You probably sleep lying down in a bed, with your eyes shut, for about nine or ten hours. But in the animal world, sleep comes in all shapes and sizes. Some animals snooze for most of the day, while others manage with just a couple of hours.
The sleepyheads
The koala of Australia is one of the sleepiest animals on Earth. It can sleep up to 22 hours a day! Bats are close behind. They sleep about 20 hours and wake for around four hours to hunt insects. Male lions can also sleep up to 20 hours a day, while lionesses, who do most of the hunting, still get more than 15 hours.
Closer to home, look at a cat curled up in a sunny corner. Cats sleep a little over 15 hours a day, taken as many short catnaps. Dogs sleep about 10 hours in total, adding daytime naps to their night-time sleep.
The light sleepers
Some big animals sleep surprisingly little. A giraffe averages only about two hours of sleep a day. Elephants and horses manage only about two to three hours.
Horses often doze while standing up. But to reach a special, deeper stage of sleep called REM sleep (short for “rapid eye movement”), a horse has to lie down.
Strange ways to sleep
- Eyes wide open: Snakes have no eyelids. So a ball python, which sleeps about 18 hours a day, does it with its eyes open!
- Tiny naps: Worker ants take roughly 250 naps a day, each about one minute long. Most workers stay awake at any one time to do jobs and guard the colony.
- Swim now, sleep later: In the water, walruses can go up to 84 hours without sleeping while swimming almost all the time. Then they come ashore to rest.
Still a mystery
Scientists are still finding out why different animals need such different amounts of sleep. Every sleepy koala and wide-awake giraffe gives them new clues to study.
Wonder about: If you could sleep like any animal for one night, which would you choose, and why?