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Rare Footage Shows the Cuddly Sleeping Habits of Sharks

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New video footage captured by scuba divers in Revillagigedo, Mexico, shows the common—but rarely recorded—sleeping habits of sharks. In it, a pack of whitetip reef sharks can be seen piled on one another in a cuddly, sleep-like state.

It is important to note that "sleep" means something much different for sharks: Unlike human beings, sharks do not enter an unconscious state when they sleep—rather, they toggle between "wakeful" and "restful" states. Little is known about what transpires during this period of rest.

Apart from its rarity, this footage is significant in that it offers a clear case against a popular myth: that sharks need continuous movement to avoid drowning. While it is true that some species, like great whites, move during resting periods for oxygen, whitetip reef sharks can remain completely motionless while still receiving water through their spiracles. They often rest during the day and feed at night on small bony fishes, octopuses, and crabs.

Watch the full video from National Geographic below:

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9 Exhilarating Close-Up Photos of Sharks
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Dive into the world of Shark, a new book by award-winning photographer Brian Skerry.

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Animals
The Mules That Help Fight California's Wildfires
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Forget dalmatians—in remote parts of Northern California, mules are the fire department's four-legged helpers of choice.

When a blaze roars to life in a residential area, firefighters can use trucks to transport the tools needed to battle it. But in the California wilderness, where vehicles—and sometimes thanks to environmental restrictions, helicopters—can’t venture, mules bear the burden. According to Business Insider, the donkey-horse hybrids can carry 120 pounds of supplies apiece while walking 4 mph up rugged terrain. Llamas are also capable of making the trek, but mules are preferred for their resilience and intelligence.

You can see them at work in the video below.

These animals do extraordinary work for the country, but they’re not the only mules assisting the U.S. government. The Havasupai village of Supai is located at the bottom of the Grand Canyon, and the mail is delivered there each day by parcel-toting mules.

[h/t Business Insider]

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