Since the discovery of whale songs almost 60 years ago, scientists have been trying to decipher their lyrics. Do these cetaceans produce messages similar to human language? Or do they share simpler information, like dancing bees do? Or are they communicating something we don’t yet understand?
In 2020, marine biologists and computational scientists joined forces to analyze the songs of sperm whales, the giants of our oceans. Scientists recently reported that whales use a much richer set of sounds than previously known, called the “sperm whale phonetic alphabet.”
People also have a phonetic alphabet, which we use to produce a virtually infinite supply of words. But Shane Gero, a marine biologist at Carleton University in Ottawa, Canada, and an author of the study, said it’s not clear whether sperm whales also convert their phonetic sounds into language.
“It has totally changed the way we have to work in the future,” Gero said.
Since 2005, his team has followed a clan of 400 sperm whales around Dominica, an island nation in the Caribbean, listening to the whales with microphones and tagging some with sensors.
Sperm whales do not produce the melodies that humpback whales sing; They make clicks that sound like a cross between Morse code and a creaking door. Sperm whales produce pulses of between 3 and 40 clicks, known as codas, raising the possibility that they communicate with each other.
One type of coda, for example, called “1+1+3,” consists of two clicks separated by a pause, followed by three clicks in rapid succession.
As part of the project, Pratyusha Sharma, a graduate student in computer science at the Massachusetts Institute of Technology (MIT), took a new look at the Dominica data. Sharma found that when a sperm whale repeated a coda, it sometimes extended the time between clicks and then gradually narrowed it. Her team called this phenomenon “rubato,” a musical term for speeding up a beat and then slowing it down.
The codas are so fast that the human ear can miss a rubato. But researchers found the pattern in thousands of recorded codas.
Researchers believe rubato plays an important role in whale communication. They found that after one whale used rubato, others matched the time change with their own codas.
Sharma’s new visualizations also revealed that sperm whales could add an extra click to the end of the coda, a behavior they call ornamentation.
The analysis showed that the conventional catalog of sperm whale codas could not capture all their complexity. The researchers identified 156 different codas, each with different combinations of tempo, rhythm, rubato and ornamentation. Gero said this variation is similar to the way humans combine lip and tongue movements to produce a set of phonetic sounds.
A single sound has no meaning on its own, but combined they become meaningful words. Sperm whales could combine coda features to convey meaning in a similar way.
“We have now set up the machinery to begin tackling a much more ambitious, long-term goal” — trying to figure out what “it really means,” said Jacob Andreas, a computational scientist at MIT and one of the study’s authors.
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