LESSON 2 - SeaTrek Programs

What are the different sounds used for? Why do dolphins make clicking sounds? Do dolphins click to
communicate or do they click for another reason? How do dolphins find their way underwater when it
is dark or the water is murky?
Do dolphins have special night vision?
Scientists have done experiments to prove that the low frequency clicks help dolphins navigate and hunt in
murky waters. The clicks travel through the water and bounce off of objects in their path. The returning echo
provides dolphins with information about objects, including size, location, density, and shape. This process is
called “echolocation.” It was not until 1960 that researchers were able to prove that dolphins used echolocation
– and not special underwater or night vision – to navigate through the waters. Bat researchers were
able to study bat echolocation by blindfolding them. Researchers needed to come up with a more creative
way to block dolphin vision: a special blindfold made of rubber suction cups was placed over the eyes of
dolphins before they swam through an obstacle course. During their swim, the dolphin sounds recorded were
identified as the clicks we now know as dolphin echolocation.
What are dolphin whistles for? Do dolphins whistle to communicate with each other?
After echolocation clicks, the second most-researched dolphin sounds are their whistles. In the 1960's, scientists
discovered that individual dolphins would mostly produce one individual distinctive whistle, almost as if
to identify themselves. Before this, researchers thought that dolphins might be whistling based on what they
were doing, not who they are.
Since 1975, researchers have recorded and stored whistles from Sarasota Bay for future studies and experiments.
The recordings show that dolphins not only have individual signature whistles, but that the signature
whistles did not change over 10 year of their life. By keeping all of the recorded signature whistles in a database,
scientists can use the information for further studies and also share the information with other scientists.
Are dolphins born with a signature whistle or do they develop one as they grow? If they are not born
with a signature whistle, how does it develop?
To study signature whistle development, scientists recorded underwater sound while observing mother-calf
dolphin pairs in the wild. They found that young dolphins made a quavery whistle that grew into a signature
whistle during the first year of life. It seems that the development of signature whistle depends on things like
the total number of whistles the calves heard in the first year, the number of whistles the mother made, the
bond between the mother and calf, and the number of other dolphins living in the same area.
Most scientist believe that dolphins learn their signature whistles. This is very different than most non-human
mammals, which are born with the ability to produce sounds for communication. Unfortunately, more studies
need to be done that record individual dolphin sounds while observing behaviors to understand more about
the learning process of signature whistles.
Are there any patterns in signature whistles? Do dolphins that are related to each other have similar
whistles?
By comparing recorded signature whistles to dolphin identification and genetic information, researchers were
able to see a pattern in signature whistles. They found that female calves tended to produce whistles that
were very different from those that their mothers made. Male calves, however, were more likely than females
to produce whistles similar to those of their mothers.
Using information learned by other researchers about dolphin behavior and social arrangements, scientists
think that one reason that females may have different whistles is that mother-daughter pairs may associate
with each other form time to time. By having different whistles, they can have distinct identities. Other scientists
think that males have similar whistles to their mothers so that possible interbreeding with female relatives
will be avoided. Scientists may not ever know exactly why this happens.
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