Most squirrel species are not nocturnal; they are classified as diurnal animals, meaning their primary period of activity occurs during the daylight hours. This includes familiar tree squirrels, such as the Eastern Gray and Fox squirrels, which are commonly observed in parks and backyards. Their schedule is tied to the sun, ensuring they are foraging when light is abundant and retreating to their nests when darkness falls.
Squirrel Activity: Diurnal and Crepuscular
The majority of tree and ground squirrels, including the Fox squirrel (Sciurus niger) and the Eastern Gray squirrel (Sciurus carolinensis), operate on a diurnal schedule. However, their activity is not evenly spread across the daylight hours; instead, they exhibit a pattern known as crepuscular activity. This means their energy peaks occur specifically around the transition periods of the day: dawn and dusk.
The highest levels of foraging and movement are observed in the early morning, shortly after sunrise, and again in the late afternoon as the sun begins to set. This crepuscular pattern helps them manage energy and avoid the intense heat of midday during warmer months, when they may take short naps in their nests, called dreys. Fox squirrels, for example, are described as strictly diurnal, spending a considerable amount of their active time foraging on the ground before returning to their dens or leaf nests.
The Exception: True Nocturnal Squirrels
The only exception to the diurnal rule among North American squirrels are the Flying Squirrels, comprising the Northern (Glaucomys sabrinus) and Southern (Glaucomys volans) species. These animals are entirely nocturnal, conducting all foraging and gliding activities under the cover of night. Their ability to thrive in the dark is supported by distinct physical adaptations that set them apart from their diurnal relatives.
Flying squirrels possess disproportionately large eyes, which are specially adapted to gather the maximum amount of available light for enhanced night vision. They do not truly fly but glide silently between trees using a specialized flap of skin called a patagium, which stretches from their wrists to their ankles. This gliding membrane, along with a flattened tail that acts as a stabilizer, allows them to navigate the forest canopy efficiently in the dark. Their nocturnal lifestyle means they are rarely seen by humans, as they retreat to tree cavities or dens to sleep during the day.
Why Squirrels Are Not Active at Night
The typical squirrel’s adherence to a daytime schedule is largely a matter of survival, tied to both physiological limitations and predator avoidance. Most diurnal squirrels lack the specialized visual hardware needed to navigate effectively in darkness. Their eyes are not adapted for low light, meaning their ability to locate food, assess distances, and detect danger is diminished after sunset.
Navigating a complex, three-dimensional environment like a tree canopy without specialized night vision would lead to frequent falls and injuries. Furthermore, darkness brings out a different set of predators, such as the Great Horned Owl, which is an efficient nocturnal hunter. By being active only during the day, squirrels avoid the peak hunting hours of these nighttime predators, choosing instead to risk encountering daytime hunters like hawks. They retreat to their well-insulated nests, often constructed of sticks and leaves high in trees or within tree hollows, to safely wait out the night.