Dolphin: The marine creature that sleeps with one eye open 

The playful dolphins that you must have seen on your trip to an underwater aquarium or a TV show is not only mischievous but are extremely clever and smart. Have you observed that they only close one eye when they sleep.  Guess why? To breathe and keep an eye out for any potential predator!  

Dolphins can’t breathe automatically  
Dolphins don’t have the luxury of sleeping safe and sound like us simply by locking the doors and switching off the lights. But why?  

That is because they must come to the surface to breathe even in their sleep. Their breathing is not automatic like ours and it is consciously controlled. You can also say that dolphins must be continually conscious to breathe and it is on them to decide when they want to breathe.  

They need to guard themselves! 
Also, to ward off any danger when they sleep, they keep one eye open. To guard themselves against potential predators when they sleep they must stay somewhat conscious and sleep with one eye open. The lefte ye stays closed while the right half of their brain sleeps, and vice versa. This type of sleep is called unihemispheric sleep as only one brain hemisphere sleeps at a given time. 

How do they manage this? 
This may sound difficult for you, but not for dolphins! They decide which half of the brain is sleeping periodically. This way they can get the rest their body requires without ever losing consciousness. When sleeping,  they can even swim very slowly and steadily, close to the surface or they rest motionless at the surface of the water, breathing regularly.  

Curious functioning of dolphin’s brain  
Studies show no physical signs of sleep deprivation in dolphins. They can stay constantly vigilant for days at a time by resting one half of their brain while the other half remains conscious. Scientists even think that they can transfer information between the two hemispheres of their brains so that both parts of their brain know what happened when they slept off.   

Dolphin facts  

• Dolphins have conical-shaped teeth? 
• The orca (killer whale) is the largest dolphin. 
• A group of dolphins is called a pod! 
• Dolphins have two stomachs; one of them is used for storage and the other is where they digest their food.