Tiger Shark
Tiger sharks (Galeocerdo cuvier) are named for the dark vertical stripes on their sides, resembling those of a tiger, which are prominent in their youth. As they grow, these stripes fade but remain partially visible into adulthood. They belong to the largest family of sharks, the Requiem shark (Carcharhinidae), known for being large predators with strong jaws and sharp teeth, including the Blue shark, Bull shark, and Oceanic Whitetip shark. Tiger sharks are the second largest predatory shark following the Great White shark.
Tiger shark anatomy and appearance
The largest of the Requiem sharks, Tiger sharks grow up to 5m long and weigh up to 900kg. Males are slightly smaller at around 4m long. Females become sexually mature at around 2.5m, and males at 2.3m. The average lifespan for a Tiger shark is 17 to 22 years.
As their distinctive juvenile stripes fade, they turn a blueish to light green above and yellowish to white below. To reduce friction, the surface of its skin is covered in tiny teeth-like structures and research shows that other marine organisms, including fish and other sharks, brush against Tiger shark skin to remove parasites from their own skin.
Unlike most other sharks who have a round jaw, Tiger sharks have blunted, square jaws, with identical amounts of razor sharp, serrated teeth in the lower and upper jaws. Serrated, sideways pointing teeth allow the sharks to slice through their prey and can even cut through turtle shells. New teeth replace worn-out teeth throughout its life.
Tiger sharks are the only Requiem sharks with spiraculi (suction holes) behind the eyes. These help to oxygenate blood in vessels that lead directly to the eyes and brain. The backs of their eyeballs also have a layer of reflective tissue called a tapetum, which enhances their night vision.
Tiger shark habitat
The Tiger shark is a solitary species and inhabits shelf, reef and slope habitats, and sometimes coral reefs. They predominantly stay in warm coastal waters 100 to 350m depth around the world but are also known to dive to depths of more than 1000m, and are found in as shallow as 3m in Hawaii. They are most abundant in the Caribbean, North America, and the Gulf of Mexico, but are often found in New Zealand, Australia, India, Africa, and China as well. This species has been spotted as far south as Cape Cod and as far north as Japan.
Tiger shark diet
The Tiger shark is predominantly an individual hunter and does not care much for social interaction, even within its own species. They have earned the nickname ‘The Garbage Cans of the Sea’ due to their ability to eat almost anything including stingrays, dolphins, seals, squids, turtles, crabs, sea birds and other sharks. There are even records of Tiger sharks eating land animals such as songbirds, horses, dogs, sheep, cats, and rats. They are even known to eat manufactured objects, with items like tyres, car license plates, baseballs and oil cans having been found in their stomach contents.
The species is a slow swimmer, but since they blend in so well with their surroundings, they do not need to be fast. Once they are within striking distance of their prey, they put on a burst of speed to catch it. They normally eat their prey whole.
Tiger shark population
Genetic research has revealed that there are two discrete populations of Tiger shark; one in the Atlantic Ocean on one in the Indo-Pacific and there is also evidence to suggest that Tiger sharks from Hawaii are genetically different.
Tiger sharks are viviparous, meaning the female lays 10 to 82 fertilised eggs inside her body and each egg contains an embryo which feeds on its own egg-yolk. The embryos then hatch inside the mother where it continues to grow until she gives birth to around 26-33 (on average) fully developed live pups, after a total gestation period of around 13 to 16 months. They can give birth to around 80 pups in some circumstances. Around 30 to 35 pups per litter are sired by one individual male.
Tiger shark Conservation
The Tiger Shark has most recently been assessed as Near Threatened (NT) for The IUCN Red List of Threatened Species in 2018.
The Tiger shark is at risk from fishing pressure in the Arabian Seas as well as shark control programmes in other regions. Overall populations have reduced by around 30% globally over the past three Tiger shark generations (53-68 years).
This species is often targeted by shark fisheries for their fins, meat, and liver oil, and as bycatch in commercial fisheries. It is often subject to illegal, unreported, and unregulated fishing practices and often also caught for sport. In the past, their skin was used to make leather.
Through their reputation as a species that attacks humans, however rare that is, they have become a target of population control efforts in Australia, South Africa, and Reunion Island, although this practice has never been endorsed by scientists anywhere this occurs. These efforts have never shown evidence to reduce already small numbers of shark attacks on humans.
There are no specific conservation or management measures in place for the Tiger Shark. However, there has been an increasing interest to intensify protection of the species in the Western North Atlantic. Currently the Fisheries Management Program for the U.S. Atlantic and Gulf of Mexico has quotas and fishing seasons in place to regulate catch of coastal shark species including the Tiger shark. Some countries in the Arabian Seas region have banned the targeted fishing for sharks (Kuwait, Saudi Arabia, Sudan, the Maldives), and others impose seasonal bans on shark fishing (Iran, the UAE).
Tiger sharks and humans
Tiger sharks have a near completely undiscerning palate, which allows them to eat a wide variety of prey. They have the second highest rate of human attacks after the Great White shark, which has led to it being unfairly addressed as a ‘man-eater.’ Fatal attacks are rare, with far more human fatalities occurring from drowning in coastal waters.
This species is frequently seen in shallow waters around Hawaii, and since Hawaii is a high touristic area with lots of swimmers and surfers, there is a high likelihood of encountering Tiger sharks here. There are typically only around 3-4 bites from Tiger sharks per year in Hawaii, which are rarely fatal. Most attacks happen due to tourists feeding the sharks, which is illegal.
