Many people associate squirrels with backyard wildlife rather than with animals like mice or rats, often wondering about their classification. Their distinct appearance and behavior contribute to this common question. This article clarifies the scientific classification of squirrels and explains the biological reasons behind it.
Squirrels: Indeed Rodents
Squirrels are classified as rodents, belonging to the scientific order Rodentia. This order includes a vast array of mammals characterized by specific biological traits. Within Rodentia, squirrels are further categorized into the family Sciuridae, encompassing tree, ground, and flying squirrels. Despite their bushy tails and arboreal habits, squirrels share fundamental anatomical features that firmly place them within the rodent group, rather than just outward appearance or perceived behavior.
Defining Characteristics of Rodents
A defining characteristic of all rodents is their unique dentition: a single pair of continuously growing incisors in both their upper and lower jaws. These chisel-shaped teeth enable rodents to gnaw on various materials. The incisors have a hard enamel layer on the front and softer dentin on the back, allowing them to self-sharpen. Constant gnawing wears down these teeth, preventing them from growing too long and impeding feeding or causing health issues.
Rodents also exhibit a specialized jaw structure and musculature adapted for gnawing. Their jaw muscles facilitate forward and backward movements, allowing for efficient chewing and grinding. A distinct gap, known as a diastema, exists between their incisors and cheek teeth, as rodents lack canine teeth. In contrast, lagomorphs, such as rabbits, hares, and pikas, have two pairs of upper incisors, with a smaller set located directly behind the larger front pair, distinguishing them from true rodents.
Diverse Members of the Rodent Family
The order Rodentia is the largest group of mammals, representing approximately 40% of all mammalian species. Common examples include mice, rats, hamsters, guinea pigs, beavers, and porcupines. Rodents vary significantly in size, from the tiny pygmy jerboa (around 0.2 ounces) to the capybara (over 100 pounds), the world’s largest living rodent.
They inhabit nearly every continent, adapting to diverse environments like forests, deserts, and aquatic habitats. This broad distribution highlights their adaptability and evolutionary success. The term “rodent” refers to a broad biological classification based on shared anatomical traits, not solely a descriptor for small, pest-like animals.