Animals' Compasses

Researchers have found that migrating animals use a variety of inner

compasses to help them navigate. Some steer 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 pollen flies rapidly home to the      

hive to report. A naturalist has discovered that the bee scout 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.

動(dòng)物的羅盤

研究人員已經(jīng)發(fā)現(xiàn)遷徙性動(dòng)物可以借助各種各樣的體內(nèi)羅盤來(lái)校正方向。  有些動(dòng)物借 助太陽(yáng)的位置辨別方向，有些則依靠星星。

還有的白天利用太陽(yáng)，晚上利用星星。  有研究 發(fā)現(xiàn)信鴿以地磁場(chǎng)為向?qū)��?lái)找到回家的路。  還有跡象表明許許多多其它生物，從昆蟲到軟

體動(dòng)物，也能利用這種磁場(chǎng)羅盤。  具有這種磁場(chǎng)羅盤，對(duì)候鳥來(lái)說(shuō)當(dāng)然非常有用，因?yàn)槿?/p>

果烏云遮日，它可以以磁場(chǎng)為向?qū)Ю^續(xù)飛行，否則它就只好著陸，等待太陽(yáng)重新出現(xiàn)。  即 使是借助太陽(yáng)或星星導(dǎo)航，其中的學(xué)問(wèn)也比它表面看起來(lái)的要復(fù)雜得多。

例如，一只工蜂 找到了花圃蜜園，急忙飛回蜂房報(bào)信。博物學(xué)家發(fā)現(xiàn)這只蜂探在蜂房里跳了一段極為復(fù)雜的

舞，通過(guò)這段舞她不但告訴其它工蜂食物有多遠(yuǎn)，而且報(bào)告了以太陽(yáng)為參照的飛行路線。 但 太陽(yáng)不會(huì)呆在天上不動(dòng)。

當(dāng)蜂群出發(fā)采食時(shí)，太陽(yáng)可能已經(jīng)多少改變了它在天空中的位置。 出發(fā)得越遲，太陽(yáng)就越偏西，可這似乎沒(méi)給尋找食物源的工蜂們帶來(lái)任何不便。  它們體內(nèi)

的時(shí)鐘告訴他們太陽(yáng)應(yīng)在的位置，據(jù)此它們相應(yīng)地改變前進(jìn)的方向。

譯路通武漢漢口翻譯公司整理

2012.7.18