Sperm Whales Adjust Clicks When Boats Are Near

Sperm whales modify their vocalizations, specifically their clicking patterns, when vessels are in their vicinity. Researchers observed that individual click sequences became shorter and certain types of clicks were used more frequently in the presence of shipping noise. This phenomenon was documented off the coast of Dominica by scientists from Project Ceti, a non-profit organisation focused on decoding sperm whale communication.

Changes in Vocalizations

Over a four-year period, researchers attached audio tags to 15 sperm whales to record their vocalisations. They collected over 1,000 distinct clicking patterns, known as codas. The study, published in the journal Ecological Informatics, found that when shipping noise was present, verified by geolocation data, the whales' click sequences shortened. Furthermore, the whales increased their use of a specific coda pattern, described as sounding like 'aaaa'.

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Gašper Beguš, linguistics lead at Project Ceti, stated that the presence of shipping noise influenced the whales' communication. "The study is actually one of the first glimpses that the vowels that we discovered might actually carry meaningful information. Because in the presence of shipping noise, they change the way they use those vowels," Beguš said. The researchers noted that this contrasts with some other marine animals, which tend to increase vocalization volume in noisy conditions. Instead, these sperm whales appeared to alter the timing and type of their clicks.

Implications and Further Research

David Gruber, founder and chief executive of Project Ceti, raised questions about the meaning of these changes. "This research begs the question: are whales talking about the ships, or is it an impact on their voices because the ships are around?" Gruber asked. He suggested that understanding these communications could potentially influence policy and laws related to marine traffic. While some scientists have raised methodological concerns about describing whale sounds with human linguistic terms, Project Ceti uses qualifiers like 'vowel-like' to address these critiques.

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Nathan Merchant, an underwater noise specialist at the UK government marine research agency Cefas, who was not involved in the study, commented on its significance. He noted that while many studies show behavioural changes in marine animals due to noise, this research highlights alterations in the fine-scale content of the calls themselves. "Something that marks this study out is that it shows changes to the fine-scale content of those calls," Merchant said. He added that further investigation is needed to fully understand the meaning behind these audible shifts, posing the question, "Are they [the whales] just struggling to say the same thing, or are they saying something different in the presence of this noise?"