• Camron Davis

Study: Dolphins simplify calls due to growing ocean noise

In a recent study from the University of Maryland Center for Environmental Science (UMCES), researchers endeavored to find out how growing noises in the ocean affect marine mammals, specifically dolphins, due to their ability to communicate through sound.

According to the center's website, Helen Baily and her assistant, Leila Fouda, are the two leading scientists behind this research project and have been studying "ambient noise levels and whistle calls by bottlenose dolphins in the western North Atlantic, which experience relatively high levels of vessel traffic between shipping lanes and recreational boaters off the coast of Maryland."

The sounds were recorded using a special underwater microphone called a "hydrophone," which was deployed 20 miles off the coast.

With the increased noise, Baily and Fouda found that it "resulted in high dolphin whistle frequencies and a reduction in whistle complexity, an acoustic feature associated with individual identification." Fouda said that "The simplification of these whistles could reduce the information in these acoustic signals and make it more difficult for dolphins to communicate."

Dolphins are extremely social and rely on complex whistles to communicate with each other. They use the whistles to stay together, when feeding, and when calling out names to new groups.

"Bailey and her team analyzed the duration, start and end frequencies, presence of harmonics, and inflection points. With background noise, such as the low frequency chug-chugging of a ship’s engine, their usually complex whistle signatures flatlined."

Possible solutions to the issue have been addressed, such as engines with reduced noise and speed limits. These solutions could help reduce the effects on dolphins and other marine animals that are sensitive to sound.