The largest toothed whale uses echolocation and vocalisation, and has the largest brain on Earth. In contrast to humpback whale songs, Sperm whales communicate using sequences of clicks, known as codas, which reveal intricate patterns.

New findings show that rubato (duration variations) and ornamentation (extra clicks) change depending on the context, and that other whales copy these sequences. 

The combination of rubato, ornamentation, rhythm and tempo creates a vast array of unique codas, indicating an expressive way of communicating among whales. The “sperm whale phonetic alphabet” allows for a greater information capacity, comparable to human phonetic systems.

“Sizeable combinatorial vocalisation systems are exceedingly rare in nature; however, their use by sperm whales shows that they are not uniquely human, and can arise from dramatically different physiological, ecological, and social pressures,” details the paper.

“Our results show that the sperm whale communication system is, in principle, capable of representing a large space of possible meanings, using similar mechanisms to those employed by human sound production and representation systems (e.g., speech, text, Morse code, and musical notation).”

Supported by Machine Learning 

The scientists at the Massachusetts Institute of Technology (MIT) and Project CETI (Cetacean Translation Initiative) used Machine Learning to help decode the codas. The mix of algorithms were used for pattern recognition and classification.

“We are venturing into the unknown, to decipher the mysteries of sperm whale communication without any pre-existing ground truth data,” says Daniela Rus, CSAIL director and professor of electrical engineering and computer science at MIT. 

“Using machine learning is important for identifying the features of their communications and predicting what they say next. Our findings indicate the presence of structured information content and also challenges the prevailing belief among many linguists that complex communication is unique to humans. This is a step toward showing that other species have levels of communication complexity that have not been identified so far, deeply connected to behaviour. Our next steps aim to decipher the meaning behind these communications and explore the societal-level correlations between what is being said and group actions.”

Social complexity

The study takes the social complexity hypothesis, which suggests animals in “complex societies” dealing with “coordination, distributed decision-making, social recognition, and social learning of cultural strategies” need complex communication systems.

In humans, contextual and combinatorial structures enable complex messages. 

Using the social complexity hypothesis, the study examines sperm whales, which have a known coda communication system but unexplored structure and capacity. The researchers studied whether sperm whale vocalisations have contextual and combinatorial features similar to human language.

Results

Scientists analyzed 8719 codas from the Dominica Sperm Whale Project, focusing on the Eastern Caribbean 1 clan, which includes recordings from 60 individual whales.

Analysis revealed the interactive exchange of codas, showing complexity in individual and longer sequences. Further, there were also “fine-grained” variations and trends over exchanges.

Codas exhibited smooth duration variations and extra clicks. Rubato involved “fine-grained” duration changes, while ornamentation added extra clicks. These features are deliberately modulated and imitated across whales, suggests the research.

However, scientists suggest further investigation is needed to understand the semantics of the vocalisations and their functional roles.

Contacting aliens?

“One of the intriguing aspects of our research is that it parallels the hypothetical scenario of contacting alien species. It’s about understanding a species with a completely different environment and communication protocols, where their interactions are distinctly different from human norms,” says Pratyusha Sharma, an MIT PhD student, and the study’s lead author. 

“We’re exploring how to interpret the basic units of meaning in their communication. This isn’t just about teaching animals a subset of human language, but decoding a naturally evolved communication system within their unique biological and environmental constraints. Essentially, our work could lay the groundwork for deciphering how an ‘alien civilization’ might communicate, providing insights into creating algorithms or systems to understand entirely unfamiliar forms of communication.”

“Many animal species have repertoires of several distinct signals, but we are only beginning to uncover the extent to which they combine these signals to create new messages,” comments Robert Seyfarth, a University of Pennsylvania professor emeritus of psychology who was not involved in the research. 

“Scientists are particularly interested in whether signal combinations vary according to the social or ecological context in which they are given, and the extent to which signal combinations follow discernible ‘rules’ that are recognized by listeners. The problem is particularly challenging in the case of marine mammals, because scientists usually cannot see their subjects or identify in complete detail the context of communication. Nonetheless, this paper offers new, tantalizing details of call combinations and the rules that underlie them in sperm whales.”

Written by Venya Patel