This allowed him to calculate the location of the calling dolphin. Dolphins surface frequently to breathe, so Janik's team could also track the direction and behaviour of individuals attracted by the calls. These brays occurred during almost all the 'feeding events' he observed. When a caller used higher pitch vocalizations, such as whistling, other dolphins approached more slowly. The real reason for the brays, Janik suspects, may be to subdue dinner into sticking around.
Hearing is a crucial sense in water, where vision is restricted.
Thus disoriented, they are far easier to catch. As fish hear at low frequencies, he adds, the dolphins' low frequency brays may have evolved as an aid to catching the salmon. Now, to work out which it is, researchers should monitor the reaction of dolphins to ready-stunned fish, he proposes. K.A. Loud impulse sounds in odontocete predation and social behavior.