First, came the news that ducks can revert to cannibalism when bored (yes, really).
And in far less horrific, but still not exactly comforting news, it turns out that dolphins only sleep with half their brains at a time. They literally fall half-asleep.
The mammals, which by the way can only last about four minutes underwater before they need to come up for air, share the trait with some whales, too.
Why?!
Because, just as dolphins can’t actually survive underwater for as long as many of us think, it’s likely they can’t breathe unconsciously either ― unlike humans, who inhale and exhale when our brains are fully switched off.
Sleeping with half of their brain at a time ― also called unihemispheric sleep ― allows them to stay conscious enough to surface and use their blowhole to breathe while still getting some rest, scientists believe.
As a result, a small study involving just two dolphins found that the pair were able to stay alert for 15 days at a time without signs of fatigue. After that, the researchers called the observation off.
Speaking to Discovery, biologist Oleg Lyamin ―affiliated with the Center for Sleep Research at the University of California and A.N. Severtsov Institute of Ecology and Evolution ― said that “Sleep in most land mammals consists of two stages, slow-wave sleep and REM [rapid eye movement] sleep,” while “Cetaceans appear to display only one sleep stage, which is slow-wave sleep.”
That’s not all
Dolphins also keep one eye open as they sleep (this is the eye on the “active” side of the brain).
This eye changes when they change the half of their brain that’s asleep, because yes, of course, they can (and do) do that.
So, if you see a dolphin hovering near the surface of the ocean with one eye shut, don’t worry ― it’s likely not sick, but is instead taking its cursed, creepy naps.