Sleeping Giants: How Do Whales Sleep?

how do whales sleep

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Whales are some of the largest and most majestic animals to ever roam planet earth, and with over 40 different species they vary in behaviors, diets, and sleep patterns.

Their size and vocalizations have fascinated humans for centuries, and one question that often comes up when discussing them is how do whales sleep?

There’s a lot to get through when discussing this topic, so today we’re going to go through everything you need to know about how whales sleep, why they sleep, and if all whales sleep, and more!

If you don’t want to read the full post (which you should!), I’ll summarize it quickly.

Whales sleep by shutting down one half of their brain at a time, allowing the other to remain active and alert in case of any threats.

Let’s take a closer look…

How Do Whales Sleep?

Whales are marine mammals, which means they have lungs and a requirement for air to breathe, just like we humans.

But living in the ocean means that they’re unable to just take a breath of air whenever they please, and instead they must return to the surface to breathe.

Unlike sharks and fish, whales don’t have gills so they’ve had to adapt to sleeping in the water whilst remaining on the lookout for predators.

To do this, whales don’t shut down all of their brains when sleeping as humans do, instead, they shut down one half of their brain at a time whilst the other remains active and alert.

This allows them to breathe, look out for threats, and get some shuteye all at the same time which is vital to their survival.

It’s known as unihemispheric slow-wave sleep and other mammals such as dolphins, sea lions, and seals do this too.

how do whales sleep
Photo by Elianne Dipp

Whales sleep near the surface so that they can breathe when they need to, and some species such as sperm whales even sleep vertically.

This allows them to use the sunlight as orientation and replenish their oxygen supplies when needed, as well as look out for any threats.

One of the challenges whales face when sleeping is that they need to retain control of their blowhole, meaning they are unable to enter a deep sleep as many terrestrial animals do.

For this reason, many whales will take short naps throughout the day to minimize the risk of being attacked whilst sleeping.

How Do Whales Breathe While Sleeping?

As mentioned, whales still need to breathe while they are sleeping, so they choose to sleep near the surface so they can surface for air when needed.

Whales are conscious breathers, meaning it’s not an automatic behavior like it is for us humans.

Some whales have larger lungs than others, for example, sperm whales are deep divers and have a large lung capacity, so they will hold their breath for as long as 90 minutes whilst sleeping.

This means they don’t need to surface as much for air and can focus on getting the crucial sleep they need to survive.

Similarly, blue whales are able to hold their breath for around 1 hour, but other smaller species may be required to breathe every 15 minutes or so.

When whales do need to breathe, they simply open their blowhole and exhale old air before then inhaling fresh clean air. This replenishes their oxygen and buys them more time to sleep.

When sleeping, whales typically breathe less than when they are awake, but the frequency of their breathing will depend on the species as well as their lung capacity.

They’ve adapted to breathing like this over millions of years and are very much are masters of conscious breathing.

How Long Do Whales Sleep?

Whilst it’s known that whales do sleep, the length of time they sleep is not so well documented and varies depending on the species.

Most whale species sleep for between five and seven hours per day, but that may be achieved by multiple naps during the day and night or long stretches of restful sleep.

Smaller whale species tend to nap more, whereas larger species like humpbacks and blue whales do engage in long deep sleep.

The sleeping behavior of whales is not well understood by science due to how rare it is to find these animals taking a snooze.

It’s also difficult to tell if a whale is actually sleeping or if they are simply resting near the surface and just breathing.

Further research is needed to gain clarity on just how long each whale species sleeps, so hopefully, we learn more about this in the near future.

Why Do Whales Sleep?

Just like us, whales need to sleep to rest and recharge their body and mind, it’s an important bodily function that allows them to stay mentally sharp.

Whilst the sleep patterns of whales may vary depending on the species, sleep is just important to whales as it is for us, so it’s non-negotiable.

It’s also thought that sleep plays a role in the social behavior and communication of some whale species.

For example, humpbacks have been observed engaging in synchronized singing during the breeding season and it’s thought that sleep plays a role in this.

The reason being that sleep plays an important role in learning and memory for many animals, so getting enough sleep allows them to better coordinate their singing with other members.

It’s also thought that sleep plays a role in regulating hormones and physiological processes that are involved in courtship and mating.

So whilst sleep is important to rest and recover, it’s thought to play a role in other functions in many species of whales.

Do All Whales Sleep?

Yes, all whales and dolphins do sleep. In fact, almost all animals in the animal kingdom require sleep to maintain a healthy lifestyle.

Different species have different sleep patterns and the duration of sleep they get may vary, but sleep is crucial to the survival of almost all animals.

how do whales sleep
Photo by Pixabay

I don’t know about you, but if I don’t get my eight hours I’m much more grumpy than usual, and it’s likely the same for whales too!

Wrapping Up

In closing, whales sleep by shutting down one half of their brain at a time so that the other half can remain active and on the lookout for threats.

Vessel strikes, predators, and fishing nets are all potential threats to a sleeping whale, so it’s important for them to remain aware even whilst getting some shut-eye.

Sleeping is a vital process for almost all animals in nature, including whales.

Whilst there’s still a lot to learn about how whales sleep and the length of time and reasons for doing so, we’re learning more every year about these magnificent marine mammals.

Thanks for taking the time to learn more about how whales sleep today and I hope you’ve enjoyed reading this post.

See you next time!