Squirrels construct homes high up in trees. While they build shelters, the structure is not technically a nest like a bird’s, but is known as a “drey.” These custom-built, spherical shelters are common sights in tree branches once the leaves have fallen. Dreys provide a safe, elevated haven constructed from local materials, allowing squirrels to thrive in diverse environments.
The Two Primary Types of Squirrel Shelters
Squirrels utilize two distinct types of shelter within trees, providing security throughout the year. The most visible is the drey, a round, exterior structure built from scratch in the branches of a tree. This constructed home is often nestled in a secure fork or directly against the tree trunk for stability.
The second type of shelter is a natural tree cavity, referred to as a den. Squirrels do not excavate these dens, but instead use existing hollows created by wood rot, broken branches, or woodpeckers. Natural hollows offer superior protection from the elements compared to a drey. A natural den is preferred for surviving severe weather and for the security it provides when raising young.
Construction and Architecture of Dreys
The construction of a drey uses a multi-layered architectural approach.
Outer Framework
The squirrel first establishes a sturdy outer framework composed of gnawed-off sticks and twigs woven together to form a rough sphere. This shell is typically built in a strong crotch of a tree, often 20 to 40 feet above the ground, ensuring stability against wind and predators. The finished drey can measure a foot or two wide, roughly the size of a football.
Insulation and Weatherproofing
The middle layer is composed of insulating materials stuffed into the outer framework to weatherproof the structure. Squirrels use damp leaves, moss, and grass to create a dense layer that repels water and blocks wind. Harvesting green, leafy branches before autumn ensures the leaves adhere tightly as they dry, enhancing the drey’s integrity through cold months.
Inner Lining
The interior is finished with a soft, warm inner lining for comfort and thermal regulation. This final layer consists of fine materials such as shredded bark, pine needles, dried grass, fur, or feathers. The entrance hole is usually small and oriented downward or toward the tree trunk, which helps to keep rain out and makes it more difficult for predators to enter.
Purpose and Seasonal Use of Nests
The primary function of both dreys and tree dens is to provide reliable shelter from predators and unpredictable weather. Squirrels are active year-round and do not hibernate, relying heavily on their nests during cold snaps and storms. The interior of a well-insulated drey can be significantly warmer than the outside air, offering refuge during freezing temperatures.
Squirrels often maintain multiple nests across their territory, using them for different purposes throughout the year. Tree cavities are usually the preferred location for the winter months and for the first litter of the year, typically born in January or February. Dreys are more commonly used as secondary shelters, summer homes, or emergency refuges when tree cavities are scarce. Females use these structures to raise their young, with the second litter of kits often being born in a drey during the warmer summer months.