2. A Squirrel’s Teeth Never Stop Growing

Like all rodents, gray squirrels have four prominent front teeth—two upper and two lower incisors—that grow continuously throughout their lives. These teeth can grow up to six inches (about 15 cm) in a single year. This constant growth is an essential adaptation for a life spent gnawing on hard materials like nutshells, tree bark, and wood.

The front surface of their incisors is coated with hard, orange-tinted enamel, while the back is made of softer dentin. As the squirrel gnaws, the softer dentin wears away more quickly than the hard enamel, creating a sharp, chisel-like edge that is self-sharpening. This allows them to crack open the toughest nuts, such as black walnuts and hickories, with incredible efficiency.

This perpetual growth, however, comes with a significant risk. A squirrel must gnaw to survive. If its incisors are not worn down through regular use, they will continue to grow, potentially curving back into the skull or jaw. This condition, known as malocclusion, can prevent the animal from eating, leading to starvation. This is why you will often see squirrels gnawing on objects that are not food, such as tree branches, deck railings, or even discarded bones. They are not just being destructive; they are performing essential dental maintenance.

Observing gnaw marks can be a key part of backyard wildlife tracking. Squirrel gnaw marks on nuts are typically rough and shattered, as they use brute force to crack the shell open. In contrast, a mouse or vole will leave fine, parallel grooves on a nut shell. This simple observation can tell you which small mammals are visiting your yard.