Squirrels are fully capable of chewing through wood, which is a common and serious concern for homeowners. This destructive behavior is not driven by hunger but is a necessary action tied directly to their survival. Understanding the biological reason behind their gnawing provides insight into why they target residential structures. The damage they inflict often compromises the integrity and safety of a building.
The Biological Imperative: Why Squirrels Must Gnaw
The primary reason squirrels chew on hard materials stems from the unique structure of their front teeth. As members of the rodent family, squirrels possess four long, chisel-shaped incisors—two on the upper jaw and two on the lower jaw—that grow continuously throughout their lives. These teeth are termed “elodonts,” meaning they are ever-growing.
If these incisors are not worn down, they quickly overgrow, causing malocclusion. This misalignment prevents the squirrel from properly closing its mouth, making feeding impossible and leading to starvation. Gnawing on various materials is the animal’s natural mechanism to maintain the correct length and sharpness of these incisors.
The growth rate is considerable, averaging about six inches per year. This rapid growth mandates a near-constant need to chew, making any suitable hard surface a target. The urge to gnaw also helps them prepare materials for nesting or access food sources.
Mechanics of Damage: How Squirrels Breach Materials
The effectiveness of a squirrel’s gnawing is due to the composition and action of its teeth. The front of the incisors is covered by specialized, hard enamel that is reinforced with iron. This iron-rich material forms an acid-resistant outer layer, providing the durability needed for constant cutting.
The back side of the incisor is made of softer dentin, which wears away faster than the iron-hardened front. This uneven wear naturally keeps the cutting edge of the tooth perpetually sharp and chisel-like. This allows them to compromise not only soft wood but also a range of other common household materials, including PVC piping, vinyl siding, and soft metals such as aluminum flashing.
Squirrels often exploit existing vulnerabilities to gain leverage, such as gaps, cracks, or softened wood. By working on a small imperfection, their continuous gnawing widens the hole until the material is breached or large enough for entry. The force and sharpness of their incisors mean that materials like wire insulation and plastic are easily penetrated.
Common Targets and Structural Impact
The most frequent targets for squirrel chewing are vulnerable areas around the roofline and exterior walls of a home. Fascia boards, soffits, eaves, and attic vents are common entry points where squirrels create access holes, often around two inches in diameter. These breaches allow water intrusion, which can lead to wood rot and compromise the structural integrity of the roof and framing over time.
Interior Damage and Hazards
Once inside the attic or wall voids, the destruction continues on interior components. Squirrels frequently gnaw on wooden support beams and joists, which weakens the home’s stability. A more immediate danger is the chewing of electrical wiring, which removes the protective plastic insulation. Exposed wires pose a significant fire hazard, especially when combined with the dry nesting materials squirrels bring into an attic.
Further damage includes:
- The destruction of insulation, which is shredded for nesting material, reducing a home’s energy efficiency.
- Damage to HVAC ductwork, particularly flexible ducts, leading to costly air loss and higher utility bills.
- The introduction of health hazards from droppings and urine, which contaminate the space and attract secondary pests.
Deterring Chewing Behavior
Deterrence focuses on making vulnerable areas physically inaccessible or chemically unpleasant. The most effective method is physical exclusion, which involves sealing all access points with materials squirrels cannot chew through. This typically means installing heavy-duty metal flashing or one-quarter inch hardware cloth over potential entry sites.
For areas where metal barriers are impractical, taste and scent deterrents can discourage gnawing. Squirrels are highly sensitive to strong, bitter, or spicy flavors, making capsaicin-based sprays effective. Products containing hot pepper extracts can be applied directly to wooden surfaces, creating a strong, unpleasant sensation upon contact.
Other deterrents include bitter apple spray or mixtures of strong-smelling substances like peppermint oil or vinegar. These require frequent reapplication, especially after rain, to maintain potency. Removing accessible food sources, such as fallen nuts and bird feeders, also helps make the area less appealing for squirrels to linger and chew.