A specialized mechanism in the dolphin's nasal passages just below the blowhole produces vocalizations. Air is
moved through a series of air sacs and across "phonic lips" to produce these sounds. For more information about this process,
see the "Blowhole & Breathing" section of this website.
Dolphins produce individually different signature whistles following birth.
These signature whistles remain unchanged for life. They serve to offer some evidence that dolphins have a self-awareness,
or the capacity to have a concept of "self" and to know that one exists as an individual being. These whistles last less than
1 second when produced by the dolphin. Using a sonogram, scientists can identify individual differences in these whistles,
making them the signature of the animal. Male dolphin calves generally develop whistles similar to their respective mothers.
Female calves tend to develop signature whistles quite different from those of their respective mothers. Some who study dolphins
believe this provides somewhat of a protective mechanism for mothers to avoid mating with their sexually mature male offspring
(although, with the size of the ocean and the years required for the males to mature sexually, one would think such chance
contact highly unlikely). The mother will whistle continuously to its calf
for several days following birth as a means to imprint this practice on the newborn and as a means to identify its mother,
should it stray away from her. A mother will whistle more often when her calf strays from her side. Whistles communicate emotional
state, level of alertness, establish a hierarchy in the pod, and provide information about the presence of food or impending
danger. Certain whistles are produced as "distress" signals and can dramatically affect other dolphins who receive these signals.
Distress whistles are unlike all other whistles the dolphin produces.
In this video the trainer is asking
the dolphin to prodce a variety of vocalizations. Listen carefully for the different vocalizations produced.
Randy Wells, a highly respected dolphin researcher with the Chicago
Zoological Society, feels there is some evidence to suggest that dolphins may be able to produce the whistle of another dolphin
as a way to "call the other dolphin by its name".This is termed "vocal copying" and appears
to be the means by which dolphins mimic those they are close to and want to see again. They use these vocal copies to indicate
to another dolphin that they want to reunite with that specific individual. Dolphins produce slight changes in these vocal
copies so as to avoid confusion to other "listeners". They have been shown to mimic computer-generated sounds, as well.
Recent studies have shown that dolphins remember the signature whistles of "friends" as well as "enemies" for up to 20
years. This so-called "social memory" is the longest recorded ever in the animal kingdom. This ability to remember these whistles
is an advantage to the dolphin who lives in a "fission-fusion" society where they continuously join and leave different groups
over a lifetime. Other than the dolphin, man is the only other animal known to use vocal copies, or names, for another of
their species.
Low
frequency (long wavelength) sound waves are wider and travel longer than do high frequency (short wavelength) sound waves.
A Bottlenose produces sounds in low frequencies for social communication and in high frequencies for echolocation. High
frequency sound waves are more effective for echolocation as they are more precise and able to "focus" onto smaller targets,
although they travel shorter distances in water. These high frequency vocalizations require very precise timing as they are
sent. They must take into account the travel speed of the dolphin as well as the temperature and density of the water at
the time the vocalizations are generated. All these conditions have an effect on the accuracy of the animal's vocalizations
(whether for communication or for echolocation purposes).
Because
dolphins typically live in murky environments, vocalization is important in order to maintain group cohesion and to coordinate
activities with one another - something that is required when sight cannot be relied upon for such coordination.
There is some
evidence to suggest that synchronous dolphin behaviors (such as bows done together) are a result of communication between
the participants prior to, during, and following these behaviors. These communications may include information from the dominant
animal regarding when to start the behavior and how it is to be performed. When observed underwater just prior to performing
synchronous behaviors, dolphins are often seen looking over at each other in an effort to time their moves. In the video
below, a single dolphin performs a bow, followed by a pair of dolphins performing complex synchronous behaviors at the request
of a trainer.
Site Content
Understanddolphins.com contains information condensed from a number of reputable technical sources,
peer reviewed journal articles, and respected dolphin research facilities, as well as from my personal experiences and
observations as a dolphin VIP Tour Guide and Educator.
I have made every attempt to support the information presented in this site with video and still
photographic images. On a regular basis I plan to produce more of these images and will continue to update the site with these
as well as with any new and scientifically verified information which becomes available.
