Adaptation

2dolphins

Two Bottlenose Dolphins(2)

Distinctive Whistle

Within the first few months of its life, a bottlenose dolphin develops its own distinctive whistle that distinguishing it from other dolphins. The value of this distinctive whistle is that it enables dolphins to recognize each other, as each dolphin has its own whistle associated with it. Also, the ability to whistle allows dolphins to communicate with each other, and allows them to remain in contact with members of the same group(1).

Different Types of Vocalizations

Dolphins can produce several types of vocalizations, each having a specific purpose. The sound produced by dolphins that is referred to as click-creaking is used for finding food, ranging and navigation(7).  Other sounds dolphins make, such as click trains, whistles and a combinations of different sounds referred to as quacks, blats and squawks are used for communication.

Distress Signal

Dolphins can also produce a sound that is recognized by other dolphins as a distress signal. The distress signal consists of two whistles. The first whistle is a crescendo, and the second one is a decrescendo. When other dolphins hear the distress signal, it immediately silences them and they begin to search for the distressed dolphin(6).

Use of Whistles for Group Cohesion

In a study conducted by Vincent M. Janik, he determined the range of the Bottlenose dolphin whistle. He found that the active space, which is the maximum distance from the dolphin producing the whistle that another dolphin can be and still recongnize the whislte as being produced by a conspecific, was variable depending on geography and sea conditions(5). At a depth of 10 meters and a sea state of 0, which is when there are no waves and the surface of the water is still, the active space ranged from 20 to 25 kilometers. When depth was the same but the sea state was 4, which is defined as moderate waves, the active space ranged from 14 to 22 kilometers. These results indicate that dolphins can use their whistle to remain in contact with other members of a group spread out over distances of several kilometers(5).