Are rats and squirrels related? A scientific examination reveals they are connected within the broader classification of mammals. They belong to the same biological order, highlighting a shared evolutionary history despite their distinct characteristics and ecological roles.
The Rodent Family Tree
Both rats and squirrels are members of the order Rodentia, the largest order of mammals, encompassing over 40% of all mammal species globally. A defining characteristic of all rodents is their unique dentition: a single pair of continuously growing, chisel-like incisors in both their upper and lower jaws. These incisors have hard enamel on the front and softer dentine behind, which wears away faster, maintaining a sharp edge necessary for gnawing.
Despite this shared feature, rats and squirrels diverge at the family level. Squirrels belong to the family Sciuridae, which includes tree squirrels, ground squirrels, chipmunks, and marmots. This family has approximately 279 species across 51 genera, found across the Americas, Eurasia, and Africa. Rats, along with mice and gerbils, are classified under the family Muridae. Muridae is the largest family of mammals, containing over 1,383 species, and these “true” rats and mice originated in Asia, though many species have been introduced worldwide.
Shared Characteristics
As members of Rodentia, rats and squirrels exhibit several common biological traits. Their continuously growing incisors necessitate constant gnawing to wear them down, a behavior observed in both species. If these teeth were not regularly worn, they would overgrow and prevent the animals from eating, leading to starvation. This gnawing also allows them to access food and modify their environment, such as chewing through materials to create nests or find sustenance.
Both animals have robust bodies, relatively short limbs, and tails. Many rodent species, including rats and some squirrels, are omnivorous, consuming a varied diet that can include seeds, fruits, and insects. They also share reproductive strategies, characterized by high reproductive rates with multiple litters per year. This ability to reproduce frequently contributes to their ecological success and widespread distribution.
Key Distinctions
While sharing a common order, rats and squirrels have distinct physical and behavioral adaptations that allow them to occupy different ecological niches. A difference is their tail characteristics; squirrels possess a long, bushy tail, which aids in balance for arboreal living and can be used for communication. In contrast, rats have thinner, scaly, and sparsely haired tails.
Their physical builds also vary; squirrels have muscular legs and sharp claws suited for climbing, particularly tree squirrels, while ground squirrels may have sturdier forelimbs for digging. Rats, conversely, have more slender bodies adapted for navigating tight spaces and live terrestrially or subterraneously in burrows. Their activity patterns differ: rats are nocturnal, whereas squirrels are diurnal. These distinctions in form and behavior reflect their separate evolutionary paths within the diverse rodent order.