Most squirrels sleep in nests they build high in trees, called dreys. These roughly football-sized balls of twigs and leaves sit at least 20 feet off the ground, tucked into a branch fork or pressed against the trunk where the tree is strongest. Ground squirrels, by contrast, sleep underground in burrow systems that can stretch 5 to 30 feet long. Where a squirrel sleeps depends entirely on its species, but all of them spend a surprising amount of time doing it: grey squirrels average about 15 hours of sleep per day.
Tree Nests: How Dreys Are Built
Tree squirrels like the eastern grey and red squirrel construct dreys from the outside in. The outer shell is a rough dome of leafy twigs woven together, looking from the ground like a messy clump of leaves wedged into a branch fork. Inside, the squirrel lines the nest with soft insulation: moss, feathers, grass, shredded bark, and pine needles. The result is a compact, waterproof shelter about the size of a football, with a small opening on one side.
Dreys are typically built at least six meters (roughly 20 feet) from the ground, high enough to discourage most predators. Squirrels choose spots where the trunk or a major branch fork provides structural support, so the nest holds up through wind and rain. A single squirrel may maintain several dreys across its territory, rotating between them. This gives it backup options if a nest is damaged or discovered by a predator.
Tree Cavities: The Preferred Option
When available, tree hollows are the first choice for sleeping. A natural cavity in an oak or maple offers better insulation than a drey and far more protection from wind, rain, and predators. Squirrels will line these cavities with the same soft materials they use in dreys, creating a dry, warm chamber. In forests with older trees, cavities are prime real estate, and squirrels compete for them. Woodpecker holes that have been abandoned are especially popular since the opening is already the right size.
Underground Burrows for Ground Squirrels
Ground squirrels take a completely different approach. Species like the California ground squirrel dig colonial burrow systems where they sleep, raise their young, store food, and retreat from threats. The entrance holes are about four inches in diameter, though well-used entrances widen over time. Underground, the tunnels branch into complex networks ranging from 5 to 30 feet in total length, with most of the system sitting within 2 to 3 feet of the surface. Some burrows reach 6 feet deep or more.
Sleeping chambers sit at the ends of tunnels, packed with dry grass and leaves for insulation. A single burrow system may have multiple entrances and exits, giving the squirrel escape routes if a predator enters. These colonies can be extensive, with dozens of squirrels sharing a network of interconnected tunnels across a hillside or field.
Winter Sleeping and Nest Sharing
Cold weather changes squirrel sleeping habits dramatically. Tree squirrels don’t hibernate, but they spend much more time in their nests during winter, venturing out only briefly to retrieve cached food. They reinforce their dreys in autumn, stuffing extra leaves into every gap and layering more insulating material inside to create a snug, well-sealed dome.
Flying squirrels take communal sleeping to an extreme. In winter, southern flying squirrels huddle together in tree cavities or nest boxes, with group sizes that can exceed 15 individuals in a single box. The colder it gets, the larger these groups become. Aggregation size and frequency increase as temperatures drop, and squirrels that would normally nest alone seek out groups when nighttime lows dip below about 10°C (50°F). Huddling conserves body heat far more effectively than sleeping alone, and the groups shift in composition throughout the season as temperatures fluctuate.
Grey squirrels also share nests in winter, though in smaller numbers. Two or three squirrels commonly sleep together in a single drey or cavity during cold snaps, combining body heat to survive freezing nights.
Where Squirrels Sleep in Cities
Urban squirrels are resourceful about finding shelter. While they still build dreys in park trees and along residential streets, they also exploit man-made structures. Attics are a common target: a gap in soffit trim or a loose vent cover gives a squirrel access to a warm, dry, predator-free space that’s far superior to any drey. Chimneys, garage rafters, and the gaps between walls and rooflines also serve as sleeping sites.
Research on urban red squirrels has found that they adapt well to city environments, using structures that have no equivalent in their natural forest habitat. They’ll nest in roof spaces, utility boxes, and building cavities alongside their traditional dreys and tree hollows. This flexibility is a big part of why squirrels thrive in cities. They treat buildings as very large, very well-insulated trees.
Daily Sleep Patterns
Grey squirrels are diurnal, meaning they’re active during daylight and sleep through the night. Their 15 hours of daily sleep means they’re only active for about 9 hours, most of it spent foraging and caching food. They’re busiest in the early morning and late afternoon, often returning to the nest for a midday rest.
Flying squirrels flip this schedule entirely. They’re nocturnal, leaving the nest after dark to forage and returning before dawn. Ground squirrels are diurnal like their tree-dwelling relatives but spend even more time in their burrows. During the hottest parts of summer, some ground squirrel species enter a state called estivation, a period of reduced activity similar to hibernation but triggered by heat rather than cold. In winter, many ground squirrel species truly hibernate, sleeping in their deepest chambers for weeks or months at a time.