Dolphin Half Brain Sleep Cycle
By tony leather, 23rd Oct 2012 | Follow this author
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This proved to the researchers that, without doubt, air breathing dolphins have the ability to continuously, perhaps indefinitely, maintain vigilant behaviour through echolocation.
Dolphin Half Brain Sleep Cycle
In what has to be a most elaborate evolutionary development, scientists have discovered that dolphins can stay alert and active for 15 days or more. Howe? They achieve this incredible feat by quite simply sleeping with one half of their brain at a time, because keeping one half of the brain continuously awake is vital to the sea mammals' survival.
Added to that, the air-breathing creatures can continue to manage to surface every so often to breath, whilst remaining constantly vigilant for sharks, as many dolphin populations are at almost constant risk of shark attack, commonly carrying bite marks on their torsos.
Californian researchers tested echo-location abilities in two bottlenose dolphins - a male called Nay and female called Say - over periods of time which would have left other animals sleep-deprived and exhausted. They had to swim around a pen looking for phantom sonar targets, each of which devices picked up dolphin sound pulses and sent back echoes.
As Nay and Say detected these echoes, they responded by pressing paddles, and over three sessions of five continuous days both dolphins had success rates of up to 99%. This proved to the researchers that, without doubt, air breathing dolphins have the ability to continuously, perhaps indefinitely, maintain vigilant behaviour through echolocation.
The team conducted brain wave measurements during the testing period, confirming that dolphins have the ability to perform unihemispheric sleep - the waking half enabling them often to keep one eye open quite literally. This biological, sensory and cognitive ecology is relatively unique, but if dolphins were to sleep like terrestrial animals, they might drown, so that for these most remarkable of creatures, half-brain sleeping is as normal as breathing to we humans, and just as important to survival.
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