Animal behaviour: A stilted story
IF THERE were a Royal Society for the Prevention of Cruelty to Ants, Matthias Wittlinger of the University of Ulm, in Germany, would probably be top of its hate list. The reason is that Dr Wittlinger and his colleagues have, as they report in this week’s Science, been chopping the feet off ants. And not only that. They have been making other ants walk around on stilts.
Saharan desert ants of the genus Cataglyphis have to travel long distances to discover food in their impoverished, sandy environment. How they find their way home once they have done so is a mystery. Ants in more temperate climates often lay down chemical trails, but Cataglyphis, apparently, does not. Like honeybees and ancient mariners, they can navigate by the sun, so they know the general direction in which to travel. But, also like ancient mariners (who knew their latitude, but not their longitude), such solar reckoning cannot tell them when to stop.
Dr Wittlinger, therefore, decided to investigate a century-old hypothesis that desert ants have internal pedometers—in other words, they count their steps out, and they count them back. When one total matches the other, they are home. To test this idea he trained his ants to walk from their nests to a feeding station through a ten-metre-long channel. When they had picked up the food, he caught them and made them return through a different channel, which also led to the nest. When they made this return journey, they began their characteristic nest-searching behaviour, quartering the ground in detail looking for the entrance, after travelling about ten metres.
Once the ants had mastered this trick, the experiment proper began. Some ants, when they arrived at the feeding station, had the ends of their legs amputated, to shorten their stride length. Others were fitted with stilts in the form of pig-bristles glued to their feet. Both lots were then returned to the feeding station, to make the journey home.
As predicted, the ants on stilts, whose stride-length meant their internal pedometers had not clicked enough times, walked blithely past their nests, and were left stranded almost five metres on the far side before they started looking for the hole. Meanwhile, the poor stumped ants travelled only about six metres before they started their search.
The story, however, has a happy ending. Having proved his point, Dr Wittlinger returned both stumped and stilted ants to the nest and gave them a few days to recover. Then he let them out for another run. Now that they could re-count their outbound journeys, they were able to calculate the journey home correctly. Ants may not be very bright, but it seems they have a head for figures.
考研詞匯：
chop[tʃɔp]
v.砍，劈，斬;n.排骨，肉塊
[真題例句] His colleague, Michael Beer, says that far too many companies have applied reengineering in a mechanistic fashion, chopping (v.) out costs without giving sufficient thought to longterm profitability.[1998年閱讀2]
[例句精譯] 他的同事邁克·比爾說，太多的企業(yè)用機(jī)械的方式進(jìn)行機(jī)構(gòu)重組，在沒有充分考慮到長期效益的情況下就降低了成本。
impoverish[imˈpɔvəriʃ]
vt.使貧窮，使枯竭
[真題例句] To take advantage of this tool, some impoverished countries will have to get over their outdated anticolonial prejudices with respect to foreign investment.[2001年閱讀2]
[例句精譯] 要想利用互聯(lián)網(wǎng)，某些貧困國家必須克服對國外投資所持的過時(shí)了的反殖民的種種偏見。
apparent[əˈpærənt]
a.①(to)明顯的，顯而易見的;②表面的，貌似的
[真題例句] It is generally recognized, (29：however), that the introduction of the computer in the early 20th century, (30：followed) by the invention of the integrated circuit during the 1960s, radically changed the process, (31：although) its impact on the media was not immediately (32：apparent) (①) .[2002年完形]
[例句精譯] 但人們普遍都承認(rèn)，20世紀(jì)早期電子計(jì)算機(jī)的出現(xiàn)，以及隨后20世紀(jì)60年代發(fā)明的集成電路，雖然對傳媒?jīng)]有產(chǎn)生立竿見影的影響，但是卻完全改變了發(fā)展進(jìn)程。
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