Squirrels are a common sight, often observed digging. While all squirrels engage in some form of digging, the nature and purpose of these excavations vary significantly by species. This article explores the scientific distinctions in squirrel digging habits, clarifying which types of squirrels create extensive burrows.
The Truth About Squirrel Digging
Tree squirrels, such as grey, red, and fox squirrels, are recognized for their digging activities. They primarily dig shallow holes for “scatter hoarding,” burying nuts, seeds, and acorns in numerous locations to secure food for colder months. These holes are typically small, about an inch deep and the size of a coin or golf ball, with minimal displaced soil. This strategy ensures a distributed food supply, reducing the risk of a complete loss if one cache is discovered.
Tree squirrels rely on spatial memory and scent to relocate buried provisions, though not all items are recovered. Unretrieved nuts contribute to forest regeneration by sprouting into new trees. While tree squirrels may occasionally dig shallow depressions for temporary shelter or to cool off, these are not extensive tunnels. Unlike ground squirrels, tree squirrels typically utilize tree cavities or build nests, known as dreys, in branches for permanent homes and raising young, rather than living underground.
Ground Squirrels and Their Subterranean Homes
Ground squirrels, in contrast to their arboreal relatives, construct complex, multi-chambered burrow systems. Species like California ground squirrels, thirteen-lined ground squirrels, marmots, and prairie dogs are true subterranean architects. These networks serve as permanent residences, offering protection from predators, harsh weather, and space for raising young. Burrows also function as food storage sites, particularly for species that “larder hoard” large quantities of food in a single underground pantry.
Burrow systems can be substantial, with tunnels often extending 5 to 30 feet, and some recorded up to 138 feet. Depths typically range from 2 to 3 feet, reaching over 6 feet, with some systems extending to 8.5 meters. Burrows frequently feature multiple entrances (6 to 20), providing various escape routes. Ground squirrels are social, often living in colonies within these shared structures, and their burrowing activities contribute to soil aeration and plant diversity.
Identifying Squirrel Digging
Distinguishing between squirrel digging activities helps identify the cause of disturbed soil. Tree squirrel holes are shallow excavations, usually with little to no excavated soil piled around the opening, and are frequently found scattered across lawns or gardens, especially near trees. The conical or bowl shape of these holes is characteristic of a tree squirrel caching food.
Ground squirrel burrows, however, present a more substantial and defined appearance, with entrances typically larger, often around 4 inches in diameter, and usually open and unobstructed. While some burrows may have a noticeable mound of excavated dirt around the entrance, other species disperse the soil widely, leaving a clean opening. Frequent use often results in worn-down vegetation, and observing multiple larger holes in a concentrated area can indicate a ground squirrel colony. A key behavioral difference is that when startled, tree squirrels tend to climb trees, whereas ground squirrels will quickly retreat into their underground burrows.