How Baleen Whales Sing Underwater须鲸如何在水下发声

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.

一项新的研究发现了鲸鱼如何在水下发声的重要线索。

南丹麦大学的Coen Elemans教授和其他研究人员研究了三头此前搁浅死亡的鲸鱼的喉部。

这三头鲸鱼分别是座头鲸、小须鲸和鳁鲸——三种不同类型的须鲸。

须鲸与其他哺乳动物不同，因为它们没有声带和牙齿。但它们的喉部有一个U形组织，可以让它们吸入大量空气。它们还有一个独特的脂肪和肌肉缓冲层，这是其他动物所没有的。

在实验室，通过向须鲸的喉部吹气，科学家们能够发现其中哪些部位通过振动产生声音。研究人员还创建了鳁鲸叫声的计算机模型，并将它们与在野外收录的类似鲸鱼的声音进行匹配。

他们得出结论，须鲸能够通过推动脂肪和肌肉缓冲层来发声。

这些发现与其他研究结论不同，其他研究显示，海豚、虎鲸和抹香鲸等齿鲸通过鼻腔中的特殊器官发声。

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.

须鲸的勺状软骨又大又硬，形成一种可以挤压脂肪和肌肉缓冲层的环状结构。当鲸鱼呼气时，这个缓冲层以波纹状的方式振动，从而发出声音。

鲸鱼被认为是大约5 000万年前由陆地哺乳动物进化而来的。

Elemans教授表示，须鲸的喉部可能是为了让它们在水下发声无窒息和溺水风险进化而来的。

这种适应对鲸鱼的生存非常重要，因为鲸鱼依靠发声进行

交流。

研究表明，虽然鲸鱼能够以不同的音高发出各种不同的声音——其中一些声音人类几乎听不见——但它们发出的声音比船只运行的声音小。

由于鲸鱼发出的声音无法盖过船只制造的噪声，因此它们可能无法正常地听到彼此的声音。这意味着一些物种，如南极蓝鲸，可能会找不到配偶难以交配，反过来威胁未来的种群数量。

Word Bank

strand /strænd/ v. 使搁浅

The ship was stranded on a sandbank.

stiff /stɪf/ adj. 硬的；不易弯曲的