Exclusive: Sperm Whale 'Codas' Contain Human-Like Vowel Sounds, Study Finds

Exclusive: Sperm Whale 'Codas' Contain Human-Like Vowel Sounds

Sperm whales do not sing like humpbacks. Instead, they produce loud, percussive clicks—often compared to a thumbnail dragged across a metal comb or an underwater jackhammer. New research, however, shows that beneath those stark sounds lies surprising complexity: parts of sperm whale vocalizations behave in ways analogous to human vowels.

Who did the research?

The study, published in the journal Open Mind, was led by linguist Gašper Beguš (University of California, Berkeley) in collaboration with Project CETI, a multidisciplinary effort to decode sperm whale communication. Project CETI has spent five years documenting hundreds of sperm whales off the coast of the Dominican Republic in the Caribbean.

What inspired the discovery?

Beguš credits part of the insight to a talk by elephant researchers Michael Pardo and Joyce Poole. Pardo described how elephants can delay responses by minutes, suggesting some species operate on markedly slower temporal scales than humans. Beguš asked whether sperm whales—long-lived animals with slow physiological rhythms—might also communicate on a slower timeframe, so that finer structure would appear if their signals were compressed in time.

How was the analysis done?

The team analyzed more than 1,000 recordings collected by whale biologist and National Geographic Explorer Shane Gero. Using a custom machine-learning model to flag promising vocalizations, researchers then closely examined the so-called "codas"—sequences of clicks used in sperm whale communication. When they removed gaps and sped up the codas to approximate human speech rates, previously hidden spectral qualities emerged.

Key findings

• When accelerated, many codas reveal sustained tonal qualities that resemble vowel-like components; the team identified two primary vowel analogues roughly comparable to human "a" and "i".
• They also observed diphthong-like glides—transitions from one vowel-like quality to another—indicating graded, continuous modulation rather than purely binary clicks.
• Sperm whales appear to shape these tones with internal anatomy ("phonic lips" and an air sac) that functionally resembles mechanisms humans use to produce vowels.

“It’s clean, razor-sharp, precise. I’ve never seen anything so structured and seemingly intentional,” Beguš said of the coda system.

Context and broader work

This study builds on earlier Project CETI research. Last year, MIT-affiliated researchers with Project CETI described four musical properties of codas—tempo, rhythm, rubato, and ornamentation—in Nature Communications. Analyzing roughly 9,000 recordings, that work expanded the documented coda repertoire from about 21 types to more than 156, suggesting a far greater vocal inventory than previously known. The discovery of vowel-like elements expands the expressive potential of codas even further.

What it doesn't yet tell us

Project CETI has not assigned specific meanings to individual codas. Decoding semantics will require far more data, computational power, and, crucially, behavioral context—knowing what whales are doing when particular codas occur. As Irene Pepperberg (Boston University) notes, context is essential: early assumptions about other species' vocalizations can underestimate their complexity.

Why it matters

The findings suggest sperm whale communication is more nuanced than previously appreciated, with graded acoustic elements that increase potential flexibility and meaning. Beyond scientific curiosity, understanding this complexity could strengthen conservation arguments by revealing the cognitive and social sophistication of these deep-diving giants.

Next steps: Researchers plan to expand datasets, refine computational models, and pair vocal analyses with careful behavioral observation to begin mapping sounds to social and ecological contexts.