4 Animals That Never Sleep

Bullfrogs never sleep

If we ask you how long you can stay up without watching upon the slightest bit of sleep, what would you say? Maybe you can go a day without sleep, and if you’re overly enthusiastic about it, you may be able to go a day and a half, but what next? The exhaustion, the need to hit the bed and fall into a deep slumber sets in, and no matter when you do catch on some zzz’s to wake up primed to perform.

Animals, too, sleep at a point, either being diurnal or nocturnal, but the post says ‘4 animals that don’t sleep at all?’ Does that mean they’ve never felt tired, or maybe they are the characters from TVD who never really feel like sleeping at all? 

Now, let’s talk a little about science: some animals can go without sleep, but the catch is they can’t go without rest (most of them). Our stereotypical definition of sleep is synonymous to resting with limited sensory activity and reduced muscular actions while also limiting our consciousness. However, for animals that don’t sleep and stay completely alert at all times, they do rest – in a sense of immobility or lowering of their metabolic rate.

So, now that you know how most animals that don’t sleep function, let us dive deeper and understand why humans and animals sleep in the first place.

Why do Animals (even Humans) need sleep?

Balances Hunger Cues

Every animal that hunts, hunts to feed itself and survive in its natural environment. But, what if we tell you sleeping is associated with balancing hunger cues? One primary reason why animals take rest and sleep is because their body is designed to balance hunger and appetite while they are asleep.

How? Sleep regulates the hormones responsible for the appetite – it is natural to find your pet or any wild animal feel hungry and nutritionally affected due to chronic lack of sleep. 

Sloths being the slowest animals in the world, sleep away a significant portion of their time because they do not eat much, and staying active would demand energy, which in turn would demand food. This leaves them with one option – sleep and sluggish movements. If you analyze closely, this is somewhat the case with Koalas too! 

Not just animals, even humans, are deeply affected by hunger cues if they go without sleep for too long or suffer from insomnia. Most insomniac or hard-sleepers usually experience weight gain, the reason being hunger and craving for junk. 

Boosts Immune Function

Have you ever realized how drained you feel if you pull an all-nighter? Yes, all of us have been there! But, only if you go a little longer without sleep, the feeling of nausea and sickness sets in apart from the general exhaustion that shrouds the body. Getting inadequate sleep in the long run only makes us (and animals) vulnerable to diseases and frequent sickness.

Animals understand the importance of resetting and repairing their body, especially because the money equation or the societal pressure to be superior doesn’t come in between. Proper sleep doesn’t just avoid their susceptibility to diseases but also strengthens their immune system, helping them survive the harsh natural environments that they consider their habitat. 

Reduces risk of Diseases and Infection

Aforementioned, sleep betters the immune system, which brings us to the next fact that sleeping reduces the risk of diseases. Most animals in the wild are prone to catching diseases, commonly because of the exposure to germs and viruses on a level that is manifold in comparison to humans. 

Thus, sleep induces the immune system to release cytokines that are protective proteins that help against infection and inflammation. Lack of sleep over a stretched period of time leads to shorter life expectancy and poor health, so we may have hospitals, but the animals have to resort to healthy living, and one important criterion to fulfill that is sleep.

Improves Coordination and Productivity

Sleep, to be succinct, increases mental functionality, which leads to better coordination and when it comes to animals, staying in the right mind becomes important, especially when there’s a food chain, and there’s always somebody at the top (unless they are at the apex). 

Apart from proper coordination, sleep also leads to productivity, and it becomes even crucial when they have to search for food in the nooks and the corners or kill one for that fact. In the jungle, it’s a simple game: either you fight for it, or you die. Thus, good sleep is equivalent to getting enough nutrition when it comes to animals.


4 Animals that Never Sleep 


Bullfrogs never sleep

BullFrogs, in general, do not fulfill the threshold or electrographic criterion of sleep, and hence they are amongst the list of animals that don’t sleep. Though the BullFrogs are amazingly immobile and clearly at rest for long periods, they remain completely alert and react to stimuli with the same speed and intensity at any phase of the rest-activity cycle. The brain waves of the BullFrogs are of low voltage and fast electrical activity, which is associated with alertness during the rest phase in them and many other animals.

A random question? Do bullfrogs look like bulls? No! Then what about the name? The bullfrogs make bellowing sounds similar to a bull while they mate and thus, the name! The BullFrogs have brown eyes with horizontal almond-shaped pupils, and their sturdy forelegs and strong limbs can allow them to jump distances ten times of their body.

BullFrogs mainly inhabit water bodies such as swamps, ponds, and lakes; however, they are also found in man-made habitats, which include pools, canals, ditches, and culverts. Bullfrogs are native to the United States and Canada; BullFrogs can also be found in China, Japan, Southeast Asia, and Europe, where they are a staple source of food.



do butterflies sleep

If you’ve ever seen a butterfly hanging down from a leaf, immobile, you must be wondering if it’s asleep. However, butterflies, in the definition of ‘human sleep,’ don’t sleep at all. They enter a quiescent state where they lie dormant or inactive; however, even in their nocturnal state, they are completely capable of flying off immediately if disturbed. 

Although the human definition of sleep is ‘eyes closed; deep slumber by shutting off most of the neural connection to the surrounding environment’, butterflies’ sleep can be defined as ‘entering a low metabolic state that helps them digest the day’s feed, produce eggs/sperm and rest without going completely dormant’. 


Sea Urchins

Do Sea Urchins sleep

Sea Urchins have a rudimentary nervous system with a simple layout that primarily includes a large nerve ring that encircles the mouth. Since they lack almost all sense organs, let alone a brain, it becomes obvious why sea urchins do not sleep.

While you’re at a beach and see an immobile sea urchin that doesn’t show any physical activity, wait till you touch it (but don’t really). Sea urchins are often found in a state of rest, but they haven’t been known to sleep, the primary reason being the absence of a brain, and eyes, of course! 

Their body mechanisms operate on stimuli, and they are extremely sensitive to light and seek to hide in crevices or under other objects. The most visible sign of life is the spine in the Sea Urchins is that, though the sea urchins appear to be incapable of moving, they move freely and slowly, crawling with their tube-like feet and sometimes pushing themselves with their spines. These slow-moving spike balls mainly feed on algae and some other slow-moving or sessile sea creatures.

Now that we just said sea urchins don’t sleep because they have no brain, does that mean jellyfish don’t sleep too? To your surprise, it has been recently found that jellies do sleep, or atleast enter a sleep-like stage, similar to humans. In a research conducted by three students Ravi Nath, Claire Bedbrook, and Michael Abrams, introduction of melatonin to the jellyfish knocked the creature out, and it was sleeping just like any regular human does. 

This finding could waive the scientific explanation that sleep is an emergent property of neurons – in non-nerd terms, sleep is a property of the brain, and the nerve cells connected to it. Thus, if you ever go to an underwater museum and see a jelly hanging upside down, completely dormant, it’s sleeping! 

How? We are not so sure of that yet!


Baby Dolphins

Do Baby Dolphins sleep

Baby Dolphins are amazing animals with a unique sleeping style; the dolphins have the special ability to put one-half of their brains to sleep at a time. The dolphins aren’t still while they put one half of their brain to sleep; rather, they swim around, and for this reason, the dolphins don’t fit into the category or the initial definition of non-sleeper.

But, wait, Newborn Dolphins do!

When new dolphins are born, they don’t sleep for more than one month, and the mothers also stay awake to keep an eye on their offspring. There is always movement both in the mother and the baby. The mothers set a frenetic pace by always coursing ahead of their offspring. 

The dolphin challenges the idea that maximum rest and sleep after birth helps in the development and healthy growth; the stress hormone cortisol is normal in the newborn dolphins and their mothers who stay awake for a month, which clearly means that they are not affected by the fact that the offspring continuously have to keep swimming to the surface and back again while the mothers keep a watch on them at all times (much like Heimdall, aye?)


4 Animals that Sleep a lot 


Sleeping Koala

On average, a Koala can sleep for up to 18 hours a day. There is a very popular myth that Koalas get high or drugged on eucalyptus leaves, and hence they sleep a lot. However, the primary reason is their diet. Koalas live in a habitat where eucalyptus leaves make an easy and abundant meal. 

Koalas have a special enzyme called cytochrome, which detoxifies the toxins present in the eucalyptus leaves and extract any amount of calories they can from the leaves. Since eucalyptus leaves are low in calories and energy while also being highly fibrous and toxic, Koalas need long sleep to conserve energy to digest the leaves.

If the leaves go undigested, they may poison the koala. If you think Koalas in the pictures on the Internet are deep in slumber, we’ll let you in on a secret- Koalas are super active and alert while they are asleep; they can move around quickly whenever they sense danger in the surrounding.



sleeping cat

Cats were genetically programmed to sleep! A cat, on average, can sleep for up to fifteen to twenty-four hours in a day. Since cats are crepuscular who are most active between dusk and dawn, they have the physiology of a predator that makes them sleep during the day to conserve energy to chase and hunt mainly at night. 

Domesticated cats also retain the wild steak and are often found creeping about in the shadows, without a whisper of warning, punching on outdoor prey or tackling a catnip toy, so that all the conserved energy is utilized for running, punching, climbing, and stalking. Cats are highly social and adaptable; they can aptly adjust their sleeping habits and their sleeping patterns to spend more time with their beloved masters.


Hairy Armadillo

Hairy Armadillo
“This Photo” by Terry Robinson is licensed under CC BY-SA 4.0

A Hairy Armadillo sleeps for up to 18 hours a day on average in their underground burrows. Armadillos are nocturnal animals who perform vigorous activities, including foraging, eating, burrowing, and mating at night. 

Armadillo (meaning ‘little armored one’ in Spanish) are solitary animals who don’t share their burrows with other Armadillos, but they do share their burrows with tortoises, snakes, and rats. They have a very low natural body temperature, and they huddle together to themselves warmer, only meeting up with other Armadillos to mate.

Armadillos’ sleep schedule depends on the season and temperature of their habitat, and they switch between nocturnality and diurnality during summer and winter, respectively, so that they don’t overheat during summer and stay warm during winter. 



sloth on tree

The sloths are so sedentary that algae grows on their furry coat, and the greenish tint is a useful camouflage in the trees of the American rainforest. The sloths are easily identified due to their long, prominent claws that give them a powerful grip to hold the branches of the trees for a long time. 

The word Sloth in many languages translates as some version of lazy, but this myth is all that it is. Sloths aren’t lazy, and their slowness is a survival skill. The sloths are slow because they have leafy, low calorie, and slow metabolism, so in order to conserve energy, the sloths move slowly and sleep a lot. Sloths sleep for up to 15 to 20 hours on average, and even if they are awake, they remain motionless; at night, they eat leaves and fruit, all of their water needs are fulfilled by juicy plants.



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