Sperm whales produce a distinct pattern of clicking noises when they detect the sounds of boats, according to a study by researchers from Project Ceti, though these patterns can now be used to predict whether ships are in the vicinity.

Research Focus on Whale Vocalisations

Scientists from Project Ceti. A non-profit organisation working to decode sperm whale communication, studied the calls of 15 sperm whales over four years off the coast of Dominica. They focused on the whales’ ‘codas,’ which are specific sequences of clicks used for communication.

When the whales encountered shipping activity, their click sequences became shorter, and one type of coda became more prominent. This finding is published in the journal Ecological Informatics.

Changes in Click Patterns

David Gruber, founder and chief executive of Project Ceti, noted that the research raises questions about whether whales are discussing the ships or if their vocalisations are affected by the ships’ presence. He added that understanding these changes could influence policy and legal decisions.

Recordings from a whale named ‘Atwood’ revealed a specific coda pattern of five clicks in a 1-1-3 rhythm. In the presence of a ship, Atwood produced the same rhythm but at a faster pace, with shorter intervals between clicks.

Gašper Beguš, linguistics lead at Project Ceti, stated that the association was so strong that vocalisations alone could predict the presence of ships. The team recorded over 1,000 codas from the 15 whales using audio tags attached by drones to minimize invasiveness.

Unique Communication Patterns

Background shipping noise was confirmed using digital geolocation data. Unlike other studies showing marine animals increase their vocal volume in response to noise, these sperm whales altered the speed and type of their codas instead.

Previously, Project Ceti researchers identified that sperm whale communication resembles human vowels. By condensing the gaps between clicks, they created sounds resembling the vowels ‘aaaa’ and ‘iiii.’

In noisy conditions, sperm whales used the ‘aaaa’ coda more frequently. Beguš noted that this suggests the ‘vowel-like’ sounds may carry meaningful information, as they change when ships are nearby.

Some researchers have critiqued Ceti’s methods, arguing that terms like ‘vowels’ and ‘language’ stretch the comparison between whale and human communication. Gruber acknowledged this by using terms such as ‘vowel-like’ or ‘language-like’ to address concerns.

Nathan Merchant, an underwater noise specialist at the UK government marine research agency Cefas, noted that while other factors could influence the changes in whale vocalisations, the relationship with shipping noise is likely causal. He highlighted that the study adds a new dimension to understanding how underwater noise affects cetaceans.

Merchant added that further research is needed to determine if the changes in vocalisations mean the whales are struggling to communicate or if they are conveying different information in the presence of ships.