Dolphin Echolocating Abilities May Diminish due to Man-made Noise

Marine mammals are significantly affected by underwater noise such as ship sonar and oil well operations, according to new research from the United States.

Study finds that man-made underwater noise can affect marine mammals' ability to echolocate. Stephanie Lam/The Epoch Times

Marine mammals may be significantly affected by underwater noise such as ship sonar and oil well operations, according to new research from the United States.

Dolphins and whales use sound echoes to navigate and communicate via a process called echolocation. A study by the U.S. Navy and the National Marine Mammal Foundation shows that anthropogenic noise in general and particular noise frequencies may affect dolphins’ ability to echolocate.

Scientists at the Navy Marine Mammal Program (NMMP) facility detected a male bottlenose dolphin’s clicks with a hydrophone, and then created a computerized echo that was played back to him with a delay.

The researchers generated echoes to simulate an object, both stationary and rotating, about 10–56 feet (3–17 meters) away from the dolphin by altering the delay. The dolphin was taught to make a buzzing sound upon detecting a change in the echo from that of a stationary to a rotating object.

During the experiment, the team played seven different man-made noises at various frequencies and durations along with the echo to see how each one affected the dolphin’s ability to hear when the echo changed.

“Preliminary results show that intermittent noise at frequencies outside of the echolocation range of the dolphin had little effect on his echolocation performance, while continuous noise and noise within the dolphin’s echolocation range decreased performance at a farther distance,” said researcher Eryn Wezensky in a press release.

However, Wezensky noted that Gaussian noise, a statistical noise outside the dolphin’s echolocation range, decreased his ability to hear the echo change.

Next, the team intends to analyze the dolphin’s clicking sounds during different noise conditions and investigate whether these mammals respond more slowly or compensate with louder clicks.

The initial results will be presented at the 162nd Acoustical Society of America Meeting in San Diego, California on Nov. 4.