Whale songs have features of language, but whales may not be speaking

Whales use complex communication systems we still don’t understand, a trope exploited in sci-fi shows like Apple TV’s Extrapolations. That show featured a humpback whale (voiced by Meryl Streep) discussing Mahler’s symphonies with a human researcher via some AI-powered inter-species translation app developed in 2046.

We’re a long way from that future. But a team of MIT researchers has now analyzed a database of Caribbean sperm whales’ calls and has found there really is a contextual and combinatorial structure in there. But does it mean whales have a human-like language and we can just wait until Chat GPT 8.0 to figure out how to translate from English to Sperm-Whaleish? Not really.

One-page dictionary

“Sperm whales communicate using clicks. These clicks occur in short packets we call codas that typically last less than two seconds, containing three to 40 clicks,” said Pratyusha Sharma, a researcher at the MIT Computer Science and Artificial Intelligence Laboratory and the lead author of the study. Her team argues that codas are analogues of words in human language and are further organized in coda sequences that are analogues of sentences. “Sperm whales are not born with this communication system; it's acquired and changes over the course of time,” Sharma said.

Seemingly, sperm whales have a lot to communicate about. Earlier observational studies revealed that they live a fairly complex social life revolving around family units forming larger structures called clans. They also have advanced hunting strategies and do group decision-making, seeking consensus on where to go and what to do.

Despite this complexity in behavior and relationships, their vocabulary seemed surprisingly sparse.

Sharma’s team sourced a record of codas from the dataset of the Dominica Sperm Whale Project, a long-term study on sperm whales that recorded and annotated 8,719 individual codas made by EC-1, a sperm whale clan living in East Caribbean waters. Those 8,719 recorded codas, according to earlier research on this database, were really just 21 coda types that the whales were using over and over.

A set of 21 words didn’t look like much of a language. “But this [number] is exactly what we found was not true,” Sharma said.

Fine-grained changes

“People doing those earlier studies were looking at the calls in isolation... They were annotating these calls, taking them out of context, shuffling them up, and then tried to figure out what kind of patterns were recurring,” Sharma explained. Her team, by contrast, analyzed the same calls in their full context, basically looking at entire exchanges rather than at separate codas. “One of the things we saw was fine-grained changes in the codas that other whales participating in the exchange were noticing and reacting to. If you looked at all these calls out of context, all these fine-grained changes would be lost; they would be considered noise,” Sharma said.

The first of those newly recognized fine-grained changes was termed “rubato,” borrowed from music, where it means introducing slight variations in the tempo of a piece. Communicating sperm whales could stretch or shrink a coda while keeping the same rhythm (where rhythm describes the spacing between the clicks in a coda).

The second feature the researchers discovered was ornamentation. “An ornament is an extra click added at the end of the coda. And when you have this extra click, it marks a critical point, and the call changes. It either happens toward the beginning or at the end of the call,” said Sharma.

The whales could individually manipulate rubato and ornamentation, as well as previously identified rhythm and tempo features. By combining this variation, they can produce a very large variety of codas. “The whales produce way more combinations of these features than 21—the information-carrying capacity of this system is a lot more capable than that,” Sharma said.

Her team identified 18 types of rhythm, three variants of rubato, five types of tempo, and an ability to add an ornament or not in the sperm whale’s communication system. That adds up to 540 possible codas, of which there are roughly 150 these whales frequently used in real life. Not only were sperm whales’ calls built with distinctive units at a coda level (meaning they were combinatorial), but they were compositional in that a call contained multiple codas.

But does that get us any closer to decoding the whale’s language?

“The combinatoriality at the word level and compositionality at the sentence level in human languages is something that looks very similar to what we found,” Sharma said. But the team didn’t determine whether meaning was being conveyed, she added. And without evidence of meaning, we might be barking up the wrong tree entirely.

Mockingbird songs

“It’s funny how people always want to compare animal communication to language—it is sexy, and it helps to sell papers. But to me, human music is a much richer, much more apt comparison,” said Tecumseh Fitch, an evolutionary biologist at the University of Vienna and author of the book The Evolution of Language. Fitch pointed out that three ingredients are necessary for a language to appear. The first is vocal learning, an ability to learn new sounds. Sperm whales have that, but so do thousands of other species.

Then there are syntax and semantics. “Syntax is the only thing this whole study is relevant to because it suggests that sperm whales have a much more complex syntax than we thought before. Semantics, though, the study says nothing about. The authors are very open about it,” Fitch said.

One thing that requires vocal learning and syntax but doesn’t have semantics is music. Let’s take a mockingbird song, for example.

“What a mockingbird has is a system of small syllables that it combines into larger song fragments, and then any given bird will sing sometimes for hours and combine thousands of these what you might call words into super complex sequences that you might call songs,” Fitch says. But there is no indication, despite lots of research, that those songs are anything like sentences carrying meaning like “I had a breakfast this morning” or “there is a really good tree in my territory.”

“No songbird researcher thinks that. Now, if we return to sperm whales, we can ask what is the difference between their communication and a mockingbird song? I mean from the structural point of view, from the point of view of comparing whether it is a language or music, the answer right now is ‘none that we can identify,’” Fitch said.

Back in the 1960s, Charles F. Hockett, an American linguist, published a list of the design features of language, basically a set of 13 boxes a communication system has to check to be considered a language. According to Sharma’s study, we can confidently say that sperm whales’ communication checks nine of those 13 boxes. The four still missing include displacement: the ability to talk about things not present in either space or time. There’s also productivity, a capacity to say things that have never been said before, and “duality of patterning,” which is organizing meaningless sounds into meaningful words and sentences. Last, and far from least, is semanticity.

“You would need all these design features in order to have a language. But you just can’t have displacement or duality of patterning without knowing anything about the semantics,” said Fitch. But testing if there are semantics in sperm whales’ calls is hardly possible without cooperation from the sperm whales. And getting them to cooperate may take an unexpected turn.

Whale in the loop

One way to figure out semantics in sperm whales’ calls is by doing playback experiments with wild whales—basically, synthesizing codas or coda sequences, playing those near sperm whales, and seeing how they react. But playback experiments have been attempted before, and there is a dark side to doing them with wild animals.

“There were experiments where they started to make contact with animals in the wild—with apes. The population exposed to those experiments got violent, and it disrupted the ecosystem,” said Sharma. “In the wild, we have no understanding of what to expect, and the species we are studying is already endangered—sperm whales are classified as such.” In her opinion, playback experiments are a no-go unless there is confidence they would do no harm. And today we’re not so sure.

According to Sharma, even collecting passive data on whales like the one gathered by the Dominica Sperm Whale Project is very expensive and takes lots of time—it took over 13 years to record the codas she used in her study.

Finally, even if sperm whales do talk Sperm-Whaleish, why would they want to talk to us? “If aliens came to Earth, they would probably have an incentive to talk to humans and [use] communication systems that are more interactive. An alien would draw something and say a word, then a human would draw something. Communication with whales has been very passive,” Sharma said. “This thing they showed in [the show] Extrapolations was like a dream system. I don’t know when we could have something like that—10, maybe even 20 years? But how we get the evidence of casual relationship between the sound and the action is not clear for me at all,” she added.

“This study kind of invites you to think sperm whales’ communication is more like language than we thought, as opposed to more like music than we thought. But the kind of questions it is asking—the leading questions, like ‘is there a language?’—a lot of people would like to think it’s true,” said Fitch.

Nature Communications, 2024.  DOI: 10.1038/s41467-024-47221-8