Dolphins can stay alert and active for 15 days or more by sleeping with one half of their brain at a time, scientists have learned.
The trick of keeping half the brain continuously awake is vital to the sea mammals’ survival, experts believe. It allows them to come to the surface every so often to breathe, and remain constantly vigilant for sharks.
Scientists in California, US, tested the ability of two bottlenose dolphins to echolocate accurately over periods of time which would have left other animals sleep-deprived and exhausted.
Dolphins use their sonar-like ability to navigate, find prey, detect predators and co-ordinate group behaviour.
Brain wave measurements have confirmed that the creatures are capable of “unihemispheric sleep” – sleeping with just one side of the brain.
Many dolphin populations are exposed to almost constant risk of shark attack, and the animals commonly carry bite marks. Continually listening to their echo signals allowed experts to counter the shark threat, even in murky waters. Source: www.telegraph.co.uk
