways to the roof, which is why trimming back overhanging limbs is such an effective deterrent.

Diet

Squirrels are primarily nut-and-seed eaters — acorns, other tree nuts, and seeds — supplementing with buds, fruit, fungi, and the occasional insect or egg. Around homes, bird feeders and fallen birdseed are a powerful draw, effectively advertising the property to every squirrel in range. Reducing accessible feed is a simple way to lower the pressure on your roofline.

Signs of Infestation

• Quick, light scurrying and scratching overhead during the day, loudest around dawn — the hallmark squirrel sound.
• Small, cleanly gnawed entry holes (around 40 mm) at soffits, vents, or fascia, often with chew marks around the edge.
• Chewed wiring, wood, or vent screening — the fire-risk sign, sometimes found during electrical or roofing work.
• Shredded insulation pushed into nesting piles.
• Droppings — small, scattered pellets, distinct from a raccoon’s larger latrine.
• Gnaw marks on soffits, fascia, and roof trim from repeated access.

Damage Caused

The headline risk is fire. Squirrels gnaw on electrical wiring inside walls and attics, stripping insulation from cables in a way that is a recognised house-fire hazard. Beyond that, they shred attic insulation to build nests, reducing its R-value and driving up heating and cooling costs, and their gnawing enlarges entry points and damages soffits, fascia, and vent screening. Because squirrels reuse and expand access holes, damage compounds over successive seasons if the roofline isn’t sealed.

Health Risks

Squirrels carry a lower disease risk than raccoons or bats — they are not a leading rabies concern in Ontario — but they are not risk-free. Their droppings and urine contaminate insulation and can harbour bacteria, and nesting debris and parasites (fleas, mites) can accompany an infestation. The most serious hazard remains indirect: chewed wiring and the fire risk it creates. As with all wildlife, droppings should be cleaned up with protection, not bare-handed.

Seasonal Activity in Ontario

Squirrels are active year-round in Ontario — they don’t hibernate — but their impact on homes concentrates around breeding and cold weather. Spring brings the first litters and a push to secure nest sites. Late summer brings a second litter, echoing the raccoon pattern of peak denning pressure. Fall is the highest-risk stretch for new attic entries, as squirrels seek warm, sheltered winter quarters and stockpile food. In cottage country — Muskoka and the Lake Simcoe area — red squirrels are common, and seasonally-closed cabins that sit undisturbed are especially vulnerable to a quiet takeover.

Where They Hide

Attics are the prize, along with soffit cavities, wall voids, and the spaces behind knee walls. Outdoors, squirrels nest in tree cavities and leafy dreys, and they’ll shelter in sheds, garages, and outbuildings. Within an attic they favour insulation-filled corners and areas near a warm chimney or vent.

How They Enter Homes

Squirrels reach the roof via overhanging branches, fences, and utility lines, then enter through gaps as small as 40 mm: soffit-to-roof gaps, loose or unscreened roof and gable vents, rotted fascia, and construction gaps at the roofline. Where no gap exists, they’ll gnaw a marginal opening to size. Chewed vent screening and gnawed fascia corners are classic squirrel entry work.

Prevention Tips

1. Trim branches back at least a couple of metres from the roof to cut off the launchpad.
2. Seal and reinforce soffit, roof, and gable vents with heavy-gauge metal screening squirrels can’t gnaw through.
3. Repair rotted fascia, soffit gaps, and lifted shingles promptly.
4. Cap the chimney and screen any roofline openings.
5. Move bird feeders away from the house and clean up fallen seed.
6. Inspect the roofline each spring and fall — the two highest-risk seasons — for fresh gnawing.
7. Never seal a hole until you’re sure no squirrel or litter is inside.

DIY vs. Professional Treatment

You can trim branches and screen vents yourself as prevention, but removing an established squirrel — especially during baby season — is a job that DIY reliably gets wrong. Trapping an adult while young are in the nest orphans them behind the drywall, and Ontario’s one-kilometre release rule means you can’t legally relocate the animal far anyway. Professional removal confirms the species, checks for and removes any young, then seals every 40 mm gap along the roofline so the problem doesn’t simply repeat. Sani IQ backs its wildlife exclusion work with the Pest-Free-Or-It’s-Free guarantee. Our guides on why squirrels and raccoons move into Ontario attics and attic wildlife in Newmarket cover the seasonal playbook.

References

• Ontario — Harass, capture or kill a wild animal damaging private property
• City of Toronto — Squirrels
• University of Minnesota Extension — Squirrels

Last updated: July 16, 2026 · Reviewed by Sani IQ licensed technicians