View from the camera near the far-field hydrophone as the dolphin captures a mullet. The camera attached temporarily to the dolphin's forehead by a rubber suction cup is positioned to record the instant of fish capture.
Dolphins have very sensitive hearing and hear across a broad range of frequencies that far exceed the hearing range of humans. Dolphins also project sound into the environment so they can image the environment. These sounds are called echolocation “clicks.” Echolocation clicks are very short, pulsed signals that sound like the snapping of fingers. The clicks have acoustic energy that spans a broad range of frequencies that overlap with the dolphins range of best hearing. As the clicks travel through the water, they encounter objects that reflect the sound back to the dolphin. It is these “echoes” that dolphins use to image their environment.

A Remarkable Ability

Dolphins have a remarkable ability to detect and identify objects through echolocation, even objects that are buried under sand on the ocean floor. Work by NMMF scientists has demonstrated that dolphin echolocation is incredibly flexible; dolphins can steer and change the width of their echolocation beams dramatically and quickly (on the order of tens of milliseconds). However, it is the ability to listen to the echoes and transform them into representations of the environment that is truly remarkable.

Current Research

The NMMF, in conjunction with the U.S. Navy Marine Mammal Program, is currently conducting a number of studies on dolphin echolocation. Current research efforts are funded by the Office of Naval Research and are part of a long-term research plan to better understand how the dolphin detects and identifies underwater objects. The NMMF is also partnering with multiple universities as part of a Multidisciplinary University Research Initiative to study the echolocation of dolphins and bats.