Squirrels are native to North America, which serves as a major center of diversity for the entire rodent family Sciuridae. Their presence is a deep-rooted part of the continent’s natural history, thriving across a wide range of habitats. These include dense forests, arid grasslands, and urban environments.
North America as a Squirrel Origin Point
The evolutionary history of the squirrel family, Sciuridae, firmly places their origins on the North American continent. The earliest definitive fossil evidence for the family dates back to the Late Eocene Epoch, approximately 36 million years ago, with these remains being discovered in western North America. This predates the fossil records found on other continents, suggesting the initial diversification of the group occurred here.
Following their emergence, squirrels rapidly diverged into five major evolutionary branches during the Oligocene and Miocene periods. This diversification coincided with significant global climate shifts. While squirrels are now found globally, the foundational and oldest lineages of the family are traceable to this ancient North American epicenter.
The Three Families of Native Squirrels
North America’s vast squirrel diversity can be organized into three distinct groups based on their behavior and primary habitat. The most familiar group is the Tree Squirrels (tribe Sciurini). These are primarily arboreal, known for their long, bushy tails and diurnal habits. They rely on trees for shelter, nesting, and food resources, rarely descending to the ground.
The second major group is the Ground Squirrels (tribe Marmotini), a diverse collection that includes species like chipmunks, prairie dogs, and marmots. These squirrels are generally more robust than their tree-dwelling relatives and possess shorter, sturdier forelimbs adapted for extensive digging and burrowing. Ground squirrels are often colonial, live in complex underground networks, and many species enter periods of hibernation during colder months.
The third, less commonly seen group consists of the Flying Squirrels (tribe Pteromyini), which are the only nocturnal sciurids found on the continent. Their unique adaptation is a specialized membrane called the patagium, a fold of furred skin that stretches from the wrist to the ankle. This structure allows them to glide, not fly, in a controlled descent from a high point in one tree to a lower point on another.
Identifying the Most Widespread Native Species
The Eastern Gray Squirrel (Sciurus carolinensis) is arguably the most recognizable native squirrel in North America. Its indigenous range covers the entire eastern and midwestern United States, extending into southern Canada. This medium-sized species typically exhibits a grizzled mix of dark and pale gray fur with a white or buff-colored underside. They thrive in mature continuous woodlands but have adapted to urban and suburban environments that provide sufficient oak and hickory trees for food and shelter.
The Fox Squirrel (Sciurus niger) is the largest species of tree squirrel found in North America. Its distribution broadly overlaps the gray squirrel’s range, extending from the Atlantic coast west to the Great Plains and south to Florida. Fox squirrels display a highly variable coat color, often featuring a reddish-orange or rust-colored underside with upper parts that can range from gray to dark brown.
The American Red Squirrel (Tamiasciurus hudsonicus) is smaller than both the gray and fox squirrels. It is widely distributed across North America wherever coniferous forests are common. This species is characterized by its reddish-gray fur and strong territorial behavior. They actively defend their food caches, known as middens, of conifer cones and seeds year-round.