Giraffes can’t afford to sleep for long, Smithsonian Earth series says.

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Ready for a catnap?

What about a dolphin doze or a squirrel snooze?

“The Secret World of Animal Sleep,” an animated series on Smithsonian Earth’s website, unlocks the secrets of sleepy wildlife, such as birds that sleep while they fly and lions’ seemingly endless naps.

The series – illustrated by hand in colorful picture-book style – follows the slumber of a variety of members of the animal kingdom in a six-episode season. There are Arctic ground squirrels, whose bodies drop to the lowest temperatures ever measured in mammals during their seven to eight months’ worth of hibernation per year. There are jellyfish, which need sleep despite lacking a brain. There are even giraffes, whose necks are long but whose sleep is all too brief – long periods of slumber would make them vulnerable to predators.

Sleep has been observed in animal species as diverse as fish, insects, birds and mammals, and scientists study animal sleep in an attempt to better understand what makes other creatures tick. Comparing human sleep with that of animals has yielded important insight into the function sleep plays in people, too.

Some day, it could even help humans hibernate. For example, the European Space Agency has conducted research on animal hibernation in the hopes of applying its lessons to humans on an eventual flight to Mars.

The series is narrated by Cara Santa Maria, a science journalist and host of the “Talk Nerdy” podcast. It’s part of Smithsonian Earth’s collection of wildlife and nature shows, which require a $3.99/month subscription. (The first episode is free, and there’s a free trial.)

Each episode is brief – just three to four minutes long – and filled with accessible information and engaging artwork that makes it ideal for short attention spans. Perhaps parents could use it to calm their little ones before they head off to bed.

Watch: “The Secret World of Animal Sleep” at Smithsonian Earth: smithsonianearthtv.com/programs/the-secret-world-of-animal-sleep