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Atlantic Spotted Dolphin porpoising out of the water
An Atlantic spotted dolphin porpoises out of the water as it races to ride Odyssey's bow wave.
Photo - Chris Johnson

April 19, 2005
Atlantic Spotted Dolphins
Real Audio Report -   28k


Log Transcript

This is Genevieve Johnson speaking to you from the Odyssey in the Canary Islands.

Since entering the Atlantic Ocean the crew made our first sightings for the Voyage of the Atlantic Spotted dolphin (Stenella frontalis).

The Atlantic spotted dolphin is one of two members of the genus Stenella that are endemic to the temperate and warm, tropical waters of the Atlantic. They are most commonly sighted inside the 250-meter depth contour along the southeastern and Gulf US coasts, in the Caribbean and off West Africa. The Clymene dolphin (Stenella clymene) is the second endemic dolphin, however, the crew has not sighted this species yet.

The pantropical spotted dolphin (Stenella attenuata), spinner dolphin (Stenella longirostris) and striped dolphin (Stenella coeruleoalba) are all close cousins. Unlike the Atlantic spotted and the Clymene dolphin, these three species are also found in the tropical and warm temperate waters of the Pacific and Indian Oceans.

Atlantic Spotted Dolphin
The most instantly recognizable characteristic of the Atlantic spotted dolphin is its spots. Spotting ranges from totally absent in calves between 2 - 6 years of age, to strikingly apparent in many mature adults where the spots increase in size and density up to 16 years.
Photo - Judith Scott

The most instantly recognizable characteristic of the Atlantic spotted dolphin is its spots. However, spotting ranges from totally absent in calves between 2 - 6 years of age, making them appear very similar to bottlenose dolphin calves, to strikingly apparent in many mature adults where the spots increase in size and density up to 16 years of age. There is much variation between spots in adults of inshore and offshore populations with more spotted animals found closer to land. Those seen further offshore, like those seen by the Odyssey crew, have far fewer spots, making them slightly harder to identify.

The Atlantic spotted dolphin closely resembles the pantropical spotted dolphin, but there are a few differences that make them distinct at sea. The Atlantic spotted dolphin has a blaze that sweeps up to the dorsal cape near the fin and this sturdy species can weigh an extra 10 - 30 kilograms, totalling 140 kilograms or more (22-66 pounds totalling over 308 pounds). In addition, their external appearance is more reminiscent of the robust bottlenose dolphin, especially the beak, head, flippers and dorsal fin.

Male Atlantic spotted dolphins reach a length of about 2.5 meters (7 feet, 5 inches), with females usually and inch or two longer. This is unusual in Odontocetes (toothed whales), where males are generally larger. Typical group sizes consist of less than 50 animals. On average, we encounter groups of 10 - 15 made up of a wide range of ages and sizes, and almost always including one or two very small calves. Dives can range in depth between 40 - 60 meters; though usually remain less than 10 meters for up to 6 minutes. They are also capable of great speed, which they require to chase prey and flee from predators that include sharks and probably killer whales and other small toothed whales.

Scientists have learned a great deal about the ecology of Atlantic Spotted Dolphins from a population that lives in the Bahamas. This community of dolphins were habituated to people in the early 1970's. Both researches and tourists are able to take advantage of the opportunity to see and learn more about this species. A long-term study of these individuals by Denise Herzing continues to provide new information about the species.

Atlantic Spotted Dolphin distribution map
The dark blue area depicts the distribution of the Atlantic spotted dolphin.
Map - Chris Johnson

As we search for sperm whales with our acoustic array (underwater microphones), we often hear the clicks, whistles and squeaks of dolphins before we see them from our observation platform. Sometimes we find them feeding, watching individuals charge back and forth in explosive bursts as they round up and drive schooling fish toward the surface cutting off their escape. It is when feeding on prey items that include small fish, cephalopods and other invertebrates, that a sharp increase in vocalization occurs. The echolocation clicks allow the dolphins to locate and hone in on their prey, while the sharp whistles ensure communication and coordination amongst the group.

    Listen to the vocalizations made by Atlantic spotted dolphins recorded on Odyssey's hydrophones -
    Real Audio -   28k   64k

The Atlantic spotted dolphin is known to be a sociable, extroverted species. Since entering the Atlantic Ocean, we sighted them 25 times - more than any other species of dolphin. On almost every occasion they enthusiastically approach Odyssey avidly riding both the stern and bow waves. Sometimes they travel along the beam, breaching and porpoising next to the vessel, often right next to the pilot house doors, giving us a clear view of their sleek grey bodies, apparently watching the crew, as we excitedly watch them. These dolphins seem to relish rough weather, surfing and bursting in perfect unison through the face of the mountainous Atlantic swells rolling by the Odyssey.

Rough seas are always a challenge for the crew, however, the appearance of spotted dolphins enjoying the large swells always lifts our spirits. They will be constant companions on our next research leg - crossing the Atlantic Ocean on our way to the Caribbean.

Atlantic Spotted Dolphin next to Odyssey in rough seas
An Atlantic spotted dolphin breaches next to the Odyssey in rough seas
Photo - Chris Johnson

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Log written by Genevieve Johnson with additional research by Judith Scott.

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