10SleeplessnessMatt Weber: September 04, 2013 | 30,106 views
Everything needs sleep. The human world record holder, Randy Gardner, stayed awake for 11 days straight. By the fourth day, he was hallucinating. Not sleeping will eventually kill you and every other mortal creature with higher brain functions—except dolphins, which have apparently found a way around sleep. Baby dolphins actually forgo sleep for the first month of life—and so, therefore, do their parents.
The trick is that these amazing sea critters can shut half of their brain off at a time. Scientists tested dolphin reactions without rest for five days straight and their reaction time never slowed. Blood tests for signs of stress or sleep deprivation turned up negative. Dolphins may be able to do this indefinitely.
Another study showed that dolphins can use their sonar for 15 days straight with almost perfect accuracy. It makes sense that dolphins evolved a way to keep an eye out for predators while they’re dozing in the open ocean. But the truly fascinating part about all of this is that tests showed visual information was being passed from the snoozing side to the active side. Even though they shut down half of their noggin at a time, the other half can take over all the functions. It’s almost as if they have two brains.
Everyone knows about dolphins and sonar. With those trademark clicks and squeaks they use sound to perceive the world around them. You would think that would mean their other faculties would be diminished. But in fact, they have better eyesight than we do. To start, dolphins have an eye on each side of their head, which gives them a panoramic visual range of 300 degrees. They can see behind themselves, and each eye can move independently of the other, meaning they can look two different directions at the same time. They also have a reflective layer of cells just behind the retina called the tapetem lucidem. This helps them to see exceptionally well in low light. And as if all of that wasn’t enough, dolphins can see just as well out of the water as in it.