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Second BoGI mistake - dolphins?

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774016.  Mon Jan 10, 2011 7:31 pm Reply with quote

In the Second Book of General Ignorance, page 39, the book states "Dolphins, who need to rest while afloat but still keep breathing, don't sleep in the traditional sense. One half of their brain and body goes to sleep at a time, while the other half is fully awake - including one of their eyes."

This is, I believe, incorrect, as it is only true of some species of dolphin. The bottlenose, for instance, is a keen example of this form of sleep-cycle, and it is not the only one, but there are some species (e.g. the Indus dolphin) which sleep in a "complete" (for lack of a better word) state, for short bursts ranging from four to sixty seconds.

It is my understanding from the statement (which may be an incorrect understanding) that the book is suggesting that all species of dolphin sleep in the former manner, so perhaps it is more a case of lack of clarity than outright mistake?

774036.  Mon Jan 10, 2011 9:35 pm Reply with quote

Bloody pedant - should fit in well here Rieru ;)

774098.  Tue Jan 11, 2011 5:04 am Reply with quote

How do other dolphins sleep, then?

774130.  Tue Jan 11, 2011 6:43 am Reply with quote

bobwilson wrote:
Bloody pedant - should fit in well here Rieru ;)

Thanks ^^ It was just something I was taught it in Psychology earlier this year, and it just glared at me when I read the book.

dr.bob wrote:
How do other dolphins sleep, then?

Bottlenose is just one example of dolphins who sleep in the one-half-of-a-brain-at-a-time method, as is my understanding, most dolphin species use that method of sleep. However, species such as the Indus use the other method, of endulging in full-sleep for periods of 4-60 seconds at a time, over the course of many hours (8, I think). I'm not sure if the Indus dolphin is the only species of dolphin to use this method of sleep, but it is definitely an alternative method to the one described in the book.

Also, as I have found out through research in the day, dolphins in captivity enter a full sleep-state, where both eyes are closed, and the do not react to external stimuli (they use a tail-flick reflex to keep their blowholes above water when necessary, as respiration is automatic).


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