大象能模仿卡車行駛時發出的聲音英語美文

Elephants Can Mimic Traffic Noises, Study Says

科學家日前表示，並不是只有小孩子在擺弄玩具汽車時會模仿引擎發動的聲音，他們發現大象也能發出類似的叫聲，只不過這種聲音更像非洲高速公路上來往卡車發出的隆隆聲。

It isn"t only children playing with toy cars who make engine noises. Elephants produce a similar roar, though in their case it"s the rumble of trucks on an African highway that the animals imitate, scientists say.

據美國《國家地理》雜誌網站3月23日報道，進行這項研究的科學家表示，與鸚鵡、某些鳴禽、海豚和人類一樣，大象具有模仿聲音的能力。動物學家喬伊斯·普爾是安博塞利大象研究計劃的負責人，也是第一個注意到這種現象的人。她在肯尼亞安博塞利國家公園(Amboseli National Park)裏，發現了一羣半野生的、孤兒大象的象羣發出了不同尋常的奇怪叫聲。普爾曾試圖通過聲音來追蹤一隻名為米愛卡的雌性大象，但是這隻10歲大象出色的模仿能力讓普爾的任務變得並不簡單。普爾説：“有些時候，我簡直分不清究竟是遠方的卡車發出的聲音還是米愛卡的叫聲，這讓我非常好奇，我想是不是米愛卡能夠模仿卡車行駛的聲音呢?”

普爾還表示，米愛卡這個象羣中的其它成員也被人們發現能夠發出類似的聲音，而這種聲音和以前曾記錄在案的任何一種大象的叫聲都明顯不同。普爾猜測，米愛卡是在繁忙的內羅畢至蒙巴薩高速公路附近，模仿卡車發出的聲音的。米愛卡的圍欄距內羅畢至蒙巴薩的高速公路間大約有2英里(3公里)的路程，為了打發無聊的夜晚，米愛卡開始模仿遠處公路上隆隆的車聲。

對於大象為何會模仿汽車的聲音，還有另外一個可能的解釋，即米愛卡模仿這種聲音可能單單是因為它喜歡卡車發出的這種隆隆聲。對此，普爾解釋説：“或許，這種聲音能讓米愛卡感到愉快，就像我們聽到嗡嗡聲會覺得舒服一樣。”她還同時指出，無論大象模仿這種聲音的`動機是什麼，最主要的一點是，大象確實能夠發出這種聲音。“這説明它們能發出不同尋常的新奇的聲音，這些聲音是它們通過模仿其它動物或是機器學來的。而這種行為在哺乳動物中極其少見。”

普爾的發現作為一項研究的中心內容被髮表在本週的科學期刊《自然》上。普爾和這篇文章的合著者認為，大象這種羣居生活的動物通過模仿聲音，來幫助各自之間保持聯繫。文章中還提到了一隻名叫卡利莫羅的23歲雄性非洲象。卡利莫羅生命中有18年的時間是和瑞士巴塞爾動物園的亞洲象生活在一起的。與非洲象不同，亞洲象通常是發出“喳喳”的聲音來彼此聯繫的。卡利莫羅學會模仿這種聲音後，它幾乎拒絕再接受任何其它的聲音。

研究者表示，這是人們首次發現非靈長類的陸地哺乳動物具有模仿，學習聲音的能力。在野生環境中，大象經常要在距離很遠的時候，彼此進行溝通和交流，這時它們會使用低頻叫聲和同一象羣中的其它成員保持聯繫。有試驗證實，大象可以在1.5英里(2.5公里)的距離之外，分辯出象羣中特殊個體的叫聲。所以，具備一種獨一無二的可識別的叫聲無疑是非常有用的，就像米愛卡發出的這種低沉的，卡車一樣的隆隆聲一樣。

普爾表示，這種與眾不同的叫聲好像是一種聲音信號，這種信號是針對這隻大象的親人或者和它關係非常緊密的其它大象發出的。她説：“在關係複雜又呈流動性的象羣中，聲音的模仿可能是被用來進行維持個體和特殊動物羣體間的關係的。”

It isn"t only children playing with toy cars who make engine noises. Elephants produce a similar roar, though in their case it"s the rumble of trucks on an African highway that the animals imitate, scientists say.

The experts behind the discovery say elephants are capable of vocal imitation, joining a select group of animals that includes parrots, songbirds, dolphins, and humans.

Zoologist Joyce Poole was the first to notice some rather unelephantine noises emanating from a group of semiwild, orphaned elephants in Tsavo National Park, Kenya. She managed to track the sounds to a female named Mlaika. But the ten-year-old"s powers of mimicry were so developed that the task wasn"t easy.

"I was sometimes unable to distinguish between the distant trucks and Mlaika"s calling," said Poole, the scientific director of the Amboseli Elephant Research Project. "This is what first made me wonder whether she could possibly be imitating the truck sounds."

Poole said others in Mlaika"s group have been heard to make a similar noise, which is quite different from any call previously recorded in elephants.

Poole suspects Mlaika began mimicking traffic on the busy Nairobi-Mombassa highway because she got bored in her nighttime stockade located two miles (three kilometers) away from the road. "It was a sound she heard every night. Just after sunset sound travels well on the savanna."

Another possible explanation is that Mlaika might simply like the rumble of trucks. "Perhaps it was pleasing to her in some way, like humming is to us," Poole speculated.

Whatever the motivation, the main point, Poole said, is that elephants can actually produce such a sound.

"It shows they are able to come up with novel sounds outside their normal repertoire—some of which they have learned through imitating other animals or machines," Poole said. "This is extremely unusual for mammals."

Poole"s findings are central to a study published this week in the science journal Nature. Poole and her co-authors suggest elephants use vocal learning to help the group-living animals stay in touch.

The study also refers to a 23-year-old male African elephant named Calimero, which spent 18 years living with Asian elephants at the Basel Zoo in Switzerland. Unlike their African counterparts, Asian elephants usually communicate using chirping sounds. Calimero has learned to imitate these calls, using them almost to the point of excluding all other sounds.

"Vocal learning enables a flexible and open communication system in which animals may learn to imitate signals that are not typical of the species," the researchers wrote.

They say this is the first time vocal learning has been recorded in a nonprimate land mammal.

In the wild, elephants often need to communicate over long distances, using low frequency calls to keep tabs on other members of their group. Experiments have shown that elephants can recognize the voices of particular individuals at distances of up to one and a half miles (two and a half kilometers). So having a uniquely recognizable call, like Mlaika"s low truck-rumble sound, could be a very useful.

"Elephants may well be able to produce unique calls, like a vocal signature, that are particular to that individual or to its family or to very closely bonded individuals," Poole said.

"Vocal learning could be used to maintain individual-specific social bonds in the complex and fluid society of elephants, where members of a social group come and go, keeping in contact over long distances and maintaining close social bonds over lifetimes."