Scientists from the United States have learned that dolphins are able to stay alert and active for 15 days or more at a time by sleeping only one-half of their brain. The experts believe that this ability to stay alert by using only half of their brain is a key to the survival of sea mammals. The scientists believe that the ability helps the dolphin to surface to breathe and remain vigilant for predators such as sharks.
The scientists conducted the research in California by testing the ability of two bottlenose dolphins to echolocate accurately over a certain period. The scientists say that the dolphins could echolocate accurately over a period long enough to have left other animals sleep-deprived. During the tests, the two dolphins swam around their enclosure looking for Phantom sonar targets.
Each of the eight test devices used with the dolphins was made up of a device that could pick up the dolphins sound pulses and return a phantom target. The dolphins then responded to the phantom targets by pressing a paddle. The dolphins were rewarded with a special tone with success and a fish. A false alarm gave the dolphins no tone and no reward.
The researchers report that over three sessions of five continuous days the Dolphins had a success rate of up to 99%. The female dolphin outperformed her male partner during the test. The scientists tested the female dolphin with the same experiment over a period of 30 days.
The scientists wrote, "From an anthropomorphic viewpoint, the ability of the dolphin to continuously monitor its environment for days without interruption seems extreme. However, the biological, sensory and cognitive ecology of these animals is relatively unique and demanding."
"If dolphins sleep like terrestrial animals, they might drown. If dolphins fail to maintain vigilance, they become susceptible to predation. As a result, the apparent 'extreme' capabilities these animals possess are likely to be quite normal, unspectacular, and necessary for survival from the dolphin's perspective."