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Biography
Other usesgood articleTaxobox| name = Tiger shark| fossil_range = Fossil range|50|0|ref= #refSepkoski|Sepkoski Early Eocene to Present| status = LR/nt | status_system = IUCN2.3| trend = unknown| status_ref = #refSimpfendorfer|Simpfendorfer | image = Tiger shark.jpg| image_width = 250px| regnum = Animal ia| phylum = Chordate|Chordata | classis = Chondrichthyes | subclassis = Elasmobranchii | ordo = Carcharhiniformes | familia = Carcharhinidae | genus = Galeocerdo | genus_authority = Johannes Peter Müller|J. P. Müller & Friedrich Gustav Jakob Henle|Henle , 1837| species = G. cuvier | binomial = Galeocerdo cuvier | binomial_authority = François Péron|Péron & Charles Alexandre Lesueur|Lesueur , 1822| range_map = Cypron-Range Galeocerdo cuvier.svg| range_map_width = 250px| range_map_caption = Tiger shark range| synonyms = Squalus cuvier François Péron|Peron and Charles Alexandre Lesueur|Lessueur , 1822 Galeocerdo tigrinus Johannes Peter Müller|Müller and Friedrich Gustav Jakob Henle|Henle , 1837The tiger shark , Galeocerdo cuvier , is a species of requiem shark and the only member of the genus Galeocerdo . Commonly known as sea tiger, the tiger shark is a relatively large macropredator, capable of attaining a length of over convert|5|m|ft|abbr=on. #refFroesePauly|Froese & Pauly It is found in many tropical and temperate waters, and is especially common around central Pacific islands. Its name derives from the dark stripes down its body which resemble a tiger 's pattern, which fade as the shark matures.
The tiger shark is a solitary, mostly nocturnal hunter. Its diet includes a wide variety of prey, ranging from crustacean s, fish , Pinniped|seals , bird s, squid , turtle s, and sea snake s; to dolphins and even other smaller sharks. The tiger shark is considered a endangered species|near threatened species due to shark finning|finning and fishing by humans.
While the tiger shark is considered to be one of the sharks most dangerous to humans, the attack rate is surprisingly low according to researchers. #refHawaiiInstitute|Hawaii Institute of Marine Biology The tiger is second on the list of number of recorded attacks on humans, with the great white shark being first. #refKnickle|Knickle #refISAF|International Shark Attack File They often visit shallow reefs, harbors and canals, creating the potential for encounter with humans.
Taxonomy
The shark was first described by François Péron|Peron and Charles Alexandre Lesueur|Lessueur in 1822, and was given the name Squalus cuvier . Johannes Peter Müller|Müller and Friedrich Gustav Jakob Henle|Henle in 1837 renamed it Galeocerdo tigrinus . The genus, Galeocerdo , is derived from the Greek galeos which means shark and the Latin cerdus which means the hard hairs of pigs. It is often colloquially called the man-eater shark.
The tiger shark is a member of the order Carcharhiniformes . Members of this order are characterized by the presence of a nictitating membrane over the eyes, two dorsal fins, an anal fin , and five gill slits. It is the largest member of the Carcharhinidae Family (biology)|family , commonly referred to as requiem shark s. This family includes some other well-known sharks, such as the blue shark , lemon shark and bull shark .
Range and habitat
The tiger shark is often found close to the coast, mainly in tropical and subtropics|subtropical waters throughout the world. Along with the great white shark , Pacific sleeper shark , Greenland shark and sixgill shark , the tiger shark is among the largest Extant taxon|extant sharks. Its behavior is primarily nomadic , but is guided by warmer currents, and it stays closer to the equator throughout the colder months. It tends to stay in deep waters that line reefs, but it does move into channels to pursue prey in shallower waters. In the western Pacific Ocean , the shark has been found as far north as Japan and as far south as New Zealand .
A number of tiger sharks can be seen at Gulf of Mexico , North America n beaches and parts of South America . It is also commonly known in the Caribbean Sea . Other locations where tiger sharks are seen include Africa , People's Republic of China , Hong Kong , India , Australia and New Zealand .
Certain tiger sharks have been recorded at depths just shy of Convert|900|m|ft|-2 but some sources claim they move into shallow water normally thought to be too shallow for a species of its size. A recent study showed the average tiger shark would be recorded at Convert|350|m|ft|-2, making it uncommon to see tiger sharks in shallow water. However, tiger sharks in Hawaii have been observed in depths as shallow as 10& nbsp;ft and regularly observed in coastal waters at depths of 20 to 40& nbsp;ft. They often visit shallow reefs, harbors and canals, creating the potential for encounters with humans. #refLad|Lad
The tiger shark is known as tababa in Gilbertese language|Kiribati and Tuvalu language|Tuvaluan . They have been observed feeding in the tidal passages between the lagoon and ocean in Tarawa , Kiribati . Spring tide s bring in plankton or animalcule , which attract small soft-shell crabs, which attract sardines , which attract the grey mullet (fish)|mullet , which attract the blue-backed Carangidae|trevally ( rereba ), which then attract the tiger shark ( tababa ).cite web| last =Grimble |first =Sir Arthur |title = A Pattern of Islands; Ch. 5 Lagoon Days|year =1952|publisher= Early New Zealand Books (NZETC)| url= http://www.nzetc.org/tm/scholarly/tei-GriPatt.html| accessdate=16 Oct. 2011
Anatomy and appearance
Size
One of the largest sharks living today, the tiger shark commonly attains a length of convert|3|-|4.2|m|ft|abbr=on and weighs around convert|385|-|635|kg|lb|0. Sometimes a male tiger shark can grow up to 4.5 meters (14–15 feet long) and females to 5.5 meters (18 feet long). A tiger shark can sometimes rival a great white shark in size. The tiger shark can grow up to 14–20 feet long.
Biology
The skin of a tiger shark can typically range from blue to light green with a white or light yellow underbelly. The advantage of this is that when it is hunting for its prey, when prey looks at the shark from above, the shark will be camouflaged since the water below is darker. And when prey is below the shark and looks up, of course because of the sun, it is lighter so that the light underbelly will also camouflage the shark. Dark spots and stripes are most visible in young sharks and fade as the shark matures. Its head is somewhat wedge-shaped, which makes it easy to turn quickly to one side. #refCanadianShark|Canadian Shark Research Laboratory They have small pits on the snout which hold electro-receptors called the ampullae of Lorenzini which enable them to detect electric fields, including the bio-electricity generated by prey. Tiger sharks also have a sensory organ called a lateral line which extends on their flanks down most of the length of their sides. The primary role of this structure is to detect minute vibrations in the water. These adaptations allow the tiger shark to hunt in darkness and detect hidden prey. #refNewBrunswick|New Brunswick
A reflective layer behind the tiger shark's retina called the tapetum lucidum allows light-sensing cells a second chance to capture photon s of visible light, enhancing vision in low light conditions. A tiger shark generally has long fins to provide lift as the shark maneuvers through water, while the long upper tail provides bursts of speed. Tiger sharks normally swim using small body movements. Its high back and dorsal fin act as a pivot, allowing it to spin quickly on its axis, though the shark's dorsal fin s are distinctively close to its tail.
Its teeth are specialized to slice through flesh, bone, and other tough substances such as turtle shells. Like most sharks, however, its teeth are continually replaced by rows of new teeth.
Foods
The tiger shark is an apex predator #refHeithaus2001a|Heithaus (2001a) and has a reputation for eating anything. It also possesses the capability to take on large prey. It commonly preys upon fish , crustacean s, mollusk s, dugong s, seabird s, seasnake s, #refHeithaus2004|Heithaus (2004) marine mammal s (e.g. bottlenose dolphins , #refHeithaus2002|Heithaus (2002) spotted dolphins #refMaldini|Maldini ), and sea turtle s (e.g. green turtle|green and loggerhead turtle s). The broad, heavily calcified jaws and nearly terminal mouth, combined with robust, serrated teeth, enable the tiger shark to take on these large prey. #refHeithaus2001b|Heithaus (2001b) In addition, excellent eyesight and acute olfaction|sense of smell enable it to react to faint traces of blood and follow them to the source. Due to high risk of predatory attacks, dolphins often avoid regions inhabited by tiger sharks. The tiger shark also eats other sharks (such as sandbar sharks) and will even eat Conspecificity|conspecifics .
Tiger sharks may also attack injured or ailing whale s and prey upon them. A group was documented attacking and killing an ailing humpback whale in 2006 near Hawaii . #OfficeNMS|Office of National Marine Sanctuaries The tiger shark also scavenges on dead whales. In one such documented incident, they were observed scavenging on a whale carcass alongside great white shark s, Carcharodon carcharias . #refDudley|Dudley
The ability to pick up low-frequency pressure waves enables the shark to advance towards an animal with confidence, even in murky water. #refLadyWildlife|Lady Wildlife The shark circles its prey and studies it by prodding it with its snout. When attacking, the shark often eats its prey whole. Because of its aggressive feeding, it often mistakenly eats inedible objects, such as automobile Vehicle registration plate|license plates , oil cans, tire s, and Baseball (object)|baseballs . For this reason, the tiger shark is often regarded as the ocean's garbage can.
Swimming efficiency and stealth
All tiger sharks generally swim slowly, which, combined with cryptic coloration, may make them difficult for prey to detect them in some habitats. They are especially well camouflaged against dark backgrounds. Despite their sluggish appearance, tiger sharks are one of the strongest swimmers of the carcharhinid sharks. Once the shark has come close, a speed burst allows it to reach the intended prey before it can escape.
Reproduction
Males reach sexual maturity at convert|2.3|to|2.9|m|ft|abbr=on and females at convert|2.5|to|3.5|m|ft|abbr=on. Females mate once every 3 years. #refRitter_b|Ritter (1999b) They breed by internal fertilization. The male inserts one of his clasper s into the female's genital opening ( cloaca ), acting as a guide for the sperm . The male uses its teeth to hold the female still during the procedure, often causing the female considerable discomfort. Mating in the Northern Hemisphere generally takes place between March and May, with birth between April and June the following year. In the Southern Hemisphere, mating takes place in November, December, or early January. The tiger shark is the only species in its family that is ovoviviparous ; its eggs hatch internally and the young are born live when fully developed.
The young develop inside the mother's body for up to 16 months. Litters range from 10 to 80 pups. A newborn is generally Convert|51|cm|in|0 to Convert|76|cm|in|0 long. This shark typically reaches Sexual maturity|maturity at lengths of convert|2|to|3|m|ft|abbr=on. #refMarineBio|MarineBio It is unknown how long tiger sharks live, but they can live longer than 12 years.
Dangers and conservation
Although shark attack s are a relatively rare phenomenon, the tiger shark is responsible for a large percentage of fatal attacks and is regarded as one of the most dangerous shark species. #refRitter_a|Ritter (1999a) They are often found in river estuaries and harbor s, as well as shallow water close to shore, where they are likely to encounter humans. The tiger shark also dwells in river mouths and other runoff-rich water. On average, three to four shark attacks occur per year in Hawaii, and most attacks are not fatal. This attack rate is surprisingly low considering thousands of people swim, surf and dive in Hawaiian waters every day. A tiger shark attack made headlines in October, 2003, when (then 13-year-old) American surfing|surfer Bethany Hamilton lost her arm near her shoulder. Despite the attack, she returned to surfing a short time later. #refHamilton|Hamilton Hamilton is now a professional surfer and inspirational speaker. A large tiger shark was killed and hung, and later measured; based on its size and bite pattern, it was presumed to be the shark which attacked Hamilton. As of 2009, there have been 119 attacks, 29 of which were fatal.
Between 1959 and 1976, 4,668 tiger sharks were culling|culled in an effort to protect the tourism industry. Despite these efforts, attacks did not decrease. It is illegal to feed sharks in Hawaii, and interaction with them, such as Shark proof cage|cage diving, is discouraged. #refWesternPacific|Western Pacific Regional Fishery Management Council South African shark behavioralist and shark diver, Mark Addison, demonstrated divers could interact and dive with them outside of a shark cage in 2007 Discovery Channel special. #refDonahue|Donahue
The tiger shark is captured and killed for its Fish anatomy#Fins|fins , flesh , and liver . It is caught regularly in target and nontarget fisheries. Several populations evidently have declined where they have been heavily fished, but in general, they do not face a high risk of extinction. Continued demand, though, especially for fins, may result in further declines in the future. Tiger sharks are considered a endangered species|near threatened species due to excessive shark finning|finning and fishing by humans according to International Union for Conservation of Nature .
While shark fin has very few nutrients, shark liver has a high concentration of retinol|vitamin A which is used in the production of vitamin oils. In addition, the tiger shark is captured and killed for its distinct skin, as well as by big-game fishing|big game fishers.
In 2010, Greenpeace International added the tiger shark to its seafood red list, which is a list of fish commonly sold around the world, and which have a very high risk of being sourced from unsustainable fisheries. #refGreenpeace|Greenpeace
Mythology
The tiger shark is considered to be sacred Aumakua|na okinaaumakua (ancestor spirits) by some native Hawaiians who think their eyeballs have special seeing powers. This aligns with the general known facts about sharks and their Sharks#Senses|highly developed senses .
See also
Portal|Sharks
Outline|Outline of sharks
List of sharks
List of prehistoric cartilaginous fish
List of fatal, unprovoked shark attacks in the United States by decade
Notes
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Sources
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Canadian Shark Research Laboratory, http://www.marinebiodiversity.ca/shark/english/tiger_shark.htm Tiger Shark - Centre for Marine Biodiversity. Marine Biodiversity. Retrieved July 2011.
cite web | url = http://latimesblogs.latimes.com/showtracker/2007/07/shark-week-dead.html | author=Donahue, Ann | publisher = LA Times | title = Shark Week: 'Deadly Stripes: Tiger Sharks' | accessdate = July 2011 | date = 30 July 2007
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http://www.greenpeace.org/international/seafood/red-list-of-species Greenpeace International Seafood Red list
cite web |title=About Me| work=Bethany's General Biography |author=Hamilton, Bethany |publisher=BethanyHamilton.com |year=2003 | url= http://bethanyhamilton.com/about/ |accessdate=July 2011
cite web |url= http://www2.hawaii.edu/~carlm/tigershark.html |title=Tiger Shark Research Program |work=Shark & Reef Fish Research |publisher=Hawaii Institute of Marine Biology |accessdate=July 2011
Cite journal| last = Heithaus| first = Michael R.| title = The biology of tiger sharks, Galeocerdo cuvier, in Shark Bay, Western Australia: sex ratio, size distribution, diet, and seasonal changes in catch rates| journal = Environmental Biology of Fishes| volume = 61| pages = 25–36| year = 2001| doi = 10.1023/A:1011021210685
Cite journal| last = Heithaus| first = Michael R.| title = Copyright: Predator–prey and competitive interactions between sharks (order Selachii) and dolphins (suborder Odontoceti): a review| journal = Journal of Zoology| volume = 253| pages = 53–68| year = 2001| doi = 10.1017/S0952836901000061
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cite web|url= http://www.flmnh.ufl.edu/fish/sharks/Statistics/species2.htm |title= ISAF Statistics on Attacking Species of Shark| publisher= Florida Museum of Natural History University of Florida |work=International Shark Attack File |accessdate=2008-05-04
cite web|url= http://www.flmnh.ufl.edu/fish/Gallery/Descript/Tigershark/tigershark.htm |title= Tiger Shark Biological Profile| publisher= Florida Museum of Natural History Icthyology Department |accessdate=July 2011 |last=Knickle |first=Craig
Lad, Kashmira. http://www.buzzle.com/articles/habitat-of-a-tiger-shark.html Habitat of a Tiger Shark. Buzzle . Retrieved July 2011.
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http://www.new-brunswick.net/new-brunswick/sharks/species/tiger.html Tiger Shark - The Province of New Brunswick Canada. New Brunswick . Retrieved 2011-06-09.
Cite web| title = Humpback Whale Shark Attack: A Natural Phenomenon Caught on Camera| author=Office of National Marine Sanctuaries |url = http://sanctuaries.noaa.gov/news/features/1106_sharkattack.html| accessdate = July, 2011
cite web|url= http://www.sharkinfo.ch/SI1_99e/attacks2.html|title=Which shark species are really dangerous? |last=Ritter|first=Erich K.| date=15 February 1999 |publisher=Shark Info|accessdate=July 2011
cite journal| last = Sepkoski| first = Jack| title = A compendium of fossil marine animal genera (Chondrichthyes entry)| journal = Bulletins of American Paleontology| volume = 450| pages = 560| year = 2002| url = http://strata.ummp.lsa.umich.edu/jack/showgenera.php? taxon=575& rank=class| accessdate = July 2011
IUCN| id = 39378| taxon = Galeocerdo cuvier | assessors = Simpfendorfer| assessment_year = 2005| version = 2011.1| accessdate = July 2011
Selachimorpha|Ca. DEFAULTSORT:Tiger Shark Category:Carcharhinidae Category:Ovoviviparous fish Category:Fish of Hawaii Category:Animals described in 1822 Category:Seafood red list