Interesting question. The whole issue of sleep in whales, dolphins and
porpoises is a bit of an unknown, but here's what we do know...
While I don't know of anyone who has ever studied sleep in killer
whales, scientists have hooked up an EEG to dolphins. What happens
there is interesting: half of the brain seems to sleep at a time, with
the two havles switching off. This makes sense, because all cetaceans
(whales, dolphins and porpoises) are violuntary breathers - that is,
they have to think to breathe. We don't - we breathe automatically.
But a diving animal that spends lots of time underwater obviously needs
to have control over its breathing. Therefore, if the entire brain shut
down (as it does in people) the whale would presumably forget to
breathe. So what we think currently is that half the brain sleeps while
the other half stays alert to keep track of respiration. This is
probably what all whales and dolphins (including killer whales) do, but
no one knows for sure.
And yes, all whales hold their breath when they're underwater.
Brian Barker wrote:
> Do Orca whales sleep? And if they do sleep, do they
> hold their breath under water while they do?
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Phillip J. Clapham, Ph.D. Large Whale Biology Program Northeast Fisheries Science Center 166 Water Street Woods Hole, MA 02543, U.S.A.
tel. 508 495-2316 fax 508 495-2066 email: email@example.com
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