Squirrels are a familiar sight in parks and forests. They are active all year, requiring reliable shelter from predators and the elements for survival in varied climates. These small mammals construct housing that provides insulation, security, and a safe nursery for their young. The design of their homes is adapted to different seasonal needs and environmental conditions.
The Official Name and Function
The bulky, spherical nest built by tree squirrels is called a drey. This structure is made of interwoven materials high in the tree branches, typically nestled in a crotch or close to the trunk for structural support. Dreys are multi-functional homes that provide shelter from harsh weather like rain and cold, and protection from climbing predators such as raccoons and opossums. The dense, enclosed design helps retain warmth, allowing squirrels to remain active even during cold periods, and provides a secure location for the female to raise her young, known as kits.
Construction Methods and Materials
The construction of a drey is a two-layer process that results in a well-insulated structure. The squirrel establishes the outer framework using small, gnawed-off branches and pliable twigs. These materials are tightly woven together to form a sturdy, hollow sphere, often reaching the size of a football, and anchored to a tree fork.
The builder often uses twigs with green leaves attached, which dry and adhere to the structure, adding stability. This exterior layer acts as a windbreak, protecting the interior. Inside this framework, the squirrel creates a soft, insulated inner chamber. This inner lining consists of fine materials such as moss, shredded bark, pine needles, grass, fur, or feathers. The entrance is typically a single, small hole, positioned near the bottom and oriented toward the tree trunk to help keep out rain and discourage intruders.
Variations in Squirrel Shelters
Not all squirrel housing is the external drey; many species also utilize a den nest or cavity nest. These homes are found inside natural hollows within tree trunks or large branches, or sometimes in abandoned woodpecker holes. The den nest is preferred for permanent housing or during extreme cold due to its superior safety and insulation.
The squirrel modifies the existing space, sometimes gnawing at the entrance to widen it for easier access. The cavity interior is lined for comfort and warmth using soft materials like moss, leaves, and shredded bark. A squirrel may maintain multiple shelters—both dreys and den nests—throughout its home range, using them interchangeably. The choice between building a drey and using a den is influenced by season and availability. Dreys are quicker to construct and offer better ventilation during warmer summer months, while tree dens provide a warmer, more secure environment for raising the first litter in late winter. If a suitable tree cavity is unavailable, squirrels will use a robustly constructed winter drey, sometimes huddling together for added warmth.