The marine mammals that are considered to be one of the most intelligent animals – Dolphins have peculiar ability to stay vigilant round-the-clock by making one half of their brain sleep, while keeping the other half awake – says a new study.

In the study, researchers tried to find out whether the persistent vigilance of dolphins tires the fishes or undermines their senses. Sam Ridgway from the US Navy Marine Mammal Program and his team of researchers from San Diego and Tel Aviv monitored acoustic and visual vigilance of two dolphins for a period of five days to test how well the two dolphins' vigilance worked persistently with break.  

Ridgway and his team educated the two dolphins to respond to a 1.5 second beep sounded randomly against a background of 0.5 second beeps every 30 seconds. The researchers found that dolphins responded and came to action every time after hearing the 1.5 second beep sound, which was too low for the dolphins, swimming in their enclosure, to notice. The researchers noted that the two fishes responded persistently to the sounds for five days without a break.     
 
The researchers Allen Goldblatt and Don Carder conducted a visual stimulus test on the two dolphins' vigilance. According to the study, as the binocular vision of dolphins is limited because their eyes are located on opposite sides of their heads, Kamolnick educated one of the dolphins – “Say” – to identify two shapes with its right eye, before education it to identify the same shapes with its left eye; the shapes includes either three horizontal red bars or one vertical green bar.

Goldblatt and Carder were expecting that with one of the dolphin’s brain asleep, the dolphin would be able to identify the shapes only through the eye connected to the awake or conscious half its brain. However, the researchers were surprised when they started to educate “Say” to identify shapes with its left eye; they found that “Say” was able to identify shapes through its left eye, even without the training.    

In the study published in the Friday issue of the Journal of Experimental Biology, Ridgway explicated that the dolphin “Say” might have transferred the visual information from conscious half of brain to asleep half of brain, connected through inter-hemispheric links. Ridgway and his team concluded that dolphins stay vigilant round-the-clock and keep transmitting information from active part to inactive part of brain.