Squirrels are common fixtures in both urban and forested environments. These agile tree-dwellers rely on structures called dreys, which serve as their primary nests for resting, escaping weather, and raising young. A drey is essentially the squirrel’s version of a house. Understanding the construction and use of these arboreal homes helps clarify their nesting habits, including the frequently misunderstood concept of whether they are reused. This close examination of the drey reveals a sophisticated system of home maintenance and strategic relocation.
Anatomy of a Squirrel Drey: Construction and Materials
A typical drey is an intricate, spherical structure built high in the branches of a tree. It is often tucked securely into a fork or crotch close to the trunk for stability. This placement, usually 20 to 45 feet above the ground, helps protect the structure from both ground-based predators and high winds. The finished nest is roughly the size of a football, sometimes reaching 30 centimeters or more in diameter.
The construction employs a dual-layer design to maximize protection and insulation. The exterior layer consists of interwoven twigs, small branches, and leafy materials that form a durable, weather-resistant shell. This outer shell provides the primary defense against the elements.
Inside this sturdy framework, the squirrel creates a hollow core lined with softer, finer materials. This inner lining is composed of shredded bark, dried grass, moss, pine needles, or animal fur. The soft materials act as a deep insulating layer, helping the squirrel maintain body temperature during colder weather. The squirrel creates one or two small entrance holes, often oriented toward the tree trunk to keep the interior dry.
Why Squirrels Maintain a Network of Dreys
Squirrels rarely rely on just one structure within their territory. Instead, they maintain a network of multiple dreys and other shelters across their home range. This housing strategy functions as a defense mechanism against immediate threats. If a primary nest is disturbed by a predator, the squirrel can quickly relocate to a pre-built backup drey.
The rotation between nests also serves a biological purpose by controlling parasite populations. Fleas, mites, and other ectoparasites can quickly build up in a frequently used nest. By moving to a fresh drey every few weeks or months, the squirrel allows the abandoned nest’s parasite load to subside.
Squirrels often utilize different dreys for specific seasonal or life-cycle needs. A large, well-insulated nest may be designated as the main winter home where multiple squirrels can huddle for warmth. A smaller, less-insulated structure may serve as a temporary summer sleeping platform. Radio-tracking studies have shown that individual squirrels use between two and eight different dreys throughout their range.
The Core Question: Do Dreys Get Reused?
Dreys are frequently reused, but this reuse is conditional upon the nest’s structural integrity and biological safety. A squirrel will readily return to a former drey if it remains intact and has not been compromised since its last use. This behavior saves significant energy, as building a completely new drey is a time-consuming and labor-intensive process.
Reuse is directly linked to an ongoing process of drey maintenance performed by the resident squirrel. They regularly inspect and repair the structure, replenishing twigs and leaves on the exterior to reinforce the walls against weather damage. The lifespan of a drey is variable; some temporary summer nests may be abandoned after only a few weeks.
A structurally solid drey may be used for a year or two before being replaced by a newer structure. In rare cases, a single drey has been observed to be continuously used and maintained by multiple generations of squirrels for over a decade. The decision to abandon a drey permanently is usually triggered by a severe breach or an overwhelming infestation of internal parasites. They will not reuse a drey that presents a health or safety risk.
Beyond the Drey: Alternative Nesting Sites
While the stick-and-leaf drey is the most visible type of squirrel home, it is often a secondary choice compared to a naturally occurring tree cavity. These hollows, referred to as dens, are found in old tree trunks or large branches and provide superior shelter. A den offers better insulation and protection from wind and rain than a drey.
Squirrels line these tree cavities with soft nesting materials to create a warm nursery or winter retreat. Studies indicate that young born in these protected dens have a higher survival rate than those born in dreys. Dens are preferred during the cold winter months because they conserve the squirrel’s body heat more efficiently.
In environments where natural tree hollows are scarce, such as suburban areas, squirrels utilize opportunistic nesting sites. This includes man-made structures like attics, sheds, or wall voids within a building. These locations mimic the secure, insulated conditions of a natural tree den, offering a safe, warm space away from predators and the elements.