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Dolphin Magnets - Customize for free |
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More About Dolphins ...
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Dolphins are certain aquatic mammals related to whales and porpoises.
The word is used in a few different ways. It can mean:
any member of the family Delphinidae (oceanic dolphins),
any member of the families Delphinidae and Platanistoidae (oceanic and river dolphins),
any member of the suborder Odontoceti (toothed whales; these include the above families and some others),
laypeople often use the term synonymously with Bottlenose Dolphin, the most common and familiar species of dolphin.
In this encyclopedia, definition two is used.
Porpoises (suborder Odontoceti, family Phocoenidae) are thus not dolphins in our sense. Killer Whales and some related species belong to the Delphinidae family and therefore qualify as dolphins, even though they are called whales in common language.
There are almost 40 species of dolphin in 17 genera. They vary in size from 1.2 metres and 40 kg (Heaviside's Dolphin), up to 7 metres and 4.5 tonnes (the Killer Whale). Most species weigh between about 50 and about 200 kg. They are found worldwide, mostly in the shallower seas of the continental shelves, and all are carnivores, mostly taking fish and squid.
The family Delphinidae is the largest in the Cetacea, and relatively recent: dolphins evolved about 10 million years ago, during the Miocene.
Dolphins are widely believed to be amongst the most intelligent of all animals, although the difficulties and expense of doing experimental work with a large marine animal, with a very different sensory apparatus from our own, mean that many of the tests required to confirm this belief have not yet been done, or have been carried out with inadequate sample sizes and methodology. See the Dolphin intelligence article for more details.
Dolphins often leap above the water surface, sometimes performing acrobatic figures (e.g. the spinner dolphin). This and other behaviour is interpreted as playing. They are capable of diving up to 260 m deep and 15 min long, but rarely stay underwater longer than few minutes.
Frequently dolphins will accompany boats, riding the bow waves. They are also famous for their willingness to occasionally approach humans and interact with them in the water. In return, in some cultures like in Ancient Greece they were treated with welcome; a ship spotting dolphins riding in their wake was considered a good omen for a smooth voyage.
Dolphins are social animals, living in so called schools of up to a dozen animals. In places with high abundance of food, schools can join temporarily forming aggregations of over 1000 dolphins. The individuals communicate using a variety of klicks, whistles and other vocalizations. They also use ultrasonic sounds for echolocation.
Membership in schools is not rigid, interchange is common. However, the animals can establish strong bonds between each other. This leads to them staying with injured or ill fellows for support.
Dolphins are predators, chasing their prey at high speed. The dentition is adapted to the animals they hunt: Species with long beaks and many teeth forage on fish, whereas short beaks and lesser tooth count are linked to catching squid. Some dolphins may take crustaceans. Usually, the prey is swallowed as a whole. The bigger species are capable of eating marine mammals, especially the orca, which kills even large whales.
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Taxonmony
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Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
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Source: Wikipedia Read more about Dolphins
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