Squirrels are common rodents found across urban parks and remote forests. Their lives are more complex than the hurried dash across a lawn, requiring specialized shelters for survival. Understanding where squirrels settle reveals their strategies for food storage, raising young, and enduring harsh weather conditions.
Above-Ground Nests: The Drey
The most visible home of a tree-dwelling squirrel is the drey, a roughly spherical nest constructed high in the branches. This structure appears as a messy ball of leaves and twigs, located in a sturdy tree fork or close to the trunk for support, usually at least six meters above the ground. The outer layer is an interwoven shell of small branches and gnawed twigs.
Inside the bulky exterior, the squirrel creates a soft, insulated central cavity. This cavity is lined with materials like moss, shredded bark, grass, and dry leaves. Dreys serve primarily as temporary shelters for daily resting, napping, or raising young during warmer months. Squirrels often maintain multiple dreys throughout their territory, using them as reserve nests if the primary one is disturbed by predators or parasites.
Secondary Shelters: Tree Cavities and Dens
While the drey is the common summer residence, tree squirrels rely on more secure structures known as dens for permanent residency. These dens are natural tree hollows, cavities within a trunk, or sometimes abandoned holes originally excavated by woodpeckers. The squirrel does not excavate the wood itself, but simply lines the existing space with soft materials like leaves and fur.
The tree den provides superior insulation and security compared to the exposed drey. This makes it the preferred shelter for deep winter rest or during severe weather events. The thick wood walls offer a consistent temperature gradient, helping the squirrel conserve energy. These protected cavities are also important as maternal sites where mothers raise their young in a secluded and well-defended space.
Ground Squirrel Habitats
Species like the California or Richardson’s ground squirrel construct extensive subterranean burrow systems instead of tree nests. These burrows serve as a comprehensive home, functioning as a refuge from weather and predators, a site for rearing young, and a secure food cache. The network of tunnels may run between 5 and 30 feet in length, typically staying within two to six feet of the surface.
A burrow system features multiple surface openings, often between five and ten, which allow for quick escape routes and ventilation. Within the tunnels, specialized chambers are dug out for specific purposes. For the deepest winter rest, ground squirrels construct a specialized hibernaculum chamber. This chamber is sealed off from the main system by soil plugs to create a closed, protected environment for true hibernation.
When and How Squirrels Sleep
Most common tree squirrels, such as the gray squirrel, are diurnal, meaning their activity cycle is confined to the daylight hours. They are most active during the early morning and late afternoon, spending the entire night resting in their drey or den to conserve energy. Tree squirrels engage in regular daily sleep and rest, often taking multiple naps throughout the day, especially when food is abundant.
During the coldest winter months, tree squirrels do not enter true hibernation but experience bouts of torpor, a state of reduced metabolic activity. In torpor, their body temperature and heart rate drop, and they remain in insulated shelters for extended periods. Unlike true hibernators, squirrels in torpor are easily roused and will venture out to forage on milder days. Ground squirrels, however, undergo true hibernation, surviving the winter on stored fat with a profound drop in body temperature and long periods of deep sleep.