Whales produce sounds loud enough to travel underwater, yet the mystery behind sound production in water remains largely unknown.
In a paper published in the journal Nature on February 21, experts Coen Elemans from the University of Southern Denmark and his colleagues studied the “distinct sound boxes” or larynxes of three stranded deceased whales – including a humpback whale, a minke whale, and a sei whale – all of which are baleen whale species.
Humpback whale. (Image: Wikipedia).
In the laboratory, scientists blew air through the unique larynxes of these whales under controlled conditions to investigate which tissues could vibrate. The researchers also created computer models of how sei whales produce sound, similar to audio recordings of these whales obtained in the wild.
Fifty million years ago, the ancestors of whales were actually a four-legged species that walked and foraged on land. Elemans notes that these animals have adapted their larynxes over tens of millions of years to create sounds underwater.
Unlike humans and other mammals, baleen whales do not have teeth or vocal cords. Instead, their larynx contains a U-shaped structure that allows these animals to inhale large amounts of air, along with a lipid cushion and large muscles not found in other animals. Elemans explains that whales produce sound by pushing tissue into the lipid cushion and muscles.
Jeremy Goldbogen, an associate professor of oceanography at Stanford University who was not involved in the new study, stated: “This is the most comprehensive and significant research to date on how baleen whales produce sound, a long-standing mystery in the field.”
He pointed out that there is still much to study due to the extremely diverse sounds of whales. For instance, humpback whales are known to have the ability to “compose” complex songs and emit those sounds in groups underwater.
However, Elemans noted that despite how loud a whale’s song may be, the new research model indicates that humpback whales and related species cannot produce sounds louder than the noise from maritime transport.
“Whales are indeed affected by the noise from transport vehicles, and this significantly reduces their communication ability,” he said.
Michael Noad, director of the Marine Science Centre at the University of Queensland, Australia, mentioned that since some whales produce sounds as mating calls, the noise from maritime transport could be concerning.
“For dispersed whale populations, like the Antarctic blue whale, they may not find mates in a noisy ocean environment,” he said, noting that species like humpback whales, which often live in large groups, are more likely to avoid this noise pollution.
The larynxes tested in this study belonged to immature whales. In contrast, adult males can produce louder sounds. Therefore, whale expert Joy Reidenberg stated that further experiments on adult males are necessary to confirm the results of this study.
Reidenberg noted that laboratory research has likely progressed to the point where humans can replicate how whales “sing.”
“Currently, our technology involves inserting specialized equipment into a whale to see exactly which tissues vibrate. We will not be able to do this in the wild, so these experiments are the best we have so far,” she said.
Although this study is based on a small sample, experts indicate that the new findings will guide future research on how whales communicate.
