Squirrels are common rodents belonging to the family Sciuridae, a diverse group. This article explores their evolutionary roots and the variety of native species in North America.
North America’s Indigenous Squirrels
Squirrels are indigenous to North America, with fossil evidence dating back approximately 36 million years to the Eocene epoch. Their presence predates human settlement by millions of years.
The squirrel family in North America classifies into three main types: tree squirrels, ground squirrels, and flying squirrels. This classification reflects their primary habitats and behaviors. Over vast stretches of geological time, these ancestral squirrels diversified and adapted, populating various ecosystems across the continent. Their long-standing presence highlights their role in North American natural history and ecosystems.
Diversity Across the Continent
North America hosts a remarkable diversity of native squirrel species, each adapted to specific geographic ranges and habitats. Among the tree squirrels, the Eastern Gray Squirrel (Sciurus carolinensis) is widely distributed across the eastern and midwestern United States, extending north into southern Canada and south to East Texas and Florida. The Fox Squirrel (Sciurus niger), noted as the largest tree squirrel in North America, inhabits much of the eastern and central United States, reaching into southern Canadian provinces and northern Mexico. The American Red Squirrel (Tamiasciurus hudsonicus) occupies a more northern range, prevalent across most of Canada, southern Alaska, the Rocky Mountains, and the northern half of the eastern United States, favoring coniferous forests.
Ground squirrels contribute significantly to the continent’s squirrel diversity, including various species of chipmunks, prairie dogs, and groundhogs. Chipmunks, such as the Eastern Chipmunk (Tamias striatus), are found throughout southeastern Canada and much of the eastern United States, extending west to areas like North Dakota and Oklahoma. Prairie dogs (Cynomys genus), which are herbivorous burrowing ground squirrels, inhabit the grasslands of central North America, from Mexico northward into Canada. The Black-tailed Prairie Dog (Cynomys ludovicianus), for example, historically ranged from southern Saskatchewan to Chihuahua, Mexico. Groundhogs (Marmota monax), also known as woodchucks and considered the largest members of the squirrel family, are found from eastern and central United States across Canada and into Alaska.
North America is also home to two species of flying squirrels, which are nocturnal and distinguished by a membrane between their limbs enabling gliding. The Northern Flying Squirrel (Glaucomys sabrinus) is distributed across coniferous and mixed forests throughout much of Canada, from Alaska to Nova Scotia, and extends south into mountainous regions of North Carolina and west to Utah. The Southern Flying Squirrel (Glaucomys volans) has a broader eastern range, spanning from southeastern Canada throughout the eastern United States, reaching from Maine to Florida and west to Minnesota and Texas, with some populations in the highlands of Mexico and Central America. This extensive array of species demonstrates the deep integration and adaptive success of squirrels within North American ecosystems.