A not-at-all exhaustive list of how (and how much) animals sleep

By Erin Oakes, producer, How the Wild Things Sleep

Sleeping animals are found throughout the animal kingdom. Mammals, birds, reptiles, amphibians, fish and even insects have been observed at rest.

In the documentary How the Wild Things Sleep from The Nature of Things, scientists explore how and why animals sleep.

Some animals, like koalas, sleep a lot up to 22 hours a day. Cats sleep for about 15 hours a day. Worker ants average almost five hours of sleep a day, but it's in the form of around 250 one-minute power naps.

How animals sleep and just how much rest they get is as varied as the creatures themselves.

Here's a look at how some of them do it.

56 seconds of cute sleeping animals, insects and invertebrates | How the Wild Thing Sleep

3 years ago

Duration 0:56

Most living creatures sleep but why? Scientists explore big ideas about shut-eye.

Super snoozers

Koalas

At 18 to 22 hours of sleep per day, koalas are among the top snoozers in the animal kingdom. They've got good reason: their digestive system must work extra hard to break down the toxins in the eucalyptus leaves they eat and extract the limited nutrients.

Lions

Male lions are among the laziest of the big cats, sleeping up to 20 hours a day. As the prides' primary hunters, females have less time to lounge around, but they still clock an impressive 15 plushours of shut-eye.

Live hard, sleep hard

Walruses

From zero to 19 hours per day, walruses' sleep habits are extreme.

While in the water, these giants can go up to 84 hours without sleeping (while almost continuously swimming). After two orthree days of activity though, researchers found the walruses would haul out on land for a break. It's no wonder they crashed for up to 19 hours at a time!

Expert nappers

Worker ants

Given how hard these ants work, it makes sense that they'd need downtime too. Masters of the power nap, worker ants were observed getting almost five hours of sleep by taking roughly 250 naps a day, each lasting about a minute. And most of the workers were awake at any given time to attend to tasks and protect the colony.

Infants

Human newborns generally sleep about 16 or 17 hours a day. Unfortunately, they sleep no longer than three hours at a time in most cases, making it unlikely their parents will get the minimum of seven hours of uninterrupted sleep they need.

Cats

Anyone who lives with a cat knows these domestic divas love to sleep, but perhaps not when we do. On average, they get a little over 15 hours a day. But unlike us humans, who usually sleep in one long block of time, cats take several catnaps, plus short periods of deeper sleep, throughout the day and night.

Dogs

Dogs sleep at night when people do, but they need a little more downtime than us. To get a full 10 hours of sleep, dogs will take several daytime naps to supplement their nighttime sleep.

Sleeping while swimming

Dolphins

Dolphins sleep about eight hours a day, but since doing so underwater can be dangerous, they get their rest by turning offhalf of their brain at a time. While one hemisphere sleeps, the other half remains alert to predators and obstacles, and to make sure the dolphin gets to the surface to breathe. Every two hours or so, the two halves switch sides.

Sleeping with both eyes open

Ball pythons

Ball pythons get an impressive 18 hours of sleep per day on average, but it's a little hard to tell since snakes don't have eyelids,their eyes are open even when they sleep.

Squirrels, they're just like us (sort of)

Grey squirrels

When they're not gathering and hoarding food, grey squirrels spend an average of 15 hours a day asleep. Like us, they're most active in the daytime, returning home in the evening to settle in for the night.

Sleep while standing or lying down

Horses

Horses sleep for three hours a day on average, and while it's true they do most of their dozing on their feet, they need to lie down to enter the crucial REM stage. Let sleeping horses lie!

Watch How the Wild Things Sleep on The Nature of Things.