The Dolphin
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Starting in July, we do on occasion, have the opportunity to see dolphin during the trip around the
Island. While the
Marine
Mammal Protection Act requires that we do not approach them any
closer than 50 yards, they are free to come as close to us as they wish as
you will see below. The probability
of seeing them increases later in the season. The photograph on the left was
taken on August the 18th, 2011 in Tom's Cove. The photo was taken using the
continuous shooting mode while pointing the camera in the general area of the most
activity. I took a series of 58 pictures and this was the only one taken that was of any value. You
can see the fishing vessel "Captain Andrew" and channel marker #14 in the
background.
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Some
of these photographs were taken in Chincoteague Channel and some between Wallops
and Assateague. All were taken during our tours around the Island. After showing
one guest a copy of the photograph to the right, she questioned whether I had
really taken it on one of our tours. We were fortunate in that she was able to
duplicate the photograph on her trip, thereby eliminating her doubt.
As
I said on a previous page it is awfully hard to get a good picture of the
dolphin as it is nearly impossible to predict where they will surface. Usually I
get an excellent picture of the splash as they return to the water. On the
picture above I was actually attempting to
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photograph the one you see just in
front of it. As it was going down the second one came up.
These
are Atlantic Bottlenose Dolphin. They are distinguished from Harbor porpoise by
shape, size, dorsal fin shape and tooth structure. The dolphin is larger 7 - 12
feet compared to 4 - 6 feet for a porpoise. The dolphin has 3" beak compared to
the blunt nose of the porpoise and the dolphin's dorsal fin is curved back as
opposed to the porpoise's triangular fin. Also the dolphin's teeth are conically
shaped while the porpoises are spade shaped. The porpoises tend to be reclusive
while the dolphin are not so. We are on the southern extreme of the harbor
porpoises range.
We will most likely see dolphin rather than porpoises.
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On the right you will see Dan with a group of dolphin beside the boat. It is
important to note
that he did not approach the dolphin, but rather they approached him. He in fact
was dead in the water at the time of the encounter.
A pod of dolphin in the area may not be good news for fishermen as they eat
about 4 to 5% of their body weight per day and a nursing mother will eat about
8%. That means a pod of 10 dolphin can daily consume up to 220 pounds of fishes,
squid or other creatures. They swallow the food whole and down it head first.
There is some question whether pod is the proper term for a group of dolphin.
According to Toni Frohoff in "Dolphin
Mysteries, Unlocking the Secrets of Communication" (Chapter 2, page 52) that
term is properly applied to groups of individuals which are genetically related.
She explains, "killer whales in the northeastern
Pacific live in stable, materilineal groups; young orcas spend their entire
lives within their mother's pod". This characteristic of orcas is not shared
with the dolphins in our area. I have not found a second source to confirm her
definition.
The
dolphin below was just coming out of the water. Notice as it rushed
forward it forced the water up the front of its rostrum and over its eyes.
There are two varieties of Atlantic Bottlenose Dolphin, the coastal and
offshore. The
coastal ecotype seems to be adapted for warm, shallow waters. Its smaller
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body
and larger flippers suggest increased maneuverability and heat dissipation.
These dolphins frequent harbors, bays, lagoons, and estuaries such as Tom's
Cove, Chincoteague Channel and Chincoteague Bay. The
offshore ecotype seems to be adapted for cooler, deeper waters. Its larger body helps to conserve heat and defend itself against
predators. Some coastal dolphins in higher latitudes show a clear
tendency toward seasonal migrations, traveling south in the winter. For
example, coastal bottlenose dolphins in our area migrate
seasonally to points south of Beaufort, North Carolina. Not all coastal
dolphin are migratory, in some areas south
of Beaufort there are groups of both migratory and non-migratory coastal
bottlenose dolphin. These determinations have been made by studying the photographs
of the dolphin's dorsal fin and comparing them to the fins seen in other areas
on the Atlantic seaboard. The supposition is that some of their dorsal fins are as
distinctive as our finger prints. Some fin samples and an interactive exercise
can be found at the
"Cardigan Bay Marine Wildlife Center" website. Note Cardigan Bay is in
the Irish Sea, Wales so the probability of seeing a dolphin previously identified on this site is
unlikely.
Dolphin rest about 8 hours in a 24 hour period which is similar to our sleep
cycle. Because for them breathing is a voluntary reflex, they can not enter a
full sleep state or stay submerged as they would suffocate. While resting only
1/2 their brain shuts down while the other 1/2 remains active. When dolphin rest
they can sometimes be seen swimming slowly along the surface, with very little
movement or at rest on the surface with their blow hole exposed. In other cases
they will remain on the bottom for up to 30 minutes surfacing regularly to
breath and return to the bottom. Also because their breathing is a voluntary
reflex they can not be totally sedated unless assisted by a
respirator. Interestingly when resting they close one eye and keep the other
open, which relates to the side of the brain that is at rest.
Their life expectancy is about 25
to 30 years in the wild, however some have lived 40 years. Their age can be determined by the rings in
their teeth. Their teeth grow an additional layer of enamel each year so
determining their age is a little like the aging of trees.
Their
normal dives can last from 8 to 10 minutes, and they regularly reach from 10 to 150
fifty feet. They hold their breath while underwater opening their blowhole to
exhale just before they surface. At the surface they quickly inhale and then
relax the muscular flap to close it. During respiration they exchange 80%
of the air in their lungs
compared to our 17%. The visible blow seen when they surface is formed by the
saltwater and water vapor condensing in the respiratory gases as they expand in
the cooler air.
Dolphins have a brain size that is comparable to humans.
Some scientists have theorized.JPG)
that comparisons of intelligence can be
made by both brain size and the ratio of brain to spinal cord weight. Others
have suggested it is the size and construction of the brain that makes the
difference. Typical ratios are for cats are 5 to 1, apes are 8 to 1, humans are 50
to 1 and bottlenose dolphin are 40 to 1. Also the dolphin's cerebral cortex is deeply
folded, which is another possible indicator of their ability to process thought.
Some additional information about dolphin social interaction and communications
can be found at the
"Dolphins and Man Equals?" website. This site includes some information from
Dr. John C.
Lilly's research. He led a project in the 80's that attempted to teach
dolphins a computer-synthesized language. There is an interesting
article about an experiment Dr. Lilly conducted which involved Ms. Margret Howe living with a dolphin for one
week. During the experiment she attempted to establish bi-directional vocal
communications with the dolphin.
Ms. Howe's notes from the experiment can be located by clicking on the
above "Ms. Howe's notes".
Dr. Lilly's full website can be found at "JohnCLilly.com".
Ms. Howe's notes from her 2 1/2 month period of living with Peter Dolphin are
include on the site. I do not recommend the second study for children. Ms. Howe
was introduced to Dr. Lilly through a third party by
Carl Sagan. More detailed information about the research can be found in the
book
"Lilly on Dolphins".
Another phenomena you might find interesting is the practice young dolphin
have of creating and playing with rings of air. The following is a link
to a
YouTube video of the effect. I have also linked to a webpage that describes the
effect. It is on the "Earth Trust" website and entitled
"The Mystery of the Silver Rings" which is linked here.
Having said all of this really they are just great fun to watch and enjoy when
they chose to make themselves available, and for me the highlight of a trip.
The source for the information on this page was "Lilly on Dolphins"
by John Lilly, "Dolphin Mysteries: Unlocking the Secrets of Communications", by
Kathleen Dudzinski & Toni Forhoff, "To Touch a Wild Dolphin, A Journey of
Discovery with the Seas Most Intelligent Creatures", by Rachel Smolker,
"Communications Between Man and Dolphin", by John Lilly and other
articles.