The Dolphin

Return to Captain Dan's Homepage

Dolphin Jumping in the cove 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.

 

Dolphin 2Some 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 Dolphin 3photograph 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.

 

Dolphin by the boatOn 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 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 theorized3741 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.

 Return to Captain Dan's Homepage