Using algorithms to decode the complex phonetic alphabet of sperm whales

Sperm Whale photo- by Istock at Istock

Using algorithms to decode the complex phonetic alphabet of sperm whales

For millennia, the allure of whales has stoked human consciousness, transforming them into enigmatic residents of the deep seas in our myths and folklore. From the biblical Leviathan to Herman Melville’s formidable Moby Dick, these ocean giants have held a central place. While cetology, or whale science, has especially improved our knowledge of these marine mammals in the past century, studying them has remained a formidable challenge.

Machine learning is bringing us closer to understanding sperm whales. Researchers at MIT’s CSAIL and Project CETI cracked the code on the “sperm whale phonetic alphabet” using algorithms. Their findings, published in a new open-access study in Nature Communications, reveal a sophisticated structure in sperm whale communication, similar to human phonetics and communication systems found in other animals.

The study analyzed 9,000 codas, short bursts of clicks used by sperm whales to communicate, collected from Eastern Caribbean sperm whale families by the Dominica Sperm Whale Project. This data, along with pattern recognition and classification algorithms, and on-body recording equipment, helped the team unlock the complexity of sperm whale communication. The research shows that these clicks are not random but structured in a complex, combinatorial way, indicating a communication system far more intricate than previously thought.

Researchers discovered a potential “sperm whale phonetic alphabet” where elements like rhythm, tempo, rubato (smooth variation), and ornamentation combine to create a vast range of unique codas. For instance, whales would adjust specific aspects of their codas based on conversation, like subtly changing call duration (rubato) or adding extra clicks. Even more impressive, these codas’ building blocks can be combined in various ways, allowing whales to construct a massive repertoire of distinct vocalizations.

The study used acoustic bio-logging tags (D-tags) attached to whales in the Eastern Caribbean to capture the intricacies of their vocal patterns. By creating new data analysis techniques, the MIT team revealed that individual whales produced various coda patterns in long exchanges, not just repeating the same coda. These patterns, they found, were nuanced and included subtle variations that other whales could also produce and understand.

“We’re venturing into uncharted territory, deciphering the mysteries of sperm whale communication without any existing reference data,” says Daniela Rus, director of CSAIL and MIT professor.

“Machine learning is crucial for identifying communication features and predicting what they might say next. Our findings suggest structured information within their calls and challenge the common belief among linguists that complex communication is unique to humans.”

This research represents a step towards understanding that other species possess levels of communication complexity previously unrecognized, with deep connections to their behavior. The next steps aim to decipher the meaning behind these communications and explore how group actions might correlate with what the whales are “saying.”

Whaling around

Sperm whales, boasting the animal kingdom’s biggest brains, exhibit intricate social behaviors within families and cultural groups. This necessitates sophisticated communication, especially for coordinating hunts in the high-pressure realm of the deep sea.

Enter Roger Payne, a pivotal figure in understanding whale communication. A former Project CETI advisor, whale biologist, conservationist, and MacArthur Fellow, Payne’s 1971 study in Science, “Songs of Humpback Whales,” revolutionized our understanding of whales as singing creatures. His work became a catalyst for the successful “Save the Whales” movement, a crucial conservation effort.

“Payne’s research exemplifies the power of science to impact society,” says David Gruber, Project CETI’s lead founder and a distinguished biology professor at City University of New York. “His discovery of whale songs led to the Marine Mammal Protection Act, safeguarding numerous whale species from extinction. This current interdisciplinary research brings us closer to deciphering what sperm whales are ‘saying.'”

Project CETI’s ongoing research delves into whether elements like rhythm, tempo, ornamentation, and rubato hold specific communicative meaning. This could unlock the secrets of “duality of patterning,” a linguistic phenomenon where simple building blocks combine to convey complex ideas, previously thought to be exclusive to human language.

Aliens among us

Sperm whale communication holds surprising parallels to deciphering messages from extraterrestrials, according to researchers. Pratyusha Sharma, the study’s lead author and an MIT Ph.D. student, highlights this intriguing aspect: “We’re essentially trying to understand a species with an entirely different environment and communication system, completely unlike human norms.”

The challenge lies in interpreting the fundamental units of meaning within their clicks and calls. Sharma emphasizes that the goal isn’t to teach whales human language, but to crack the code of their natural communication system, shaped by their unique biology and habitat. “Our work could pave the way for understanding how an ‘alien civilization’ might communicate,” she says, “providing insights for creating algorithms to decipher entirely foreign communication forms.”

This research adds to the growing understanding of complex animal communication. Robert Seyfarth, a non-participating professor emeritus of psychology from the University of Pennsylvania, acknowledges the increasing focus on how animals combine signals to create new messages. “The key questions are: Do these combinations vary based on social context, and do they follow recognizable rules understood by other animals?” he ponders. “Studying marine mammals is particularly challenging because we can’t observe them directly or fully grasp the communication context. However, this study offers exciting new details about sperm whale call combinations and the potential rules governing them.”

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