Individual-specific Vocalizations
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 L. Miksis Olds). |
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Click either choice below to hear the bottlenose dolphin:
QuickTime (32K)
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Bottlenose dolphin whistle recorded at Mystic Aquarium while the dolphin was isolated in a side pool.
Sound clip provided by Jennifer L. Miksis Olds. Released under Creative Commons License, non-commercial - no derivs.
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 Olds). From looking at the shape of the whistles, they appear very different. Listen and see if you can pick out the differences by ear.
Click either choice below to hear the bottlenose dolphin:
Click either choice below to hear the bottlenose dolphin:
Click either choice below to hear the bottlenose dolphin:
Sperm whales produce rhythmic patterns of clicks when they are resting or socializing at the surface. These clicks are much shorter than dolphin whistles and have a much broader frequency. They sound very similar to a loud human handclap. The click patterns are called
codas, and it is thought that each sperm whale has its own individually distinctive coda pattern. It is common to hear whales exchange codas during social behaviors.
This is a recording of sperm whale codas. The sound clip contains the same coda used three times in succession by a single sperm whale off Hawaii. The spectrogram shows the patterned sets of clicks that make up the coda. Note the timing of the click sequence within a single coda - the interval of time between the first and second clicks is longer than the time between the second and third click. The timing of the clicks in the sequence is what makes each coda pattern unique. The sperm whale coda wasrecorded near Hawaii.
Sound courtesy of WhaleAcoustics, LLC.
Seals and sea lions that breed in colonies have also developed a form of communication that uses individually distinctive vocalizations to reunite mom and pup when the moms return to the crowded colony after feeding. A mother will give a pup-attraction call when she returns. Her calls are heard by her pup and are often returned with calls from the pup. Both mother and pup recognize each other's vocalizations, which allow them to find each other in a very crowded rookery.
