Sperm whales change the way they communicate when boats are nearby, according to a new study that highlights the impact of ocean noise pollution on marine life. Scientists found that the animals alter their vocalizations so distinctly that researchers can now predict whether ships are in the area simply by listening to whale calls.
For four years, researchers from Project Ceti, a non-profit organization focused on decoding sperm whale communication, recorded and analyzed the calls of 15 sperm whales off the coast of Dominica in the Caribbean. They discovered that when ships were nearby, the whales' click sequences—known as "codas"—became faster and shorter.
Normally, one whale named Atwood would produce a five-click pattern. When a ship was in the background, Atwood would repeat this pattern much faster, reducing the time between clicks.
Additionally, the whales changed how they used "vowels." Sperm whale communication consists of Morse-code-like clicks, but if these click sequences are sped up, they form continuous sounds that resemble human vowels, specifically "aaaa" and "iiii". In noisy conditions, whales used the "aaaa" sound more frequently. Researchers suggest this might be one of the first clues that these vowel-like sounds carry specific meanings, as their usage changes in response to shipping noise.
While some scientists warn against comparing whale sounds too closely to human language, other experts agree that this study adds a new layer of understanding to how noise pollution affects marine animals. While marine mammals are known to raise their volume in response to noise, sperm whales instead modify the rhythm and structure of their calls.
It remains unclear whether the whales are trying to communicate differently or are simply struggling to be heard over the noise. However, the findings could eventually help shape environmental policies and laws to protect marine life from shipping noise.