We’re one step closer to understanding the sperm whale ‘alphabet’

When sperm whales communicate with each other, they produce clicks in patterns that may parallel our own system of language, according to a study published today in the Proceedings of the Royal Society B.  

The research is the latest to come out from the multidisciplinary group Project CETI (Cetacean Translation Initiative) and its Founder and President David Gruber, a marine biologist and National Geographic Explorer who co-authored the new study. CETI’s previous scientific findings, aided by artificial intelligence, have already revealed a strikingly intricate system of sperm whale communication—including groups of clicks, called codas, with elements that can function like human vowels. 

“In vast communication systems, humans have evolved vowels across almost all human languages,” says Gruber. “Now we're seeing that sperm whales have independently evolved a very vowel-like system and they’re using it in similar ways.” 

To decode these vowel-like patterns, Gruber worked closely with Project CETI’s linguistics lead, Gašper Beguš, who has studied ancient languages like Hittite, Tocharian, and Sanskrit. Now, his focus is on sperm whales, part of the group of marine mammals known scientifically as cetaceans.  

For Beguš, the process is similar to studying dead languages. “You're just trying to connect with these animals that are not thousands of years apart but are different environments apart—oceans apart.” 

The quest to understand whales 

Through understanding sperm whale vocalizations, Project CETI hopes to inspire the public and policymakers to push for legal protections, similar to how the 1970s “Save the Whales” movement was inspired by humpback whale songs.  

When sperm whales communicate—as they roll at the surface, say, or in preparation for a hunt—they produce rhythmic pulses of clicks called codas. In 2024, CETI discovered that these rhythmic sequences form a kind of ‘phonetic alphabet’, a rich system of sounds the researchers likened to a form of Morse code. The research showed the whales can combine codas depending on context, and even tweak them through rhythm, tempo, expressive changes in timing, and by adding additional clicks.   

An analysis published last November revealed yet more complexity. Sperm whales communicate very slowly compared to us. (Their world is in general more unhurried—their hearts can slow to just a few beats per minute). But when their codas are sped up with the silences removed, they contain elements that function like human vowels. So far, two whale “vowels” have been identified by Project CETI, distinct sounds that function similarly to our a and i.  

These vowels sometimes rise and fall in a similar way to human diphthongs, a term that refers to how vowels subtly change from one sound to another. The word cow, for example, starts with an ‘ah’ sound that glides seamlessly into a ‘oo’ vowel-like sound. 

In their latest study, Beguš and his team analyzed the structures within and between these “vowels” and looked for any parallels with human language. The researchers used statistical analysis and a machine learning algorithm to parse through over 1,100 sperm whale codas, recorded through hydrophones in a wild population of 15 females and calves off the Caribbean island of Dominica.  

Part of the analysis focused on the codas of four sperm whales, Atwood, Fork, TBB, and Pinchy, a particularly vocal grandma.  

“She's very chatty, she's very structured,” says Beguš. “She’s the best.”  

Uncovering parallel sonic structures  

In some human languages, certain vowels are more likely to be paired with different tones.  

Slovenian has two ‘e’ vowels, for example, and one is normally used when the pitch is higher (which can change its meaning). Meanwhile, in one common whale coda, 1+1+3, two spaced clicks are followed by three in succession (click…click…click-click-click). The team found half of these click sequences contained a-coda vowels and half contained i-coda vowels. In other sequences they analyzed, a-codas were more common.  

The whales use different physical mechanisms to produce their clicks and vowel-like acoustics. If these vowels were just random sounds resulting from click production, those patterns wouldn’t appear, the study’s authors argue. “That suggests there is a complex hierarchical order in this system,” says Beguš.  

Sperm whale vowels contain different lengths, too, the study found, with a-codas lasting significantly longer than their i-s. In humans, to produce the lower a, we must open our jaw wider, naturally making the sound longer (think ‘sat’, vs ‘sit’). While the researchers don’t know the exact mechanism in whales, their production of sounds is somewhat similar: they have internal “phonic lips” in their noses that vibrate like our vocal chords, connected to an air sac thought to shape the quality of the sound.  

The CETI team found more variation in i-codas, which have long and short versions. In some human languages, lengthening a vowel entirely changes its meaning. In Hungarian, bor and (the longer) bór mean wine and boron, respectively. A mispronunciation would affect your experience in a Budapest bar.  

Perhaps the most sophisticated finding was that the first click of a whale vowel is sometimes shaped by the one that came before. This feature, known as coarticulation, is everywhere in human language: adjacent sounds impact the structure of each other. When we say ‘handbag’, we merge two meaningful sounds, and the d is softened as they connect.

When switching between a-codas to i-codas or vice-versa, the whales were more likely to swap out the initial click to match the type before. This suggests whales are making structural adjustments in linked sounds and highlights the potentially key role of a coda’s first click.  

"The fact that they show coarticulation is one of the most striking points to me," says Maël Leroux, an evolutionary biologist at the University of Rennes who wasn't involved in the research and studies non-human primates.

Combining meaningless sounds into meaningful ones, phonemes into words, is a key part of our ability to say almost anything we want. “That's also the next step for us in the primate world, to look for these coarticulation patterns that we know are present in human language.” 

The CETI team says the findings suggest sperm whale communication is one of the most complex in the animal kingdom, with remarkable similarities to our own.  

The research is “a really nice example of the further parallels between animal communication and human language,” says Simon Townsend, an evolutionary anthropologist at the University of Zurich who was also not involved in the research. “It'd be interesting to know to what extent these sounds also play a role in meaning,” he says. 

In human languages, changing these vowel patterns can alter meaning, though whether this is true for whales is still unclear. “We're showing that these differences are structurally there, and they're probably controlled,” says Beguš. “We don't know their language fully yet, but we're writing down all the rules that exist.” 

From patterns to meaning 

Around 90 million years have passed since the time of the shared ancestor of sperm whales and humans. This study suggests both species may have developed similar elements of communication independently at some point along our separate evolutionary paths. And the more we learn about sperm whales, the more their behaviors surprise us. They are hypersocial animals that form tight-knit clans, each with their own dialects and cultures. They are matrilineal animals with grandmothers that help to raise the young and pass on family traditions. They can even support each other through childbirth.  

The origin of human language remains a mystery, perhaps influenced by our exposure to certain social and ecological forces—and perhaps so, too, with whales and their clicks, says Townsend. “This probably provides even further support that sociality plays an important role in the evolution of complex communication systems,” he says. 

So what’s next in the study of sperm whale codas? We’re already starting to predict simplistic behaviors, like diving, based on their voices, which is much further than expected at this point, says Gruber. But we have a long way to go to truly understand their complex communications, he says.  

“In one regard, we're baby sperm whales,” he says. “I think in the next five years we'll know a lot more than we know now.”