Researchers find a reduction in the complexity of dolphin whistles as a result of increased ship noise.
How can this impact dolphin communication?

Dolphin Calls And Whistles

It is popularly known that dolphins are very social animals that are quite adept at communicating with each other. They whistle when they feed, when they talk to each other, and they even whistle to call out names, whether if it's with members of their own group, or with members of another group. Simply put, communicating with each other is an integral part of their lives.

Their whistles are complex with rises and falls in pitch and frequency, and they also display their individual personalities through individual vocalization. However, a research team discovered that such complexities may be disappearing because of the growing noise in the ocean as a result of increasing human activity.

Flatlined Whistle Signatures

To test dolphin response in areas with relatively high levels of sea vessel traffic between recreational boaters and shipping lanes, researchers deployed hydrophones to the bottom of the ocean, about 20 miles off the coast of Maryland.

What they found was that the increases in vessel noises resulted in higher whistle frequencies with reductions in complexity. In other words, the dolphins whistled more, but with much less complexity. Analyzing the data, the researchers found that with background noise, the dolphins’ typically complex whistles essentially flatlined.

'The Shortest Answer Possible'

Communication Is very important for dolphins, and they rely on sounds to do so. However, evidence shows that increasing vessel traffic hinders dolphin communication in that their usually complex communication ends up being simplified. This not just makes it difficult for them to communicate, but it masks their individual identification, and might also reduce the information in their whistles.

“It’s kind of like trying to answer a question in a noisy bar and after repeated attempts to be heard, you just give the shortest answer possible,” said Dr. Helen Bailey of the University of Maryland Center for Environmental Science, coauthor of the study. “Dolphins simplified their calls to counter the masking effects of vessel noise.”

As such, researchers propose looking for other, quieter means of travelling by water so as not to disrupt the lives of marine creatures.

The study is published in the journal Biology Letters.