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 ...

In the animal kingdom, sleeping can be dangerous. Lying completely motionless and unconscious for hours at a time is just asking for trouble. There are, however, some sleepy risk-takers who spend ...

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, ...