Squirrels are known for their bushy tails, love of nuts, and ability to leap between trees with ease. But have you ever wondered if squirrels actually sleep with their eyes open? It’s an interesting question that reveals some unique aspects of squirrel behavior and biology.
If you’re short on time, here’s a quick answer: squirrels do not technically sleep with their eyes completely open. However, their eyes often remain partially open while sleeping. This helps them stay vigilant against predators even when resting.
Squirrels Close Their Eyes Partially When Sleeping
Light Sleep Allows for Vigilance
Squirrels tend to sleep with their eyes partially open. Their eyes often remain half-shut as a protective mechanism while resting. This allows squirrels to keep vigilant for potential predators that may threaten them.
Even when sleeping, squirrels need to stay somewhat aware of their surroundings to stay safe.
Squirrels do not sleep as deeply as many mammals. Their slumber is quite light and easily interrupted. This gives squirrels the chance to wake up and scurry to safety if a predator approaches their nest.
So while their eyes may appear open, squirrels are indeed sleeping – just not in a profoundly deep sleep.
Sleep Positions Keep Eyes Partially Open
The sleep postures squirrels choose also lead to their eyes staying somewhat open. Squirrels often sleep curled up with their tails wrapped around for warmth and security. Their heads may rest on their front legs or on their fluffy tails as they snooze.
These curled body positions make it difficult for squirrels’ eyes to fully close. The placement of their heads and the curl of their spines cause their eyelids to remain parted halfway as they rest. If they slept very stretched out, they may be able to shut their eyes more completely.
But that would be unsafe and expose them to attack.
Squirrel Sleep Habits and Behaviors
Squirrels Don’t Hibernate But Do Sleep Deeply
Unlike some mammals, squirrels do not actually hibernate during the winter months. However, they do experience periods of deep sleep known as torpor. During torpor, a squirrel’s heart rate and breathing slows down dramatically. Their body temperature can decrease by up to 10°C from normal levels.
This helps squirrels conserve crucial energy when harsh weather or food scarcity makes conditions difficult.
Squirrels enter torpor multiple times each winter for up to two weeks at a time. Nestled snugly in a leafy drey or tree cavity den, bushy tails covering their faces, they sleep deeply with twitching eyelids and paws.
But hibernation it is not; torpid squirrels wake frequently to urinate or snack on cached nuts. Come springtime, squirrels resume normal rapid eye movement (REM) sleep cycles of hiding nuts during the day and restfully dozing off at night.
Sleep Locations Depend on the Species
Squirrels build two types of nests—dreys and dens. The locations they sleep in differs by species. For example, dreys suit tree squirrels like Eastern grays. They construct these leafy, teardrop nests on branches high in the trees.
Lined with moss, grass, feathers and more for warmth and shelter, dreys mimic birds nests.
In contrast, ground squirrels like prairie dogs dig tunnel dens underground. These holes have various chambers for sleeping, storing food, and keeping young. Some squirrels even repurpose woodpecker holes or other tree cavities when available.
The small opening and enclosed space helps squirrels conserve body heat and keep safe as they sleep or rest in winter’s cold temperatures with eyes peacefully closed.
Reasons for Squirrels’ Unique Sleep Habits
Vulnerability to Predators
As small, tree-dwelling mammals, squirrels face constant threats from aerial and terrestrial predators like hawks, owls, coyotes, foxes, raccoons, and even household pets. Remaining vigilant is crucial for their survival.
Squirrels only allow half of their brain to sleep at a time, keeping one eye open to watch for threats. Their light and interrupted sleep pattern likely evolved to reduce their vulnerability.
Tree squirrels like eastern gray squirrels sleep in leaf nests called dreys that are hidden high up in the trees. This offers safety, but they can still fall victim to predators like the red-tailed hawk.
According to the Cornell Lab of Ornithology, over 75% of documented gray squirrel deaths are caused by predation.
Adaptation to an Arboreal Lifestyle
Life in the trees requires superb balance and grip. Squirrels have evolved a range of physical and behavioral adaptations to avoid deadly falls. Their supple spine allows them to stretch out on branches and flatten themselves. Long limbs with sharp claws provide a firm hold.
Fluffy tails act as a counterbalance. Unique wrist joints let them climb head first down trunks. Squirrels can even rotate their back ankles 180 degrees for a sure-footed backward descent.
However, sound sleep might lead squirrels to lose their grip or balance. Scientists theorize this is why tree squirrels never fall into a deep slumber. Their light dozing allows them to adjust positions and remain anchored.
By budgeting sleep and keeping part of their brain always alert, squirrels remain safely perched in high branches through the night.
Conclusion
In summary, squirrels tend to sleep with their eyes slightly open rather than fully closed. This unique sleep behavior helps them remain alert to threats even when resting. It is an adaptation that allows tree-dwelling squirrels to survive despite the many predators they face.
So the next time you spot a sleeping squirrel, take a close look – you may notice their eyes aren’t completely shut!
