HALF ASLEEP
Spending your entire life living in water as a mammal makes sleeping without drowning a difficult feat. But dolphins have evolved an ingenious way to remain fully rested without filling their lungs with water. Rather than slipping into unconsciousness, dolphins can temporarily ‘turn off’ one side of their brain to rest, closing the opposite eye. The active hemisphere of the brain will remain conscious to ensure the dolphin rises to the surface to take a breath. Like humans, dolphins sleep at night, but only allocate around two hours of their time resting each hemisphere.