How Do Animals Sleep?

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October 9, 2009

Ever wonder how a dolphin can sleep without drowning or why a bat sleeps upside down? Well, you won't have to wonder any more.

Check out how our favorite animals sleep below.

Dolphins
Can you sleep and swim at the same time? For dolphins, this is an easy task. They can turn off half their brain and close one eye, allowing them to be partly asleep and awake at the same time. According to an article in the Scientific American , dolphins sleep this way so they can be ready to protect themselves from predators and swim to the surface for air. ScienCentral News reports that mothers and their baby calves often don't sleep at all for the first few months after birth.

Walruses
According to HowStuffWorks.com, walruses can sleep and swim at the same time, too. While in the water, walruses can choose between sleeping underwater or above. A walrus can hold its breath for five minutes, just enough time for a nap. For a deeper sleep, walruses inflate spaces inside their body, called pharyngeal pouches, with up to 13 gallons of air. These pouches act like a life-jacket, allowing them to remain in the water by bobbing up and down while keeping their head above for air. For the deepest sleep, walruses will either hook their tusks onto a stable piece of ice or move to land. Walruses can sleep up to 19 hours at one time. Unlike most animals, walruses do not need to sleep every day, and they can swim without stopping to sleep for more than three days.

Giraffes
Giraffes need less sleep than any other mammal. According to the Smithsonian publication, Zoogoer, giraffes sleep for five minutes at a time, adding up to an average of 30 minutes per day. Why don't they sleep all night like other mammals? Because giraffes are considered to be a prey animal, which means that they are often hunted by other animals for food. Lying down to sleep for a long time would make it easier to get caught. According to the University of Michigan Museum of