Let’s delve into the fascinating world of whale sleep patterns. Similar to humans, whales are mammals with essential sleep needs, but their underwater lifestyle necessitates unique adaptations for rest. From unihemispheric slow-wave sleep to their conscious breathing mechanism, discover how these marine giants manage their sleep in the vast oceans.
The basics
Let’s start from the beginning. All whales are mammals like humans, and they require sleep to survive. Different species, tho, have different sleeping requirements and methods.
Unique Sleep Patterns of Whales
Like all other mammals, their bodies require sleep for regeneration, but their sleep defers from all other mammals. The reason for that is they can’t lay down, and also they have to remember to breathe. But we will get back to that.
Unihemispheric Slow-Wave Sleep
Whales can rest only one half of the brain (hemisphere) at a time, and they have the opposite eye opened to look for predators or obstacles. This technique is called unihemispheric slow-wave sleep. After maximum of 2 hours they can switch and rest the other side of the brain. This process if referred as “cat-napping“.
Sleeping Positions
Whales can sleep in different positions. They can rest a few meters beneath the water surface or on the water surface. The last one is called »logging«, because in this state the whale resembles a log floating. Another technique is that they sleep while swimming slowly next to another animal or in a group.
Sleeping Habits of Newborn Whales
Newborn whales rest, sleep and eat while their mother swims. She is towing her baby along in her sleep stream. Because they don’t have enough body fat or blubber yet, they don’t have the buoyancy and can’t float easily. That’s why their mother can’t stop swimming for the first few weeks of their life, otherwise they would sink. In that time, the mother only sleeps on the move, constantly swimming. What a mother, right!
Breathing Challenges During Sleep
Now let’s return to the most important question. How do they without breathing? Humans are unconscious breathers, that means that even when we sleep, and we are unconscious our body will automatically breathe to take air. Whales, on the other side, are conscious breathers. That means that they have to actively decide when to breathe.
Adaptations for Underwater Life
Beside voluntary respiratory system, whales have also developed other adaptations. They can hold their breath longer then other mammals, because they can inhale and hold more air. This is made possible because of their lungs, which are proportionally larger than those of humans.
Where do Whales Sleep?
So we already established that whales sleep in the oceans, underwater (close to the surface so that they can take a breath) or on water’s surface. Scientists have not yet discovered if whales have some special places that they use for sleeping, but this is very difficult to locate or discover, because ocean is quite a big place!
Factors Affecting Whale Sleep
Mostly they sleep in short periods throughout the day or while they are swimming. But the resting period also depends on their food. For example, krill migrates vertically at the approach of dusk to avoid predators like fish, but that is the best time for the baleen whales to feed on it. Ironic, isn’t it!
Unique Sleeping Needs of Whales
Unlike other mammals, whales have different sleeping needs. If us humans didn’t get enough sleep, we could eventually die, but whales are different. Sperm whales can sleep for only 7 % of the time, usually around 10 m below surface. For this time they go into a deeper sleep with less acute awareness. Beluga and gray whales sleep for 32 % to 41 % of the time, as for the humpback whale, they can only rest at the water’s surface for up to 30 min, otherwise they would lose too much of their body temperature when inactive. They also did a research where they noted a pilot whale had only 6 minutes of REM (Rapid Eyes Movement – stage of sleep associated with dreaming and memory consolidation) in a single night.
Conclusion
So there is some data about the sleeping habits of whales, but there is a lot of work that has to be done before we know everything, if ever.
