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第1段
1 .<-NARRATOR:->Now listen to part of a lecture on the topic you just read about.
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第2段
1 .<-MALE PROFESSOR:->The theory that humpback whales use the stars to navigate the open seas is a fascinating one.
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2 .But the evidence supporting the theory is not very convincing.
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第3段
1 .First, there doesn't seem to be any real connection between intelligence and an animal's ability to use stars for navigation.
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2 .You know, there are other animals that use stars to navigate.
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3 .Some birds have this ability—like ducks, for example.
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4 .Now, the general cognitive ability of ducks is only average—they are not highly intelligent.
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5 .The fact that the ducks evolved the ability to use stars for navigation does not seem to have much of a connection to their overall intelligence.
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6 .It's just an instinct they were born with, not a sign of intelligence.
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7 .So, the fact that humpback whales happen to be intelligent does not make them particularly likely to use stars for navigation.
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8 .The two things just don't seem to be connected.
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第4段
1 .Second, there may be a different explanation for the humpback whales' ability to navigate in straight lines.
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2 .Remember that for animals to be able to do this, they have to sense some external object or force.
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3 .Well, the external force the whales could be sensing is Earth's magnetic field.
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4 .Humpback whales have a substance in their brains called biomagnetite.
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第5段
1 .Generally, the presence of biomagnetite in an animal's body makes that animal sensitive to Earth's magnetic field.
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2 .The fact that there's biomagnetite in the brains of humpback whales suggests that they orient themselves by the magnetic field rather than the stars when they migrate.
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第6段
1 .Third, spy-hopping probably has nothing to do with looking at stars.
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2 .Spy-hopping is rare, but there are other animals that exhibit it.
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3 .Some sharks do it for example.
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4 .But sharks don't migrate or look at stars.
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5 .Sharks spy-hop to look for animals they want to hunt.
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6 .And another thing: humpback whales often spy-hop during the day when no stars can be seen.
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7 .So to suggest that the function of spy-hopping is to look at stars is pure speculation.
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