While rats and squirrels may appear quite different, they are indeed related, sharing a common biological classification within the same broad group of mammals.
Shared Rodent Ancestry
Both rats and squirrels belong to the order Rodentia, the largest group of mammals. This classification means they share a common evolutionary ancestor. The name “Rodentia” comes from the Latin “rodere,” meaning “to gnaw,” a defining characteristic of this order.
The evolutionary history of rodents traces back to the Paleocene epoch, roughly 60 million years ago. Early rodent-like mammals were small, insectivorous creatures. Over time, this diverse group spread across various continents, adapting to different environments and evolving into the wide array of species seen today.
Common Traits and Behaviors
A defining characteristic shared by all rodents is their unique dentition. They possess a single pair of continuously growing incisors in both their upper and lower jaws. These incisors have hard enamel on the front and softer dentine on the back, allowing them to maintain a sharp, chisel-like edge as they wear down. This continuous growth necessitates constant gnawing on various materials to keep their teeth at a manageable length.
Beyond their specialized teeth, rodents exhibit a general body plan with robust bodies, short limbs, and tails. They demonstrate remarkable adaptability to diverse environments, from forests and grasslands to human-made settings. Their agility and ability to navigate different terrains are common behavioral traits.
Distinct Characteristics
Despite their shared ancestry, rats and squirrels exhibit distinct characteristics. Physically, squirrels possess a thick, bushy tail, while rats typically have a scaly, thin, and largely hairless tail. Squirrels are also generally larger than most rat species.
Their head and ear shapes differ: rats have more pointed heads and smaller, hairless ears, whereas squirrels have blunter heads and larger eyes. Fur color varies, with rat fur often brown, gray, black, or white, and squirrel fur commonly gray, brown, or red. Rats also have hairless hands and feet, unlike squirrels which have fur on these areas.
Behaviorally, their activity patterns are a distinguishing factor. Squirrels are diurnal, active primarily during the daytime. In contrast, rats are predominantly nocturnal, active at night. Their diets also differ: squirrels primarily forage for nuts, seeds, and flowers. Rats are omnivorous, consuming a wider variety of food, including grains, meat, and household garbage.
The specialized function of their tails highlights their differences. A rat’s tail is important for balance and plays a significant role in thermoregulation, helping to dissipate body heat. Squirrels use their bushy tails for balance while climbing and leaping, as a form of communication, for warmth, and as a “parachute” to help break falls.