The common sight of a squirrel racing up a tree or burying a nut during the day naturally leads to curiosity about their activity after sunset. For most frequently observed species, such as the Eastern Gray Squirrel, the answer is straightforward: they are strictly diurnal animals. Diurnal means their activity is focused entirely on the daytime, so once the sun goes down, these rodents are settled in their shelters and sound asleep. This behavior is a fundamental survival strategy dictated by their biology and the presence of nocturnal threats.
When Squirrels Are Most Active
Squirrels maintain a schedule that closely follows the sun, spending their days foraging, socializing, and building nests. Their activity is not evenly spread throughout the day but instead exhibits a bimodal pattern within the broader diurnal period. This means they are busiest during two distinct windows: the early morning just after sunrise and the late afternoon before sunset.
During the middle of the day, when the sun is highest and temperatures are warmest, squirrels retreat to a shady spot or their nest for a period of rest. This conserves energy until the late afternoon peak. This cycle allows them to maximize foraging time while avoiding the hottest part of the day and getting a head start on nocturnal predators. A few species, such as the flying squirrel, are truly nocturnal, but these are an exception to the common tree squirrel.
Where Squirrels Sleep
When darkness approaches, tree squirrels seek refuge in one of two primary types of sheltered homes: dreys or tree cavities. The choice of shelter is often based on the season, with both serving the purpose of protection from weather and predators. Dreys are spherical nests constructed from interwoven twigs, leaves, and moss, typically built high in the fork of a tree’s branches.
Dreys are used most often during the warmer months, but they offer less protection than a cavity. Tree cavities, often called dens, are the preferred shelter, especially when winter arrives. A den is a hollow space inside a tree trunk or branch, sometimes an abandoned woodpecker hole, which offers superior insulation and protection from the elements.
During the coldest periods, squirrels may engage in communal nesting, with multiple individuals sharing a den to conserve body heat. By curling into a tight ball and wrapping their large, bushy tail around their bodies, they minimize surface area exposure to the cold night air. The shelter’s primary purpose is to regulate temperature and provide a secure location for a deep, nightly sleep cycle.
Why Squirrels Avoid Activity After Dark
The strict diurnal schedule of the tree squirrel is a survival adaptation rooted in biological and environmental factors. One deterrent to nocturnal activity is the increased threat of specialized predators that emerge after sunset. Animals like owls, raccoons, and certain snakes are highly adapted to hunt in low-light conditions and pose a significant danger.
Staying hidden inside a well-constructed drey or deep within a tree cavity is the safest strategy to avoid being detected by these hunters. This passive defense is significantly more effective than attempting to forage or travel in the dark. Furthermore, the squirrel’s visual system is not built for nighttime navigation.
The squirrel retina is rich in cone photoreceptor cells, which are responsible for high visual acuity and color discrimination in bright daylight. In contrast, they have far fewer rod cells, which are necessary for effective low-light vision. This cone-dominant vision means that moving around after dark would be extremely disorienting and dangerous.
Resting at night is important for metabolic conservation. Periods of intense daytime activity, such as rapid climbing and foraging, are followed by a period of low resting metabolic rate (RMR) during sleep. This nightly rest helps the squirrel conserve energy reserves, a mechanism that is important for survival during cold periods when food is scarce.