Difference between revisions of "Dolphin"
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Revision as of 15:25, 9 January 2015
Dolphins are found in shallow waters near continental shelves throughout the world’s oceans. Some species inhabit rivers in China, India and South America. Dolphins mainly eat fish, squid and shrimp. Their average lifespan varies by species, but bottlenose dolphins can live up to 50 years in captivity.
- Scientific & Common Names
- Present Status
Scientific & Common Names
There are close to 40 dolphin species. Some of these include Tursiops truncatus (common bottlenose dolphin, bottle-nosed dolphin), Stenella frontalis (Atlantic spotted dolphin, bridled dolphin) and Orcaella brevirostris (Irrawaddy dolphin, snubfin dolphin).
Dolphins have a sleek build that helps them swim fast. Most species are gray in color and have lighter bellies. Their heads have an organ called a melon, which is used for echolocation, and a large brain. Some dolphin species have a prominent beak, while others have a shorter one. All species have blowholes, tail fins, pectoral fins and dorsal fins. Adult dolphins vary in size, depending on the species. Killer whales are the largest species, with adults measuring around 25 feet long and weighing around 19,000 pounds. Hector’s dolphins are the smallest species, with adults measuring about 4.5 feet long and weighing around 110 pounds.
Dolphins breed throughout the year, but peak breeding typically occurs during the warmer months. The gestation period of female dolphins varies by species. For example, Peruvian river dolphins gestate for about 11 or 12 months, while killer whales gestate for around 17 months. Female dolphins usually produce one calf at a time, and they provide most of the parental care for their young, including nourishment and protection from predators.
Dolphins are known for being curious, playful and intelligent. They are also very social, and they live in pods that vary in size, depending on the species. Dolphins use vocalizations, such as clicks and whistles, as a form of communication. They also use physical contact and posturing to communicate with other dolphins. While some dolphins are aggressive toward other members of their species, others have been known to assist other species, such as pilot whales.
Dolphins descended from land-dwelling mammals that moved to water around 55 million years ago. In more recent times, dolphins have been used by the military for search and rescue purposes and to find mines. They have also been used as therapy animals, and many are still kept in marine parks.
Most dolphin species are listed as “Least Concern,” but Hector’s dolphin and the Ganges River Dolphin are endangered. The Baiji dolphin is listed as critically endangered, and a few other species are vulnerable or near threatened. The main threats dolphins face include pollutants, boat collisions and accidental capture by fishing nets. Conservation measures include legal protection from wildlife trade and the use of safer fishing nets.
- <a href="http://animaldiversity.ummz.umich.edu/accounts/Tursiops_truncatus/" target="_blank">http://animaldiversity.ummz.umich.edu/accounts/Tursiops_truncatus/</a>
- <a href="http://animals.nationalgeographic.com/animals/mammals/bottlenose-dolphin/" target="_blank">http://animals.nationalgeographic.com/animals/mammals/bottlenose-dolphin/</a>
- <a href="http://www.defenders.org/dolphin/basic-facts" target="_blank">http://www.defenders.org/dolphin/basic-facts</a>
- <a href="http://www.iucnredlist.org/details/12119/0" target="_blank">http://www.iucnredlist.org/details/12119/0</a>
- <a href="http://www.iucnredlist.org/details/22563/0" target="_blank">http://www.iucnredlist.org/details/22563/0</a>