KNOW: Why Dolphins only close one eye and half of the brain when they Sleep
Dolphins🐬 only close one eye when they sleep the left eye will be closed when the right half of the brain sleeps, and vice versa. This type of sleep is known as unihemispheric sleep as only one brain hemisphere sleeps at a time.
Dolphins are conscious breathers, which means they must consciously think about breathing. It is not a reflex as it is in terrestrial animals. Which means that sleeping as we do is not possible, because if they lose consciousness, they will stop breathing and die.
Whales and dolphins have developed a
fascinating strategy to handle their need for sleep. They sleep with one half of
their brain only at a time, while the other half is awake and keeps them
swimming and coming to the surface for a breath of air. When a whale or dolphin
is sleeping, it is usually in a restful state, either resting just under the
surface or near the bottom and then coming up for a breath and back down to
sleep some more.
Dolphins sleep swimming slowly, usually in tight formations with their pod mates. Because one half of their brain is awake, one eye is open on that side and the other eye is closed.
- This strategy also helps them keep an eye out for any dangers or threats that might try and attack while they are resting. When they do sleep it is for short periods, 30–60 minutes. They do not sleep for many hours like humans do.
- Sleeping with one eye open: they need to periodically come up for air and keep an eye out for potential predators, dolphins can't curl up and zonk out at night like land mammals can. So they must stay somewhat conscious and sleep with the proverbial one eye open
- Sleeping with half of the brain: Dolphins alternate in which half of the brain is sleeping periodically so that they can get the rest they need without ever losing consciousness.
