Kategorie: News
Ship noise affects whale communication
Sperm whales are considered the largest toothed whales on Earth—and apparently also remarkably adaptable communicators. A new study shows that as soon as ship noise is heard in the water, the animals measurably alter their characteristic click sounds.
A team led by David Gruber from the nonprofit Project CETI (Cetacean Translation Initiative) analyzed over 1,000 so-called codas—short, distinctive sequences of clicks that sperm whales use to communicate with one another. The data came from 13 tagged animals that were fitted with acoustic transmitters off the Caribbean island of Dominica. Background noise and ship traffic data made it possible to determine when ships were nearby.
The analysis focused on two click patterns, known as A- and I-codas, whose acoustic properties resemble the vowels “a” and “i” in human speech. The result: When ship noise was audible, the whales used A-codas significantly more often, and the intervals between clicks became shorter. This inter-click interval could be measured so reliably that the researchers were able to predict whether a ship was nearby based solely on the click patterns.
Are the whales talking about the ships—or is their communication simply being disrupted?
That is precisely the exciting, as yet unanswered question. It is possible that the animals are actively responding to the noises and, in a sense, incorporating them into their communication. It is equally conceivable that the noise simply disrupts their communication and that the altered click patterns represent an acoustic adaptation to more challenging “listening conditions”—similar to how humans automatically speak louder or more clearly in noisy environments.
One indication pointing in this direction: In the presence of ship noise, the research team itself found it more difficult to clearly distinguish between the different coda types. This suggests that the whales themselves may also have difficulty reliably understanding one another when exposed to noise pollution.
A Growing Problem Underwater
The findings are part of a trend that many divers are familiar with from their own experience: Underwater noise from shipping has been increasing for decades, with noticeable consequences for marine mammals—ranging from stress responses to changes in foraging and reproduction. Independent experts view the study as an important building block: For the first time, it shows in great detail how deeply ship noise affects even the finest structure of whale “language.”
Anyone who regularly travels in waters where sperm whales are found—such as the Caribbean or the Mediterranean—has, thanks to this study, yet another reason to keep an eye on the issue of underwater noise. Quieter boats, adjusted routes, and exercising caution when operating one’s own vessel are small but effective measures to protect the acoustic environment of these highly social animals—and thus also the encounters that divers and snorkelers find so special.
Also interesting:
Sperm whales speak different dialects
Study / Source: Smithsonian Magazine