For all we know, there are around 1.2 million known animal species. The total number of animals in the world goes up to approximately 8.7 million and is continuously growing.
There are many things we don’t know about animals. It’s usually because we never think about some things although we can learn something new and maybe apply that to ourselves.
Today, we’ll talk about how animals sleep.
There are various sleeping patterns among animal species, but there are also a few strict and general rules of sleeping. Did you know for example, that SOME animals sleep upright?
Sleeping is equally as important for animals as it is for humans. Sleep provides an evolution of functions, but sleeping patterns also help create food supply and defense mechanisms.
Animals with a bigger brain need more REM sleep because sleep consolidates animal memories and learning.
Sleeping patterns evolved naturally because of all the difficulties around them. For example, animals mostly get attacked by other predators during the night while they’re sleeping.
So, in order to stay alive, they needed to build some defense mechanisms that will collaborate with sleeping patterns.
Otters are a perfect example because they sleep holding hands, wrapped together in seaweed to protect young ones, and stay afloat while sleeping.
Some animals sleep only when the whole herd is sleeping for better protection.
- Carnivores (cats, cheetahs, dogs, dolphins, lions, foxes, hyenas, little brown bats, fish-eating bats, etc.) sleep more than herbivores (cows, rabbits, bees, kakapos, rhinos, common iguanas, earthworms, etc.).
- Cathemeral species are species that can socialize with other species and live in groups. These animals sleep in short intervals two to three times a day.
- In general, animals sleep based on how much they eat because of the energy-saving and calories that move their bodies, etc.
- Giraffes and elephants that eat herbs don’t need more than 30 minutes to 3 hours per day, but they move slowly.
Which animals sleep the most during the day?
Did you know that armadillos sleep 20.4 hours every day to keep the immune system active and healthy?
Have you ever heard about an animal called a little pocket mouse?
Well, this pocket mouse needs 20.1 hours of sleep per day!
The brown bat is right behind mice, requiring 19.9 hours of sleep per day. North American opossum sleeps 18 hours per day, while python needs 18 hours as well. An owl monkey needs 17 hours of sleep per day.
Quite amazing, right!?
Prey animals sleep short rounds like 3 to 4 hours per night, and they sleep in herds for better protection. Pray, and small animals always sleep less than predators of any kind because they need to keep moving, and they can even sleep upright too.
Walruses can stay awake for 84 hours at once. After that period, they still don’t need much sleep. While they’re awake, they’ll fil up pharyngeal pouches with air, so while they’re asleep, they can be relaxed and floating at the same time.
One of the strangest ways of sleeping that Walruses commonly practice, is sleeping upside down by hanging on to an ice sheet by their teeth.
Elephants a.k.a. large to massive mammals sleep only 2 to 3 hours per day because of their plant-based diet.
This type of diet requires animals to eat 600 pounds of food in 18 hours. Elephants can sleep leaning against a tree, but they sleep in stay apparatus position – in other words sleeping while standing straight.
They do this to prevent their body from crushing their internal organs because of the huge weight.
Some species, like frogs, don’t need to sleep for months; they just close and rest their eyes.
Giraffes can sleep 30 minutes per day while horses can sleep for 2 hours. Both can just sleep in short intervals of 15 minutes, standing still while their herd is awake.
Big animals like Giraffes put themselves at great risk while sleeping on the ground because it takes too long to stand up and start running in the case of an emergency, such as if dangerous predators hit the herd.
Large animals sleep stay apparatus to prevent predators from eating them.
How do animals sleep in stay apparatus position – sleep straight up?
You may have already seen many animals sleeping while standing. These are usually horses, giraffes in zoos, cows, and elephants in zoos.
It’s easier for these animals to start running in case of danger if they’re already on their feet.
At this point, you’re probably wondering how animals do this. Is it uncomfortable for their limbs?
In reality, animals are relaxing their muscles even while sleeping upright. The only catch is that REM sleep can’t be experienced this way.
Birds sleep upright for different reasons than large mammals. They lock their legs into position while sleeping on the branch.
What about hibernation, and how does it work?
Hibernation time can be during summertime or winter months, depending on species and their purpose.
Why animals hibernate?
Well, while humans can cover their bodies with clothes and easily adjust to new seasons – many animals can’t.
Different types of animals live on different terms, so a lot of species can’t adjust to the changing weather, which is why they hibernate – saving energy in the state of coma.
What is happening inside of animal bodies at that faze?
Everything slows down: blood flow, brain activity, and heart rate. Even body temperature drops down.
It is not like sleeping, because an animal needs to wake up from sleep and eat food. In hibernation, it stacks its body with food supply to use during hibernation months.
Most of the species don’t need to urinate or eat at all during this period.
Mammals and Sleep
Mammals usually sleep like humans and have three phases of sleep –REM sleep, light sleep, and deep sleep.
Mammals can sleep for 18 hours (like armadillos and opossums) or less than 3 hours per day (like horses).
Most mammals sleep multiple times per day rather than a few hours in a row.
Primates sleep only during the one period, which is mostly at night – much like humans.
Marine Animals and Sleep
What about marine animals? How do marine mammals sleep, or do they sleep at all?
Animals that live in water, but go to the surface to breathe are called marine mammals, and they have a unihemispheric sleep.
Unihemispheric sleep is present with dolphins, seals, walruses, and manatees.
This means that this animal sleeps while half of their brain is awake because of the brain waves that are active during sleep. Their eyes are open and correspond to the awake part of the brain, and they breathe normally as well.
Dolphins sometimes just float on the surface, which is called logging. They are swimming in a circle while sleeping by using their cognition as a compass.
The most amazing part is that dolphins have high cognition while sleeping, so if they are in danger (like when people are trying to fish them), they’ll accomplish complex tasks and stay safe without waking up.
Indus dolphins sleep in small spurts of microsleep. This means that they sleep only a few seconds repeatedly, which then accumulates to a maximum of 7 hours of sleep. This allows them to swim very long distances.
Newborn orca whales go without any sleep for the first few weeks as they’re learning how to live.
Who has the weirdest sleeping position?
It has to be a sperm whale among marine mammals because it sleeps straight up.
Sperm whales will put the tip of the top on the surface in a vertical line and sleep upright the whole time. Interestingly, it’s the only way they can rest their bodies.
Birds and Sleep
Birds can’t sleep during migration – at least not like when they land.
The migration period is different for all species. With that said, note that the maximum known migration of the Alpine swift is 200 days long.
Migratory birds – swift, seabird, songbird, and sandpipes sleep unihemispherically because they need to keep functional during long flights.
The brainwaves of birds can function for 1.850 miles without stopping during migration time. In other words, birds can fly and sleep at the same time, moving automatically.
REM sleep when migrating is terrible for the flock. However, the good side is that birds wake up during flight in case they reach REM sleep.
Reptiles and Sleep
Reptiles are bizarre animals. Did you know that 80 seconds of sleep for lizards is like 700 to 100 minutes of sleep for humans?
Sleep has three stages known as light, REM, and deep sleeping because of different brainwaves cycle. It goes to 350 cycles per night for reptiles, while only five humans in the whole world experienced all stages with a full capacity of 350 cycles.
Most species have eyelids that they use when sleeping. It’s to protect the eye and keep it wet during sleep. However, reptiles don’t have this nether.
Snakes have transparent scales called spectacles that are the same as eyelids for mammals. Because spectacles are all over the snake’s body, we can never tell when the snake is actually sleeping. This mechanism is an excellent shield for snakes.
Snakes can be still for several hours while waiting for their pray. However, staying still is often risky because it can make snakes fall asleep.
Fish and Sleep
When the fish sleeps, it floats and looks like it’s daydreaming.
When asleep, fish floats at the bottom, appearing motionless. They sometimes flick their fin just to stay in one position and keep the body steady.
Their sleeping pattern depends on their environment requiring constant ventilation of their gills.
Sharks never sleep with eyes closed, not even during REM. Their eyes are always open!
Zebrafish is the only fish in the world that can experience insomnia and die because of it.
Animals and Sleep Deprivation
Sleep deprivation can cause death for some animals if it lasts a long time.
Sleep deprivation a.k.a. sleeplessness is a chronic disorder of sleep, and it has deadly effects for cognitive functions and can cause brain damage.
Long term problem with sleep deprivation has caused death in lab animals.
Mammals, rats, and some types of insects can die due to a long period of sleep deprivation.
It’s well-known that predators have issues when it comes to navigating while sleeping, but they aren’t the only ones with this problem.
Sea otters share this problem too. They have a strange and uncommon “holding hands” pattern.
They lie on their backs at the surface of the water, holding hands to prevent floating apart while sleeping. In most cases, they sleep in groups surrounded by seaweed forest that keeps them protected.
What is the deal with albatrosses?
Albatross is a sea bird that dedicates its life to hunting. They are the best hunters among see birds.
For this reason, their lifestyle doesn’t leave much time for sleeping. Albatross can multitask all the time, which has them sleeping while flying.
It’s a common thing among migrant birds, although albatross sleep a bit differently.
Albatrosses only sleep while flying!
They don’t practice any other way of sleeping. In other words, sleeping in combination with some napping can actually be very deadly for albatross.
Also, did you know that ducks sleep with one eye open?
Ducks have a very strange technique called a clique.
When it’s time to hit the hay, they will queue up in a row. The last duck in the line focuses one eye facing away from the whole group, keeping it open. This way, the duck watches out for dangerous predators with one eye, while also sleeping at the same time.
The whole row is safe while they’re asleep, thanks to this system.
Ducks rotate their position every few weeks so that all ducks get to be on duty.
Meerkats spend nights sleeping in burrows – the underground sleeping quarters with a very complex tunnel system that only Meerkats from that burrow know.
Their burrow is created for 40 members, with only one alpha male and female. This is called a community.
The gang leader sleeps at the bottom of the pile while other members cover and protect it, keeping the entire group warm and safe.
This is something that a lot of animals do. Puppies, bats, and squirrels like to huddle up and sleep like this as well, protecting the Alpha member.
Now let’s spend some time on the animals that we didn’t know sleep at all. One such animal is the desert snail.
Desert snails sleep for years in a row!
This animal appears like it doesn’t need sleep because of the slow lifestyle. But it does. This slimy animal can sleep for several years a row once they fell asleep.
How did we found out that snails sleep this much?
One time the British Museum found a very rare Egyptian desert snail they assumed to be dead. The museum affixed it to the identification card and exposed it for everybody to see.
Four years after they moved the card to some other place, they saw something strange. What they saw were slime marks on the card.
Once the staff removed the shell, they found a shocking surprise.
The animal crawled out!
That’s an interesting story on how we learned that these snails could sleep for a long time.
Frogs can stay awake for months without any damage to their body.
They survive the winter by hibernation thanks to their animal antifreeze. In other words, the ice crystal may form under the skin and in the body cavities, but a high concentration of glucose prevents it from freezing.
Some weird frog types are capable of freezing just to stay alive during wintertime. A frozen frog can stay alive because it stops breathing, although the heart keeps beating.
Frogs can stay like that until the springtime. Springtime raises body temperature, allowing frogs to come back to life as if nothing happened at all.
Bullfrogs are strange because they sleep with one eye open, which allows them to be prepared. When danger actually happens, they can’t move their bodies so quickly, so they start producing painful stimuli to wake up and start running away from predators.
Apes sleep just like humans!
Animals like apes, gorillas, orangutans, chimpanzees, etc. sleep just like humans. They curl up and even hug others.
They make beds using platforms that allow them to stay away from predators.
That’s not all since many other animals sleep in fascinating ways.
Let’s check some animals that sleep very little or not at all.
A male impala rarely ever sleeps if it’s the only male in the herd. He’s a protector, and as you know, protectors never sleep.
Orca calves don’t sleep at all in the few first years because they take care of their parents. When parents sleep, orca calves circle to protect them from other predators. When parents are awake, they swim to the next destination.
Deer sleep only 3 hours maximum. When it’s in danger, it can stay awake for days without sleeping at all.
Ants sleep! Ants actually sleep. They rest all the time when doing some hard work. They only stop for a minute or two to sleep and move on with work.
Meanwhile, the queen of ants sleeps all the time.
The queen needs to sleep for at least 9 hours a row!
In case of danger, other ants move the queen without waking her.
Koalas need to sleep 22 hours per day, but they rarely ever sleep for that long. If they’re not sleeping, they’re resting. They’re extremely lazy and won’t move unless they want or have to.
The reason why Koalas have so much food in Zoos is that food is the only thing that keeps them from falling asleep.
When high temperatures hit, Lemurs sleep 16 hours per day because their bodies can’t survive long at these high temperatures. Sleeping is the only way to stop the body functions or keep them on a minimum level.
Sloths are known to be very slow, but they can be fast when in danger. The reason why they can do that is that they sleep twenty hours a day. This allows them to conserve energy like no other animal.
Octopuses are capable of changing color while they’re in REM sleep.
An octopus doesn’t have a spine, which means it’s an invertebrate animal. These are very intelligent animals that enjoy REM sleep the most. They focus while sleeping, which allows them to go through all three stages of sleep.
Octopuses dream just like humans while they’re in the REM stage. They enjoy the dreaming part, so they change colors according to the environment to stay in the REM sleep as long as they can. They twitch every 15 minutes for some added protection.
You’re probably wondering what happens when animals dream.
Dreams are not only for joy and energy. Dreams are the reason why animals have better memory and can learn better.
The most common animals that can dream are cats and dogs. We can actually see that cats move while sleeping. Dogs usually bark and make funny noises while dreaming.
During the stage of REM sleeping, the brain of an animal behaves the same as when awake.
Did you know that intelligent animals and all mammals can dream more than humans?
While humans can stay in the REM stage a few minutes up to one hour, animals can be in the REM stage all the time while sleeping. So REM faze can be 5 hours non-stop.
Dolphins are the only intelligent animals that can’t experience REM sleeping. In most cases, dolphins may dream for a very few minutes of their entire lives.
Dolphins that experienced the REM stage can easily become depressed.
REM atonia is the stage in which we’re paralyzed while dreaming in the REM stage. This mostly appears with humans because animals need to stay alert for predators.
So, animals have a different structure of the brain because humans can live while sleeping without danger to themselves even when doctors remove a part of the brainstem.
Because some types of birds can experience the REM stage, they can learn tasks, do tasks, and memorize things.
That is why we have speaking parrots for pets.
Scientists learned that you could “make” zebra do things if you teach it a few signals, matching them with some parts of a song while they’re in REM sleep.
So, if a zebra is in REM sleep and you play the verse of a song, hitting it to run, it’s going to run immediately after hearing the verse even when it’s awake.
What happens with insects?
Insects stay mysterious on this topic. We know that some types are capable of sleeping while we don’t know anything about others.
Most likely, insects can sleep, but they don’t have eyelids. This is what confuses most people.
Insects have central nervous systems and circadian rhythms (essential parts that are needed for sleep), so they can stop moving when they want to relax. It makes sense that they sleep but nobody can know for sure.
For example, cockroaches hit the torpor state that is similar to sleep, although this isn’t really sleeping.
Fruit flies rest for 2.5 hours a day without moving. They just twitch without any sensory stimuli.
Fruit flies that don’t rest for 2.5 hours will rest 2.5 hours the next day. However, the next day, they will sleep five hours to make up the time they lost yesterday.
Interestingly, fruit flies die if they don’t sleep for a few days in a row.
Honeybees and bees, in general, can’t perform any tasks when they’re rest-deprived. They can die if they don’t control their sleeping hours.
We can all agree that animals are strange creatures. There are so many things that we still don’t know about animals and how they sleep. Some of them can’t live without sleeping long while others can. Their sleeping patterns and cycles differ, depending on their lifestyles.
It’s interesting how some animals sleep to stay alive, while others choose not to sleep in order to stay alive. This just shows how sleep has a different meaning for different species.