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Why do animals sleep?

  1. Dec 7, 2008 #1
    I've always been curious about the answer to this question. Can anyone point me to some research regarding this subject matter? Have we made any advances on finding out the answer to this question? I am assuming that it would be pretty inefficient, and toiling on the body and brain to be active 24/7.
  2. jcsd
  3. Dec 7, 2008 #2


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    Some animals are very well-adapted to operate at night, and some by day. It makes sense that if an animal's ability to get food, etc is optimized to a time of day, that animal should expend its energies at that time, and use the less-optimal times to rest, recharge, digest food, heal, etc. I am not a biologist, nor do I play one on TV, but I have slept in lots of Holiday Inns.

    Your mileage may vary.
  4. Dec 7, 2008 #3


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    There is also evidence that in humans the brain has to have a 'down-time' to process, store, discard, or otherwise deal with information that it received during the waking period. Sleep deprivation is one sure way of bringing on insanity. I've never seen anything referencing such a need in lower animals, but dogs and cats definitely appear to dream.
  5. Dec 7, 2008 #4


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    I think you have it the wrong way round.
    Cats need to dream to stop them going (anymore) insane, they don't know why us lower animals have to sleep and frankly don't care as long as there is a sunny patch to nap in.
    Last edited: Dec 8, 2008
  6. Dec 8, 2008 #5


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  7. Dec 9, 2008 #6

    Is this why we have dreams that are directly related to what's been on our mind during the day?
  8. Dec 9, 2008 #7


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    I believe so, but I'm not qualified to answer. If memory serves, MIH knows a lot about the subject.
  9. Dec 10, 2008 #8

    jim mcnamara

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    The why answer is probably already answered by turbo-1. Expending energy when the return is the highest, and being able to avoid predators while out foraging.

    Adult ungulates - deer, cows, etc., sleep very little (and then with legs locked in a standing position), it is posited, because when they sleep or lay down for any reason they are more vulnerable to predation. Ungulates like sheep and that will lay down more often are adapted to living on sheer rocky slopes. So the assumption is the predation penalty for laying down was less for them.

    Reef fish exhibit the same diurnal behavior patterns: a "slow" time when they hide in the coral, and another active time for foraging.

    My opinion: the other benefits of sleep mentioned in this thread are secondary benefical outcomes, not the primary reason for diurnal behavior patterns. The primary reason is being out and about with predators that have extra predatory advantages related to time of day is not adaptive.
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