Researchers with Project CETI have found that sperm whales off the coast of Dominica change the structure and rhythm of their click vocalizations when shipping noise is present. The whales do not simply get louder, as some other marine species do. They alter the speed and the types of click patterns they produce, according to findings published in the journal Ecological Informatics. The study draws on four years of field data collected from a 15-member pod using drone-deployed audio tags, with vessel proximity confirmed through digital geolocation data (The Guardian, 2026-07-22; Ecological Informatics).

The researchers recorded more than 1,000 codas from the Dominica clan. A coda is a short, structured sequence of clicks that sperm whales use to communicate. Under normal conditions, a whale identified as Atwood produced a five-click coda in a 1-1-3 pattern: two clicks at a steady pace, followed by three quicker ones. That specific 1-1-3 pattern is unique to this clan, one of several regional sperm whale groups distinguished by their coda repertoires.

When vessels were nearby, Atwood produced the same 1-1-3 pattern but at a faster tempo, with shorter gaps between clicks. Across the full dataset, sperm whales produced shorter individual click sequences when exposed to shipping noise. Crucially, they did not simply raise the volume of their vocalizations, a compensatory strategy documented in other marine species. Instead, they altered both the speed and the types of codas they produced.

Gašper Beguš, the linguistics lead at Project CETI, stated that researchers can predict whether ships are present from sperm whale vocalizations alone, a signal of how systematic the noise-induced shifts are.

Earlier Project CETI research, reported in April 2026, found that condensed gaps between clicks in a coda sequence produced continuous sounds resembling two human vowels: "aaaa" and "iiii." In the current study, sperm whales used the "aaaa" coda type more frequently under noisy shipping conditions. That shift in coda-type distribution, layered on top of tempo changes, suggests that human-generated noise is affecting not just acoustic output but the combinatorial structure of whale communication.

Project CETI had previously identified 156 distinct click patterns constituting the sperm whales' sound system, which the initiative has characterized as a "sperm whale phonetic alphabet" with vowels serving as building blocks of their speech (UC Berkeley, 2025-11-12; National Geographic Society). David Gruber is the founder and chief executive of the initiative.

The broader context here is the collision between industrialized maritime traffic and the acoustic ecology of a deep-diving species that depends entirely on sound for communication, navigation, and social coordination. Sperm whales live in an environment where light fades quickly and where clear acoustic signals are essential. The Dominica clan's 1-1-3 coda is not merely a call; it is a culturally transmitted identity marker. If shipping noise systematically compresses the temporal structure of these codas and shifts the distribution of phonetic units used, the question is whether those modifications degrade information transfer or represent a functional adaptation that preserves communicative efficacy under interference.

The study cannot yet answer that question directly. It establishes a measurable, predictable relationship between vessel noise and coda modification, but the downstream consequences for social cohesion, maternal-calf communication, or long-term cultural transmission remain untested. What the data do show is that the modification is not random. Whales are selecting specific coda types and adjusting temporal parameters in a manner that correlates with noise exposure, which implies at minimum a perceptual and motor response to acoustic interference rather than a simple stress reaction.

The distinction matters for policy. Shipping noise is already a recognized stressor under several international frameworks, but regulatory responses have largely focused on amplitude thresholds. If whales are reorganizing the internal structure of their communication system rather than merely shouting louder, then noise-mitigation strategies calibrated only to decibel levels may miss the functional impact. Speed restrictions and routing measures that reduce the duration and proximity of vessel exposure could matter as much or more than quieting the vessels themselves.

Dominica, which has declared a sperm whale sanctuary in its waters, sits at a geographic bottleneck for Caribbean maritime traffic. The intersection of a protected habitat and a dense shipping corridor makes the island's eastern waters a natural laboratory for studying this kind of acoustic competition, and Project CETI's longitudinal dataset is among the richest available for doing so.

The next phase of research will likely need to address whether these coda modifications persist over generational timescales or whether they are purely situational adjustments that revert once the noise source recedes. The difference between the two carries distinct implications for how one assesses the long-term fitness consequences of anthropogenic acoustic intrusion into a culturally structured communication system.