3 Animals That Never Sleep


Whether you toss and turn all night or wait all day long just to shut your eyes at the end, no one can erase the concept of sleep from their lives. The amount of sleep we get determines both our performance and our energy levels. But if we go ahead and explore the animal kingdom, this is not always the case.

The sleeping habits of different animals vary based on the nature of their habitat and their anatomy. Their sleeping habits also depend on their predators and the overall environment.

Would you believe us if we said some animals don’t sleep at all? Although we still require substantial research regarding animal sleep, we have a few animals that might fascinate you.

Three Animals That Never Sleep — And Why

1.   Bullfrogs — The All-nighters 365/365

Bullfrogs are incredibly famous for their no-sleep schedule. This fascinating creature has grabbed the attention of many researchers due to its unique characteristics. Bullfrogs are also known for their excellent preying abilities, and since their anatomy is similar to that of many other animals, they are the ideal candidate for research.

Many scientists believe that instead of sleeping, bullfrogs simply take a rest once in a while. They’ve concluded the activity as “rest” and not sleep after closely observing their respiratory system and brain activity.

These species of frogs are carnivores and feed mainly on bugs, so the bugs acted as the stimulus in most of these experiments. The scientists observed and found that bullfrogs are always alert, reacting to triggers, and ready to prey throughout the day. Another experiment that involved a painful stimulus, also known as a shock stimulus, gave the same results with no alterations in the respiratory and brain activity.

Sleeping vs. Hibernation

The lack of a difference in their “sleeping” and “waking” states makes many people wonder why bullfrogs don’t sleep like other species. However, bullfrogs are known to hibernate, so that period could be considered as sleeping to some extent.

The results of many such experiments, combined with their constant respiratory and nervous activity, have convinced the world that bullfrogs don’t need any sleep. But no matter how convincing this may seem, there is still a need for further research on the subject. As of right now, all we can say is that bullfrogs don’t go into a sleep state, but they do rest throughout the day.

2.   Jellyfish — Can They Sleep Without A Brain?

At one point in our science class, it came as a shocker when we found out that jellyfish don’t have a brain. Yes, that’s right. Jellyfish are primates, meaning they have a relatively basic neural network, with some nerves and sensors to get them going. But have you ever wondered how their bodies work — how they eat, move, sleep, and survive?

Even if we consider the most basic activities, such as sleeping, you will find that it is not as simple as it seems. This is because when you are asleep, your brain is performing most of the activities in the background, similar to when you are awake. So, one thing we know for sure is that a brain is necessary for sleeping.

Since jellyfish don’t have a developed nervous system, does this mean they don’t sleep? In the search for answers to this question, many experimental results have come to light. While many concluded that jellyfish don’t sleep, there were some uncertainties regarding the jellyfish as borderline sleepers.

Borderline Sleepers

Under controlled conditions, jellyfish were exposed to different stimuli, such as changes in the environment. The varying light and the pulses in the water all night showed a disturbance in their behavior the following day. The results of this and many such experiments were all highly inconclusive.

Some people believe that since jellyfish don’t have a nervous system, they don’t have a sleep drive either. Instead, the few nerves and sensors focus on conserving energy instead of sleeping. This would check off the inactive sleeping behavior, but there is more to it that the jellyfish don’t entirely fulfil.

The studies and experiments conducted on jellyfish didn’t declare a definite result, but we do have some evidence to go by. We know that jellyfish don’t sleep but become inactive for some time. Until that is all cleared up, it is hard to conclude if this should be considered sleeping or simply taking some rest.

3.   Dolphins — Sleeping Without Drowning

Whether you go in for a swim or watch a documentary, seeing a chirpy dolphin can always put you in a good mood. These social mammals are fun and playful, but did you know they are also one of the most intelligent animals? With a brain four to five times larger than ours, dolphins are great at social interaction, problem-solving, and even passing down information to and from one another.

Let’s see how this fascinating species tackles the sleeping problem we’re curious about. For starters, dolphins breathe through their blowhole. And since their breathing is not involuntary, they need to periodically rise to the surface, which isn’t feasible when sleeping.

Because they can’t be unconscious and breathe at the same time, dolphins never truly sleep. Sure, they rest like every other creature on the planet, but they do it in a unique fashion. The sleeping hours are divided by the left and right sides of their brains. As a result, only half of the brain sleeps at a time, while the other half manages voluntary functions. This type of behavior is referred to as unihemispheric.

Unihemispheric Sleep Pattern

Dolphins need an average of eight hours of sleep every night. As a result, one half of the brain will stay up and work for four hours while the other half is asleep. You may now be wondering what dolphins look like while they sleep. And well, the answer is that they don’t exactly look like they are sleeping.

However, dolphins are not their usual playful selves and usually remain stationary or inactive for that time. But in some cases, they may swim and wander around while sleeping. Since half of the brain is still awake, they also keep one eye open to watch for predators.

We can deduce that dolphins do not sleep. While part of them is dozing off, the other is entirely awake. This behavior makes them one of the most intriguing species on the planet.


If we dive deeper, we may uncover many other species that behave in a similar fashion. For example, some animals take periodic rests during the day, while others sleep partially; some need 20 hours of sleep, and others survive on less than a minute per day. Similarly, some keep their eyes open all night, such as snakes, while others, like insects, prefer to enjoy a cozy night of sleep.

Each species has unique patterns of behavior that help it survive. Having said that, we still need a lot more studies on animal sleeping behaviors. This will help us understand why and how animals behave the way they do. Until then, we hope you found this article informative.

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