The Sleeping Habits of Different Animal Species

People aren’t the only ones that need a restful night of sleep to stay healthy. Sleep is also important for many types of animals, big and small, living in the wild and in our homes as pets. And, like people, animals all have different sleeping habits and routines that help them to feel rested.

Do All Animals Sleep?

Sleeping is extremely important for humans, and a majority of the animals that people easily recognize, sleep for some portion of the day or night. Scientists are not, however, 100% certain that all animals actually sleep, but they believe that most animals need to at least rest.

For many animals, sleeping or resting helps them to conserve and renew their energy. It also helps them to function as they should and keeps their brains functioning properly.

Which Animals Sleep the Most?

The time an animal spends sleeping depends on several things. Being a cold- or warm-blooded species can affect sleep as can diet and habitat. Animals that are common prey typically sleep less than animals that have few natural predators. The size of an animal can also dictate how much sleep they require.

Some of the animals that sleep the most include:

Koalas, which sleep high in trees and away from many predators, can sleep 18 to 22 hours a day.
Sloths sleep between 10 and 20 hours, based on their living conditions. A sloth in the wild sleeps 10 hours at night. A sloth that’s in captivity can sleep as much as 20 hours a night.
Brown bats are also animals that sleep as much as 20 hours a day.
Male lions sleep between 18 to 20 hours a day while female lions get between 15 and 20 hours of sleep daily.
Tigers are also wild cats that sleep 18 to 20 hours a day.
North American Opossums and Giant Armadillos also sleep up to 20 hours.
Squirrels sleep for 15 hours a day and, during hibernation, are only awake between 12 to 20 hours a week.
Domestic animals also fall into the category of long sleepers. House cats, for example, sleep between 12 to 16 hours a day while dogs sleep 13 hours in a 24-hour period.

Sleeping Habits of Land and Air Mammals

Land mammals and birds cycle between Rapid Eye Movement (REM) and non-REM sleep. REM sleep is a deep sleep where people dream. While it is uncertain if all animals actually have dreams, scientists believe that many mammals and birds experience deep REM sleep and that their brains are as active as when they are awake.

REM is important for a healthy brain that functions as it should. It helps to warm animals’ brains! REM sleep is also important for growth and helps to balance metabolism and bodily function.

Certain mammals that hibernate, such as bears, don’t undergo REM sleep because their level of sleep during this time is deeper so that they can conserve their energy.

Birds are diurnal or nocturnal. Diurnal birds sleep at night and are awake during the day. Nocturnal birds are the opposite because they sleep during the day and are awake at night. Owls are an example of nocturnal birds. They sleep in small bouts and are easily awakened by threats, weather, or other disturbances.

When birds sleep, they find a place to perch and put their weight on their feet. The muscles in their legs cause their feet to tighten and lock on their perch. When this happens, they can sleep without falling.

Some birds can control how much of their brain falls asleep. This is called unihemispheric slow-wave sleep (USWS). During migration, USWS makes it possible for certain birds to sleep while they are in flight.

Sleeping Habits of Marine Life

The sleeping patterns of marine animals differ from most land animals. Fish, for example, slow their metabolism and go into a state of rest rather than full sleep. While resting, they may hide out in a tight place where they can safely rest or they may simply float. They also awaken regularly, which helps them to filter oxygen.

Dolphins and whales also enter unihemispheric sleep and can stay conscious while they rest because only part of their brain is asleep. This is important because they must be aware to take breaths. With only part of their brain asleep, they can also keep one alert eye open and on the lookout for threats. Dolphins and whales sleep either vertically or horizontally, with some swimming slowly and close to the surface or staying still.

Sleeping Habits of Amphibians

Whether frogs sleep is a question that scientists have not fully explored. There is some research that suggests that frogs enter a state of rest in which they look like they are sleeping. When this happens, their eyes are closed, their limbs are tucked, and their bodies are still. Although some think that frogs are sleeping or resting during this time, scientific research has yet to confirm it.

There are some studies about the sleeping habits of other amphibians, like salamanders and newts. Depending on the species, certain salamanders and newts sleep under the ground, beneath stones, or in piles of dirt or compost. This helps to protect them from heat and predators. Their sleeping habits depend on the species, with some being nocturnal and others diurnal.

Sleeping Habits of Reptiles

Reptiles are cold-blooded creatures that include snakes, turtles, crocodiles, and alligators. Reptilian sleep habits vary. For turtles, how they sleep depends on whether they are land or aquatic turtles. Land turtles can sleep longer than their aquatic counterpart, by taking quick naps or sleeping for hours. Aquatic turtles may sleep underwater for short periods, or poke their head out of the water when sleeping. They can even choose to sleep completely under the water or on dry surfaces.

Snakes slow their brain function and go into a state of rest instead of sleep. They don’t close their eyes while resting because they don’t have eyelids!

Crocodiles, most of which are nocturnal, can also sleep with half of their brain still aware. This helps to alert them to prey as they rest. Because half of their brain is awake, they have one eye that stays open as they sleep.

Alligators are also nocturnal and aware of the presence of prey or other issues that will make them awaken fully. In severe weather, such as extreme heat or cold, alligators will create a tunnel called a gator hole. They use this hole as a place to hibernate until the weather is no longer extreme.

Sleeping Habits of Insects

Insects are creatures that can be nocturnal or diurnal. To sleep, they often find a safe place to make their bed and go into torpor, which is a state of rest. While in torpor, insects typically stay still and look like they are sleeping. Things like movement quickly awaken them from their rest. Sounds and even the transition from night to day can awaken them from torpor.

In some ways, insects are like humans in some of their sleeping habits. There are insects, like fruit flies and paper wasps, that doze off when tired. Some insects that typically sleep at night, like bees, may even take daytime naps if they aren’t busy, just like people do!

Other insects display human-like sleeping requirements as well. Some can become sleep-deprived and may even behave differently if they don’t get enough rest. Cockroaches and fruit flies need sleep for good function, and caffeine and chemicals that can make people sleepy also affect fruit flies.

Animal Research Resources

About Derek Hales

Derek Hales is the Founder and Editor-in-Chief of NapLab.com. He has been featured in Fast Company, Reader's Digest, Business Insider, Realtor.com, Huffington Post, Washington Post, AskMen, and She Knows. Derek has personally tested over 320+ mattresses and hundreds of pillows, sheets, beds, and other sleep products.