Creatures that sleep strangely

Bat

Bats prefer to sleep upside down because, for them, it makes perfect sense. Bat wings are not the same powerful structures as those of birds, so taking off from the ground tends to be difficult and embarrassing. Hanging upside down helps them to launch quickly and elegantly.

Sleeping the wrong way up also conserves energy. At bedtime, bats just hook their talons into place and gravity does the rest. Safe among beams and rafters, bats also are able to sleep long and contentedly.

One species, the little brown bat, which lives for up to 33 years, nods off for almost 20 hours at a time.

Walrus

Not only do these marine mammals appear to be able to sleep anywhere, they probably hold the world record for continuously staying awake.

Scientists from the University of California have observed Pacific female walruses swimming continuously for up to three and a half days.

Yet these blubbery beasts have no problems nodding off when the time is right. Walruses will fall into a deep rapid eye movement (REM) sleep that can last for up to 19 hours. In water, they sleep floating on the surface, lying on the bottom, standing up or leaning against each other. Some have even been seen using their tusks to 'hang out' from ice floes.

Hazel dormouse

These tiny mammals do most of their sleeping by day. By night, they shuffle about in trees, foraging for food.

Like birds, dormice live in fear of predators. As a consequence, these creatures sleep lightly, carefully balanced on a branch. The slightest twitch of the twig will send them scuttling for cover.

In October, they go into hibernation, snuggled beneath leaf litter on the forest floor. Even in summer, if the weather is cold and wet, the hazel dormouse simply curls up into a 'torpor'...the dormouse equivalent, perhaps, of the human duvet day.

Giraffe

Not only is the giraffe the tallest of all land-living animal species and the largest ruminant on the planet, it is also a notorious insomniac.

This gangly, long-legged, long-necked safari favourite, has one of the shortest sleep requirements of any known mammal. Giraffes sleep for as little as two hours a day, kneeling down with their neck and heads wrapped around them. A giraffe lie-in tends to be no more than four hours.

According to ancient eastern cultures, giraffes are not sleeping, but meditating, in a manner similar to yoga.

Frog

While humans fumble about in the winter months in search of hot water bottles and electric blankets, frogs have their hibernation sleeping arrangements pretty well sorted.

The frog's body has its own natural antifreeze. This means that even in extreme northern parts of the globe, they can survive, trapped deep under ice for up to nine months of the year.

Some species can actually sleep, frozen solid, with no obvious heartbeat or breathing, for weeks at a time. Cold and motionless, they cling onto life by absorbing oxygen through the skin.

Dolphin

Dolphins do not have the luxury of deep REM sleep. They need to remain conscious at all times in order to breathe. If they slept like humans, they would suffocate.

Happily for dolphins and their many fans, nature provides strategies for ensuring decent spells of rest. Like birds, dolphins and other large marine mammals are able to sleep up to eight hours a day, with one eye open and half the brain active.

However, life is rather more strenuous for dolphin mothers. For the first few months of a calf's life, mother and baby tend not to sleep at all.

Albatross

The great albatross has the longest wing span of any living bird on Earth, at almost 12 feet. Close observers of these stunningly beautiful birds believe that they sleep in flight, even while cruising at 25mph.

The evidence for this feat is mainly circumstantial. The birds gather on land only to breed and they certainly cannot sleep on water, because of attacks by both animal and human predators. So scientists conclude that albatrosses have sleep patterns that enable them to fly and to navigate, while asleep.

One day, perhaps, small recording devices fixed to the birds' heads will prove things beyond doubt.

Guinea baboon

That hairy, bloke-like creature, perched in a tree, fast asleep, strangely on its heels, is most likely to be a beast known as a Guinea baboon.

Baboons and their relatives are the largest - and among the most ferocious - monkeys in the world.

Guinea baboons are also renowned for their yawning. They do this, not necessarily because they are tired, but to frighten predators and other baboons. Weighing up to 90lbs and equipped with monstrous canine teeth, the Guinea baboon can yawn to blood curdling effect, especially when they do it with ears flattened and eyebrows raised.

Swainson's thrush

Known also as the olive-backed thrush, these birds have an ingenious way of staying alert on long-haul flights. Travelling south from northern US and Canada to the warmth of Argentina and Mexico, they take micro-naps.

In common with other species of migratory birds, the Swainson's thrush is able to sleep for mere seconds at a time. In a day, this can amount to hundreds of naps.

For a bird weighing no more than one ounce, the stress-laden journey runs to thousands of miles over several weeks. And micro-napping is what makes it all possible.

Source: Creatures that sleep strangely