双语有声阅读：动物的罗盘

Animals' Compasses

 

Researchers have found that migrating animals use a variety of inner compasses to help them navigate¹. Some steer² by the position of the Sun. Others navigate by the stars. Some use the Sun as their guide during the day and then switch to star navigation by night. One study shows that the homing pigeon uses the Earth's magnetic fields as a guide in finding its way home and there are indications that various other animals from insects to mollusks, can also make use of magnetic compasses. It is of course very useful for a migrating bird to be able to switch to a magnetic compass when clouds cover the Sun; otherwise it would just have to land and wait for the Sun to come out again.

 

Even with the Sun or stars to steer by, the problems of navigation are more complicated than they might seem at first. For example, a worker honeybee that has found a rich source of nectar and pollen³ flies rapidly home to the hive to report. A naturalist⁴ has discovered that the bee scout⁵ delivers her report through a complicated dance in the hive, in which she tells the other workers not only how far away the food is, but also what direction to fly in relation to the Sun. But the Sun does not stay in one place all day. As the workers start out to gather the food, the Sun may already have changed its position in the sky somewhat. In later trips during the day, the Sun will seem to move farther and farther toward the west. Yet the worker bees seem to have no trouble at all in finding the food source. Their inner clocks tell them just where the Sun will be and they change their course correspondingly.

 

动物的罗盘

 

研究人员已经发现迁徙性动物可以借助各种各样的体内罗盘来校正方向。 有些动物借助太阳的位置辨别方向，有些则依靠星星。 还有的白天利用太阳，晚上利用星星。 有研究发现信鸽以地磁场为向导来找到回家的路。 还有迹象表明许许多多其它生物，从昆虫到软体动物，也能利用这种磁场罗盘。 具有这种磁场罗盘，对候鸟来说当然非常有用，因为如果乌云遮日，它可以以磁场为向导继续飞行，否则它就只好着陆，等待太阳重新出现。 即使是借助太阳或星星导航，其中的学问也比它表面看起来的要复杂得多。 例如，一只工蜂找到了花圃蜜园，急忙飞回蜂房报信。博物学家发现这只蜂探在蜂房里跳了一段极为复杂的舞，通过这段舞她不但告诉其它工蜂食物有多远，而且报告了以太阳为参照的飞行路线。但太阳不会呆在天上不动。 当蜂群出发采食时，太阳可能已经多少改变了它在天空中的位置。出发得越迟，太阳就越偏西，可这似乎没给寻找食物源的工蜂们带来任何不便。 它们体内的时钟告诉他们太阳应在的位置，据此它们相应地改变前进的方向。

1 navigate   

v.航行，飞行；导航，领航

参考例句：

• He was the first man to navigate the Atlantic by air.他是第一个飞越大西洋的人。
• Such boats can navigate on the Nile.这种船可以在尼罗河上航行。

2 steer   

vt.驾驶，为…操舵；引导；vi.驾驶

参考例句：

• If you push the car, I'll steer it.如果你来推车，我就来驾车。
• It's no use trying to steer the boy into a course of action that suits you.想说服这孩子按你的方式行事是徒劳的。

3 pollen   

n.[植]花粉

参考例句：

• Hummingbirds have discovered that nectar and pollen are very nutritious.蜂鸟发现花蜜和花粉是很有营养的。
• He developed an allergy to pollen.他对花粉过敏。

4 naturalist   

n.博物学家(尤指直接观察动植物者)

参考例句：

• He was a printer by trade and naturalist by avocation.他从事印刷业，同时是个博物学爱好者。
• The naturalist told us many stories about birds.博物学家给我们讲述了许多有关鸟儿的故事。

5 scout   

n.童子军，侦察员；v.侦察，搜索

参考例句：

• He was mistaken for an enemy scout and badly wounded.他被误认为是敌人的侦察兵，受了重伤。
• The scout made a stealthy approach to the enemy position.侦察兵偷偷地靠近敌军阵地。