Whales have evolved a unique way to sleep while staying safe underwater, employing unihemispheric sleep and logging behaviors to rest half their brain at a time.
Whales have evolved a unique way to sleep while staying safe underwater. Unlike humans, whales don’t have the ability to shut down their entire brain at once, so they must find alternative ways to rest.
Whales, like other mammals, need to sleep.
However, they don't have a single brain region that can shut down at once, so they sleep with only half their brain at a time.
This is known as unihemispheric slow-wave sleep (USWS).
While one half of the brain sleeps, the other half remains awake and alert to potential threats.
Whales can also sleep with their blowhole above water, allowing them to quickly resurface if needed.
Scientists estimate that sperm whales spend around 4-6 hours per day sleeping.
The key to how whales sleep lies in unihemispheric sleep – a process where only one half of the brain rests at a time while the other half remains alert. This allows the animal to remain conscious, surface for air, and keep an eye out for potential predators. This specialized sleeping pattern is common among marine animals like bottlenose dolphins and humpback whales.
Unihemispheric slow-wave sleep (USWS) is a unique sleep pattern where one half of the brain is in a state of deep sleep, while the other half remains awake and alert.
This phenomenon is observed in some marine mammals, such as dolphins and whales, who need to surface for air but still require rest.
During USWS, the sleeping hemisphere shows reduced neural activity and slower brain waves, whereas the awake hemisphere maintains normal activity levels.
Whales also use a behavior called logging, where they float near the surface, motionless, resembling logs. This often occurs during the day, a behavior known as day sleeping. In this state, they conserve energy and still get the rest they need. Young whales and calves usually sleep alongside their mothers, sometimes aided by the mother’s slow, rhythmic swimming. In larger pods, whales may synchronize their rest periods for safety.
Whales and dolphins don’t get the long hours of deep sleep we enjoy. Instead, they may rest for short intervals, often up to two hours at a time, ensuring they regularly return to the surface for oxygen. Their blood, rich in red blood cells, helps carry more oxygen and supports these short rest cycles.
Whales, like humans, need to rest and recharge.
However, their sleep patterns are vastly different from ours.
Unlike humans who sleep in a continuous block, whales sleep in short intervals of around 5-20 minutes, known as polyphasic sleep.
During this time, only half of the brain is asleep, while the other half remains alert to ensure the whale's survival.
This unique adaptation allows them to rest while still keeping an eye out for predators and navigating their surroundings.
Because whales and dolphins spend their entire lives in the ocean, their resting behavior is finely tuned to balance safety, movement, and oxygen intake. From the surface calm of a log-floating humpback to the synchronized sleep of a pod, whales’ sleep strategies are a necessity of marine adaptation.
- howstuffworks.com | How Do Whales Sleep? Theyre Always Half Awake (Literally)
