Yes, a squirrel is a rodent, placing these familiar bushy-tailed animals within the diverse order Rodentia. This classification is based on specific biological characteristics that squirrels share with other members of this large group of mammals.
What Makes an Animal a Rodent
Animals belonging to the order Rodentia are primarily identified by a unique dental structure. All rodents possess a single pair of continuously growing, chisel-like incisors in both their upper and lower jaws. These front teeth have a hard enamel layer on the front and softer dentine on the back, which allows them to self-sharpen as they gnaw. This continuous growth necessitates constant gnawing to prevent the teeth from becoming too long.
Rodents lack canine teeth, featuring a noticeable gap called a diastema between their incisors and their cheek teeth. Their jaw musculature is also highly specialized, with powerful masseter muscles that enable the forward and backward movement of the lower jaw, crucial for effective gnawing and chewing. These adaptations allow rodents to process a wide range of plant materials.
Squirrels Share Rodent Traits
Squirrels, including tree squirrels, ground squirrels, and flying squirrels, are members of the family Sciuridae. Squirrels exhibit continuously growing incisors. This necessitates gnawing on hard materials such as nuts, seeds, and tree bark.
Gnawing is essential for their dental health, wearing down their teeth. Squirrels also possess the characteristic rodent jaw structure, including the absence of canine teeth and the presence of a diastema. Their specialized jaw muscles, particularly the large deep masseter, make them efficient at biting with their incisors.
More Rodents and Common Mix-Ups
The order Rodentia is the largest group of mammals, encompassing about 40% of all mammal species worldwide. Beyond squirrels, this diverse order includes well-known animals such as mice, rats, beavers, hamsters, porcupines, guinea pigs, chipmunks, marmots, voles, and prairie dogs. These animals share the fundamental characteristics of rodents, particularly their specialized teeth and jaw structure.
However, some animals are frequently mistaken for rodents but belong to different scientific orders. Rabbits, hares, and pikas, for instance, are often confused with rodents but are classified under the order Lagomorpha. The primary distinction is that lagomorphs have two pairs of upper incisors, one behind the other, while rodents have only one pair.
Similarly, shrews and moles are not rodents; shrews are insectivores, and moles are also primarily insectivorous, both lacking the characteristic rodent incisors. Opossums and hedgehogs are also sometimes mistakenly identified as rodents but are not.