Every animal with a brain needs sleep. A few creatures without one do, too; even jellyfish enter a sleep-like state.

What has puzzled researchers and philosophers for many centuries is the ‘why’ of sleep, along with the ‘how’. We human animals know from experience that we need to sleep, and that the longer we go ...

Ever wondered how some animals manage to survive without the luxury of a good night's rest while we humans desperately need our eight hours? The animal kingdom is packed with creatures that seem to ...

This is read by an automated voice. Please report any issues or inconsistencies here. Animals such as penguins and frigatebirds have evolved extreme sleep strategies — naps that last a few seconds, ...

The animal kingdom is full of fascinating adaptations, and one of the most intriguing is the ability to sleep with one eye open. While humans drift into deep slumber with both eyes closed, several ...

Every animal with a brain needs sleep — and even a few without a brain do, too. Humans sleep, birds sleep, whales sleep and even jellyfish sleep. Sleep is universal “even though it’s actually very ...

Sleep in fish may look different from humans, but rest is essential for survival. Here’s what experts have to say about fish sleep. A protective mucous cocoon surrounds this parrotfish as it sleeps in ...

Despite decades of research, scientists admit that they still have a lot to learn about sleep. In general, sleep can be defined as a period of reduced activity that is relatively easy to reverse.

Why do animals sleep? Why do humans "waste" a third of their lives sleeping? Researchers now reveal a novel and unexpected function of sleep that could explain how sleep and sleep disturbances affect ...

Most animals don't keep the same schedule we do. While we try to squeeze in eight hours and call it a good night, many animals snooze through more than half the day—and some barely stay awake at all.