Baby dolphins don’t sleep in the first month of their lives, so their parents need to do the same to watch over their children.

Dolphins can let one half of their brain rest and work with the other half of their brain. Scientists tested the reaction of non-resting dolphins for 5 consecutive days and their reaction time did not slow down. Blood tests looking for signs of stress or lack of sleep are negative.

Another study found that dolphins can use ultrasound waves for 15 consecutive days with near-perfect accuracy. Tests show that image information is transmitted from the paused side to the active side. Even though dolphins shut down half of their brains, the other half can still take on all the normal functions. It can be said that they have up to two brains.