Marine mammals establish or maintain contact with specific individuals using short-range vocalizations. The most striking example of marine mammals using sound to make or maintain contact is between mother and offspring. It is very important for a mother to remain in close communication with her offspring for feeding and protection from predators.

Dolphin societies need a highly developed communication system because group numbers and members are constantly changing. Bottlenose dolphins use whistles to maintain contact between mom and calf, as well as between individuals in a group. Whistles are tonal sounds that change in frequency over time. Each bottlenose dolphin has its own unique whistle. This is referred to as its signature whistle, and it is used to broadcast the identity and location of the animal that produced it. The spectrogram below shows a dolphin whistle containing three sound loops. The unique feature of each dolphin's signature whistle is the loop shape. The number of loops from the same dolphin may change from whistle to whistle, but the unique loop shape remains the same. The dolphin whistle below has a frequency of 7-23 kHz.

This is a spectrogram of a bottlenose dolphin whistle. Time is shown in seconds on the x-axis. Frequency in kilohertz is plotted on the y-axis and increases in pitch as the numbers increase. The static in the lower portion of the image is lower frequency noise in the background of the recording. (Courtesy of Jennifer Miksis, University of Rhode Island) Click below to hear the sample: QuickTime (48K) Or click the MP3 button below to use any media player

The whistle sounds like a chirp repeated three times. Listen to the whistle while looking at the spectrogram. Can you hear the three separate loops?

Below are three signature whistles from different dolphins for comparison (Courtesy of Jennifer Miksis, University of Rhode Island). From looking at the shape of the whistles, they appear very different. Listen and see if you can pick out the differences by ear.

A		B		C
QuickTime (15K) Or click the MP3 button below to use any media player		QuickTime (19K) Or click the MP3 button below to use any media player		QuickTime (8K) Or click the MP3 button below to use any media player