Bizarre sleeping habits of these 8 animals will amaze you

Sea otters came up with a perfect idea of how to avoid dangerous predators while sleeping: they sleep in water, floating on their backs! They really love sleeping in groups: up to 100 otters can gather in a sleeping raft. Not to get away with the currents, otters wrap themselves in seaweed or hold each other's paws – and it looks absolutely cute.

Giraffes are highly noticeable animals, and living in the middle of open plains is highly dangerous for them: predators can attack giraffes at any moment. That's why these creatures can't sleep for long periods. Giraffes sleep in 5-minute intervals several times a day. They sleep standing up most of the time, but sometimes they curl up just like cats, by sitting down and resting their heads on their backs.

Can you imagine that these incredible marine animals can stay awake for more than 80 hours? Moreover, walruses can be swimming all this period long. Perhaps they are so enduring because of their professionalism in the field of sleeping: walruses can do it anywhere!

Sleeping on land is easy, while doing it in water requires some resourcefulness. Just like otters, walruses sleep floating on water, sometimes filling their pharyngeal pouches with air. They also use their tusks while sleeping: with their help, walruses hang from ice floes, letting their body rest in water.

Meerkats really love to cuddle: they usually sleep together in their special underground burrows. As many as 50 meerkats can live in one burrow, which is divided into several rooms. Alpha males and females usually sleep in the middle of a heap, that's how the mob protects them. During the summer months, they prefer to sleep outside – also together.

It's not a secret that ducks sleep in long lines to be on the safe side, but one detail about that is really surprising: the ducks at the ends of the row can keep one eye open all night long. And they are not awake! The ducks at the ends are usually engaged in a single-hemisphere sleep, meaning that only half of their brain is asleep, while the other side is responsible for keeping an eye out.

Great frigatebirds have found a way to fly continuously for several weeks without sleep breaks – they power nap while flying in 7-12 second bursts. Just like ducks, they sleep with only one side of their brain, letting the other one control their flight.

Snails are not among the fastest creatures on Earth, but they do need a lot of sleep. An average snail sleep for 15 hours, but after that it can stay awake and active for approximately 30 hours.

Anyway, when the surroundings are not inspiring enough, snails just withdraw into their shells and secrete a layer of mucous to avoid drying and starvation. Such hibernation can last for several years – the snail will wake up when the conditions improve. The longest recorded snail hibernation lasted for 4 years.

During winter frogs also hibernate, but up to 65% of their total body water can freeze, which doesn't harm frogs at all. A frog's heart ceases beating, the animal doesn't breeze, but when spring comes the body starts functioning again.