Sperm whales, which make clicking sounds to communicate, use different “vowels” in ways similar to human speech

By Allison Parshall edited by Claire Cameron

Sperm whales’ click-based communication system has patterns that echo how human languages use vowels, according to a new study published today in Proceedings of the Royal Society B: Biological Sciences.

“On the surface, [these vocalizations] sound like this alien, ocean intelligence that has nothing to do with us,” says lead author Gašper Beguš, a linguist at the University of California, Berkeley, who works with Project CETI, a nonprofit that is dedicated to studying sperm whale communication. “But when you actually look at it closely, you realize, ‘Oh, we’re way more similar.’”

Sperm whales flap “phonic lips” (a structure akin to human vocal cords) in their nose to create clicking sounds. They combine these clicks into rhythmic series called codas, which can vary from whale clan to whale clan. In the past, scientists trying to make sense of their communication have tended to focus on the rhythm of these patterns, almost as if deciphering morse code.

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But last year researchers at Project CETI discovered a whole new dimension of sperm whale communication. These clicks come in two different types based on the relationship between the different frequencies present in the sound—a feature that is technically known as a “formant.” In human languages, formants determine each vowel’s distinct sound.

In the following recording of a whale named Pinchy, both whale “vowel” types are present.

The vowel-like differences in sperm whale clicks are hard to hear with the human ear unless they are sped up.

Here are the two types of sounds alternating in real time. Can you notice the difference?

This subtle difference between the two “vowels” shows up clearly on spectrograms—graphs of the frequencies present within a sound. These graphs can be used to distinguish between vowel sounds in recordings of human speech, too. For a given sound, the graphs show which bands of frequencies are resonating within the vocal tract. We humans can change this resonance to make a different vowel sound by changing the shape of our mouth and throat; whales appear to do the same thing by changing the shape of a structure inside their nose called the distal air sac.

Project CETI scientists (somewhat arbitrarily) called the newly identified sperm whale vowel types the “a-coda” and “i-coda.” But it remained a mystery how the whales use these different vowel types to communicate. If both types were just peppered at random throughout the whales’ communication, that might suggest that the sound changes weren’t intentional. But that doesn’t seem to be the case: there appear to be extensive patterns in how these vowel types are used, the new study found.

One rhythmic pattern with timing that the new paper described as “click ... click ... click-click-click” employed an even split of a- and i-codas, while other patterns used mainly a-codas and rarely i-codas. The a-codas tended to be shorter than the i-codas overall, while the latter had both short and long forms. Such patterns show up in human languages when we pair different speech sounds, too. For example, languages such as Arabic distinguish between vowels based on their length; changing the length of a vowel can alter the meaning of the word.

The new results suggest that the whales are actively controlling which type of click to use according to a system. But why they employ different clicks in specific patterns remains a mystery. “We don’t know for certain whether they carry meaning,” says Beguš, adding that this ability likely has evolved for some purpose, even if we don’t yet know what that is.

In principle, distinguishing between different vowel-like sounds could give whales more ways to carry meaning in their communication, says Mason Youngblood, who studies songbird and whale communication at Stony Brook University and was not involved in the new study.

“These sounds are able to convey more information than we previously thought. And I think that, in and of itself, is undeniable,” he says.