The staccato clicks of sperm whales may sound like meaningless background noise to human ears, but a new analysis suggests they may be part of a communication system with a level of complexity approaching that of our own. According to researchers with Project CETI, a US non-profit working to understand sperm whales, the clicks known as “codas” are more complex than a 2024 study indicated. That earlier work found the sounds had an acoustic resemblance to human vowels. Now, a new paper investigating five properties of the codas shows that these sounds are used in patterns that follow structured rules similar to those seen in human speech. “All five properties have close parallels in the phonetics and phonology of human languages, suggesting independent evolution,” writes a team led by linguist Ga&ringsper Beguåsi of Project CETI and the University of California, Berkeley. “Sperm whale coda vocalizations are thus highly complex and represent one of the closest parallels to human phonology of any analyzed animal communication system.” Sperm whales (Physeter macrocephalus) are large marine mammals that live in closely-knit, matrilineal clans, with strong bonds and cooperative relationships that give them a competitive advantage in the cruel seas. Such complex social structures usually necessitate concomitantly sophisticated communication skills. It’s long been suspected that cetacean communication has a lot more going on than we can discern, especially in sperm whales. Their gatherings are often accompanied by a soundscape of clicks that can propagate through the ocean for miles. In 2024, researchers from Project CETI analyzed 8,719 coda vocalizations from at least 60 individual whales recorded between 2005 and 2018, and found them “more expressive and structured than previously believed,” with features that can be combined in ways comparable to elements of human speech. That work suggested whale communication is built from flexible, combinable parts, but did not explore how those parts are structured internally In the new paper, Begu&ringsi and colleagues analyzed 3,948 codas from 15 individuals recorded between 2014 and 2018 as part of The Dominica Sperm Whale Project in the Eastern Caribbean to reveal at least some of those internal structures. The team found that sperm whale codas fall into distinct categories that behave like vowel sounds in human speech, with consistent differences in length, patterns, and interactions with neighboring sounds. They identified two different types of codas with different formant structures – that is, the structures of the resonant frequencies of the sound. They called codas with one formant “a-codas”, and those with two formants “i-codas”. These a- and i-codas don’t just resemble human vowels acoustically, but also behave like them in several ways, too. For example, a-codas are longer than i-codas, and i-codas also have shorter and longer forms. Individual whales have their own timing for how they use these codas, too, and neighboring sounds can influence each other, similar to compound sounds in human speech, such as an a and a u coming together to make an ow sound. “We show that the sperm whale communication system has previously undocumented characteristics that make it similar to human phonology,” the researchers write. They are careful not to go so far as to call it a language, but a “communication system”, a broader category of information propagation under which language falls. A communication system becomes a language when it can combine sounds into structured, meaningful messages. Without knowing what sperm whale codas mean, we cannot with confidence define them as language. However, the analysis does take us a step closer to decoding whale communication, the central goal of Project CETI. The collaboration is using machine learning to break down sperm whale communication to the tiniest detail in an attempt to actually understand what the whales may be saying to each other. The implications of this would be tremendous. It would tell us whether language is unique to humans, and give us insight into how language evolved. It could also give us a way to communicate with another species on their own terms – one that lives dramatically differently from human cultures. And the skills and tools acquired to do so may then be applied to other animals, potentially opening up a new way to learn about our planet. This work is a tantalizing step on that ambitious journey, one that hints at a whole world of discovery nearing our grasp. “Taken together,” the researchers write, “our findings demonstrate that sperm whale vocalizations are highly complex and likely constitute one of the most phonologically sophisticated (currently known) communication systems in the animal kingdom.” The research has been published in the Proceedings of the Royal Society B: Biological Sciences.
