The Eastern Gray Squirrel, along with species like the Red Squirrel and Fox Squirrel, is highly arboreal, relying completely on trees for survival. They spend most of their lives navigating the canopy, rarely touching the ground unless necessary. This tree-dwelling existence means that shelter from weather and predators is a constant concern. Squirrels dedicate significant energy to establishing and maintaining one or more secure residences to ensure their safety and well-being.
The Two Primary Types of Squirrel Homes
Squirrels utilize two fundamentally different types of residences in the tree canopy, each offering distinct advantages. The most visible home is the drey, a large ball of leaves and twigs constructed externally within the branches of a tree. Dreys are built by the squirrel and are often located high up, nestled in the crotch of a major limb or close to the trunk for stability.
The second type of home is a den or cavity, which is an internal space found within the tree itself. These dens are not built by the squirrel but are naturally occurring hollows, often caused by rot or previous excavation by woodpeckers. A tree cavity provides a permanent, enclosed shelter, offering superior protection from wind and moisture. Squirrels line the interior with soft bedding materials for comfort and insulation, and often maintain multiple homes of both types within their territory.
How Squirrels Build a Drey
The construction of a drey is a process of deliberate engineering, resulting in a robust, spherical structure. The squirrel begins by gathering coarse material like small twigs and branches to form a sturdy, foundational shell. Twigs with leaves attached help fill gaps and create a dense, wind-resistant outer layer as they dry.
The outer shell is interwoven into a ball shape, typically situated in a stable fork of branches 20 to 40 feet above the ground. Inside this protective layer, the squirrel creates a hollow core and lines it with finer, softer materials for thermal regulation. This inner lining consists of shredded bark, dried grass, moss, pine needles, and feathers, which create a snug sleeping chamber. This multi-layered design provides an insulated, weatherproof refuge with a small entrance hole.
Seasonal Selection of Habitat
The choice between a drey and a tree cavity is heavily influenced by the changing seasons. During the warmer months, the ease of construction and ventilation make a drey a suitable summer home for resting and raising young. These summer dreys tend to be less dense and more open, allowing for better airflow and helping the squirrel manage heat stress. Squirrels often build these nests in deciduous trees like oaks and maples that provide a reliable food source nearby.
As winter approaches, squirrels seek out or reinforce a tree cavity because the enclosed space offers superior insulation and protection from extreme cold and wind. Being surrounded by thick wood, a den cavity maintains a temperature substantially warmer than the outside air. If a suitable cavity is unavailable, the squirrel will build a much thicker, more insulated winter drey. These winter dreys are sometimes shared with other squirrels to conserve body heat.
The Essential Function of the Nest
The squirrel’s home, whether a drey or a den, serves several functions fundamental to its survival and reproductive success. One primary role is offering protection from predators, such as hawks, owls, and climbing mammals like raccoons and snakes. Building the home high up in the canopy, often 30 feet or more above the ground, helps place the squirrel out of reach from many threats.
The nest is also a tool for thermal regulation, helping the non-hibernating squirrel conserve energy throughout the year. The insulated walls of a winter drey or the natural wood of a tree cavity provide a thermal buffer against freezing temperatures and intense summer heat. The secure structure also functions as a nursery, providing a safe, warm environment for the mother to raise her litters of two to five young.