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For the scientists eavesdropping on sperm whales, it’s a race to decode their mysterious clicks and whistles in a very alien environment. A new study discovered a fresh component of their various vocalizations and could hint at potential language structures. Sperm whales exhibit patterns similar to human vowels and diphthongs–a connected pair of vowels in a word, such as the “oi” in coin. The findings, led by research initiative Project CETI (Cetacean Translation Initiative) and the University of California, Berkeley, are detailed in a study published November 12 in the journal Open Mind. The research also offers more insight into how these marine mammals may deliver meaning in their communication.

“We uncovered a whole new dimension in the communications system of sperm whales,” Gašper Beguš, Project CETI’s linguistics lead and study co-author tells Popular Science. “What used to be conceived of as this alien-looking Morse-code like system just became much more human-like. We have a case of underwater vowels–in a very different world from ours, the communication system appears very similar to our speech.”

Synced drone and underwater audio sperm whale footage. CREDIT: © Project CETI.

Decoding vowels and diphthongs

In 2024, scientists decoded sperm whale codas. These structured sequences of clicks that the cetaceans use for communication are built on a growing sperm whale phonetic alphabet that researchers are deciphering.

Traditionally, these codas have been analyzed based on the number of clicks and their timing. This new study shows that sperm whales can modulate the frequency of these clicks and that their vocalizations have some similar building blocks to our own. Specifically, they have something akin to human vowels (the letters A, E, I, O, U, and sometimes Y) and diphthongs.

The team found discrete coda-level patterns that appear across individual sperm whales: the a-coda vowel and i-coda vowel. Whales exchange these vowels in structured conversation. The sperm whales even have rising, falling, and a combination of the two frequencies in their vocalization patterns, suggesting that the whales are actively controlling these “coda vowels.”

For example, the* i *vowel can be long or short in sperm whale vocalizations, similar to how some languages have long or short vowels. The a-coda vowel is preferred on some coda types, paralleling some human languages where tones are preferred on some vowels. This could indicate that sperm whale coda vocalizations may represent close parallels to how human speech is organized.

“Based on the number of formants, two different coda quality categories have been described within the research: a-codas and i-codas,” study co-author and Project CETI Founder and President David Gruber tells Popular Science. “This elucidation of sperm whale vowel and diphthongs combined with CETI’s previous findings of a sperm whale phonetic alphabet, now showcases the sperm whale communication system one of the most sophisticated systems seen across the animal kingdom.”

A pod of sperm whales swimming and socializing off the coast of Dominica in the Caribbean. CREDIT: © Amanda Cotton/Project CETI

Matters of time

According to the team, changing the human-based perception of timing was crucial to these findings. In humans, vowels are produced by vocal folds, which vibrate fast. Sperm whales produce codas using phonic lips that move much more slowly.

“Whales clicks are very slow compared to our vowels. But we realized that their perception of time must be just slower,” explains Beguš. “Once we removed timing from their vocalizations and made them faster, we started observing patterns that match those of human vowels. In fact, the patterns become so clear that one can transcribe them with our human letters (such as a or i).”

These new findings challenge older assumptions about sperm whale vocalizations, indicating it is far more intricate than we understood. Their ability to control speech properties in a structured way hints that sperm whales may be encoding additional layers of meaning, similar to what humans do.

By uncovering these complex vocal structures, this research marks a crucial step in deciphering the meaning behind sperm whale communication. Also, better understanding how elements of human-like communication, such as vowels, emerge in nature offers valuable insights into the evolution of intelligence and language across species.

Project CETI’s biology lead Shane Gero added, “from a biological perspective, these findings show us that sperm whales are actively modulating sound in structured and repeatable ways. This suggests the possibility of transmitting nuanced layers of information essential to their social lives.”

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