Sleep is fundamental for the development of body and brain. This axiom comes from basic observation of both humans and other animals, with sleep being optimal at birth and gradually declining through adulthood. Dolphins are highly intelligent mammals, with enough evidence attesting to this fact. They live in close-knit social groups known as pods, and their communication system is a complex affair, which includes their own names and signature whistles.
Dolphins can be found in oceans all over the world. They are sleek creatures and aerodynamically-formed, with their skin tight but feeling rubbery to the touch. Over thirty dolphin species exist and one can tell between them not just by their size but also by their shape and special markings.
One of the reasons dolphins continue to amaze us is their ability to sleep with one eye open. During this time, one half of their brain remains active, a condition referred to as unihemispheric sleep. They will close one eye with the other remaining open to keep guard against predators and since these creatures are conscious breathers, should they sleep like we do they will drown. After sometime, one eye will close and the other will open and this drill goes on for the entire nap. Birds also exhibit the same behavior as our friends from the waters.