Tiger shark

The tiger shark (Galeocerdo cuvier)<ref name=ITIS>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is a species of ground shark, and the only extant member of the genus Galeocerdo and family Galeocerdonidae. It is a large apex predator, with females capable of attaining a length of over Template:Convert.<ref name=FroesePauly/> Populations are found in many tropical and temperate waters, especially around central Pacific islands. Its name derives from the dark stripes down its body, which resemble a tiger's pattern, but fade as the shark matures.<ref name=SharkInfo/>

The tiger shark is a solitary, mostly nocturnal hunter. It is notable for having the widest food spectrum of all sharks, with a range of prey that includes crustaceans, fish, seals, birds, squid, turtles, sea snakes, dolphins, and others, even smaller sharks. It also has a reputation as a "garbage eater",<ref name=SharkInfo/> consuming a variety of inedible, man-made objects that linger in its stomach. Tiger sharks have only one recorded natural predator, the orca.<ref name="auto1">Template:Cite journal</ref> It is considered a near-threatened species because of finning and fishing by humans.<ref name="iucn status 19 November 2021" />

The tiger shark is second only to the great white in recorded fatal attacks on humans, but these events are still exceedingly rare.<ref name=flmnh/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Taxonomy

The shark was first described by Peron and Lesueur in 1822, and was given the name Squalus cuvier.<ref name=FroesePauly/> Müller and Henle in 1837 renamed it Galeocerdo tigrinus.<ref name=flmnh/> The genus, Galeocerdo, is derived from the Greek galeos, which means shark, and kerdo, the word for fox.<ref name=flmnh/> The species name honors naturalist Georges Cuvier.<ref name="FroesePauly" /> It is often colloquially called the man-eater shark.<ref name=flmnh/>

The tiger shark is a member of the order Carcharhiniformes, the most species-rich order of sharks, with more than 270 species also including the small catsharks and hammerhead sharks.<ref name=FroesePauly/> 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 order, commonly referred to as ground sharks. It is the only extant member of Galeocerdo, the only member of the family Galeocerdonidae.<ref>Pollerspöck, J.; Straube, N. Bibliography Database of Living/Fossil Sharks, Rays and Chimaeras (Chondrichtyes: Elasmobranchii, Holocephali)—List of Valid Extant Species; List of Described Extant Species; Statistic, World Wide Web Electronic Publication, Version 10/2021; ISSN: 2195-6499. Available online: www.shark-references.com (accessed on 23 November 2021).</ref> The oldest remains of Galeocerdo extend back to the Eocene epoch, while the oldest fossils of the modern tiger shark Galeocerdo cuvier date to the Middle Miocene, around 13.8 million years ago.<ref name=":0">Template:Cite journal</ref>

Description

The tiger shark commonly attains an adult length of Template:Convert and weighs between Template:Cvt.<ref>Template:Cite journal</ref><ref name="auto">Template:Cite journalTemplate:Dead link</ref> The International Game Fish Association's all-tackle record is Template:Cvt.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is sexually dimorphic, with females being the larger sex. Mature females are often over Template:Convert while mature males rarely get that large.<ref name=flmnh/><ref>Marin-Osorno, R., Ezcurra, J. M., & O’Sullivan, J. B. (2017). Husbandry of the Tiger shark, Galeocerdo cuvier, at the Acuario de Veracruz, México. The elasmobranch husbandry manual II: Recent advances in the care of sharks, rays and their relatives, 23–32.</ref><ref name= Meyer>Meyer, C. G., O'Malley, J. M., Papastamatiou, Y. P., Dale, J. J., Hutchinson, M. R., Anderson, J. M., Royer, M. A. & Holland, K. N. (2014). Growth and maximum size of tiger sharks (Galeocerdo cuvier) in Hawaii. PLoS One, 9(1), e84799.</ref><ref>Randall, J. E. (1986). Sharks of Arabia. University of California.</ref> Exceptionally large females reportedly can measure over Template:Convert, and the largest males Template:Convert. Weights of particularly large female tiger sharks can exceed Template:Convert.<ref name= Meyer/><ref>Hinman, B. (2015). Keystone Species That Live in the Sea and Along the Coastline. Mitchell Lane Publishers, Inc.</ref><ref>Ramirez, F., & Davenport, T. L. (2013). Elasmobranchs from marine and freshwater environments in Colombia: A review. Current Politics and Economics of South and Central America, 6(4), 483.</ref><ref name="auto"/> One pregnant female caught off Australia reportedly measured Template:Convert long and weighed Template:Convert. Even larger unconfirmed catches have been claimed.<ref name=Wood>Template:Cite book</ref> Some papers have accepted a record of an exceptional Template:Convert, Template:Convert tiger shark, but since this is far larger than any scientifically observed specimen, verification would be needed.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> A 2019 study suggested that Pliocene tiger sharks could have reached Template:Convert in maximum length.<ref>Template:Cite journal</ref> There is variation in the speed of growth rates of juvenile tiger sharks depending on the region they inhabit, with some growing close to twice as fast as others.<ref>Template:Cite journal</ref>

Among the largest extant sharks, the tiger shark ranks in average size only behind the whale shark (Rhincodon typus), the basking shark (Cetorhinus maximus), and the great white shark (Carcharodon carcharias). This makes it the second-largest predatory shark, after the great white.<ref>https://oceana.org/marine-life/sharks-rays/tiger-shark#:~:text=Reaching%20lengths%20of%20at%20least,or%20are%20able%20to%20capture Template:Webarchive.</ref> Some other species such as megamouth sharks (Megachasma pelagios), Pacific sleeper sharks (Somniosus pacificus), Greenland sharks (Somniosus microcephalus), and bluntnose sixgill sharks (Hexanchus griseus) broadly overlap in size with the tiger shark, but as these species are comparatively poorly studied, whether their typical mature size matches that of the tiger shark is unclear.<ref name=flmnh/><ref name=Wood/> The great hammerhead (Sphyrna mokarran), a member of the same taxonomic order as the tiger shark, has a similar or even greater average body length, but is lighter and less bulky, with a maximum known weight coming from a heavily pregnant Template:Convert long individual at Template:Convert.<ref name="record">Template:Cite news</ref>

Tiger shark teeth are unique with very sharp, pronounced serrations and an unmistakable sideways-pointing tip. Such dentition has developed to slice through flesh, bone, and other tough substances, such as turtle shells. Like most sharks, its teeth are continually replaced by rows of new teeth throughout the shark's life. Relative to the shark's size, tiger shark teeth are considerably shorter than those of a great white shark, but they are nearly as broad at the root as the great white's teeth and are arguably better suited to slicing through hard-surfaced prey.<ref name=MarineBio/><ref name= Randall>Randall, J. E. (1992). Review of the biology of the tiger shark (Galeocerdo cuvier). Marine and Freshwater Research, 43(1), 21–31.</ref>

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. The tiger shark normally swims using small body movements.<ref name=overview/>

• Galeocerdo cuvier jaws.jpg

  Jaws

• Galeocerdo cuvier jaws2.jpg

  Jaws, wide open

• Galeocerdo cuvier upper teeth.jpg

  Upper teeth

• Galeocerdo cuvier lower teeth.jpg

  Lower teeth

Skin

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. When prey is below the shark and looks up the light underbelly will also camouflage the shark with the sunlight. This is known as countershading. 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.<ref name=SharkInfo/><ref name=CanadianShark/> They have small pits on the snout which hold electroreceptors called the ampullae of Lorenzini, which enable them to detect electric fields, including the weak electrical impulses generated by prey, which helps them to hunt.<ref name=MarineBio/> 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.<ref name=brunswick/>

Vision

Sharks do not have moveable upper or lower eyelids, but the tiger shark—among other sharks—has a nictitating membrane, which is a clear eyelid that can cover the eye.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> A reflective layer behind the tiger shark's retina, called the tapetum lucidum, allows light-sensing cells a second chance to capture photons of visible light. This enhances vision in low-light conditions.<ref>Template:Cite book</ref>

Distribution and habitat

File:Tigershark3.jpg

Juvenile tiger shark in the Bahamas

File:Reef-Fidelity-and-Migration-of-Tiger-Sharks-Galeocerdo-cuvier-across-the-Coral-Sea-pone.0083249.s002.ogv

Video of juvenile female tiger shark at Lord Howe Island, Australia, from PLOS ONE

The tiger shark is often found close to the coast, mainly in tropical and subtropical waters throughout the world.<ref name=flmnh/> 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.<ref name=FroesePauly/> It has also been recorded in the Mediterranean Sea, but rarely, off Malaga (Spain), Sicily (Italy) and Libya.<ref name = ciesm>Atlas of Exotic Fishes in the Mediterranean Sea (Galeocerdo cuvier). 2nd Edition. 2021. 366p. CIESM Publishers, Paris, Monaco.https://ciesm.org/atlas/fishes_2nd_edition/Galeocerdo_cuvier.pdf</ref>

Tiger sharks can be seen in the Gulf of Mexico, North American beaches, and parts of South America. It is also commonly observed in the Caribbean Sea. Other locations where tiger sharks are seen include off Africa, China, India, Australia, and Indonesia.<ref name=SharkInfo/> Certain tiger sharks have been recorded at depths just shy of Template:Convert.<ref name=flmnh/>

Feeding

The tiger shark is an apex predator<ref name=Heithaus2001a/> and has a reputation for eating almost anything.<ref name=flmnh/> These predators swim close inland to eat at night, and during the day swim out into deeper waters.<ref>Tiger Sharks, Galeocerdo cuvier Template:Webarchive. marinebio.org</ref> Young tiger sharks are found to feed largely on small fish, as well as various small jellyfish, and mollusks including cephalopods. Around the time they attain Template:Convert, or near sexual maturity, their selection expands considerably, and much larger animals become regular prey.<ref name=Lowe/> Numerous fish, mollusks (including gastropods and cephalopods), crustaceans, sea birds, sea snakes,<ref name=Heithaus2004/> marine mammals (e.g. bottlenose dolphins (Tursiops), common dolphins (Delphinus),<ref name=Heithaus2002/> spotted dolphins (Stenella),<ref name=Maldini/> dugongs (Dugong dugon), seals and sea lions), and sea turtles (including the three largest species: the leatherback (Dermochelys coriacea),<ref>Tiger Sharks Killed for Eating Leatherback Turtles Template:Webarchive. Shark Defenders (2011-04-16). Retrieved on 2013-03-23.</ref> the loggerhead (Caretta caretta)<ref>Shark Bay Ecosystem Research Project Template:Webarchive. .fiu.edu. Retrieved on 2013-03-23.</ref> and the green sea turtles (Chelonia mydas)<ref name=Lowe/>), are regularly eaten by adult tiger sharks.<ref>Galeocerdo cuvier summary page. (n.d.). FishBase. https://www.fishbase.se/summary/886</ref> In fact, adult sea turtles have been found in up to 20.8% of studied tiger shark stomachs, indicating somewhat of a dietary preference for sea turtles where they are commonly encountered.<ref>Witzell, W. N. (1987). Selective predation on large cheloniid sea turtles by tiger sharks (Galeocerdo cuvier). Japanese Journal of Herpetology, 12(1), 22–29.</ref> They also eat other sharks (including adult sandbar sharks (Carcharhinus plumbeus)), as well as rays, and sometimes even other tiger sharks.<ref name=SharkInfo/><ref name=Lowe/>

Due to high risk of predation, dolphins often avoid regions inhabited by tiger sharks.<ref name=Competition/><ref>Template:Cite journal</ref> Injured or ailing whales may also be attacked and eaten. A group was documented killing an ailing humpback whale (Megaptera novaeangliae) in 2006 near Hawaii.<ref name=OfficeNMS/> A scavenger, the tiger shark will feed on dead whales, and has been documented doing so alongside great white sharks.<ref name=Dudley/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Tiger sharks have also been observed to feed on dead manta rays in the German Channel of Palau.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Evidence of dugong predation was identified in one study that found dugong tissue in 15 of 85 tiger sharks caught off the Australian coast.<ref>Template:Cite journal</ref> Additionally, examination of adult dugongs has shown scars from failed shark attacks.<ref>Template:Cite journal</ref> To minimize attacks, dugong microhabitats shift similarly to those of known tiger shark prey when the sharks are abundant.<ref>Template:Cite journal</ref>

The broad, heavily calcified jaws and nearly terminal mouth, combined with robust, serrated teeth, enable the tiger shark to take on these large prey.<ref name=Competition/> In addition, excellent eyesight and acute sense of smell enable it to react to faint traces of blood and follow them to the source. The ability to pick up low-frequency pressure waves enables the shark to advance towards an animal with confidence, even in murky water.<ref name=overview/> The shark circles its prey and studies it by prodding it with its snout.<ref name=overview/> When attacking, the shark often eats its prey whole, although larger prey are often eaten in gradual large bites and finished over time.<ref name=overview/>

Notably, terrestrial mammals, including horses (Equus ferus caballus), goats (Capra aegagrus hircus), sheep (Ovis aries), dogs (Canis lupus familiaris), cats (Felis catus), and brown rats (Rattus norvegicus), are fairly common in the stomach contents of tiger sharks around the coasts of Hawaii.<ref name=Lowe/> In one case, remains of two flying foxes were found in the stomach of this shark,<ref>Template:Cite journal</ref> and in another, an echidna (Tachyglossus aculeatus) was regurgitated by a tiger shark being tagged off Orpheus Island, Queensland.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Because of its aggressive and indiscriminate feeding style, it often mistakenly eats inedible objects, such as automobile license plates, oil cans, tires, and baseballs.<ref name=SharkInfo/> Due to their habits of eating essentially anything, Tiger sharks are often referred to as the "garbage can of the sea".

Predation by orcas

Tiger sharks are preyed on by orcas. Orcas have been recorded hunting and killing tiger sharks by holding them upside down to induce tonic immobility in order to drown the shark. The orcas bite off the shark's fins before disemboweling and devouring it.<ref name="auto1"/>

Swimming efficiency and stealth

All tiger sharks generally swim slowly, which, combined with cryptic coloration, may make them difficult for prey to detect in some habitats. They are especially well camouflaged against dark backgrounds.<ref name=Competition/> 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.<ref name=Competition/>

Reproduction

Males reach sexual maturity at Template:Convert and females at Template:Convert.<ref name=MarineBio/> Typical weight of relatively young sexually mature specimens, which often locally comprise the majority of tiger sharks encountered per game-fishing and scientific studies, is around Template:Convert.<ref name= Randall/><ref>Pepperell, J. 1992. Trends in the distribution, species composition and size of sharks caught by gamefish anglers off southeastern Australia, 1961–1990. In: J. Pepperell (ed.), Sharks: Biology and Fisheries. Australian Journal of Marine and Freshwater Research, pp. 213–225. CSIRO Publications, Melbourne, Australia.</ref> Females mate once every three years.<ref name=SharkInfo/> They breed by internal fertilization. The male inserts one of his claspers into the female's genital opening (cloaca), acting as a guide for the sperm. The male uses his 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.<ref name=flmnh/> Tiger Sharks are unique among all sharks in the fact that they employ embrytrophy to nourish their young inside the womb. The young gestate in sacks which are filled with a fluid that nourishes them. This allows for the young to dramatically increase in size, even though they have no placental connection to the mother.<ref>Template:Cite journal</ref>

The young develop inside the mother's body up to 16 months. Litters range from 10 to 80 pups.<ref name=flmnh/> A newborn is generally Template:Convert long.<ref name=flmnh/> How long tiger sharks live is unknown, but they can live longer than 12 years.<ref name=SharkInfo/>

Ontogeny

Tiger shark ontogeny has been little studied until recently, but studies by Hammerschlag et al., indicated that as they grow, their tails become more symmetrical with age. Additionally, while the heads on juvenile tiger sharks are more conical and similar to requiem sharks, adult tiger sharks have a head which is relatively broader. The reason for the larger caudal fin on juvenile tiger sharks is theorized to be an adaptation to escape predation by larger predators and to catch quicker-moving prey. As tiger sharks mature, their head also becomes much wider and their tails no longer become as large in proportion to their body size as when they are juveniles because they do not face elevated levels of predation risk upon maturity. The results of this study were interpreted as reflecting two ecological transitions: as tiger sharks mature they become more migratory and having a symmetrical tail is more advantageous in long-distance traveling, and that tiger sharks consume more diverse prey items with age, which requires a greater bite force and broader head.<ref>Template:Cite journal</ref>

Conservation

[[File:Tiger shark, Hawaii Aii.jpg|thumb|A large female tiger shark caught in [[Kane'ohe Bay|KaneTemplate:Okinaohe Bay]], [[Oahu|OTemplate:Okinaahu]] in 1966|alt=Photo of shark hung by its tail on the shore]] The tiger shark is captured and killed for its fins, flesh, and liver. It is caught regularly in target and nontarget fisheries. Several populations have declined where they have been heavily fished. Continued demand for fins may result in further declines. They are considered a near threatened species due to excessive finning and fishing by humans according to International Union for Conservation of Nature.<ref name="iucn status 19 November 2021" /> In June 2018, the New Zealand Department of Conservation classified the tiger shark as "Migrant" with the qualifier "Secure Overseas" under the New Zealand Threat Classification System.<ref>Template:Cite book</ref>

While shark fin has very few nutrients, shark liver has a high concentration of 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 fishers.<ref name=flmnh/>

In 2010, Greenpeace International added the tiger shark to its seafood red list, which is a list of commonly sold fish likely to come from unsustainable fisheries.<ref name=Greenpeace/>

Relationship with humans

File:Shark Feeding.jpg

A female tiger shark pup in the Aquarium of the Pacific's Shark Lagoon exhibit

Although sharks rarely bite humans, the tiger shark is reported to be responsible for a large share of fatal shark-bite incidents, and is regarded as one of the most dangerous shark species.<ref name=sharkAttackStats/><ref name=Ritter/> They often visit shallow reefs, harbors, and canals, creating the potential for encounter with humans.<ref name=SharkInfo/> The tiger shark also dwells in river mouths and other runoff-rich water.<ref name=flmnh/><ref name=MarineBio/> While it ranks second on the list of number of recorded shark attacks on humans, behind only the great white shark, such attacks are few and very seldom fatal.<ref name=flmnh/><ref name=sharkAttackStats/> Typically, three to four shark bites occur per year in Hawaii; one notable survivor of such an attack is surfing champion Bethany Hamilton, who lost her left arm at age 13 to a tiger shark in 2003. This bite rate is very low, considering that thousands of people swim, surf, and dive in Hawaiian waters every day.<ref name=hawaii/> Human interactions with tiger sharks in Hawaiian waters have been shown to increase between September and November, when tiger shark females are believed to migrate to the islands to give birth.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

On 8 June 2023, a tiger shark attacked and killed a 23-year-old Russian man in the Red Sea off the coast of the Egyptian city of Hurghada. The attack was filmed by onlookers and the recording went viral. The shark was later captured by fishermen and killed. This was the third fatal tiger shark attack in the area since 2022.<ref>Template:Cite news</ref>

Between 1959 and 1976, 4,668 tiger sharks were culled in the state of Hawaii in an effort to protect the tourism industry.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Despite damaging the shark population, these efforts were shown to be ineffective in decreasing the number of interactions between humans and tiger sharks. Feeding sharks in Hawaii (except for traditional Hawaiian cultural or religious practices) is illegal,<ref name=Hawaii_Statutes/><ref name=WPRFMC/> and interaction with them, such as cage diving, is discouraged. South African shark behaviorist and shark diver Mark Addison demonstrated divers could interact and dive with them outside of a shark cage in a 2007 Discovery Channel special,<ref name=Donahue/> and underwater photographer Fiona Ayerst swam with them in the Bahamas.<ref name=Donahue/><ref>Riveting Shark Encounters: Fiona Ayerst recounts ... gentle tiger shark in the warm silky waters of the Bahamas Template:Webarchive. Magazines.co.za (June/July 2009)</ref> At "Tiger Beach" off Grand Bahama, uncaged diving with – and even the handling of – female tiger sharks has become a routine occurrence.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Warming Atlantic Ocean currents have caused tiger shark migration paths to move further north, according to a University of Miami study.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Mythology

Tiger sharks are considered to be sacred [[Aumakua|Template:Okinaaumākua]] (ancestor spirits) by some native Hawaiians.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Tiger sharks possess a unique significance as Template:Okinaaumakua, revered as family guardians in Hawaiian culture. The tiger shark, regarded as an intelligent and highly perceptive spiritual entity, assumes the role of a messenger bridging the gap between humans and the divine. In the Hawaiian belief system, Template:Okinaaumakua take on various forms, either animals or objects, representing ancestral connections and manifestations of departed family members. This perspective underscores the intricate web of interdependence among plants, animals, elements, and humans, underscoring the imperative to honor and coexist harmoniously with nature.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

See also

• List of sharks
• List of prehistoric cartilaginous fish genera

External links

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• General information Enchanted Learning. Retrieved January 22, 2005.
• "Different diet information" Shark Info. Retrieved January 22, 2005.
• "Tiger sharks in Hawaii" Research program. Retrieved January 22, 2005.
• "Tiger shark: Fact File" from National Geographic
• Tracking research on tiger sharks
• Pictures of tiger sharks
• Template:SealifePhotos
• Diver Has Been Friends With Tiger Shark For 20 Years!