Dolphins Can stay vigilant for Up to 15 Days at a Time
Dolphins can 
stay alert and energetic for 15 days or more by sleeping with one half of their 
brain at a time according to new research published on Oct. 17 in the open 
access journal PLOS ONE.
 It indicates they can continue to exhale at the surface of water, and preserve 
vigilance in case predators approach.
