Squirrel chew marks are small, narrow grooves roughly 1/16 of an inch wide, left in parallel pairs by their front teeth. You’ll find them on wood trim, tree bark, plastic vents, roof flashing, and electrical wires. If you’ve spotted mysterious gnaw marks around your home or yard, squirrels are one of the most common culprits, and the damage they cause ranges from cosmetic to genuinely dangerous.
What Squirrel Chew Marks Look Like
Squirrel incisors leave fine, scratch-like grooves that run parallel to each other. Each groove is only about 1/16 of an inch wide, which makes them noticeably smaller than the marks left by rats (about 1/8 inch) or raccoons. On wood surfaces, the marks often appear as shallow, repeated scrapes where the animal has worked at the same spot over time. On softer materials like plastic vent covers or foam insulation, you’ll see rougher, more torn-up edges.
When squirrels strip bark from trees, they pull off small pieces, typically the size of a nickel or quarter. You’ll often find these bark chips scattered on the ground beneath a targeted branch. This is a useful clue for telling squirrel damage apart from porcupine damage, which produces much larger bark strips and wider tooth marks.
On your home’s exterior, look for chew marks around soffits, roof vents, fascia boards, and the edges of any existing gap or opening. Squirrels tend to enlarge small holes rather than create them from scratch, so the gnawing is often concentrated around a specific weak point.
Why Squirrels Chew on Everything
Squirrel teeth never stop growing. Like all rodents, they have to gnaw constantly to wear their incisors down and keep them at a functional length. If they don’t, the teeth grow in a curving pattern until the upper and lower incisors no longer meet. This condition, called malocclusion, eventually prevents the animal from eating and is fatal.
This biological need means squirrels aren’t picky about what they chew. Wood, plastic, aluminum flashing, lead pipe boots on your roof, even copper gutters are all fair game. There’s a persistent belief that squirrels chew lead because it tastes sweet, but researchers at Loyola University note that nobody really knows why they target metals specifically. The warmth or smell of electrical wires may also draw them in once they’ve accessed an attic or wall cavity.
Damage to Trees and Branches
Squirrels damage trees in two ways: stripping bark and clipping twig tips. The twig clipping is mostly harmless and actually mimics the kind of tip-pruning that increases canopy density. Bark stripping is the real concern. Gray squirrels target a wide range of deciduous trees, with American beech, honeylocust, and maples among the most common victims. Bark stripping season typically runs from April through early July.
The biggest risk is girdling, which happens when a squirrel strips bark in a complete ring around a branch or trunk. This cuts off the flow of water and nutrients, killing everything above the stripped section. Squirrels have a frustrating habit of focusing their bark stripping on a single tree while completely ignoring identical trees nearby, so the damage can be severe and concentrated. If you see long slivers of bark removed from branches high in the canopy, too high for deer to reach, squirrels are almost certainly responsible.
Electrical Wire Damage and Fire Risk
Of all the things squirrels chew, electrical wiring is the most dangerous. They gnaw through the protective insulation to get at the firm material underneath, leaving bare copper exposed inside your walls or attic. This creates a real risk of electrical fires, short circuits, and power loss. The damage is especially common in quiet, tucked-away spaces like attics and crawl spaces where squirrels feel safe enough to nest.
Signs of wire damage include flickering lights, circuits that trip for no obvious reason, or a faint burning smell in your attic. If you find squirrel droppings or nesting material near your electrical panel or along wire runs, inspect the wiring closely. Chewed wires often show the same narrow, parallel tooth marks you’d see on wood, but on a smaller scale, with the plastic coating shredded or peeled back in strips.
Roof, Siding, and Vent Damage
Squirrels commonly chew around roof vents, soffits, and the rubber or lead pipe boots that seal plumbing vents on your roof. These spots give them access to attic spaces where they can nest. Plastic roof vents are particularly vulnerable because squirrels can chew through them quickly. Aluminum flashing and lead pipe boots also show gnaw marks, sometimes with visible tooth grooves scored into the metal surface.
On wood siding and trim, chew marks often cluster around corners and edges where a squirrel can get a good grip. You might also notice small holes chewed into eaves or along the roofline. These entry points tend to be roughly 1.5 to 2 inches across, just large enough for the animal to squeeze through.
How to Stop Squirrel Chewing
Physical barriers are the most reliable long-term solution. Start by walking the exterior of your home and identifying every gap near vents, soffits, and the roofline. These areas need to be sealed with metal flashing or hardware cloth, materials squirrels can’t easily chew through. Chimney caps are essential if your chimney is uncapped, since open chimneys are a common entry point.
For electrical wires, PVC piping slipped over exposed runs creates a protective layer that squirrels can’t grip well enough to gnaw through. This is especially worth doing for any wiring that runs along your roofline or through your attic.
Natural repellents like hot pepper sprays, peppermint oil, garlic, and vinegar can make surfaces temporarily less appealing. These work in the short term but lose effectiveness as squirrels get used to the smell, so they’re best used as a supplement to physical barriers rather than a standalone fix. Predator urine products follow the same pattern: initially effective, quickly diminished.
For trees, metal trunk wraps or sheet metal bands placed around the trunk at least six feet off the ground can prevent squirrels from climbing. This only works if the tree isn’t close enough to other trees, fences, or structures for the squirrel to jump across, since they can leap eight feet or more horizontally. Pruning branches that overhang your roof also reduces their access to your home.
Squirrel Marks vs. Other Animals
If you’re not sure a squirrel is responsible, tooth mark width is your best identifier. Squirrel grooves are about 1/16 inch wide. Rat teeth leave marks roughly twice that width, and the gnawing pattern tends to be more chaotic and concentrated in lower areas. Porcupine damage produces broad, scooped-out patches on tree trunks with individual tooth marks around 1/8 to 3/16 inch wide, and the stripped bark pieces on the ground are much larger than the nickel-to-quarter-sized chips squirrels leave behind.
Location also helps. Squirrel damage on trees is often high in the canopy, on branches that only an agile climber could reach. On homes, squirrel chewing is concentrated at the roofline and upper stories. Rats tend to work closer to ground level and along foundation lines. If the chew marks are on your roof, soffit, or high on a tree trunk, squirrels are the most likely suspect.