英语听力文摘 English Digest 368、屎壳郎的“导航仪”（在线收听）

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.

屎壳郎的眼睛

很多的动物都根据阳光的自然偏振作用来为自己寻找方向，这些动物甚至包括蜂鸟和蝴蝶。然而，大千世界无奇不有，科学家们发现屎壳郎很不一样——它们依靠月光的偏振来完成它们的“旅行”。这种偏振现象是由于阳光与大气中的粒子相互作用，使光在一个单一的平面上振动而产生的。在这里必须提及的是——人眼是感受不到光的偏振的。

人们很早就发现了一点：动物的眼睛很是敏感，它们能够感受到光的偏振。这就不足为奇了，屎壳郎最值得让我们去注意的是——月光的强度仅仅是阳光强度的百万分之一，必须要多很多对眼睛才能够感受得到。

屎壳郎之间食物的竞争很激烈，往往是很多只屎壳郎齐齐盯上一堆粪。因此，当一只屎壳郎滚好了一个粪球后最好就是尽快离开。当然，最快的就是走直线了。科学家们发现，在月明星稀的夜里，屎壳郎就是这样做的，它们都走直线。但是，如果是在乌云密布的夜里，无法看到月亮，这个时候的屎壳郎所走的路线就会歪歪扭扭。
为了确定屎壳郎是凭借着月光的偏振作用而不是月光来看路，研究者们使用了一个滤光器，这个滤光器将月光的偏振改变了90度，这个时候他们发现，屎壳郎的路线也随之改变了90度。

科学家们还推测，屎壳郎并不是唯一一种凭借月光偏振作用为自己“导航”的动物，相信很快也会发现其它的此类生物。

Note：  interact with    与……相互作用