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Pythons, bats and giant armadillos are |
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among the longest sleepers at over 18 hours a day. |
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Human babies need 16 hours, |
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and most of us probably feel |
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we need around eight hours sleep to function well. |
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Professor Jerry Seigel from the University of California, |
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Los Angeles, conducted a study of the sleep times |
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of a broad range of animals |
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and found that they vary widely. |
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Some, like migrating birds, |
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can survive long periods without sleeping at all. |
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He believes that shows sleep evolved to conserve energy: |
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"It's animals that are needlessly active that will not survive, |
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but animals that are most efficient |
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and use their waking time to do vital functions, |
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and are otherwise asleep that will survive." |
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Sleep helps make best use of limited resources. |
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In humans, when we're awake, |
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our brain accounts for 20% of the energy |
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we use when just sitting around. |
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Sleeping also makes us less likely to get injured |
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and less likely to be detected by predators. |
