Dolphins have been used in entertainment, attacking enemies and even detecting sea mines. For couples looking to tap into the playful animal’s talents even more, however, there are now dolphin-assisted births. (Photo : Reuters)

Dolphins can stay alert for 15 days in a row by resting only one half of their brain at a time, a new study has revealed.

Researchers from the National Marine Mammal Foundation in San Diego have found that dolphins evolved developing unihemispheric sleep, an ability to allow one half of the brain to sleep and the other to remain alert.

It was believed that the dolphins evolved this sleeping behavior to breathe at the water surface when they are half asleep. The new study suggests that dolphins developed the sleeping technique to remain alert and detect predators.

Experts studied two bottlenose dolphins (one male and one female) and monitored their sleeping patterns, while testing their echolocation skills for five days in a portable floating pen. The dolphins were required to use their echolocation skills to search for phantom targets spread all over the pen.

Echolocation is a technique used by dolphins to find their prey in the dark environment of the oceans. They emit some sounds like clicks and listen to the echoes to get information about its environment.

When experts tested the echolocation skills of the dolphins, they noticed that the marine creatures successfully detected and reported targets for five days in a row without showing any signs of fatigue.

While the overall performance of one dolphin was 75 to 86 percent correct, the performance of the female dolphin was 99 percent correct.

When the female dolphin was tested for a 15-day period, it responded correctly and its performance did not deteriorate. However, researchers did not study for how many days the dolphins could have continued to locate targets with accuracy.

The study suggests that dolphins can remain vigilant and report the presence of targets with near perfect performance over longer periods of time. It concludes evolution of dolphins' sleeping behavior may not only help them to breathe continuously in the ocean, but also to remain alert and search for targets.

"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," said lead researcher Brian Branstetter, from the National Marine Mammal Foundation.

The findings of the study, "Dolphins Can Maintain Vigilant Behavior through Echolocation for 15 Days without Interruption or Cognitive Impairment," are published in the journal PLOS ONE.