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Exploring the mysterious alphabet of sperm whales

MIT CSAIL and Project CETI researchers reveal complex communication patterns in sperm whales, deepening our understanding of animal language systems.
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Underwater photo of a large sperm whale diving with two small baby whales near her
Using machine learning, MIT CSAIL and Project CETI researchers revealed complex, language-like structure in sperm whale communication with context-sensitive and combinatorial elements.
Photo: Amanda Cotton
Photo illustration with two images of a sperm whale superimposed on a blue background. Lines representing sound waves emanate from each one's head. They are surrounded by characters representing phonemes.
“Our findings indicate the presence of structured information content and also challenges the prevailing belief among many linguists that complex communication is unique to humans," says Daniela Rus. "Our next steps aim to decipher the meaning behind these communications and explore the societal-level correlations between what is being said and group actions."
Image: Alex Shipps/MIT CSAIL

The allure of whales has stoked human consciousness for millennia, casting these ocean giants as enigmatic residents of the deep seas. From the biblical Leviathan to Herman Melville's formidable Moby Dick, whales have been central to mythologies and folklore. And while cetology, or whale science, has improved our knowledge of these marine mammals in the past century in particular, studying whales has remained a formidable a challenge.

Now, thanks to machine learning, we're a little closer to understanding these gentle giants. Researchers from the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL) and Project CETI (Cetacean Translation Initiative) recently used algorithms to decode the “sperm whale phonetic alphabet,” revealing sophisticated structures in sperm whale communication akin to human phonetics and communication systems in other animal species. 

In a new open-access study published in Nature Communications, the research shows that sperm whales codas, or short bursts of clicks that they use to communicate, vary significantly in structure depending on the conversational context, revealing a communication system far more intricate than previously understood. 

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The Secret Language of Sperm Whales, Decoded

Nine thousand codas, collected from Eastern Caribbean sperm whale families observed by the Dominica Sperm Whale Project, proved an instrumental starting point in uncovering the creatures’ complex communication system. Alongside the data gold mine, the team used a mix of algorithms for pattern recognition and classification, as well as on-body recording equipment. It turned out that sperm whale communications were indeed not random or simplistic, but rather structured in a complex, combinatorial manner. 

The researchers identified something of a “sperm whale phonetic alphabet,” where various elements that researchers call  “rhythm,” “tempo,” “rubato,” and “ornamentation” interplay to form a vast array of distinguishable codas. For example, the whales would systematically modulate certain aspects of their codas based on the conversational context, such as smoothly varying the duration of the calls — rubato — or adding extra ornamental clicks. But even more remarkably, they found that the basic building blocks of these codas could be combined in a combinatorial fashion, allowing the whales to construct a vast repertoire of distinct vocalizations.

The experiments were conducted using acoustic bio-logging tags (specifically something called “D-tags”) deployed on whales from the Eastern Caribbean clan. These tags captured the intricate details of the whales’ vocal patterns. By developing new visualization and data analysis techniques, the CSAIL researchers found that individual sperm whales could emit various coda patterns in long exchanges, not just repeats of the same coda. These patterns, they say, are nuanced, and include fine-grained variations that other whales also produce and recognize.

“We are venturing into the unknown, to decipher the mysteries of sperm whale communication without any pre-existing ground truth data,” says Daniela Rus, CSAIL director and professor of electrical engineering and computer science (EECS) at MIT. “Using machine learning is important for identifying the features of their communications and predicting what they say next. Our findings indicate the presence of structured information content and also challenges the prevailing belief among many linguists that complex communication is unique to humans. This is a step toward showing that other species have levels of communication complexity that have not been identified so far, deeply connected to behavior. Our next steps aim to decipher the meaning behind these communications and explore the societal-level correlations between what is being said and group actions."

Whaling around

Sperm whales have the largest brains among all known animals. This is accompanied by very complex social behaviors between families and cultural groups, necessitating strong communication for coordination, especially in pressurized environments like deep sea hunting.

Whales owe much to Roger Payne, former Project CETI advisor, whale biologist, conservationist, and MacArthur Fellow who was a major figure in elucidating their musical careers. In the noted 1971 Science article “Songs of Humpback Whales,” Payne documented how whales can sing. His work later catalyzed the “Save the Whales” movement, a successful and timely conservation initiative.

“Roger’s research highlights the impact science can have on society. His finding that whales sing led to the marine mammal protection act and helped save several whale species from extinction. This interdisciplinary research now brings us one step closer to knowing what sperm whales are saying,” says David Gruber, lead and founder of Project CETI and distinguished professor of biology at the City University of New York.

Today, CETI’s upcoming research aims to discern whether elements like rhythm, tempo, ornamentation, and rubato carry specific communicative intents, potentially providing insights into the “duality of patterning” — a linguistic phenomenon where simple elements combine to convey complex meanings previously thought unique to human language.

Aliens among us

“One of the intriguing aspects of our research is that it parallels the hypothetical scenario of contacting alien species. It’s about understanding a species with a completely different environment and communication protocols, where their interactions are distinctly different from human norms,” says Pratyusha Sharma, an MIT PhD student in EECS, CSAIL affiliate, and the study’s lead author. “We’re exploring how to interpret the basic units of meaning in their communication. This isn’t just about teaching animals a subset of human language, but decoding a naturally evolved communication system within their unique biological and environmental constraints. Essentially, our work could lay the groundwork for deciphering how an ‘alien civilization’ might communicate, providing insights into creating algorithms or systems to understand entirely unfamiliar forms of communication.”

“Many animal species have repertoires of several distinct signals, but we are only beginning to uncover the extent to which they combine these signals to create new messages,” says Robert Seyfarth, a University of Pennsylvania professor emeritus of psychology who was not involved in the research. “Scientists are particularly interested in whether signal combinations vary according to the social or ecological context in which they are given, and the extent to which signal combinations follow discernible ‘rules’ that are recognized by listeners. The problem is particularly challenging in the case of marine mammals, because scientists usually cannot see their subjects or identify in complete detail the context of communication. Nonetheless, this paper offers new, tantalizing details of call combinations and the rules that underlie them in sperm whales.”

Joining Sharma, Rus, and Gruber are two others from MIT, both CSAIL principal investigators and professors in EECS: Jacob Andreas and Antonio Torralba. They join Shane Gero, biology lead at CETI, founder of the Dominica Sperm Whale Project, and scientist-in residence at Carleton University. The paper was funded by Project CETI via Dalio Philanthropies and Ocean X, Sea Grape Foundation, Rosamund Zander/Hansjorg Wyss, and Chris Anderson/Jacqueline Novogratz through The Audacious Project: a collaborative funding initiative housed at TED, with further support from the J.H. and E.V. Wade Fund at MIT.

Press Mentions


On NPR’s Short Wave, climate correspondent Lauren Sommer reports on MIT researchers using artificial intelligence to decode the secret language of sperm whales. Prof. Daniela Rus says, “it really turned out that sperm whale communication was indeed not random or simplistic but rather structured in a very complex, combinatorial manner.”

Smithsonian Magazine

MIT researchers have used advancements in machine learning and computing to help decode whale vocalizations, reports Sarah Kuta of Smithsonian Magazine. “If researchers knew what sperm whales were saying, they might be able to come up with more targeted approaches to protecting them,” Kuta explains. “In addition, drawing parallels between whales and humans via language might help engage the broader public in conservation efforts.”


Using machine learning, MIT researchers have discovered that sperm whales use “a bigger lexicon of sound patterns” that indicates a far more complex communication style than previously thought, reports Lauren Sommers for NPR. “Our results show there is much more complexity than previously believed and this is challenging the current state of the art or state of beliefs about the animal world," says Prof. Daniela Rus, director of CSAIL. 

New Scientist

New Scientist reporter Clare Wilson writes that a new analysis by MIT researchers of thousands of exchanges made by east Caribbean sperm whales demonstrates a communication system more advanced than previously thought. “It’s really extraordinary to see the possibility of another species on this planet having the capacity for communication,” says Prof. Daniela Rus.

Associated Press

Associated Press reporter Maria Cheng spotlights a new study by MIT researchers that identifies a “phonetic alphabet” used by whales when communicating. “It doesn’t appear that they have a fixed set of codas,” says graduate student Pratyusha Sharma. “That gives the whales access to a much larger communication system.” 


A new analysis of years of vocalizations by sperm whales in the eastern Caribbean has provided a fuller understanding of how whales communicate using codas, reports Will Dunham of Reuters. Graduate student Pratyusha Sharma explained that: "The research shows that the expressivity of sperm whale calls is much larger than previously thought."

New York Times

MIT researchers have discovered that sperm whales use a “much richer set of sounds than previously known, which they call a ‘sperm whale phonetic alphabet,’” reports Carl Zimmer for The New York Times. “The researchers identified 156 different codas, each with distinct combinations of tempo, rhythm, rubato and ornamentation,” Zimmer explains. “This variation is strikingly similar to the way humans combine movements in our lips and tongue to produce a set of phonetic sounds.”


Researchers from MIT and elsewhere have uncovered a phonetic alphabet used by sperm whales, which provides “key breakthroughs in our understanding of cetacean communication,” reports Brain Heater for TechCrunch. “This phonetic alphabet makes it possible to systematically explain the observed variability in the coda structure,” says Prof. Daniela Rus, director of CSAIL. “We believe that it’s possible that this is the first instance outside of human language where a communication provides an example of the linguistic concept of duality of patterning. That refers to a set of individually meaningless elements that can be combined to form larger meaningful units, sort of like combining syllables into words.”

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