The tiger shark (Galeocerdo cuvier) is a species of ground shark, and the only extant member of the genus Galeocerdo and family Galeocerdonidae. It is a large predator, with females capable of attaining a length of over . It is considered a near-threatened species because of finning and fishing by humans.

Taxonomy

The shark was first described by Peron and Lesueur in 1822, and was given the name Squalus cuvier. 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 . The International Game Fish Association's all-tackle record is . It is sexually dimorphic, with females being the larger sex. Mature females are often over while mature males rarely get that large. Exceptionally large females reportedly can measure over , and the largest males . Weights of particularly large female tiger sharks can exceed . Some papers have accepted a record of an exceptional , tiger shark, but since this is far larger than any scientifically observed specimen, verification would be needed. A 2019 study suggested that Pliocene tiger sharks could have reached in maximum length. 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.

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. 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.

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.

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. 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.

Distribution and habitat

250px|right|thumb|Juvenile tiger shark in the Bahamas|alt=Profile photo of shark, accompanied by [[remora, swimming just above a sandy seafloor]]

thumb|250px|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.

Fuvahmulah, an island in the Maldives, has been identified as home to the world’s largest known aggregation of tiger sharks (Galeocerdo cuvier).

The finding is based on a long-term scientific study using non-invasive methods such as photo identification and laser photogrammetry, which recorded at least 239 individual tiger sharks in the waters around the island.

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. Young tiger sharks are found to feed largely on small fish, smaller elasmobranchs like other sharks like small tiger sharks and reef sharks, rays, as well as various small jellyfish, crustaceans, and mollusks including cephalopods. Around the time they attain , or near sexual maturity, their selection expands considerably, and much larger animals become regular prey. the loggerhead (Caretta caretta) and the green sea turtles (Chelonia mydas) 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. They also eat other sharks (including adult sandbar sharks (Carcharhinus plumbeus)), as well as rays, and sometimes even other tiger sharks. 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. Tiger sharks have also been observed to feed on dead manta rays in the German Channel of Palau.

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

The broad, heavily calcified jaws and nearly terminal mouth, combined with robust, serrated teeth, enable the tiger shark to take on these large prey. and in another, an echidna (Tachyglossus aculeatus) was regurgitated by a tiger shark being tagged off Orpheus Island, Queensland. Because of its aggressive and indiscriminate feeding style, it often mistakenly eats inedible objects, such as automobile license plates, oil cans, tires, and baseballs. Females mate once every three years.

The young develop inside the mother's body up to 16 months. Litters range from 10 to 80 pups.

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.

Conservation

thumb|A large female tiger shark caught in [[Kane'ohe Bay|Kaneohe Bay, Oahu 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.

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.

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.

Between 1959 and 1976, 4,668 tiger sharks were culled in the state of Hawaii in an effort to protect the tourism industry. 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, 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.

See also

  • List of sharks
  • List of prehistoric cartilaginous fish genera

References

  • 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
  • Diver Has Been Friends With Tiger Shark For 20 Years!