The familiar sight of a squirrel darting through a yard or up a tree leads to curiosity about their whereabouts once the sun disappears. These energetic animals are not active throughout the night. Instead, they follow a precise and predictable daily schedule tied closely to the cycles of light and darkness. Their routine maximizes activity during daylight hours for foraging and building nests, ensuring they are safely tucked away before the nocturnal world begins to stir.
The Diurnal Rhythm and Daily Timing
Squirrels are classified as diurnal creatures, meaning they conduct their primary activities during the day and rest through the night. Their internal biological clock is synchronized with the sun, prompting them to leave their nests at or just before sunrise and return shortly after sunset. This schedule allows them to capitalize on the safety and visibility of daylight for essential tasks like collecting and caching food.
The daily activity pattern is often described as bimodal, featuring two peak periods of intense movement separated by a less active midday period. The first peak occurs in the early morning, often within an hour of sunrise, as the squirrels emerge to begin foraging. The second peak happens in the late afternoon or early evening, when they focus on collecting a final meal before settling in for the night.
This bimodal pattern means squirrels are frequently observed as being crepuscular, active during the twilight hours of dawn and dusk. The midday dip in activity, where they may return to a nest or simply rest on a shady branch, serves several purposes. This rest conserves energy and helps them avoid the most extreme temperatures, particularly during the intense heat of a summer afternoon.
Where Squirrels Rest and Sleep
For nightly rest, squirrels retreat to secure, elevated structures that offer protection from predators and the elements. The most common sleeping location is a drey, a sturdy, spherical nest built high in tree branches. Dreys are constructed from interwoven twigs and leaves, with an inner cavity lined with softer materials like moss or grass for insulation.
These leaf nests, which can resemble a large, messy ball, are often situated in the fork of a branch close to the tree trunk for stability. While dreys are common and relatively quick to build, a more secure option is a natural tree cavity, also known as a den. These hollow spaces within the tree trunk offer superior protection from rain and cold against many threats.
Squirrels often maintain multiple dreys or dens within their territory, providing shelter if one is damaged or discovered by a predator. Once inside their chosen shelter for the night, they curl up tightly. They frequently wrap their bushy tail around their body like a blanket to conserve body heat, ensuring they remain safe and insulated until the morning sun cues their awakening.
Seasonal Influences on Sleep Patterns
The squirrel’s daily schedule is significantly modified by the changing seasons, primarily due to shifts in daylight hours and food availability. During the long days of summer and early fall, squirrels are active for the longest duration, sometimes logging over eleven hours a day outside the nest. This extended activity is driven by the urgent need to forage and cache the large amounts of food necessary to survive the coming winter.
As the year progresses into winter, the active period shortens dramatically, sometimes reducing the daily foraging time to four or five hours, often centered around a single peak of activity near midday. Unlike true hibernators, such as ground squirrels, common tree squirrels remain active year-round. They may enter periods of deep rest, or torpor, which is a temporary state of lowered body temperature and metabolic rate lasting less than 24 hours.
During severe cold snaps, a tree squirrel may remain inside its insulated nest for several consecutive days, shortening its active season to conserve energy. This extended rest period is a survival strategy to minimize heat loss and avoid expending calories when searching for food is difficult or unproductive. In winter, they rely heavily on cached food and the superior insulation of their dens, sometimes nesting communally to share body heat and increase their chances of survival.