Animals And Sleep: Ultimate Guide

Discover how animals rest peacefully.
Animals And Sleep: Ultimate Guide
Tom Greenspan
December 21, 2022

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Sleep is as important for animals as it is for humans, as it replenishes the glycogen levels in the brain, which proves important for survival. 

However, sleeping habits and patterns vary significantly between different animal species. Some animals require more sleep than others, and many use unique techniques to ensure they get enough of it. 

In this guide, we’ll be looking at the different sleeping habits and techniques of animals in detail, so let’s get started!

Sleep Habits Of Animals

The sleep patterns and habits of animals usually depend upon food availability, safety concerns, and size. Large animals generally require more rapid eye movement or REM sleep, which is crucial for memory and brain development. 

Additionally, many animals, such as otters, have evolved their sleep habits to ensure their safety. These mammals wrap their young and themselves in seaweed and hold hands while sleeping to avoid sinking and protect themselves from danger. 

Other animals, like sheep or cows, sleep in herds, where the chances of getting attacked by predators are lower.

This shows that the sleeping patterns of many species have been influenced by predation and survival instincts. But the availability of food and feeding habits also determine how much time animals spend sleeping. 

Carnivores tend to spend more time sleeping than herbivores. For instance, animals like lions have short sleep cycles both during the day and at night, so they can hunt for food depending on its availability. In contrast, species that rely on food with a lower calorific value spend more time awake searching for enough food to sustain them.

That is why herbivores such as elephants, horses, and giraffes sleep as little as a few hours or even just 30 minutes. However, there are a few exceptions to this, like the Koalas whose main diet is eucalyptus leaves, which do not provide much nutrition. Despite that, these mammals spend around 15 hours per day sleeping and spend the rest of the time feeding. 

Animals That Spend The Maximum Time Sleeping 

It is a common misconception that sloths top the list of animals that spend the most time sleeping. They spend around 14 hours a day sleeping, which is the same as dogs. 

Here are some animals that spend the maximum time sleeping:

  • Large hairy armadillo - sleeps for 20.4 hours a day
  • Little pocket mouse - 20.1 hours a day
  • Brown bat - 19.9 hours
  • North American opossum - 18 hours
  • Python - 18 hours
  • Owl monkey - 17 hours

Animals like sheep, deer, and similar animals sleep only around three to four hours per day and often sleep in a herd. This is true for most smaller and prey species but not for everyone.

Animals With Unique Sleeping Habits

1. Walruses

Some animals sleep differently than others, like walruses, who are both prey and predator. They are large in size but do not spend too much time sleeping. They can remain awake for up to 84 hours at a time and use special sleeping techniques when they go to sleep.

A common technique that walruses use is to grab onto the ice sheets below them to prevent sinking into the water while sleeping. Or, they can fill air into their pharyngeal pouches to keep afloat. Interestingly, walruses can even sleep standing up when required.

2. Elephants

Elephants, despite having a large size, need just two to four hours of REM sleep a day. Being herbivores, they survive only on plants, which requires them to spend most of the day feeding. 

When elephants need to sleep, they lean against a termite mound or tree and sleep standing up. They usually do not sleep on their side for more than 30 minutes at a time, or their body weight can crush their internal organs.

3. Giraffes    

Giraffes spend just 30 minutes sleeping each day, and they generally sleep standing up. This helps them move quickly in case of predator attacks. However, they may sometimes rest while sitting down, placing their neck on their backs.

4. Horses

Like elephants, horses sleep standing up and in intervals of 15 minutes for as little as two hours. Being large animals, horses cannot spend much time lying down as that will restrict the blood flow to various organs. They only lie down for REM sleep and can keep their eyes open while sleeping.

5. Frogs

Some smaller prey species, like certain frogs, do not need to sleep for several months at a time. They simply rest their eyes during the colder months while their vital organs continue functioning thanks to the glucose present in their bodies. When spring arrives, they become active again.

How Can Some Animals Sleep In A Standing Position? 

The sleeping habits of some animals, like giraffes, horses, elephants, and cows, have evolved to allow them to protect themselves from predator attacks. These animals can lock their legs without requiring any muscular effort and, thus, sleep without needing to lie down. 

However, when animals sleep standing up, they cannot experience REM sleep, which is important for rest. That is why such animals also occasionally lie down for deep sleep. 

Many birds also sleep in a standing position, but not as a protective measure against predators. They can clamp the tendons of their legs on branches and sleep while standing up when they do not find any comfortable resting place to lie down.

Hibernation Vs. Sleep

Certain animal species can go into a state of inactivity during winter or summer months. This state of inactivity is called hibernation, when it occurs during winter, and aestivation, when it happens during summer. But animals like the elegant fat-tailed mouse opossum and the American badger enter into such states daily. 

At what time an animal enters into hibernation or aestivation usually depends on temperature signals, the available food supply, and the day length. As the animal enters into such a state, its brain activity and heart slow down, with a drop in the blood flow and core body temperature. 

Hibernation is different from sleep since it is a technique that allows animals to survive for long periods without needing to eat or excrete. It is a survival tactic for times when food availability is limited. Animals like bears wake from hibernation when it is time to give birth and return to hibernation soon after. 

The Sleeping Habits Of Mammals

The sleeping habits of most mammals are very similar to that of humans, and their sleep can be divided into REM sleep, deep sleep, and light sleep. However, the time for which different mammals sleep can vary considerably. 

While animals like giraffes and horses only require around two to three hours of sleep in a day, other mammals like opossums and armadillos sleep for up to 18 hours. Primates, including humans, sleep only during a specific period of the day.

But unlike humans, many mammals sleep in short intervals multiple times a day. Diurnal animals mostly sleep at night, while nocturnal animals sleep during the day. Some mammals, like monkeys, prefer to sleep while sitting upright so that they can move quickly if attacked.

In contrast, great apes, such as bonobos, gorillas, orangutans, and chimpanzees, create nesting platforms in trees where they lie down to sleep. These platforms provide such mammals with better sleep quality and protect them from insects and predators. They also allow them to experience better REM sleep, which aids in developing their cognitive abilities. 

Sleep Techniques Of Marine Animals

Marine mammals include seals, porpoises, orcas, whales, and dolphins, which live in water but come to the surface to breathe. These animals sleep in just one brain hemisphere at a time, a technique called unihemispheric sleep. So, when animals like whales and dolphins sleep, one hemisphere of the brain remains awake. 

This allows such animals to breathe, move, and even see through one eye. Some dolphins experience logging, which is a behavior where they float on the surface while sleeping. Others might swim in a circle while asleep, indicating that cognitive abilities are reduced. However, in some cases, dolphins can be extremely vigilant when asleep.

Blind Indus dolphins use a different technique by spending just a few seconds asleep at one time, which adds up to a total of seven hours. Then there are newly born orcas, which, along with their mothers, can spend weeks without sleeping. 

Similarly, sperm whales sleep in an upright position instead of utilizing unihemispheric sleep. 

Sleep Habits Of Birds

Birds need to undertake long migrations every year without breaks, and these migrations can often take months. For instance, it takes alpine swifts 200 days to complete their yearly migration. To do so, many bird species, especially migratory ones, such as sandpipers, seabirds, songbirds, and swifts, can undertake unihemispheric sleep like marine mammals.

Some birds, like frigatebirds, remain awake while migrating during the day but experience slow wave sleep that lasts for a few minutes at a time when flying at night. They can even enjoy REM sleep for a few minutes without experiencing flight disruptions. 

Such birds sleep for less than an hour while migrating but up to 12 hours a day when they reach land. This may indicate that they suffer from sleep deprivation during migration, while other birds, like Swainson’s Thrushes, can take power naps to catch up on lost sleep. 

Then there are those birds that use unihemispheric sleep to protect themselves from predators. Ducks are an excellent example of this, as they sleep in a row, and ducks on both ends keep one eye open to detect approaching threats.

How Do Reptiles Sleep?

It was believed that only mammals and birds could experience true sleep because they had different types of brain activity. The reason was that the part of the brain responsible for sleep is present in the cerebrum, which is missing in reptiles. 

But it has now been proven that lizards, snakes, and other creatures sleep in a similar manner. The difference often lies in how long the sleep cycle lasts; as in the case of lizards, it lasts for about 80 seconds. However, they can go through 350 cycles in a night.

Some animals, like the Australian bearded dragon, experience slow wave brain activity in the anterior dorsal ventricular ridge, while it occurs in the hippocampus in mammals. Most animals sleep with their eyelids shut since it protects the eyes, but snakes have transparent scales called spectacles over the eyes instead of eyelids. 

How Do Fish Sleep?  

When fish sleep, they become motionless and can be found near the bottom of their habitat. Their sleep pattern depends on their activity level and environment. Some fish, like sharks, need to keep swimming to keep their gills ventilated so they do not experience REM sleep.

Others, like the zebrafish, are known to show symptoms of insomnia similar to humans. Parrotfish keep themselves protected while sleeping by secreting a mucous jelly around them.

Sleep Deprivation In Animals

Rebound sleep after experiencing sleep deprivation does not occur in the case of certain fish and insects. This may be because they experience more intense sleep after the period of deprivation. But most animals, including insects, can die if they go too long without sleep. 

Thus, it is obvious that all animals require sleep, though their sleep may differ from that of mammals. For instance, fruit flies experience a biochemical reaction in the brain similar to human sleep.

Final Thoughts

All animals require some form of sleep to allow their brains and bodies to rest and recharge. However, their sleep pattern and habits can vary significantly from one animal to another. Some can stay awake for extended periods, while others can go into a state of inactivity for months to conserve energy, like hibernating animals. 

Like humans, animals suffer when they do not get enough sleep and experience symptoms similar to us. In extreme cases, they can even die, as research has proven. That is why evolution has provided them with various techniques to prevent extreme sleep loss in most cases.