Whooz-z-z Snooz-z-zing? - sleep in animals - Brief Article

Ranger Rick, Nov, 2000 by Deborah Churchman, Ellen Lambeth

What a slumber party THIS is going to be. . . . While these nutrias settle down, turn the page for answers to all your sleepytime questions.

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What is sleep, anyway? Sleep is like nature's "pause button." It's a regular time of rest when people and many other animals tune out from the world around them. During sleep, the muscles relax. Breathing gets slower and so does the heartbeat. The brain works differently too.

Why do animals sleep? Scientists aren't sure, but most agree that sleep is something the brain needs. Try staying awake when you're really, really tired. You might become cranky and clumsy and unable to think straight. Then, after a snooze, everything seems to work much better. It's kind of like re-booting a computer to re-set all the programs.

Do all animals sleep? That's a tough question. The brain sends out electrical signals that scientists can measure with a special instrument. These brain signals change when a mammal or a bird falls asleep. But the signals never change in animals such as fish or frogs--even when these animals look as if they're sleeping. (They stop moving, and they don't seem to pay attention to what's going on.) Some scientists think that these animals might have a different kind of sleep. They say that their sleep can't be measured the same way yours can. Other scientists think these animals don't sleep at all--they just sort of "space out." But no one really knows for sure.

When do animals sleep? It depends on the animal. Lots of animals, such as songbirds and apes, are busy during daylight hours. Then they settle down at nightfall. Others, such as cats and owls, are just waking up then. Still other animals, such as deer and rabbits, are awake mostly around sunrise and sunset.

Ahhhh! Time to kick back and reeeelax. This hyena may have hunted hard the night before and eaten its fill. There's nothing like sprawling out for a snooze after a big meal!

These baby wrens are in snuggle-heaven. They won't tip over because their toes lock on to branches when they sleep.

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How long do they sleep? That might depend on the "danger factor." Big meat-eating animals such as lions are rarely in much danger. So they can sleep a lot--as much as 17 hours a day. But so do animals that can sleep in really well-protected places. Bats sleeping in caves, for example, might snooze for 19 out of every 24 hours. Then there are hoofed creatures that live on wide-open plains and have lots of enemies. They have no place to hide, so they need to be awake most of the time and ready to run. These animals may sleep only a couple of hours each day--often on their feet.

A fork in the branches is a great place for this dozing koala to "hang out." A koala on the ground isn't very safe. But high up in a tree, it can rest easy.

Some animals can tuck themselves in! Even on a bed of cold snow, this red fox is toasty-warm, wrapped in its own fuzzy blanket.

Squatting on its perch for the night, this warbler rests its head on its back. It also fluffs up its feathers for warmth.

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Like this lion cub, baby mammals often snuggle and snooze with their mothers. What better way for a sleepy mom to make sure her little one is safe?

How do animals sleep? In all kinds of ways and in all kinds of places. Some snooze right out in the open, while others hide themselves away. Some nap alone, while others cuddle together. Manatees sleep underwater, bobbing to the surface now and then to take a breath. Leopards stretch out on tree limbs. Chipmunks nestle in underground burrows. Sea otters snooze afloat on their backs. And birds called swifts can sleep while flying! Some animals, such as gorillas and chimpanzees, make soft beds for themselves. But others use no beds at all. Mountain goats can even sleep standing on narrow rocky ledges. (It helps to lean against a cliff!) Lots of birds perch on tree branches to sleep. Why don't they fall off? Because squatting down on a perch makes a bird's toes curl. The toes can't uncurl until the bird straightens up.

Which animals dream? Scientists know that humans dream during a kind of sleep when the brain becomes super active. It's called REM (Rapid Eye Movement) sleep. Scientists have measured REM sleep in mammals and also in some birds. So they think that these animals probably dream too.

There's still a lot to learn about sleep. But one thing's for sure: A good snooze is good news for any sleepy creature.

This tiny, balled-up dormouse isn't exactly sleeping. It's hibernating. Hibernation looks a lot like sleep, but it's different. A hibernating animal's body slows way down. That saves energy until winter's over and there's plenty of food again.

Can you see the "safety net" this colorful parrotfish has made around itself? The slimy bubble seems to keep enemies from bothering the fish as it rests in a sleep-like trance on the reef.