英語聽力文摘 屎殼郎的“導(dǎo)航儀”

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The Eye of the Dung Beetle

A number of animals, including honeybees and butterflies, use sunlight’s polarization in their navigations, but the dung beetle is the first animal ever discovered to use moonlight’s polarization to guide its travels. Polarization happens when some of the light from the sun interacts with particles in the atmosphere, causing the light to vibrate along a single plane. Polarized light is invisible to the human eye.

It’s been known for some time that the eyes of some insects are sensitive to polarized sunlight, but what is remarkable about the dung beetle is that moonlight is one millionth the strength of sunlight and requires a good deal more of a pair of eyes.

There are many dung beetles competing for a limited amount of food at a dung pile, so when an individual is finished rolling a ball of dung it is in its best interest to make a quick escape. And the fastest way to travel is in a straight path. Scientists noticed that when the moon was visible, these dung beetles did just that; they traveled in straight paths. But when it was a cloudy night, the beetles’ paths became shaky and erratic.

To be sure the beetles were indeed using the moon’s polarization and not the moon itself, the researchers used a filter that changed the pattern of the polarized moonlight by 90 degrees. The beetles responded by changing their course by 90 degrees.

Scientists suspect that the dung beetle isn’t the only animal to navigate by the moon’s polarization and that more such creatures will soon be discovered.

屎殼郎的眼睛

很多的動物都根據(jù)陽光的自然偏振作用來為自己尋找方向，這些動物甚至包括蜂鳥和蝴蝶。然而，大千世界無奇不有，科學(xué)家們發(fā)現(xiàn)屎殼郎很不一樣——它們依靠月光的偏振來完成它們的“旅行”。這種偏振現(xiàn)象是由于陽光與大氣中的粒子相互作用，使光在一個單一的平面上振動而產(chǎn)生的。在這里必須提及的是——人眼是感受不到光的偏振的。

人們很早就發(fā)現(xiàn)了一點(diǎn)：動物的眼睛很是敏感，它們能夠感受到光的偏振。這就不足為奇了，屎殼郎最值得讓我們?nèi)プ⒁獾氖?mdash;—月光的強(qiáng)度僅僅是陽光強(qiáng)度的百萬分之一，必須要多很多對眼睛才能夠感受得到。

屎殼郎之間食物的競爭很激烈，往往是很多只屎殼郎齊齊盯上一堆糞。因此，當(dāng)一只屎殼郎滾好了一個糞球后最好就是盡快離開。當(dāng)然，最快的就是走直線了?？茖W(xué)家們發(fā)現(xiàn)，在月明星稀的夜里，屎殼郎就是這樣做的，它們都走直線。但是，如果是在烏云密布的夜里，無法看到月亮，這個時候的屎殼郎所走的路線就會歪歪扭扭。

為了確定屎殼郎是憑借著月光的偏振作用而不是月光來看路，研究者們使用了一個濾光器，這個濾光器將月光的偏振改變了90度，這個時候他們發(fā)現(xiàn)，屎殼郎的路線也隨之改變了90度。

科學(xué)家們還推測，屎殼郎并不是唯一一種憑借月光偏振作用為自己“導(dǎo)航”的動物，相信很快也會發(fā)現(xiàn)其它的此類生物。

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