Dolphins sleep with one eye open
Dolphins achieve rest through unihemispheric sleep, keeping half their brain alert to breathe and evade dangers, a crucial adaptation for ocean survival.
Dolphins can't fully power down like land animals. Instead, they practice unihemispheric sleep, resting one brain hemisphere while the other stays active. This unique adaptation allows them to keep one eye open, remaining aware of their surroundings. The awake half of their brain controls breathing and swimming, ensuring they surface for air and stay vigilant against predators like sharks. This incredible survival strategy was first documented in bottlenose dolphins in the 1960s. It highlights the evolutionary ingenuity of cetaceans, who traded deep sleep for constant readiness after millions of years transitioning from land to sea.