Researchers with Project CETI have documented that sperm whales off the coast of Dominica modify the structure and tempo of their click vocalizations in the presence of shipping noise, altering not just amplitude but the combinatorial properties of their codas. The findings, published in the journal Ecological Informatics, draw 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 study recorded more than 1,000 codas from the Dominica clan. Under ambient conditions, a whale identified as Atwood produced a five-click coda in a 1-1-3 pattern, consisting of two clicks 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 click pattern but at a noticeably faster tempo, with reduced inter-click intervals. Across the dataset, sperm whales produced shorter individual click sequences when exposed to shipping noise. Crucially, they did not simply increase vocalization volume, a compensatory strategy documented in other marine species. Instead, they altered both the speed and the types of codas they produced.

Gašper Beguš, 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 anthropogenic 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 operate in a medium where light attenuates rapidly and where acoustic signal integrity is paramount. 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.