Every animal with a brain needs sleep, and even a few brainless animals do too. Humans sleepBirds sleep, whales sleep, and even jellyfish sleep.
Sleep is universal, “although it is actually risky,” said Paul-Antoine Lebourel, a researcher at the Center for Neuroscience Research in Lyon, France.
When animals nap, they are more vulnerable to sneaky predators. But despite the risks, Need for sleep So powerful that no creature can completely overcome it, even when it’s extremely inconvenient.
Animals navigating extreme conditions and environments have evolved to sleep in extreme ways, for example, stealing Seconds at a time While parenting around the clock, getting winks on the wing during long migrations and even drowsiness while swimming.
For a long time, scientists could only make educated guesses about when wild animals were asleep, observing when they lay still and closed their eyes. But in recent years, trackers and tiny helmets that measure brain waves — scaled-down versions of equipment used in human sleep laboratories — have allowed researchers to glimpse for the first time the diverse and sometimes astonishing ways in which wild animals fall asleep.
“We found that sleep is really flexible in response to environmental demands,” said Niels Rattenburg, a specialist in animal sleep research at the Max Planck Institute for Biological Intelligence in Germany.
Call it the emerging science of “extreme sleep.”
takes Penguins chin strap In Antarctica studied by Leporel.
These penguins mate for life and share parenting duties – one bird babysits the egg or a tiny, fluffy gray chick to keep it warm and safe while the other swims off to catch fish for a family meal. Then they exchange roles, and continue this continuous work for weeks.
Penguin parents face a common challenge: getting enough sleep while keeping a close eye on their newborns.
They survive by taking thousands of naps daily – each averaging just 4 seconds long.
These short “sleeps,” as Korean Polar Research Institute biologist Won Young Lee calls them, appear to be enough to allow penguin parents to carry out their caregiving duties for weeks inside their crowded, noisy colonies.
When a clumsy neighbor passes by or predatory seabirds approach, the penguin father blinks to alert attention and is soon dozing off again, nodding with his chin on his chest, like a sleepy driver.
Naps add up. Each penguin sleeps 11 hours a day, scientists found by measuring the brain activity of 14 adults over the course of 11 days on King George Island in Antarctica.
In order to remain mostly alert, but also sneak around with enough winks, penguins have evolved an enviable ability to operate in highly fragmented sleep — at least during the breeding season.
Researchers can now tell when either hemisphere – or both at the same time – is asleep.
Poets, sailors, and bird watchers have long wondered whether birds that fly for months at a time actually get any winks on their wings.
In some cases, the answer is yes, as scientists discovered when they attached devices that measure brain wave activity to the heads of large seabirds that nest on the Galapagos Islands, called great frigatebirds.
While in flight, frigatebirds can sleep with half their brain at a time. The other half remains semi-alert, with one eye still watching for obstacles in its path.
This allows the birds to fly for weeks at a time, without touching the ground or water, which could damage their delicate, non-water-repellent feathers.
Frigatebirds cannot perform difficult maneuvers such as flapping, foraging, or diving with only half of their brain. When they dive for prey, they must be fully awake. But in flight, they have evolved to sleep by gliding and rotating upward on huge currents of rising warm air that keep them aloft with minimal effort.
Returning to the nest among trees or bushes, frigatebirds change their nap routine – they are more likely to sleep whole-brain at once and for a much longer period. This suggests that their in-flight sleep is a specific adaptation for long flight, Rattenborg said.
Few other animals have similar sleeping methods. Dolphins can sleep with half their brain at a time while swimming. Scientists say that some other birds, including humpbacks and albatrosses, can sleep while flying.
Other researchers have found that frigatebirds can fly 255 miles (410 kilometers) per day for more than 40 days before touching the ground, a feat that would not be possible without the ability to sleep on their wings.
On land, life is easy for the 5,000-pound (2,268-kg) northern elephant seal. But sleeping in the sea is dangerous, where sharks and killer whales prey on seals lurk.
These seals go on long foraging trips, lasting up to eight months, frequently diving to depths of several hundred feet (meters) to catch fish, squid, rays, and other marine meals.
Each deep dive may last about 30 minutes. For about a third of that time, the seals may be asleep, research led by Jessica Kendall Barr of the Scripps Institution of Oceanography revealed.
Kendall Barr’s team created a neoprene headpiece similar to a swim cap with equipment to detect motion and stamp out brain activity during a dive, and they recovered the caps with recorded data when the seals returned to beaches in Northern California.
The 13 female seals studied tended to sleep during the deeper parts of their dives, when they were below the depths where predators would normally patrol.
This sleep consists of slow wave sleep and rapid eye movement sleep. During rapid eye movement, or REM, sleep, the seals were temporarily paralyzed—just like humans are during this deep sleep phase—and their diving motion changed. Instead of controlling the downward gliding motion, they sometimes turn upside down and spin in what researchers call a “sleep spiral” during REM sleep.
Within 24 hours, the seals slept at sea for about two hours. (Back at the beach, their average time was about 10 hours.)
Scientists are still learning about all the reasons why we sleep – and only How much do we really need?.
It is unlikely that any tired human will be able to try these extreme animal sleep tricks. But learning more about how diverse naps are in the wild shows the resilience of some species. Nature has evolved to make eye sleep possible even in the most dire situations.
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