VOA科学技术2024--How Do Whales 'Sing?'（在线收听）

How Do Whales 'Sing?'

　　It is one of Earth's loudest sounds in the ocean: the "singing" of whales.

　　Now scientists think they have an idea of how baleen whales do it. They say the large air-breathing sea animals use a special voice box that enables them to make sound underwater.

　　Scientists say the discovery is based on a very small study. But it will direct future research into how whales communicate.

　　The new findings are in a study published recently in the scientific publication Nature. Coen Elemans of the University of Southern Denmark and other international scientists studied the voice boxes, or larynxes, of three dead whales from the beaches of Denmark and Scotland. The three were humpback, minke and sei whales. All three are part of the family of baleen whales, a group that includes the blue whale, the largest animal that ever existed on Earth.

　　Voice box

　　In the laboratory, the scientists blew air through the voice boxes under controlled conditions to see what tissues might vibrate. They also created computer models of the sei whale's vocalizations and matched them to recordings of similar whales taken in the wild.

　　Whales' ancestors were land animals that moved into the oceans about 50 million years ago. Elemans said the animals' voice box changed over tens of millions of years in order to make sounds underwater.

　　Baleen whales do not have teeth or vocal cords like humans and other mammals. Instead, they have U-shaped tissue in their voice boxes that permits them to breathe a lot of air very quickly. Their voice boxes also contain a large "cushion" of fat and muscle not seen in other animals. Whales "sing" by pushing the tissue against the fat and muscle cushion.

　　Elemans said baleen whales depend on the production of sound to communicate in the dark of the deep oceans. "For example, humpback females and their calves communicate with each other by voice, and humpback males sing to attract females," he added.

　　Jeremy Goldbogen is a professor of oceans at Stanford University, who was not involved in the research. He said, "This is the most comprehensive and significant study to date on how baleen whales vocalize, a long-standing mystery in the field."

　　The whale voice boxes tested were from younger animals, not adult males, who do the singing. Because of that, whale expert Joy Reidenberg said further experiments on adult males are needed to confirm the study's findings.

　　Reidenberg works for the Center for Anatomy and Functional Morphology at the Icahn School of Medicine at Mount Sinai in New York City. She noted that the research is probably as close as we can get to reproducing how whales sing.

　　"Right now, our technology involves sticking a scope into a whale to see what exactly is vibrating," she said. "Since you're never going to be able to do that in a wild animal, these experiments are the next best thing."

　　Shipping noise

　　As loud as whales' songs are, the study suggests that whales cannot produce sounds louder than noise from the shipping industry, Elemans said.

　　"They're really affected by (shipping noise) and it significantly reduces their ability to communicate," he said. "There's just no way for them to get louder."

　　Because some whales sing as a mating call, the shipping industry's interference with those songs is a concern, said Michael Noad. He is director of the Center for Marine Science at the University of Queensland in Australia. He also was not part of the Nature study.　　"For whale populations that are really dispersed, like the Antarctic blue whales, they might not be able to find mates in a noisy ocean environment," he said. However, whales like humpbacks that gather in big numbers are more likely to ignore such noise pollution.

　　Words in This Story

　　baleen –n. a hard material in the mouth of some kinds of whales that permits them to eat very small shrimp in the ocean

　　vibrate –v. to move back and forth quickly, often producing sound

　　vocalization –n. the act of making a sound, such as speech or singing, using the throat