Sperm whales have been found to alter their unique 'vowel-like' sounds when boats are near, a groundbreaking discovery by researchers at Project Ceti. This significant finding comes from four years of listening to the calls of 15 sperm whales off the coast of Dominica in the Caribbean.
The study, published in Ecological Informatics, reveals that when encountering shipping noise, individual click sequences became shorter and the whales prioritised changing the speed and types of 'codas' – their distinctive patterns of clicks used for communication. In fact, they did not simply increase their volume, a common response seen in other marine animals facing noise pollution.
For instance, one whale, named "Atwood", typically produced a coda of five clicks in a 1-1-3 pattern unique to its clan. When a ship's background hum was present, Atwood maintained this rhythm but noticeably quickened the pace, reducing the intervals between each click. Gašper Beguš, Project Ceti's linguistics lead, stated that the association was so strong they could generally predict the presence of ships from vocalisations alone.
The research has built upon previous work by Project Ceti, which suggested that sperm whale communication includes 'vowel-like' sounds. The latest study observed differences in these vowel-like sounds when whales were in noisy conditions, with them using the 'aaaa' coda more frequently.
This alteration in vowel-like sounds suggests they might carry meaningful information, according to Beguš. While some researchers have previously criticised Project Ceti's use of terms like "vowels" and "language", the team clarifies they use these terms to address concerns. Nathan Merchant, an underwater noise specialist at Cefas, acknowledged the potential link but noted that other unknown factors could also influence whale vocalisations.
Researchers at Project Ceti say their findings have significant implications for marine conservation and management, potentially enabling them to predict shipping traffic from whale vocalisations alone in future. The team believes this breakthrough has opened doors to a new area of research into the complex communication patterns of sperm whales.