Baleen whales (须鲸) play a vital role in marine ecosystems. To communicate across vast distances and find each other, baleen whales depend mainly on the production of sounds that travels far in dark oceans. However, since whale songs were first discovered more than 50 years ago, it remained unknown how baleen whales produce their complex sounds — until now.
A new study led by voice scientist Coen Elemans reported that baleen whales evolved unique structures in their throat that enable their low-frequency sounds, but also limit their communication range.
To understand how muscle activity could change the calls, the researchers built a model of the entire whale throat. As a result, the researchers found baleen whales have a U-shaped tissue in their throat that allows them to breathe in huge amounts of air. They also have a unique fatty cushion (垫子)that isn’t found in other animals. When the whales push air from their lungs past the fatty cushion, it starts to produce very low-frequency underwater sounds. What’s more, the throat evolution of baleen whales lets them sing underwater without the risk of choking and drowning.
However, the researchers found while baleen whales are able to make a wide range of different sounds, they can’t produce sounds louder than noise from shipping lanes (航道), drilling activity and so on, which limits their communication range. Since baleen whales can’t sing loud enough to gloss over the noise from ships, they can’t hear each other properly, which means some can’t mate. Being unable to find a mate would in turn threaten their future population numbers.
“Regrettably, the frequency range and maximum communication depth of 100 meters we predict, overlaps completely with the dominant frequency range and depth of human-made noise caused by shipping traffic. Now we show despite baleen whales’ amazing physiology, they can’t escape the noise humans make in the oceans. We need strict regulations for such noise, because these whales are dependent on sound for communication,” Elemans said.
【小题1】What is the result of the evolution of baleen whales’ throat?| A．They breathe in more air than other species. |
| B．They send their low sounds farther than before. |
| C．They communicate with other whales more easily. |
| D．They have a lower risk of dying while singing underwater. |
| A．Decrease. | B．Control. | C．Cover. | D．Change. |
| A．Baleen whales’ physiology needs to be studied. |
| B．Measures should be taken to control man-made noise. |
| C．Baleen whales can communicate in 100-meter deep sea. |
| D．The damage from shipping traffic is beyond expectation. |
| A．Baleen Whales Have a Unique Throat |
| B．Baleen Whales Are Getting into Trouble |
| C．Man-Made Noise Causes Pollution to the Ocean |
| D．Human Noises Disturb Baleen Whales’ Communication |
