Thetiger shark (Galeocerdo cuvier)[3] is a species ofground shark, and the only extant member of the genusGaleocerdo andfamily Galeocerdonidae. It is a largepredator, with females capable of attaining a length of over 5 m (16 ft 5 in).[4] Populations are found in manytropical andtemperate waters, especially around centralPacific islands. Its name derives from the dark stripes down its body, which resemble atiger's pattern, but fade as the shark matures.[5]
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 includescrustaceans,fish,seals,birds,squid,sea turtles,sea snakes,dolphins, and others, even smaller sharks. It also has a reputation as a "garbage eater",[5] consuming a variety of inedible, man-made objects that linger in its stomach. Tiger sharks have only one recorded natural predator, theorca.[6] It is considered anear-threatened species because offinning and fishing by humans.[1]
The tiger shark is second only to thegreat white in recorded fatal attacks on humans, but these events are still exceedingly rare.[7][8]
The shark was first described byPeron andLesueur in 1822, and was given the nameSqualus cuvier.[4]Müller andHenle in 1837 renamed itGaleocerdo tigrinus.[7] The genus,Galeocerdo, is derived from the Greekgaleos, which means shark, andkerdo, the word for fox.[7] The species name honors naturalistGeorges Cuvier.[4] It is often colloquially called the man-eater shark.[7]
The tiger shark is a member of the orderCarcharhiniformes, the most species-rich order of sharks, with more than 270 species also including the smallcatsharks andhammerhead sharks.[4] Members of this order are characterized by the presence of anictitating membrane over the eyes, two dorsal fins, ananal fin, and fivegill slits. It is the largest member of the order, commonly referred to asground sharks. It is the only extant member ofGaleocerdo, the only member of the family Galeocerdonidae.[9] The oldest remains ofGaleocerdo extend back to theEocene epoch, while the oldest fossils of the modern tiger sharkGaleocerdo cuvier date to the MiddleMiocene, around 13.8 million years ago.[10]
The tiger shark commonly attains an adult length of 3.5 to 4.7 m (11 ft 6 in – 15 ft 5 in) and weighs between 300 and 900 kg (700 and 2,000 lb).[11][12] TheInternational Game Fish Association's all-tackle record is 810 kg (1,790 lb).[13] It issexually dimorphic, with females being the larger sex. Mature females are often over 3.7 m (12 ft 2 in) while mature males rarely get that large.[7][14][15][16] Exceptionally large females reportedly can measure over 5 m (16 ft 5 in), and the largest males 4 m (13 ft 1 in). Weights of particularly large female tiger sharks can exceed 1,300 kg (2,900 lb).[15][17][18][12] One pregnant female caught off Australia reportedly measured 5.5 m (18 ft 1 in) long and weighed 1,524 kg (3,360 lb). Even larger unconfirmed catches have been claimed.[19] Some papers have accepted a record of an exceptional 7.4-metre (24 ft 3 in), 3,110-kilogram (6,860 lb) tiger shark, but since this is far larger than any scientifically observed specimen, verification would be needed.[20][21][22] A 2019 study suggested thatPliocene tiger sharks could have reached 8 m (26 ft) in maximum length.[23] 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.[24]
Among the largestextant sharks, the tiger shark ranks in average size only behind thewhale shark (Rhincodon typus), thebasking shark (Cetorhinus maximus), and thegreat white shark (Carcharodon carcharias). This makes it the second-largest predatory shark, after the great white.[25] Some other species such asmegamouth sharks (Megachasma pelagios),Pacific sleeper sharks (Somniosus pacificus),Greenland sharks (Somniosus microcephalus), andbluntnose 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.[7][19] Thegreat 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 4.4 m (14 ft) long individual at 580 kg (1,280 lb).[26]
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.[27][28]
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.[29]
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 ascountershading. 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.[5][30] They have small pits on the snout which hold electroreceptors called theampullae of Lorenzini, which enable them to detect electric fields, including the weak electrical impulses generated by prey, which helps them to hunt.[27] Tiger sharks also have a sensory organ called alateral 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.[31]
Sharks do not have moveable upper or lower eyelids, but the tiger shark—among other sharks—has anictitating membrane, which is a clear eyelid that can cover the eye.[32] A reflective layer behind the tiger shark'sretina, called thetapetum lucidum, allows light-sensing cells a second chance to capturephotons of visible light. This enhances vision in low-light conditions.[33]
Juvenile tiger shark in the BahamasVideo of juvenile female tiger shark at Lord Howe Island, Australia, fromPLOS ONE
The tiger shark is often found close to the coast, mainly intropical andsubtropical waters throughout the world.[7] Its behavior is primarilynomadic, 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 intochannels to pursue prey in shallower waters. In the westernPacific Ocean, the shark has been found as far north asJapan and as far south asNew Zealand.[4] It has also been recorded in theMediterranean Sea, but rarely, off Malaga (Spain), Sicily (Italy) and Libya.[34]
Tiger sharks can be seen in theGulf of Mexico, North American beaches, and parts of South America. It is also commonly observed in theCaribbean Sea. Other locations where tiger sharks are seen include off Africa, China,India,Australia, andIndonesia.[5] Certain tiger sharks have been recorded at depths just shy of 900 m (3,000 ft).[7]
The tiger shark is anapex predator[35] and has a reputation for eating almost anything.[7] These predators swim close inland to eat at night, and during the day swim out into deeper waters.[36] Young tiger sharks are found to feed largely onsmall fish, as well as various smalljellyfish, andmollusks includingcephalopods. Around the time they attain 2.3 m (7.5 ft), or near sexual maturity, their selection expands considerably, and much larger animals become regular prey.[37] Numerousfish, mollusks (includinggastropods and cephalopods),crustaceans,sea birds,sea snakes,[38]marine mammals (e.g.bottlenose dolphins (Tursiops),common dolphins (Delphinus),[39]spotted dolphins (Stenella),[40]dugongs (Dugong dugon),seals andsea lions), andsea turtles (including the three largest species: theleatherback (Dermochelys coriacea),[41] theloggerhead (Caretta caretta)[42] and thegreen sea turtles (Chelonia mydas)[37]), are regularly eaten by adult tiger sharks.[43] 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.[44] They also eat other sharks (including adultsandbar sharks (Carcharhinus plumbeus)), as well asrays, and sometimes evenother tiger sharks.[5][37]
Due to high risk of predation, dolphins often avoid regions inhabited by tiger sharks.[45][46] Injured or ailingwhales may also be attacked and eaten. A group was documented killing an ailinghumpback whale (Megaptera novaeangliae) in 2006 near Hawaii.[47] A scavenger, the tiger shark will feed on dead whales, and has been documented doing so alongside great white sharks.[48][49] Tiger sharks have also been observed to feed on deadmanta rays in theGerman Channel of Palau.[50]
Evidence ofdugong predation was identified in one study that found dugong tissue in 15 of 85 tiger sharks caught off the Australian coast.[51] Additionally, examination of adult dugongs has shown scars from failed shark attacks.[52] To minimize attacks, dugong microhabitats shift similarly to those of known tiger shark prey when the sharks are abundant.[53]
The broad, heavily calcified jaws and nearly terminal mouth, combined with robust, serrated teeth, enable the tiger shark to take on these large prey.[45] In addition, excellenteyesight and acutesense 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.[29] The shark circles its prey and studies it by prodding it with its snout.[29] When attacking, the shark often eats its prey whole, although larger prey are often eaten in gradual large bites and finished over time.[29]
Notably, terrestrial mammals, includinghorses (Equus ferus caballus),goats (Capra aegagrus hircus),sheep (Ovis aries),dogs (Canis lupus familiaris),cats (Felis catus), andbrown rats (Rattus norvegicus), are fairly common in the stomach contents of tiger sharks around the coasts of Hawaii.[37] In one case, remains of twoflying foxes were found in the stomach of this shark,[54] and in another, anechidna (Tachyglossus aculeatus) was regurgitated by a tiger shark beingtagged offOrpheus Island,Queensland.[55] Because of its aggressive and indiscriminate feeding style, it often mistakenly eats inedible objects, such as automobilelicense plates,oil cans,tires, andbaseballs.[5] Due to their habits of eating essentially anything, Tiger sharks are often referred to as the "garbage can of the sea".
Tiger sharks are preyed on byorcas. Orcas have been recorded hunting and killing tiger sharks by holding them upside down to inducetonic immobility in order to drown the shark. The orcas bite off the shark's fins before disemboweling and devouring it.[6]
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.[45] 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.[45]
Males reach sexual maturity at 2.3 to 2.9 m (7.5 to 9.5 ft) and females at 2.5 to 3.5 m (8.2 to 11.5 ft).[27] 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 80 to 130 kg (180 to 290 lb).[28][56] Females mate once every three years.[5] They breed by internal fertilization. The male inserts one of hisclaspers into the female's genital opening (cloaca), acting as a guide for thesperm. 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 isovoviviparous; its eggs hatch internally and the young are born live when fully developed.[7]Tiger Sharks are unique among all sharks in the fact that they employembrytrophy 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.[57]
The young develop inside the mother's body up to 16 months. Litters range from 10 to 80 pups.[7] A newborn is generally 51 to 76 cm (20 to 30 in) long.[7] How long tiger sharks live is unknown, but they can live longer than 12 years.[5]
Tiger sharkontogeny has been little studied until recently, but studies by Hammerschlaget 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 torequiem 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.[58]
While shark fin has very few nutrients, shark liver has a high concentration ofvitamin 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 bybig-game fishers.[7]
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.[60]
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.[61][62] They often visit shallow reefs, harbors, and canals, creating the potential for encounter with humans.[5] The tiger shark also dwells in river mouths and other runoff-rich water.[7][27] 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.[7][61] Typically, three to four shark bites occur per year in Hawaii; one notable survivor of such an attack issurfing championBethany 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.[63] 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.[64]
On 8 June 2023, a tiger shark attacked and killed a 23-year-old Russian man in theRed Sea off the coast of the Egyptian city ofHurghada. The attack was filmed by onlookers and the recording wentviral. The shark was later captured by fishermen and killed. This was the third fatal tiger shark attack in the area since 2022.[65]
Between 1959 and 1976, 4,668 tiger sharks wereculled in the state of Hawaii in an effort to protect thetourism industry.[66] 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,[67][68] and interaction with them, such ascage 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 2007Discovery Channel special,[69] and underwater photographerFiona Ayerst swam with them inthe Bahamas.[69][70] At "Tiger Beach" off Grand Bahama, uncaged diving with – and even the handling of – female tiger sharks has become a routine occurrence.[71]
Warming Atlantic Ocean currents have caused tiger shark migration paths to move further north, according to a University of Miami study.[72]
Tiger sharks are considered to be sacredʻaumākua (ancestor spirits) by somenative Hawaiians.[73] Tiger sharks possess a unique significance as ʻaumakua, 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, ʻaumakua 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.[74]
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