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)用機械的方式進行機構(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，20世紀早期電子計算機的出現(xiàn)，以及隨后20世紀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)展進程。
reckon[ˈrekən]
v.①認為，估計;②指望，想要;③測算
[真題例句] In science generally, however, the nineteenth century must be reckoned (①) as the crucial period for this change in the structure of science.[2001年閱讀1]
[例句精譯] 然而，從科學這個整體來看，19世紀必須被視為科學結(jié)構(gòu)發(fā)生變化的關(guān)鍵時期。
hypothesis[haiˈpɔθisis]
n.假說，假設(shè)，前提
[真題例句] Later, this idea became to be known as the Sapir-Whorf hypothesis, but this term is somewhat inappropriate.[2004年翻譯]
[例句精譯] 后來此觀點成為著名的Sapir-Whorf假說，但這一說法并不適當。
stride[straid]
v.大步走(過)，邁進，跨過;n.邁步，闊步
[真題例句] Every morning, its people (41：swarm) into the offices and factories of America, seeking a days work for a days pay, one day at a time.[1997年完形]
(41)[A] swarm[B] stride
[C] separate[D] slip
[例句精譯] 每天早晨，公司的人們涌入美國的工廠和辦公室，求得當日即付工資的工作，一次只干一天。
(41)[A] 云集，涌往[B] 大步走
[C] 分離的，分開的[D] 滑倒，滑掉
背景常識介紹：
說來也許令人難以置信，不少動物懂得計數(shù)，有些動物還是數(shù)學天才。有人對鴿子做了一項實驗：給它喂食玉米，一粒一粒喂給它吃，每次都喂6粒。突然喂給它第7粒玉米，它竟不吃�？茖W家發(fā)現(xiàn)了灰松鼠在越冬之前要貯存食品，它將許多松果藏在不同的地方。可是以后它找到其中的六、七堆之后，別的地方就不再找了�？赡芑宜墒笾荒軘�(shù)到7。美國的動物學家試驗過黑猩猩的計數(shù)本領(lǐng)：把香蕉放在箱子里，每次放10根，讓黑猩猩自己打開箱子吃。有一次，箱子里只放8根香蕉，黑猩猩吃完后不肯離去;再給它吃1根，它還不肯走;直到吃滿10根，它這才離去。黑猩猩也許能數(shù)到10。還有小小的螞蟻，其計數(shù)本領(lǐng)也毫不遜色。
參考譯文：
動物行為：踩高蹺的故事
假如有一個皇家防止殘害螞蟻協(xié)會的話，德國烏爾姆大學的馬提亞·威特林格可能會首當其沖地成為其憎恨對象。這是因為威特林格博士和他的同事們在本周《科學》雜志上報道說他們砍去了一些螞蟻的腳。這還不算，他們還讓別的螞蟻踩著高蹺走路。
撒哈拉沙漠的箭蟻不得不在貧瘠的沙質(zhì)環(huán)境中長途跋涉尋找食物。它們找完食物后如何返回蟻巢卻一直是個謎。溫和氣候環(huán)境下的螞蟻往往會在路途中留下化學記號，可箭蟻顯然不會。它們跟蜜蜂和古代海員一樣，可以通過日照導航，從而知道出行的大致方向。但是也跟古代海員一樣(他們只會辨認緯度不會辨認經(jīng)度)，這種根據(jù)太陽測算位置的方法無法告知它們該在何時結(jié)束行程。
所以，威特林格博士決定驗證一下這個世紀猜想——沙漠螞蟻體內(nèi)含有步數(shù)計(里程表)，換言之，它們在出行時算好步數(shù)，然后再一步步數(shù)著返回。等到兩者總數(shù)吻合時，就“到家”了。為此，威特林格博士對其養(yǎng)殖的螞蟻進行了訓練，讓它們經(jīng)過一條十米長的溝從蟻巢走到一個飼喂點。當它們獲取食物后，就把它們捉住，讓它們通過另一條通往蟻巢的溝返回。返回時，它們特有的覓巢行為就開始了，即在行走了大約10米遠后，它們會在地上仔細地刻下指向蟻巢入口的標記。
等到螞蟻學會了這一竅門，實驗才真正開始。有的螞蟻抵達飼喂點后，它們的腿部末端被切除，以縮短其步長。其他的螞蟻則在其腳部粘上豬鬃，做成高蹺。然后，兩群螞蟻均被放還至飼喂點，讓其返回蟻巢。
不出所料，踩高蹺的螞蟻由于其步長造成體內(nèi)步數(shù)計無法運作足夠次數(shù)，因此竟似閑庭信步一般走過了蟻巢，結(jié)果在離蟻巢近5米遠的地方愣住了，然后才開始繼續(xù)尋找洞穴。與此同時，遭“截肢”的那些可憐的螞蟻只走了大約6米遠就開始尋找洞穴。
不過，這個故事的結(jié)尾還是令人高興的。威特林格博士證實其猜想后，又把“截肢”螞蟻和踩高蹺螞蟻都放回蟻巢，給它們幾天時間來康復。然后，他把它們放出去開始又一輪試驗。這一次它們可以重新計算出行步數(shù)，因此也就可以準確地計算出返程的步履了。螞蟻也許并不太聰明，但似乎天生就是數(shù)字高手。
