THE SECRET WORLD OF ANIMAL SLEEP

Some snooze only half a brain at a time. Others take 4-second micronaps. It pays to be able to multitask.

- BY CHRISTINA LARSON, NICKY FORSTER, HYOJIN YOO, PETER HAMLIN AND CALEB DIEHL

CHINSTRAP PENGUINS have a remarkable sleep strategy while caring for their newborns.

(NATACHA PISARENKO Associated Press)

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 risky," said Paul-Antoine Libourel, a researcher at the Neuroscience Research Center of Lyon in France.

When animals nod off, they're most vulnerable to sneaky predators. But despite the risks, the need for sleep is so strong that no creature can skip it altogether, even when it's highly inconvenient.

Animals that navigate extreme conditions and environments have evolved to sleep in extreme ways - for example, stealing seconds at a time during around-the-clock parenting, getting winks on the wing during long migrations and even dozing while swimming.

For a long time, scientists could only make educated guesses about when wild animals were sleeping, observing when they lay still and closed their eyes. But in recent years, tiny trackers and helmets that measure brain waves-miniaturized versions of equipment in human sleep labs have allowed researchers to glimpse for the first time the varied and sometimes spectacular ways that wild animals snooze.

"We're finding that sleep is really flexible in response to ecological demands," said Niels Rattenborg, an animal sleep research specialist at the Max Planck Institute for Biological Intelligence in Germany.

Call it the emerging science of "extreme sleep."

Take chinstrap penguins in Antarctica that Libourel studies. These penguins mate for life and share parenting duties with one bird babysitting the egg or tiny gray fluffy chick to keep it warm and safe while the other swims off to fish for a family meal. Then they switch roles-keeping up this non stop labor for weeks.