Eternally Vigilant Dolphins Sleep With One Half of Brain

An interesting study on dolphins shows how they use just one half of their brain at a time.  And it is this trait that gives them the energy to stay constantly alert for a minimum of 15 days in a row.

This study was conducted by Brain Branster and colleagues from the National Marine Mammal Foundation.

They claim the dolphins can use echolocation with near-perfect accuracy continuously for up to 15 days, easily identifying their prey and monitoring their environment.

Echolocation, the process of determining the distance and direction of objects by using sound is performed by certain animals to locate food or obstacles in darkness, such as in caves and in the ocean. 

For the study the researchers studied 2 dolphins, one male and one female and found that they were capable of this task with no signs of fatigue for 5 days. The female dolphin performed additional tasks for 15 day period.

But it is not known for how many more days the dolphins could continue with this.

Earlier, this trait of unihemispheric sleep (sleeping with one half of the brain) was believed to have evolved in dolphins to enable them to breathe at the surface of water even when half-asleep.

But this study reveals an interesting fact stating the need to remain vigilant may also have played a role in the evolution of this sleeping behavior.

"These majestic beasts are true unwavering sentinels of the sea. The demands of ocean life on air breathing dolphins have led to incredible capabilities, one of which is the ability to continuously, perhaps indefinitely, maintain vigilant behavior through echolocation" says Branstetter.

The study is being published in the open access journal PLOS ONE.