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Learn
about Dolphins
Introduction
Scientists understand the importance of studying dolphins
in the wild, to begin to comprehend their incredibly complex
lives. Our film is a window to just one research project
that studies the communicative lives of dolphins in the
Bahamas and off the shores of Argentina. Yet there are
hundreds of scientists studying dolphins worldwide. They're
discovering where dolphin species live and travel; how
dolphin families and societies form; how these marine
mammals compete and cooperate with other species; and
how humans adversely affect their health and mortality.
All of their work contributes to our understanding of
dolphins and the wonderfully intricate and fragile ocean
that is their home.
There are about 40 species of dolphins known to exist
in Earth's oceans and fresh water rivers. Some, like the
bottlenose dolphin, are much more known to the public
and to scientists. Research on dolphin intelligence, for
instance, has been done predominantly with bottlenose
dolphins in captivity. Others, like the rough-toothed
dolphins that stranded in Florida and are featured in
our film, are less understood. Scientists are still trying
to discover, for example, where these animals can be found!
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Similar to the herds of animals that have roamed the
plains of Africa and North America, dolphins travel
the ocean in communities of varying size; and they maintain
societies for mating, feeding, detecting predators and
nurturing their young. Some dolphins live in deep water,
and are more likely to travel in large communities numbering
in the hundreds or even thousands. Others live nearer
to shore, traveling in bands of maybe dozens or hundreds.
Generally, we know more about dolphins that live out
their lives nearer our coastlines, than those that roam
the wide ocean, far from our view.
All dolphins belong to the scientific order cetacea,
which comprises both whales and dolphins. Dolphins are
further subdivided into various families, the largest
of which is called Delphinidae. There are 32 dolphins
in this family, including the bottlenose, Atlantic spotted
dolphins, dusky dolphins, spinners, even orcas (also
known as killer whales), the largest of all dolphins.
Porpoises and river dolphins belong to different families.
Porpoises are usually smaller than dolphins, have different
shaped teeth, no beak, and their dorsal fins are shaped
differently (and sometimes porpoises have no dorsal
fin).
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Scientists tell us that the ancestors of dolphins, whales
and porpoises were land mammals called ungulates, or hoofed
animals. Fifty million years or so ago these animals adapted
to the rising ocean, eventually becoming mammals of the sea.
Our film introduces you to just three dolphin species in the
Delphinidae family: the Atlantic spotted dolphins, dusky dolphins,
and bottlenose dolphins.
Atlantic spotted dolphins (Scientific Name: Stenella
frontalis)
The first recorded encounters between people and Atlantic
spotted dolphins along the Little Bahamas Bank was in the
late 1960's when divers were salvaging the wreck of a Spanish
galleon. Divers were frequently visited by friendly spotted
dolphins that would approach, investigate, and often mimic
divers' actions. In the mid-1980's, scientists began studying
their distribution, associations with one another, behavior,
even identifying individuals by gender and the pattern of
their spots. Beginning at about four years old, young dolphins
in this species begin developing black spots on their light
underside and white spots on their dark topside. The older
the dolphin, the more spots.
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Dr. Kathleen Dudzinski, featured in our
film, uses the spots and markings, such as scars from
encounters with sharks or other dolphins, to help her
identify each dolphin. In order to understand the communicative
lives of these animals she must first understand who is
"talking." Is it an older female reacting to
a young dolphin? Is it two teen-aged dolphins interacting
with one another? The more she knows about the animals,
over time, the better she can search for clues and correlation's
between certain sounds dolphins make and their behaviors.
Atlantic spotted dolphins live in the shallow, tropical
waters off the Atlantic Coast of the United States, the
Gulf of Mexico, and the Bahamas. It is when they're near-shore
that Kathleen studies them. During the afternoon, they
swim out to deeper waters in search of fish and squid.
Atlantic spotted dolphins are relatively small compared
to other dolphins. They are about six feet long and weigh
approximately 200 pounds when they reach adulthood. The
females of this species are generally larger than the
males. |
Dusky dolphins(Scientific Name: Lagenorhynchus cruciger)
Dr. Bernd Würsig, featured in our film, knows more about
dusky dolphins than anyone in the world. He's been studying
these acrobatic marvels since the 1970's. His dusky dolphin
research takes him from Argentina to New Zealand, as duskies
live in the temperate waters of the southern hemisphere.
Duskies are smaller than many dolphins, reaching a length of
five to six or so feet. They have very short beaks and distinctive
black and white coloring, but the most noted characteristic
of the duskies is their highly acrobatic leaps. In addition
to helping propel them more quickly through the water, duskies
may be leaping for their dinner. By leaping high, they may be
locating their prey by spotting flocks of birds feeding on schooling
fish, sometimes miles away. These leaps also might communicate
to other dolphins that dinner is near.
In Patagonia, off the shores of Argentina, Drs. Würsig,
Alejandro Acevedo, and Dudzinski study the dusky dolphins
that come in to the local bays in the spring, summer and
fall to eat anchovies. The dolphins begin their search
for food in groups of 20 or more. Würsig thinks that
duskies watch for birds circling above the water and feeding
on fish as a signal that anchovies are near. The several
groups then race toward the school of anchovies and begin
cooperatively herding the fish into a swirling school.
The dolphins drive the fish toward the ocean's surface,
using it as a barrier or wall that the anchovies cannot
escape. At this point, there may be hundreds of dolphins
working together to herd and consume the anchovies. The
duskies call to one another in loud, excited squawks and
whistles, leaping and slapping the water with their tails
as they take turns herding and feeding.
Scientists want to know: who feeds first and how is that
determined? Is it based on kinship ties or dominance?
What signals do they give one another during this frenzied
activity? The more we |
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learn about dolphins, the more questions
we are inspired to ask. And as long as there are dolphins, there
will be ample opportunity for future scientists to make important
contributions
Bottlenose dolphins (Scientific Name: Tursiops truncatus)
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The 1960's television show "Flipper,"
as well as oceanariums that care for captive dolphins,
have made the bottlenose the most recognized dolphin species
in the world. In fact, bottlenose dolphins inhabit temperate
and tropical waters of almost every ocean, including the
Mediterranean Sea and the Gulf of Mexico. Their popularity
and anatomical "smile" cause many people to
think dolphins are merry, friendly creatures eager to
interact with humans. In some respects this is true. Dolphins
are highly social animals, and in captivity, they tend
to be eager to interact with humans and are more easily
trained than other animals. Even in the wild, there have
been many documented accounts of dolphins seeking human
companionship, but generally speaking, they far prefer
the company of their own kind. Why some dolphins separate
from their group and interact with people is still a mystery.
In Dolphins, we meet Dean Bernal, a marine naturalist
in the Turks & Caicos, West Indies, who has befriended
a wild, bottlenose dolphin named JoJo. (see The JoJo Dolphin
Project). |
Bottlenose dolphins are much bigger than spotteds and duskies.
At about ten feet long and 600 pounds, JoJo is a powerful force!
In fact, dolphins can be quite aggressive with one another and
with other species, including humans. Several people have been
injured and one person killed by a dolphin, but the blame often
falls on the humans who don't understand how their actions can
be interpreted as aggressive by the dolphin. It's interesting
to know that the "killer whale," the largest of all
dolphins, has never been known to kill a person. They are the
top predator in the oceans, but have not harmed people.
Dean leads a public education program that stresses the importance
of appropriate behavior around dolphins. While swimming with
dolphins is illegal in U.S. waters, "swim with dolphin"
programs are abundant and becoming more popular in other locations.
Scientist Kathleen Dudzinski spent this last year in Japan studying
bottlenose dolphins in an area that's becoming more popular
with tourists as a "swim with dolphins" destination.
Kathleen, Dean, and others concerned for the well-being of dolphins,
tell us we need to understand dolphin communication, behaviors
and life cycles, as well as their feeding and rest patterns,
so that we don't disrupt their lives, or cause injury to dolphins
or ourselves. Kathleen, Dean, and other scientists want us all
to realize that, when we're in the ocean, we're in the dolphins'
home. |
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