A Whale’s Sleep
The world’s largest mammal is magnificent, beautiful, and interesting. The more you learn about them, the more fascinating they are.
Whales are mammals and need air to absorb oxygen. They may live underwater but come up to the surface to breathe. This may have you wonder how and where whales sleep.
Imagine diving into the ocean and coming across a pod of sperm whales floating upright and immobile in the open water. What one wouldn’t give to witness such a surreal sight. If you do come across such a sight, know that you have stumbled upon cetaceans sleeping. February is an excellent time to learn about whales in Sitka, Alaska, as they migrate there, usually with their infants, to feed in the nutrient-rich waters of Alaska.
How Do Whales Sleep?
Like all mammals, dolphins and whales need sleep to survive, but their manner of sleeping is very different from humans and other mammals.
Humans and other terrestrial mammals are unconscious sleepers, which means that breathing to inhale air is an involuntary movement our body does when we sleep. Whereas dolphins and whales are conscious breathers, which means they have to think before they breathe. They have to stay attentive and make sure their blowhole is at the surface of the water when taking a breath, which can seem complicated as they spend almost all their time underwater.
This conscious breathing process stops the whales from passing out from lack of oxygen or drowning.
Fortunately, dolphins and whales have evolved to live their lives underwater. While all cetaceans sleep, different species appear to have varied sleeping methods and requirements. The amount of sleep they get and how they sleep differ widely between species, and because studying their sleep in the wild is challenging; different information has been recorded.
Common Sleeping Positions
There are a few common sleeping positions; sleeping while swimming next to another animal or in a pod, resting in the water vertically or horizontally, or floating on the surface (also known as logging). Humpback whales are most commonly found motionless, resting on the surface for up to 30-minute intervals. If they sleep longer than this, they risk losing too much body heat when they are sedentary.
One Eye Open During Sleep.
When whales sleep, they allow only one hemisphere of their brain to sleep at a time, while the other half of the brain, along with the opposite eye, remains alert. This helps them remember to breathe when they reach the surface, remain alert of potential predators or obstacles, and keep track of their group members. After approximately two hours, the whale repeats this process on the other half of the brain. This process of sleeping is also called “catnapping.”
Larger cetaceans like Sperm Whales are known to hold their breath longer than Orcas and remain motionless underwater while they sleep. Sperm whales have a more extensive respiratory system which increases carbon dioxide tolerance and allows them to hold more air with each breath.
A few years ago, scientists accidentally stumbled upon a pod of sperm whales swaying close to the surface of the water, vertically. The creatures were so engrossed in a state known as “drift diving” that they didn’t even see the approaching boat.
Baby whales rest, feed, and sleep as their mothers swim in her slipstream, dragging them along. This is known as echelon swimming. The mother will also sleep on the move at these times. In fact, for the first several weeks of a newborn’s life, she cannot stop swimming.
It’s like being stuck behind a semi on the highway. Because of the aerodynamics, it creates a suction that pushes you along.
The calf will begin to sink if she does so for an extended period of time, as it was not born with enough blubber or body fat to float freely.
Because the young ones can’t swim large distances yet, their mother is training and assisting them in increasing their muscle and fat reserves. Remember that if a calf becomes weak from swimming too much, they risk endangering themselves and the pod by alerting predators.
While there is still much to learn about whales and their sleeping patterns, including whether they dream or not, we think whales are the most incredible ocean animal with a lot of mystery that surrounds them.