They document the extraordinary “phonetic alphabet” of the sperm whale

The different species of whales that inhabit the oceans use different types of vocalizations to communicate. Sperm whales, the largest of the toothed whales, communicate using bursts of clicks – called codas – that sound a little like Morse code.

A new analysis of years of sperm whale vocalizations in the eastern Caribbean has found that their communication system is more sophisticated than previously known, featuring a complex internal structure replete with a “phonetic alphabet.”

The researchers detected similarities with aspects of other animal communication systems, and even with human language.

Like all marine mammals, sperm whales are very social animals and their calls are an integral part of this. The new study has allowed us to better understand how these cetaceans communicate.

“The research shows that the expressiveness of sperm whale calls is much greater than previously thought,” says Pratyusha Sharma, a doctoral student in robotics and machine learning at the Massachusetts Institute of Technology and lead author of the study published this Tuesday in the magazine Nature Communications.

“We don’t know what they say yet. We are studying the calls in their behavioral contexts to understand what the sperm whales might be communicating,” Sharma said.

Sperm whales, which can reach about 18 meters in length, have the largest brain of all animals. They are deep divers that feed on giant squid and other prey.

The researchers are part of the Machine Learning Team of the CETI (Cetacean Translation Initiative) Project.

Using traditional statistical analysis and artificial intelligence, they examined calls made by about 60 whales recorded by the Dominica Sperm Whale Project, a research program that has assembled a large set of data on the species.

“Why are they exchanging these codas? What information could they be sharing?” asks Shane Gero, co-author of the study, lead biologist of the CETI Project and founder of the Dominica Sperm Whale Project, also affiliated with Carleton University in Canada.

“I think it’s likely that they use codas to coordinate as a family, organize care of young individuals, forage and defense,” Gero said.

The researchers found that variations in the number, rhythm and tempo of the clicks produced different types of codas. The whales, among other things, altered the length of the codas and sometimes added an extra click at the end, like a suffix in human language.

“All of these different codas that we see are actually built by combining a comparatively simple set of smaller pieces,” says study co-author Jacob Andreas, a professor of computer science at MIT and a member of the CETI Project.

People combine sounds – often corresponding to letters of the alphabet – to produce words with meaning, and then produce sequences of words to create phrases that convey more complex meanings.

For people, Sharma said, “there are two levels of matching.” The lowest level is sounds to words. The top level is from words to phrases.

Cachalots, according to Sharma, also use a combination of two levels of features to form codas, and the codas are sequenced together when whales communicate. The lower level has similarities with the letters of an alphabet, Sharma said.

“Each communication system is adapted to the environment and the animal society in which it has evolved,” Sharma added.

The communication system of sperm whales differs, for example, from the “songs” of humpback whales and from the whistles, chirps, squawks and other vocalizations of various animals.