Decoding sperm whales’ ‘phonetic alphabet’

By Cherie Beling

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Author: Mark ‘Crowley’ Russell

sperm whales swimming together in a group near the surface
A pod of sperm whales possibly discussing their future travel plans (Photo: Shutterstock)


Scientists recently discovered that sperm whales make decisions by consensus, and now they’re hoping to find out what they say when they do, as part of a research effort called Project CETI, the ‘Cetacean Translation Initiative.’

Sperm whales (Physeter macrocephalus) are highly social animals with a society structured into distinct clans, each of which has its own ‘ethnolinguistic’ characteristics. In other words, the clicks and whistles through which they communicate are only understood by members of the same clan, rather like humans can’t understand people who do not speak the same language.

The clicks that sperm whales make are known as ‘codas’, parts of which are already known to represent the individual making the call, and the clan to which it belongs.

Beyond the sperm whale’s ‘caller ID’, science has so far not decoded any of the remaining conversation. A new paper, however, recently published in the online journal Nature Communications, has found that the sequence of the clicks, when combined with variations the scientists refer to as ‘rhythm and tempo’, appear to have some form of contextual meaning.

In human terms, we continually use our own languages by combining a set of predefined concepts to provide contextual information. We string together sounds – or phonemes – to create our sentences, and the way we do so has varied over the millennia; from Egyptian hieroglyphs and East-Asian characters to the Arabic and Latin alphabets in use today.

group of sperm whales at the surface looking like they are having a meeting
A family of sperm whales stops for a quick chat (Photo: Shutterstock)

It’s possible that the codas used by the whales provide a similar function – a series of distinct sounds which, placed together in combination, might communicate a preferred direction to swim or place to hunt, or perhaps reassure a juvenile. All are behaviours which we know cetaceans are able to communicate, and the researchers hope that analysis of the sperm whales’ vocalisations might provide clues as to how they do so.

The study was based on recordings taken from members of the Eastern Caribbean clan of sperm whales between 2005 to 2018, which inhabited an area of around 2000 sq km around the island of Dominica. A total of 8719 different codas were analysed, but the scientists found that although the pattern of each remained the same, the whales would sometimes change the duration of the patterns, or add extra clicks at the end.

The change in the duration of a coda was named ‘rubato’, a musical term in which the tempo of a piece of music is not strictly adhered to, allowing an orchestra’s conductor to vary the speed of a piece of music to suit a particular mood or effect. The extra clicks are referred to as ‘ornamentation’, in that they were appended to a regularly defined coda, rather than being a separate series of sounds.

The whales were found to string each of these codas together – complete with tempo changes and ornamentation – int regular sequences, in a fashion analogous to human sentences. This does not necessarily mean the whales are actually talking to each other – they could simply be singing using sounds they have learned from other members of the clan – but the methodical combination of smaller elements into longer phrases strongly implies a form of ‘spoken’ language.

The trick now is for future studies to try and pair up these sequences with particular behaviours – an extraordinarily difficult task given that the whales need to be observed performing an action after making a vocalisation. Some could be quite easy to spot using acoustic tags, which might record the whales making a regular series of sounds before diving into the depths. Other, more nuanced communications, however, could be impossible for us to ever comprehend.

While there may never be a page on Google Translate for whalesong to human speech, if we could learn to understand enough to figure out where the whales are planning to travel in advance, it would make it easier to provide the whales with protection from human activities.

‘Our results demonstrate that sperm whale vocalisations form a complex combinatorial communication system,’ write the paper’s authors. ‘Sizable 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.

The paper ‘Contextual and combinatorial structure in sperm whale vocalisations’, is published in Nature Communications under an open access license.

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