Dolphins sleep only with one half of their brain at a time. Dolphins are conscious breathers. Sleeping dolphins can be seen as resting, floating at the surface, with one eye open. After a time, they will close the one eye and open the other one. read more
So they must stay somewhat conscious and sleep with the proverbial one eye open. Sam Ridgway of the U.S. Navy Marine Mammal Program wondered if this constant watchfulness would dull their senses, like sleep deprivation does in humans (as anyone who has pulled an all-nighter knows). read more
Dolphins are conscious breathers. Should they sleep and go unconscious as we do they would simply suffocate or drown. Sleeping dolphins can be seen as resting, floating at the surface, with one eye open. read more
Dolphins do sleep with one eye open, a skill that is necessary for survival. When dolphins sleep, only half of their brains shut down, which enables them to remain vigilant to the threat of predators and to regulate their breathing to avoid drowning. read more