Researchers test how long a dolphin can remain alert

New research has found that dolphins can stay constantly alert for over two weeks, allowing them to avoid drowning or becoming easy prey.

Though studies have already found that dolphins sleep with part of their brains, scientists are discovering how mindful dolphins can be whilst half of their brain is asleep, by testing their ability to scan the environment.

Dolphins use echolocation to work out where they are by emitting clicks, which are echoed off of surfaces. Clicks emitted by two dolphins, a male called Nay and a female called Say, were echoed back by researchers using devices, effectively creating a phantom surface to the dolphins.

The scientists found that the dolphins' echolocation performance showed no sign of deterioration for up to 15 consecutive days, however, were unable to test how much longer their accuracy could last.

"Dolphins can continue to swim and think for days without rest or sleep, possibly indefinitely," said Brian Branstetter, a marine biologist at the National Marine Mammal Foundation in San Diego. "These findings suggest that dolphins evolved to sleep with only half their brains not only to keep from drowning, but also to remain vigilant."

The study has been published in the PLoS ONE journal. Scientists are now looking at ways to record the dolphins' ability to remain alert beyond 15 days.