The tiger shark ( Galeocerdo cuvier)[ Populations are found in many tropics 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.][
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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 , fish, Pinniped, , squid, , Hydrophiinae, , and others, even smaller sharks. It also has a reputation as a "garbage eater",[ consuming a variety of inedible, man-made objects that linger in its stomach. Tiger sharks have only one recorded natural predator, the orca.]
The tiger shark is second only to the great white in recorded fatal attacks on humans, but these events are still exceedingly rare.
Taxonomy
The shark was first described by Peron and Lesueur in 1822, and was given the name Squalus cuvier.[ Müller and Henle in 1837 renamed it Galeocerdo tigrinus.][ The genus, Galeocerdo, is derived from the Greek galeos, which means shark, and kerdo, the word for fox.][ The species name honors naturalist Georges Cuvier.][
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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 Scyliorhinidae and .[ 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.][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).] 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.
Description
The tiger shark commonly attains an adult length of and weighs between .[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.][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.][Randall, J. E. (1986). Sharks of Arabia. University of California.] Exceptionally large females reportedly can measure over , and the largest males . Weights of particularly large female tiger sharks can exceed .[Hinman, B. (2015). Keystone Species That Live in the Sea and Along the Coastline. Mitchell Lane Publishers, Inc.][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.]
Among the largest neontology 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
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[ 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 long individual at .]
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.[Randall, J. E. (1992). Review of the biology of the tiger shark (Galeocerdo cuvier). Marine and Freshwater Research, 43(1), 21–31.]
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.[
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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.[ 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.][ 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.][
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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.
Distribution and habitat
The tiger shark is often found close to the coast, mainly in tropical and subtropics waters throughout the world.[ 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.][ It has also been recorded in the Mediterranean Sea, but rarely, off Malaga (Spain), Sicily (Italy) and Libya.][Atlas of Exotic Fishes in the Mediterranean Sea ( Galeocerdo cuvier
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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.[ Certain tiger sharks have been recorded at depths just shy of .][
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Feeding
The tiger shark is an apex predator[ and has a reputation for eating almost anything.][ These predators swim close inland to eat at night, and during the day swim out into deeper waters.][ Tiger Sharks, Galeocerdo cuvier . marinebio.org] Young tiger sharks are found to feed largely on Teleostei, as well as various small jellyfish, and including . Around the time they attain , or near sexual maturity, their selection expands considerably, and much larger animals become regular prey.[ Numerous fish, mollusks (including and cephalopods), , , ,][ (e.g. bottlenose dolphins ( Tursiops), ( Delphinus),][ ( Stenella),][ ( Dugong dugon), Pinniped and ), and (including the three largest species: the leatherback ( Dermochelys coriacea),][ Tiger Sharks Killed for Eating Leatherback Turtles . Shark Defenders (2011-04-16). Retrieved on 2013-03-23.] the loggerhead ( Caretta caretta)[ Shark Bay Ecosystem Research Project . .fiu.edu. Retrieved on 2013-03-23.] and the green sea turtles ( Chelonia mydas
/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.[Witzell, W. N. (1987). Selective predation on large cheloniid sea turtles by tiger sharks (Galeocerdo cuvier). Japanese Journal of Herpetology, 12(1), 22–29.] They also eat other sharks (including adult ( Carcharhinus plumbeus)), as well as Batoidea, and sometimes even cannibalism.[
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Due to high risk of predation, dolphins often avoid regions inhabited by tiger sharks.[ A scavenger, the tiger shark will feed on dead whales, and has been documented doing so alongside great white sharks.]
Evidence of dugong predation was identified in one study that found dugong tissue in 15 of 85 tiger sharks caught off the Australian coast.
The broad, heavily calcified jaws and nearly terminal mouth, combined with robust, serrated teeth, enable the tiger shark to take on these large prey.[ In addition, excellent eyesight and acute olfaction 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.][ The shark circles its prey and studies it by prodding it with its snout.][ When attacking, the shark often eats its prey whole, although larger prey are often eaten in gradual large bites and finished over time.][
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Notably, terrestrial mammals, including ( Equus ferus caballus), ( Capra aegagrus hircus), sheep ( Ovis aries), ( Canis lupus familiaris), ( Felis catus), and ( Rattus norvegicus), are fairly common in the stomach contents of tiger sharks around the coasts of Hawaii.[ In one case, remains of two were found in the stomach of this shark,][ Due to their habits of eating essentially anything, Tiger sharks are often referred to as the " garbage can of the sea".
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Predation by orcas
Tiger sharks are preyed on by . Orcas have been recorded hunting and killing tiger sharks by holding them upside down to induce Apparent death in order to drown the shark. The orcas bite off the shark's fins before disemboweling and devouring it.
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.[ 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.][
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Reproduction
Males reach sexual maturity at and females at .[ 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 .][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.] Females mate once every three years.[ They breed by internal fertilization. The male inserts one of his 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.][
Tiger Sharks are unique among all sharks in the fact that they employ embryotroph 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.]
The young develop inside the mother's body up to 16 months. Litters range from 10 to 80 pups.[ A newborn is generally long.][ How long tiger sharks live is unknown, but they can live longer than 12 years.][
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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 , 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.
Conservation
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 shark 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, 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 fishers.[
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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.[
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Relationship with humans
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.[ They often visit shallow reefs, harbors, and canals, creating the potential for encounter with humans.][ The tiger shark also dwells in river mouths and other runoff-rich water.][ 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.][ 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.][ 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.]
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 video. The shark was later captured by fishermen and killed. This was the third fatal tiger shark attack in the area since 2022.
Between 1959 and 1976, 4,668 tiger sharks were culling in the state of Hawaii in an effort to protect the tourism industry.[ 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,][ and underwater photographer Fiona Ayerst swam with them in the Bahamas.][ Riveting Shark Encounters: Fiona Ayerst recounts ... gentle tiger shark in the warm silky waters of the Bahamas . Magazines.co.za (June/July 2009)] At "Tiger Beach" off Grand Bahama, uncaged diving with – and even the handling of – female tiger sharks has become a routine occurrence.
Warming Atlantic Ocean currents have caused tiger shark migration paths to move further north, according to a University of Miami study.
Mythology
Tiger sharks are considered to be sacred Aumakua (ancestor spirits) by some native Hawaiians.
See also
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List of sharks
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List of prehistoric cartilaginous fish genera
External links
