Ground squirrels are a diverse group of rodents that spend most of their lives on or beneath the earth’s surface. Unlike tree squirrels, which primarily seek refuge by climbing, ground squirrels are adapted for a terrestrial and fossorial lifestyle. They are found across a wide variety of ecosystems throughout the United States, from arid deserts to high-altitude tundra. They utilize complex underground burrow systems for shelter, food storage, and reproduction.
Defining the Ground Squirrel Groups
The term “ground squirrel” is an umbrella for a large taxonomic group of burrowing rodents within the squirrel family, Sciuridae. This grouping includes prairie dogs (Cynomys), marmots (Marmota), and chipmunks (Tamias), alongside the medium-sized species most commonly referred to as ground squirrels. Historically, many medium-sized species were placed in the genus Spermophilus, but modern genetics has split them into genera like Otospermophilus, Ictidomys, and Urocitellus.
These animals are diurnal, meaning they are active during the day, which contrasts with some other squirrel types. They are characterized by stocky bodies, short legs, and less bushy tails compared to their arboreal relatives, features that make them efficient at burrowing. Their social structure often involves living in colonies, relying on alarm calls to warn neighboring individuals of approaching predators.
Geographic Distribution Across US Regions
The distribution of ground squirrels is extensive, with different species adapting to specific environmental conditions across US regions. The Western US, characterized by mountains, deserts, and the Pacific coastline, is a major center of diversity. The California Ground Squirrel (Otospermophilus beecheyi) thrives in California, western Oregon, and parts of Nevada, favoring open grasslands, coastal scrub, and agricultural areas. The drier southwestern deserts are home to Antelope Ground Squirrels (Ammospermophilus), which are adapted to arid environments, and various rock squirrels inhabiting rocky outcrops throughout the Southwest.
Moving eastward into the Great Plains and Midwest, the landscape is dominated by prairie-dwelling species. The Thirteen-lined Ground Squirrel (Ictidomys tridecemlineatus) is widespread across the central US, inhabiting grasslands, prairies, and open agricultural fields from Ohio to the Texas coast. This species prefers areas with short grass, which provides clear lines of sight to watch for threats. Further north, Richardson’s Ground Squirrel (Urocitellus richardsonii) is found in the northern plains of Montana, North Dakota, and Minnesota, utilizing fields and rolling hills.
In the northern reaches and high-altitude areas, ground squirrels inhabit some of the most extreme environments. The Arctic Ground Squirrel (Urocitellus parryii) represents the northernmost distribution, living across northern, eastern, and southwestern Alaska. This species is adapted to the cold, existing in alpine and arctic tundra habitats, often above the tree line. Their presence across these varied biomes demonstrates the group’s adaptability to nearly every non-forested habitat type in the country.
Essential Habitat Features and Burrow Function
Regardless of geographic location, ground squirrel habitats share common features that support their underground lifestyle. They require well-drained soil, typically sandy or loamy, that is easy to excavate and resists flooding. Open sightlines are also necessary, allowing them to stand upright on their hind legs to scan the area for predators before retreating.
The burrow itself is a complex, engineered subterranean network paramount to the ground squirrel’s survival. These systems feature multiple entrances, often 3 to 5 inches in diameter, that serve as immediate escape routes from threats. The tunnels can extend from 5 to 30 feet in length and two to four feet deep, providing security from most surface predators.
Deep within the burrow are specialized chambers for nesting and separate areas for caching or storing food. The burrow is also the site of two forms of prolonged dormancy: hibernation during cold winter months, and aestivation, a state of inactivity some species enter to survive intense heat or drought. This reliance highlights how ground squirrels utilize the burrow for protection, reproduction, and long-term survival.