How Baleen Whales Sing Underwater須鯨如何在水下發聲

Important clues into how whales are able to sing underwater have been found in a new study.

Professor Coen Elemans and other researchers at the University of Southern Denmark studied the larynges， or voice boxes， of three whales that had previously been stranded and died.

The whales were a humpback， a minke and a sei—three different types of baleen whales.

Baleen whales are different to other mammals because they don’t have vocal chords or teeth. Instead， they have a U-shaped tissue in their voice box that allows them to breathe in huge amounts of air. They also have a unique cushion of fat and muscle that isn’t found in other animals.

By blowing air through the voice boxes in the lab， the scientists were able to find out which parts of the voice box vibrated in order to produce sound. The researchers also created computer models of the sei whale’s songs and matched them to recordings of similar whales taken in the wild.

They concluded that baleen whales were able to sing by pushing the tissue against the fat and muscle cushion.

The findings were different to other studies that showed toothed whales， such as dolphins， orcas and sperm whales， sing by using a special organ in their nasal passages.

一項新的研究發現了鯨魚如何在水下發聲的重要線索。

南丹麥大學的Coen Elemans教授和其他研究人員研究了三頭此前擱淺死亡的鯨魚的喉部。

這三頭鯨魚分別是座頭鯨、小須鯨和鳁鯨——三種不同類型的須鯨。

須鯨與其他哺乳動物不同，因為它們沒有聲帶和牙齒。但它們的喉部有一個U形組織，可以讓它們吸入大量空氣。它們還有一個獨特的脂肪和肌肉緩沖層，這是其他動物所沒有的。

在實驗室，通過向須鯨的喉部吹氣，科學家們能夠發現其中哪些部位通過振動產生聲音。研究人員還創建了鳁鯨叫聲的計算機模型，并將它們與在野外收錄的類似鯨魚的聲音進行匹配。

他們得出結論，須鯨能夠通過推動脂肪和肌肉緩沖層來發聲。

這些發現與其他研究結論不同，其他研究顯示，海豚、虎鯨和抹香鯨等齒鯨通過鼻腔中的特殊器官發聲。

In baleen whales， arytenoids are large and stiff， forming a kind of ring that can press against the cushion of fat and muscle. When a whale breathes out， this cushion vibrates in a rippling way， which makes the sound of a whale call.

Whales are thought to have evolved from land mammals about 50 million years ago.

Prof Elemans said the larynges of baleen whales had probably evolved as a way to let them sing underwater without the risk of choking and drowning.

The adaptation would have been very important to the survival of whales， who depend on vocalizing， or singing， to communicate with each other.

The study showed that while whales are able to make a wide range of different sounds at different pitches—some of which humans can barely hear—they can’t produce sounds louder than the ones made by ships.

Since whales can’t sing loud enough to drown out noise pollution from ships， they may not be able to hear each other properly， which means some species， like the Antarctic blue whale， could be finding it hard to mate. Being unable to find a mate would in turn threaten future population numbers.

須鯨的勺狀軟骨又大又硬，形成一種可以擠壓脂肪和肌肉緩沖層的環狀結構。當鯨魚呼氣時，這個緩沖層以波紋狀的方式振動，從而發出聲音。

鯨魚被認為是大約5 000萬年前由陸地哺乳動物進化而來的。

Elemans教授表示，須鯨的喉部可能是為了讓它們在水下發聲無窒息和溺水風險進化而來的。

這種適應對鯨魚的生存非常重要，因為鯨魚依靠發聲進行

交流。

研究表明，雖然鯨魚能夠以不同的音高發出各種不同的聲音——其中一些聲音人類幾乎聽不見——但它們發出的聲音比船只運行的聲音小。

由于鯨魚發出的聲音無法蓋過船只制造的噪聲，因此它們可能無法正常地聽到彼此的聲音。這意味著一些物種，如南極藍鯨，可能會找不到配偶難以交配，反過來威脅未來的種群數量。

Word Bank

strand /str?nd/ v. 使擱淺

The ship was stranded on a sandbank.

stiff /st?f/ adj. 硬的；不易彎曲的