For how many hours do animals sleep?

As this graph shows, animals have a wide range of daily sleep times.  Some animals get their sleep by taking short naps. These brief naps might add up to only a few hours of sleep in a 24-hour day. Other animals snooze for hours at a time, sleeping for half the day or more.

A variety of factors affect how long an animal sleeps.  Perhaps the most important factor is its size. In general, smaller animals need more sleep than larger animals.  Small bats, chipmunks and opossums all sleep for 15 hours or more per day.  In contrast, big elephants, giraffes and horses all sleep for about five hours or less.

Another factor is whether the animal is a hunter or is hunted.  Predators such as lions and tigers get plenty of sleep; they have little to fear.  But animals that are prey, such as deer, tend to get less sleep.  They need to remain alert and aware of nearby predators.

Age is another factor that affects the sleep of animals.  Like humans, animals may sleep for different lengths of time at different life stages.  For example, young animals may need to sleep more than adults.

Captivity also can affect an animal’s sleep.  Wild animals often get more sleep when they are in a zoo. Food is provided for them, and they are safe from predators. So they can relax and sleep for longer periods of time.

In contrast, animals have to spend time hunting or gathering their food in the wild. Some animals have to migrate for weeks across long distances. Many also have to remain alert when predators are nearby. So they may spend less time sleeping in their natural environment.

For example, in captivity the slow-moving sloth sleeps for about 16 hours per day. But a team of scientists went to a rainforest to study sloths. Results show that brown-throated, three-toed sloths slept for less than 10 hours per day in their natural environment.  Watch this video from National Geographic to learn more: