When observing tree squirrels, people often notice a messy-looking ball of leaves high in the branches. This structure is called a drey, and it serves as the primary shelter for these common tree-dwelling rodents. Unlike a simple bird’s nest, the drey is a complex, specifically constructed home used for resting, raising young, and escaping danger. These large, spherical structures represent a significant investment in time and energy, appearing frequently in both dense forests and neighborhood park settings.
The Anatomy of a Drey
The construction of a drey uses a two-layered design providing structural integrity and protection from the elements. The outer layer forms a robust framework of interwoven twigs, bark strips, and stiffer leaves. This dense shell acts like a waterproof barrier, deflecting rain and minimizing wind penetration to stabilize the internal temperature.
Once the outer shell is secure, the squirrel creates the internal chamber. This space is meticulously lined with softer, finer materials, such as grasses, moss, shredded plant fibers, or scavenged cloth. This lining creates an insulated thermal pocket, beneficial for surviving cold temperatures. The structure is generally spherical or dome-shaped, often ranging from 12 to 19 inches in diameter.
The entrance is a small, strategically placed hole, usually located near the bottom. This restricted opening helps conserve internal heat and makes it difficult for larger predators to gain access. The careful weaving ensures the drey can withstand significant wind and precipitation.
Location and Seasonal Use
Squirrels select drey sites emphasizing stability and concealment, typically placing them high in the tree canopy. The structures are often nestled in a fork where several branches meet or positioned close to the main trunk. This placement offers structural support and helps to camouflage the drey against the foliage or bark.
The type of tree influences selection; deciduous trees provide ample leaf material, while conifers offer year-round cover. The use of the drey varies significantly depending on the season. Summer dreys are often smaller, less insulated, and may only be used temporarily as a daytime retreat from heat. Winter dreys, conversely, are built for maximum robustness and insulation to withstand severe weather.
During the coldest months, a squirrel may seek out a pre-existing tree cavity. These tree holes, known as dens, offer unmatched protection from freezing temperatures and high winds, often becoming the preferred winter residence.
Why Dreys Matter to Squirrels
The drey serves several functions related to the squirrel’s survival. The dense, multi-layered structure provides protection against weather, shielding the occupant from heavy rain, snow, and temperature extremes. Maintaining a stable body temperature requires less energy within the insulated walls of the drey.
Beyond environmental protection, the drey acts as a secluded refuge from numerous ground and aerial predators, such as raccoons, snakes, and birds of prey. By retreating into the elevated, enclosed space, the squirrel minimizes its exposure to danger. The single, small entrance further enhances this defensive function by creating a physical barrier.
The drey’s primary function is as a nursery for raising the young, known as kits. The secure, warm interior provides a safe environment for the neonates until they are old enough to forage independently. During periods of extreme cold, multiple family members may share the drey, huddling together to conserve collective body heat and maximize energy efficiency.