- Whales have to think to breathe, so they remain half-awake when they sleep to know when they need to come up for air.
- Most whales only sleep for about 10 to 15 minutes at a time.
- To stay aware of their surroundings and protect themselves from predators, whales typically sleep with one eye open.
How do whales breathe while they sleep?
Whales stay half-conscious in order to sleep underwater and breathe. Unlike humans and other land mammals, whales have to think about breathing to do it. Instead of fully shutting off their brains to sleep underwater, they keep one half active! The active half of their brain is aware of how much air is in their lungs so they know when to return to the surface for more. Most mammals’ breathing, including ours, is automatic and done without thinking about it. When we sleep, we are fully unconscious.
Whales usually sleep just below the surface to easily come up for air. Many whales like to sleep vertically in the water with their head close to the surface or just poking out of the water. They simply bob up for air as they need it and then sink back down to rest some more. Whales also sleep horizontally below the surface, which is known as logging. When they sleep in this position, they often look like floating logs of wood! Some whale species also swim slowly as they rest. This helps them maintain their body heat. While they typically stay close to the surface, researchers have encountered whales sleeping at depths of 30 to 50 feet (10-15 m) below the surface.
How long do whales sleep underwater?
Most whales rest for several minutes at a time before coming up for air. Instead of sleeping for hours on end like humans, whales nap in spurts. They typically rest for 5 to 15 minutes, return to the surface for air, then sink back down and rest some more. How long a whale rests before returning to the surface depends on the species. Sperm whales tend to sleep for 10 to 15 minutes at a time, while humpback whales usually rest for 30 minutes before needing to surface. How much a whale sleeps each day in total also depends on the species. Sperm whales only spend about 7% of their day sleeping, while beluga whales and gray whales spend about ⅓ of their day sleeping.
How do whales protect themselves as they sleep?
Whales keep one eye open as they sleep to stay aware of any threats. While their brain staying half awake allows whales to come up for air, it also lets them watch for any predators or disturbances as they rest. This means that they’re not fully vulnerable as they sleep, and can easily wake up and swim away if they need to. Whales also typically sleep alongside their pod, or group of other whales they’re related to, to stay protected as they rest. While whales mostly rest with one eye open, researchers have stumbled upon sleeping whales that didn’t wake up from their presence. So, some researchers believe that whales can sleep with both of their eyes closed.
Can whales drown?
If a whale becomes fully unconscious, they can drown. It’s super important that whales stay partially awake and aware even as they sleep so they know when to come up for air and breathe. If they slept like humans, who are completely unconscious when we sleep, they would go for too long without breathing and drown. A whale drowning while sleeping is very uncommon. Their bodies are made for living in the sea, which they’ve successfully done for millions of years! Usually, whale drownings happen because one swam into shallow waters that they couldn’t get out of. The water is often high enough to still cover their blowhole, so they can’t exhale and get more air.
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