Sleeping underwater might sound peaceful — but for ocean animals, it’s a matter of survival. Some dolphins sleep with one half of their brain at a time, keeping one eye open to avoid danger and ...

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 ...

For the first time, scientists have recorded brain activity in a free-ranging, wild marine mammal, revealing the sleep habits of elephant seals during the months they spend at sea. The new findings ...

Jellyfish and sea anemones are curious creatures: these organisms evolved without a brain and, as scientists discovered in the past several years, don’t need one to sleep. The animals do, however, ...

Brainless upside-down jellyfish, like this one in its natural habitat near Eilat, Israel, spend about one-third of their time asleep. Gil Koplovitch Why do animals—including humans—sleep? This ...

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 ...