The habitat of a squirrel depends entirely on its species. Common species like the Eastern Gray or American Red squirrel are primarily arboreal and do not reside underground. However, the diverse family Sciuridae includes many species classified as ground squirrels, such as chipmunks and prairie dogs, which permanently live in subterranean tunnel systems. While familiar tree squirrels make their homes high above the ground, many of their relatives are exclusively burrowing creatures.
The Primary Habitats of Tree Squirrels
Tree squirrels, including the Eastern Gray and Red squirrels, establish their permanent residences high above the forest floor, utilizing one of two main structure types: the drey or the den. A drey is a constructed nest, typically a spherical mass of twigs and leaves, built in the fork of a tree or close to the trunk. The exterior framework is made of interwoven branches, while the interior is lined with insulating materials like grass, moss, and feathers to create a warm, dry chamber.
Squirrels often maintain several dreys within their home range, using them as emergency backups. Dreys can be seasonal, with summer versions being more open and less insulated than winter structures. The most secure residence is a den, which is a natural cavity found within a hollow tree trunk or a large branch. Dens offer greater protection from weather and predators, and they are the preferred location for females to raise their young, especially during colder periods.
The Burrowing Squirrels
The Sciuridae family contains a distinct group known as ground squirrels, for whom burrows are a permanent habitat. This group includes species like the California Ground Squirrel, Chipmunks, Marmots, and Prairie Dogs. These animals are physically adapted for a subterranean life, possessing shorter legs and stronger claws than their tree-dwelling relatives, allowing them to efficiently dig and navigate underground.
For these species, the underground network of tunnels serves every purpose, including sleeping, raising young, storing food, and providing refuge from predators and extreme temperatures. A single burrow can extend anywhere from five to thirty feet in length and two to four feet deep, with multiple chambers for different functions. Unlike tree squirrels, which remain active year-round, many ground squirrels use these burrows for hibernation, relying on the stable underground temperature to survive the winter. They rarely venture far from their burrow openings and typically run to the safety of their tunnels when frightened.
Ground Use for Non-Burrowing Species
Even though tree squirrels reside exclusively in trees, they are frequently seen on the ground performing necessary, temporary activities. The most common ground interaction is scatter hoarding, their strategy for caching food. Tree squirrels dig hundreds of small, temporary holes in the soil or leaf litter to bury individual nuts and seeds for later retrieval. This survival technique prevents the loss of an entire winter’s supply to a single raid.
The squirrel’s spatial memory, aided by landmarks like trees and rocks, helps them locate these numerous caches. While a tree squirrel may occasionally seek temporary shelter in a small ground depression or under a deck to evade a predator, these sites are not used as permanent dwellings or for raising young. Their core existence remains arboreal, with the ground serving as a foraging and storage area.