The question of whether squirrels tunnel underground does not have a simple yes or no answer because the term “squirrel” covers two major and distinct groups of rodents with radically different lifestyles. While all squirrels belong to the family Sciuridae, their habits regarding the earth depend entirely on their evolutionary adaptations. Understanding this division is the first step in determining whether the small mammal digging in your yard is creating a temporary cache or a permanent subterranean home.
The Key Distinction: Tree vs. Ground Squirrels
The two major categories of squirrels, tree squirrels (genus Sciurus and others) and ground squirrels (members of the tribe Marmotini), have evolved to occupy separate ecological niches that dictate their interaction with the soil. Tree squirrels, such as the Eastern Gray Squirrel or Fox Squirrel, are built for arboreal life, possessing long, bushy tails for balance and sharp claws for climbing. Ground squirrels, including species like the California Ground Squirrel, are built for a terrestrial existence, typically having stockier bodies and shorter, less bushy tails. When startled, a tree squirrel will instinctively run up a tree, while a ground squirrel will dart into a hole in the ground. This difference in survival strategy drives their respective digging habits.
Ground Squirrels and Complex Burrow Systems
Ground squirrels are the true tunnelers of the squirrel family, excavating intricate networks that serve as their permanent residences. These burrows are complex, multi-chambered systems used for protection from predators, raising young, and escaping inclement weather. For species that hibernate, the burrow includes a specialized, sealed-off chamber called a hibernaculum where they can remain underground for four to eight months.
The structure of these subterranean dwellings can be extensive. California Ground Squirrel burrows average around 3 to 10 meters (10 to 33 feet) in length, though some systems can extend up to 42 meters (138 feet). Depths range from 0.2 to 1.7 meters (0.7 to 5.6 feet). These systems often feature multiple entrances, sometimes between 6 and 20 openings, which provide quick escape routes. The interconnected tunnels and chambers are utilized for sleeping, food storage, and even as a subterranean latrine.
Tree Squirrels: Cache and Retreat
Tree squirrels, the more common backyard species, engage in digging, but their activity is limited to shallow, temporary actions for food storage, not for creating homes. The common behavior of burying nuts and seeds is known as scatter hoarding, where the animal digs a small hole, places a food item inside, and covers it up. These digs are only deep enough to conceal the cached item, contrasting sharply with the deep, permanent tunnels of ground squirrels.
This process is a survival mechanism for the winter, relying on a combination of spatial memory and scent to retrieve the food later. While a tree squirrel may dig dozens of small divots in a yard during the fall, they are not building a dwelling or preparing a network for hibernation. Their homes, called dreys, are bulky nests made of leaves and twigs constructed high in tree branches, or they utilize natural tree cavities.
Identifying Burrow Types Near Your Home
Distinguishing between the two types of squirrel activity comes down to observing the physical evidence and the animal’s behavior. A ground squirrel burrow entrance is a distinct, visible hole, typically round and open, measuring about 5 to 10 centimeters (2 to 4 inches) in diameter. It is often accompanied by a crescent-shaped mound of freshly excavated soil, known as a spoil fan, near the opening.
In contrast, tree squirrel digging is characterized by numerous small, randomly scattered disturbances across the lawn or garden, appearing as shallow scrapes with no significant spoil mound. These small holes result from burying or recovering food items. If the animal you see digging scurries up a fence or tree, it is likely a tree squirrel scatter hoarding; if it disappears quickly into the hole, you have a resident ground squirrel.