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General Bottlenose Dolphin Information Bottlenose dolphins (Tursiops truncatus) are a robust species of dolphin with a characteristic "bottlenose" beak. Bottlenose dolphins fall into the scientific order of Cetacea. Two different body types exist in the bottlenose dolphin species. Coastal dolphins average 2.5-2.7 meters in length and weigh 190-260 kg. Pelagic (off-shore) dolphins average 3.6-3.8 meters and weigh 400-454 kg. On average male bottlenose dolphins are larger and weigh more than females, but the difference is not extreme (http://www.seaworld.org/infobooks/Bottlenose). The average life span for a bottlenose dolphin is 20 years. Also, a special characteristic of the bottlenose dolphin is the highly developed audio cortex of the brain. This evolutionary development allows dolphins to use echolocation to communicate, find prey, and orient themselves in their three dimensional environment (Hersh and Duffield, 1990). . Figure 1: Physical characteristics of a bottlenose dolphin (image courtesy of Sea World)
The scientific order Cetacea includes all whales and is further divided into three suborders: Odontoceti (toothed whales): dolphins, porpoises, beluga whales, beaked whales, and sperm whales Mysticeti (baleen whales): blue whales, gray whales, and right whales Archaeoceti: The archaeocetes are an extinct group of whales, of which only fossils remain. Dolphins are one of thirty species included in the scientific family Delphinidae. Some scientist beleive that early whales arose 50 million years ago from (now extinct) primitive mammals that ventured back into the sea. The genus Tursiops first appears in the fossil record about five million years ago (Barnes, 1990).
Where? Bottlenose dolphins inhabit temperate and tropical waters all over the world. They are very widely distributed and inhabit almost every ocean except for the poles. In the Pacific Ocean, bottlenose dolphins are found from northern Japan and California to Australia and Chile. They are also found offshore in the eastern tropical Pacific as far west as the Hawaiian islands. Off the California coast bottlenose dolphins have been observed as far north as Monterey, particularly during years of unusual warmth (Wells, 1991).
Figure 2: Bottlenose dolphin distibution (image courtesy of Enchanted Learning) Bottlenose dolphins inhabit the pelagic zone (open ocean) as well as harbors, bays, lagoons, and estuaries. In the Pacific Ocean, bottlenose dolphins are found from northern Japan and California to Australia and Chile. In the Atlantic Ocean, bottlenose dolphins are found from Nova Scotia and Norway to Patagonia and the tip of South Africa. They are the most abundant dolphin species along the United States from Cape Cod through the Gulf of Mexico. Bottlenose dolphins are also found in the Mediterranean Sea, and in the Indian Ocean from Australia to South Africa. There seem to be at least two ecotypes (forms) of the bottlenose dolphin. They can be differentiated by skull and body measurements as well as by characteristics of their blood. In general, 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. In general, the offshore ecotype seems to be adapted for cooler, deeper waters. Certain characteristics of their blood indicate that this form may be better suited for deep diving. Its larger body helps to conserve heat and defend itself against predators. (Hersh and Duffield, 1990).
Figure 3: Two coastal ecotype bottlenose dolphins (Image Courtesy of http://www.charliephillipsimages.co.uk) Dolphins have a large home range which they stay within to feed and mate. Changes in temperature, movement of food source, predators, and mating may all be factors that contribute to dolphin migration. At different times of the year dolphins may relocate their homerange based on these external pressures (Barros and Odell, 1990).
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