Squirrels chew wires because their teeth never stop growing. Their incisors grow roughly 6 inches per year, and constant gnawing is the only way to keep them filed down to a functional length. Wires happen to be the perfect size, texture, and accessibility for this purpose, and modern insulation materials can make them even more appealing.
Teeth That Never Stop Growing
Like all rodents, squirrels have incisors that grow continuously throughout their lives in a curved trajectory. The front surface of each tooth is coated in hard, orange-tinted enamel that maintains a sharp cutting edge as the softer back side wears away. When a squirrel gnaws on a hard object, the upper and lower teeth grind against each other and stay trimmed to the right length.
This isn’t optional behavior. A squirrel that can’t wear its teeth down will see them grow until they curve into the skull or jaw, or until the animal can no longer eat. Chewing on firm materials like wood, bark, nuts, bones, and yes, wires, is a survival mechanism. Electrical cables, phone lines, and automotive wiring all provide the right amount of resistance to serve as natural tooth files.
Modern Wire Insulation Smells Like Food
Biology explains the need to chew, but it doesn’t fully explain why squirrels target wires so specifically. Part of the answer is a materials change the automotive and electronics industries made over the past couple of decades. Many manufacturers shifted from petroleum-based wire insulation to soy-based alternatives, motivated by lower costs and environmental goals. The unintended consequence: rodents, including squirrels, perceive soy-based coatings as a food source.
This attraction intensifies in colder months, when squirrels are actively seeking both warmth and calories. A car engine bay that’s recently been driven is warm, sheltered, and full of wires coated in something that smells edible. It’s an ideal combination for a squirrel looking to gnaw and forage at the same time.
Nesting and Exploration Play a Role Too
Squirrels also chew wires as part of their nesting behavior. When they move into attics, crawl spaces, sheds, or engine compartments, they strip and shred materials to build nests. Wire insulation is soft, pliable, and easy to pull apart, making it useful bedding material. The wire itself is simply what’s left behind after the coating has been removed.
There’s also an exploratory element. Squirrels investigate their environment largely through their mouths, testing objects by biting into them. A wire running along a roofline, through an attic, or under a car hood is something a curious squirrel will naturally sample. Once they discover it’s satisfying to chew, they keep going.
The Damage Is More Serious Than You’d Think
Squirrels are among the top causes of power outages in the United States. In 2016 alone, utilities reported 3,456 squirrel-caused outages that cut power to more than 193,000 customers, according to the American Public Power Association. These aren’t momentary flickers. They’re sustained outages lasting five minutes or longer, and they happen year-round with peaks in warmer months when squirrels are most active.
Vehicle damage is equally costly. Chewed wiring can short-circuit critical systems including anti-lock brakes, airbag sensors, traction control, and engine management. The symptoms often aren’t obvious until something fails: a check engine light, flickering headlights, or a car that won’t start. By that point, the damage is already extensive.
Repair costs vary widely depending on severity. A few chewed wires that can be spliced typically run $150 to $500. Moderate damage requiring partial wiring harness replacement lands between $500 and $2,500. Severe cases involving full harness replacement or damaged control modules can reach $7,000 or more. In homes, chewed wiring inside walls creates a fire hazard that may go undetected for months.
How to Protect Your Wires
Physical barriers are the most reliable defense. For vehicles, wrapping exposed wiring in metal foil or thin sheet metal makes the surface unpleasant and impossible for squirrels to grip with their teeth. Some automakers, including Honda, now sell rodent-deterrent electrical tape treated with capsaicin (the compound that makes hot peppers burn). Wrapping vulnerable wiring with this tape adds a chemical deterrent on top of the physical one.
For cars parked outdoors, keeping the hood open at night removes the warm, enclosed feeling that attracts squirrels in the first place. Bright LED lights or ultrasonic repellent devices placed near the engine bay can also discourage nesting. If you’re parking in a garage, sealing entry points so squirrels can’t get inside is more effective than any repellent.
For homes, the priority is keeping squirrels out of attics and crawl spaces entirely. Trim tree branches that hang within 8 to 10 feet of the roofline, seal gaps around eaves and soffits, and cover any exposed wiring runs with metal conduit. Plastic conduit won’t help. Squirrels chew through it just as easily as they chew through insulation. Any protective barrier needs to be metal to be truly squirrel-proof.