Squirrels are common in many environments, from city parks to forests. These agile rodents often capture attention with their quick movements and resourceful behaviors. Their teeth are uniquely adapted for their lifestyle, allowing them to thrive in diverse habitats.
The Distinctive Appearance of Squirrel Teeth
Squirrels have teeth designed for their dietary needs and continuous use. Their most noticeable teeth are the four prominent incisors at the front of their mouths—two on the upper jaw and two on the lower. These incisors are long, thin, and chisel-shaped, making them effective for cutting and stripping tough materials.
The front surface of these incisors is covered in a hard, often orange or yellow-tinted enamel. This coloration is due to iron compounds within the enamel, which provides increased hardness and wear resistance. The back of the incisors consists of softer dentin, which wears away more quickly than the iron-rich enamel, contributing to a continuously sharp, chisel-like edge.
Beyond these front teeth, squirrels also have molars at the back of their mouths. These molars are flatter and primarily used for grinding food after it has been processed by the incisors. Most squirrel species have 20 teeth, including four incisors and sixteen premolars and molars. Some species, like the Eastern gray squirrel, can have 22 teeth due to an extra premolar on each side. A gap, called a diastema, exists between their incisors and molars, as squirrels, like other rodents, do not possess canine teeth.
The Mechanism of Continuous Growth
A defining characteristic of squirrel incisors is their continuous growth throughout the animal’s life. These incisors are “open-rooted,” meaning they lack a closed root structure that would halt their growth. This constant growth compensates for the wear their teeth experience from daily gnawing. Without this continuous regeneration, their teeth would quickly wear down, making it impossible for them to eat. Squirrel incisors can grow at an average rate of about 6 inches (15 cm) per year.
Constant gnawing on various materials keeps squirrel teeth at a manageable length. If their teeth do not wear down properly, perhaps due to misalignment (malocclusion) or insufficient gnawing, they can become excessively long. Overgrown incisors can curl and even grow into the squirrel’s jaw or skull, causing severe pain and preventing them from eating. This can lead to starvation if not addressed.
Functional Adaptations for Gnawing
The dental structure of squirrels, particularly their continuously growing, self-sharpening incisors, is suited for their primary activity: gnawing. This behavior allows them to access food sources, which often include hard-shelled nuts, seeds, and bark. The chisel-like shape of their incisors allows them to strip, cut, and break open tough materials. Squirrels also have powerful jaw muscles, such as the masseter, which enable them to exert force when gnawing. These muscles contribute to the bite force required for processing hard foods.
Gnawing is not only about breaking open food but also about maintaining dental health. As squirrels gnaw, the upper and lower incisors rub against each other, ensuring even wear and maintaining the sharpness of the cutting edges. After the incisors have opened a food item, the molars at the back of the mouth take over, grinding the contents into a digestible pulp. This coordinated action of specialized teeth and strong jaw muscles links their dental anatomy to their diet and survival.