How Do Whales Sleep?


Do whales sleep? Yes, whales do sleep, but they sleep differently from humans and other land mammals. While you drift into a deep unconscious state during sleep, whales must stay partially alert to breathe and stay safe in the ocean. Most whales use a method called unihemispheric sleep, where one half of their brain sleeps while the other half stays awake. This lets them surface for air, watch for dangers, and get the rest they need.
The following AnimalWised article explores how whales sleep without drowning, their various sleep patterns, and what scientists have learned about their rest behaviors.
Do whales sleep?
Yes, whales do sleep, though they sleep very differently from humans and other land mammals.
Since whales must consciously breathe by surfacing for air, they cannot fall into a deep unconscious sleep like we do. Instead, most whales use a fascinating adaptation called unihemispheric sleep, where one half of their brain sleeps while the other half stays awake. This allows them to continue surfacing for air and remain alert to potential dangers while still getting the rest they need.
Do whales REM sleep?
Scientists have found little evidence of REM (Rapid Eye Movement) sleep in whales. While you spend about 25% of your sleep in REM state, whales show only brief moments of REM-like sleep lasting seconds rather than hours.
Studies [1]of bottlenose dolphins (Tursiops truncatus) and beluga whales (Delphinapterus leucas) show these short REM periods include muscle twitches, eye movements, and changes in breathing patterns. The rarity of REM sleep likely relates to whales' need to stay partially conscious for breathing, as REM sleep usually requires complete muscle relaxation.
Scientists continue studying how whales manage brain functions typically linked to REM sleep, like memory and learning, with such brief REM periods.
Did you know whales can hold their breath for over an hour? Discover more in our article about whale breathing.
How do whales sleep without drowning?
Whales have developed certain physical adaptations that prevent them from drowning during sleep. To begin with, their bodies are naturally buoyant, which helps them float near the surface without much effort. They also maintain specific sleeping positions that keep their blowholes, which are the equivalent of your nose, close to the surface for easy breathing.
Not only that, but their muscles stay partially active during sleep, allowing small movements that help maintain their position in the water. Even during rest, whales can make slight adjustments with their tail flukes to stay stable and surface when needed. Their breathing rate also slows while sleeping, reducing how often they need to take breaths.
Different whale species have adapted distinct sleeping positions and patterns. These examples show how different whales rest:
- Sperm whales (Physeter macrocephalus) sleep vertically in the water, positioning themselves head-up near the surface. They also often cluster together in small groups, a behavior that helps protect them during vulnerable rest periods.
- Humpback whales (Megaptera novaeangliae), on the other hand, keep moving while they sleep, swimming at a slow, steady pace.
- Blue whales (Balaenoptera musculus) and gray whales (Eschrichtius robustus) float just under the surface while they rest, which takes little energy and keeps them close to air. This position makes breathing easy while still allowing them to rest.
Did you know there are over 90 whale species? Find out what makes each one special in our other article.

How much do whales sleep?
Whales have irregular sleep schedules that differ from most mammals. Unlike your regular 7-9 hours of continuous sleep, whales rest in shorter periods throughout the day and night. The amount and pattern of sleep varies by species and situation.
Most whales get about 5-7 hours of total rest in each 24-hour period. However, they break this into many short sessions.
Young whales face special sleeping challenges. In their first few weeks of life, baby whales and their mothers barely sleep at all. The calves need to keep swimming to stay alongside their mothers, and both need to stay alert for predators. As the calves grow stronger, they develop sleep patterns similar to adult whales. Most whales sleep in short bursts throughout the day and night.
Furthermore, during migrations, whales can travel thousands of miles with little rest. Some species, like gray whales (Eschrichtius robustus), make annual trips of up to 19,000 kilometers (12,000 miles). During these long journeys, they reduce their sleep dramatically.
Research shows migrating whales might sleep as little as 30 minutes per day, often taking very short microsleeps while swimming. Scientists think these whales might use their unihemispheric sleep more efficiently during migration, getting just enough rest to keep going while staying on course.
Curious if other animals have unusual sleep patterns? Discover some creatures that barely sleep at all.

If you want to read similar articles to How Do Whales Sleep?, we recommend you visit our Facts about the animal kingdom category.
- Lyamin, O. I., Manger, P. R., Ridgway, S. H., Mukhametov, L. M., & Siegel, J. M. (2008). Cetacean sleep: An unusual form of mammalian sleep. Neuroscience & Biobehavioral Reviews, 32(8), 1451-1484.
- Lyamin, O. I., Mukhametov, L. M., & Siegel, J. M. (2002). Relationship between sleep and eye state in Cetaceans and Pinnipeds. Archives italiennes de biologie, 140(1), 57-70.
- Dell, L.A., Karlsson, K.A., Patzke, N., Spotter, M.A., Siegel, J.M., & Manger, P.R. (2016). Organization of the sleep‐related neural systems in the brain of the minke whale (Balaenoptera acutorostrata). Journal of Comparative Neurology, 524(10), 2018-2035.
- Lyamin, OI, Manger, PR, Ridgway, SH, Mukhametov, LM, & Siegel, JM (2008). Cetacean sleep: an unusual form of mammalian sleep. Neuroscience & Biobehavioral Reviews, 32(8), 1451-1484.
- Lyamin, O.I., Mukhametov, L.M., & Siegel, J.M. (2004). Relationship between sleep and eye state in Cetaceans and Pinnipeds. Archives italiennes de biologie, 142(4), 557.
- Lyamin, OI, Mukhametov, LM, Siegel, JM, Nazarenko, EA, Polyakova, IG, & Shpak, OV (2002). Unihemispheric slow wave sleep and the state of the eyes in a white whale. Behavioral brain research, 129(1-2), 125-129.