Tiger shark

Appearance

The tiger shark commonly attains a length of 3.25–4.25 m and weighs around 385–635 kg. Sometimes, an exceptionally large male tiger shark can grow up to 4 m. Females are larger, and exceptionally big ones can reportedly measure over 5 m. One female specimen caught off Australia reportedly measured 5.5 m long and weighed an exceptional 1,524 kg, although her weight is thought to have been bolstered by her pregnant state at the time. Even larger specimens have been reported, but are unconfirmed.

Among the largest extant sharks, the tiger shark ranks in average size only behind the whale shark, the basking shark, and the great white shark. Some other species such as megamouth sharks, Pacific sleeper sharks, Greenland sharks, and bluntnose sixgill sharks broadly overlap in size with the tiger shark, but as these species are comparatively poorly studied, it is unclear whether their typical mature size matches that of the tiger shark. The great hammerhead, 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 of 580 kg.

Its teeth are specialized 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.

Distribution

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, Hong Kong, India, Australia, and Indonesia.

Status

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 in the future. 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.

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.

Habitat

The tiger shark is often found close to the coast, mainly in tropical and subtropical 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. A tiger shark tagged in the Caribbean has been tracked migrating to Cape Cod; although they are a tropical species, the warm Gulf Stream brings the coast of Cape Cod to within the extreme north of its range during the summer.

Certain tiger sharks have been recorded at depths just shy of 900 m, 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 350 m, making it uncommon to see tiger sharks in shallow water. However, tiger sharks in Hawaii have been observed in depths as shallow as 3 m and regularly observed in coastal waters at depths of 6 to 12 m.

Reproduction

Males reach sexual maturity at 2.3 to 2.9 m and females at 2.5 to 3.5 m. Females mate once every three years. They breed by internal fertilization. The male inserts one of his claspers into the female's genital opening, 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.

The young develop inside the mother's body up to 16 months. Litters range from 10 to 80 pups. A newborn is generally 51 to 76 cm long. How long tiger sharks live is unknown, but they can live longer than 12 years.

Food

The tiger shark is an apex predator and has a reputation for eating anything. These predators swim close inland to eat at night, and during the day swim out into deeper waters. Young tiger sharks are found to prey largely on small fish, as well as various small jellyfish, cephalopods, and other mollusks. Around the time they attain 2.3 m, or near sexual maturity, their prey selection expands considerably, and much larger animals become regular prey. Numerous fish, crustaceans, sea birds, sea snakes, marine mammals, common dolphins, spotted dolphins, dugongs, seals and sea lions, and sea turtles, the loggerhead and the green sea turtles,) are regularly eaten by adult tiger sharks. They also eat other sharks ), as well as rays, and sometimes even eat other tiger sharks.

Due to high risk of predatory attacks, dolphins often avoid regions inhabited by tiger sharks. They may also attack injured or ailing whales and prey upon them. A group was documented attacking and killing an ailing humpback whale in 2006 near Hawaii. The tiger shark also scavenges on dead whales. In one such documented incident, they were observed scavenging on a whale carcass 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. Additionally, examination of adult dugongs has shown scars from failed shark attacks. Finally, 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. 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. 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.

Notably, terrestrial mammals, including horses, goats, sheep, dogs, cats, and brown rats, are fairly common in the stomach contents of tiger sharks around the coasts of Hawaii. In one case, remains of two flying foxes were found in the stomach of this shark. Because of its aggressive and indiscriminate feeding style, it often mistakenly eats inedible objects, such as automobile license plates, oil cans, tires, and baseballs.