The tiger shark, scientifically known as Galeocerdo cuvier, is a marine predator that dominates the warm and temperate waters of the oceans. Its presence extends across various regions, being the only living representative of its genus.
This shark stands out for its mighty size, with females reaching lengths of over 5 meters. Its populations are distributed in tropical and temperate waters, especially in the central Pacific islands. Although its name refers to the dark stripes running along its body, reminiscent of a tiger's pattern, these fade with age.
It is a solitary hunter, mostly active at night. Its varied diet includes crustaceans, fish, seals, birds, squid, turtles, sea snakes, dolphins, and even smaller sharks. It is also known for consuming non-edible objects, a product of human activity. Only the orca figures as its natural predator.
Considered nearly threatened, the tiger shark faces fishing pressure and accidental capture. Its record of fatal attacks on humans positions it as the second most dangerous shark after the great white, although these encounters are exceptional.
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Origins and Taxonomy
The name "tiger" is due to the dark stripes on its skin, reminiscent of the Asian feline. This shark exhibits effective camouflage, especially when lurking from the depths. Its morphology includes a flattened head with a large mouth and sharp teeth adapted to break bones and shells.
First described in 1822, it has gone through various classifications until being recognized as Galeocerdo cuvier. It belongs to the order Carcharhiniformes and the family Carcharhinidae, characterized by nictitating membranes over the eyes and dorsal fins. It is the largest representative of this order and the only one in its genus and family.
Classification of the Tiger Shark: Galeocerdo cuvier
- Kingdom: Animalia
- Phylum: Chordata
- Class: Chondrichthyes (cartilaginous fishes)
- Order: Carcharhiniformes
- Family: Carcharhinidae
- Note: Family Galeocerdonidae (according to some sources, although historically it is Carcharhinidae).
- Genus: Galeocerdo
- Species: Galeocerdo cuvier
Characteristics: What is the Tiger Shark Like?
The tiger shark reaches a length of between 3.5 and 4.7 meters in adulthood, with weights ranging from 300 to 900 kilograms. Mature females are larger than males, with some exceptions exceeding 5 meters. Even larger individuals have been reported, although their veracity is debated. Thus, regarding the question of how long the tiger shark is, it measures between three and 5 meters in its normal size in adulthood.
Compared to other sharks, Galeocerdo cuvier stands out for its unique, sharp, and sideways-curved teeth. Its anatomy includes long fins for propulsion and a powerful tail for bursts of speed. Its swimming is characterized by smooth and small body movements.
Bite
To examine the bite of the tiger shark, Brocq Maxey conducted an experiment with a meter specially designed to measure the bite force of various shark species. This device was created with the necessary sensitivity to obtain precise readings but also with the required resistance to withstand the strong jaws of sharks. Then, in the Bahamas, they used bait to attract the sharks and provoke them to bite the meter to measure and compare the force of each of them.
The results showed that a three-meter-long hammerhead shark registered a bite force of 229 kg, while a 2.7-meter-long tiger shark registered a bite force of 391 kg. Despite being smaller in size, the tiger shark showed a bite force 70% greater than the hammerhead shark.
Although this experiment did not report the bite pressure of other sharks, there are records that the bull shark reaches 1350 kg of force, which is below the 1800 kgf of the great white shark.
Teeth
Tiger sharks can have between 24 and 37 rows of teeth in their upper and lower jaws. Each row can contain up to 7 functional teeth in the upper jaw and up to 6 teeth in the lower jaw, totaling approximately between 300 and 350 teeth in a single adult tiger shark. These numbers may vary slightly depending on the size and age of the shark. The teeth are continuously replaced throughout the shark's life, with new teeth emerging to replace lost or damaged ones, thus maintaining its ability to hunt and feed effectively.
The teeth are a distinctive feature of this species. They are large, robust, and serrated, specifically designed to capture and tear apart large prey. They are arranged in multiple rows, with the largest teeth in the front row and smaller teeth in the posterior rows. Their shape is triangular and pointed, facilitating penetration into the prey's skin and subsequent tearing. Additionally, they are also serrated on the edges, increasing their efficiency for cutting and tearing flesh. This dental structure allows the tiger shark to consume a wide range of prey.
Skin
The skin of the tiger shark exhibits shades ranging from blue to light green, with a belly of white or light yellow color. This camouflage is strategic: from below, the shark blends with the darkness of the water, while from above, its bright belly mixes with the sunlight. This phenomenon, known as countershading, helps it stalk its prey effectively.
Detection of Electric Fields and Prey
In its wedge-shaped head, it has small pits in the snout that house electrosensory receptors called ampullae of Lorenzini, allowing it to detect electric fields generated by its prey. It also has a sensory organ called the lateral line, which extends along its flanks, enabling it to detect vibrations in the water. These sensory adaptations grant the tiger shark outstanding hunting abilities, especially in the dark.
Vision
Unlike other sharks, the tiger shark has a nictitating membrane, a type of transparent eyelid that protects its eyes. It also has a reflective layer called the tapetum lucidum, located behind the retina, which enhances its vision in low light conditions.
Habitats and Geographic Distribution Worldwide
Its habitat encompasses tropical and subtropical waters around the world, showing a preference for coastal areas and reefs. While its behavior is nomadic, it tends to follow warm currents and remains in deep waters near the coast.
Its behavior is mostly nomadic, although it follows warm currents and tends to stay closer to the equator during the colder months. Generally, it is found in deep waters bordering reefs but also ventures into channels in search of prey in shallower waters. In the western Pacific Ocean, tiger sharks have been sighted as far north as Japan and as far south as New Zealand. Additionally, sightings have been recorded in the Mediterranean Sea, although they are rare, in areas such as Málaga (Spain), Sicily (Italy), and Libya.
Galeocerdo cuvier has also been spotted in the Gulf of Mexico, the coasts of North America, and parts of South America. They are common in the Caribbean Sea and have been observed in various parts of the world, including Africa, China, India, Australia, and Indonesia. Some specimens have even been recorded at depths of nearly 900 meters (approximately 3000 feet).
Feeding: What Does a Tiger Shark Eat?
The tiger shark is a super predator known for its varied and voracious diet. From small fish to marine mammals such as dolphins and sea turtles, this shark is capable of consuming a wide range of prey. Its ability to detect hidden prey and its aggressiveness in hunting make it a formidable predator. Generally, the shark species Galeocerdo cuvier has a reputation for consuming a wide variety of prey. At night, these predators swim inland in search of food, while during the day they venture into deeper waters.
When young, they primarily eat small fish, jellyfish, and mollusks, but as they grow, their prey selection expands considerably. They begin to hunt much larger animals, including larger fish, crustaceans, seabirds, sea snakes, marine mammals, and even sea turtles. It has been observed that up to 20.8% of the stomachs of studied tiger sharks contained sea turtle remains, suggesting a dietary preference for these animals. Additionally, these sharks are known to eat other sharks, including sandbar sharks and rays, and sometimes even other tiger sharks.
Due to their position as super predators, dolphins tend to avoid regions inhabited by tiger sharks. Even wounded or sick whales can become prey for these sharks. In addition to hunting live prey, tiger sharks also feed on carrion, such as dead whales. Evidence of predation on dugongs has been documented, with dugong tissue found in the stomachs of some tiger sharks. The wide jaws and nearly terminal mouth, along with their robust and serrated teeth, allow them to capture and consume large prey. They possess excellent vision and a keen sense of smell, which enables them to detect faint traces of blood and follow them to their source. Occasionally, tiger sharks may ingest inedible objects by mistake, such as car license plates, oil cans, tires, and baseballs. This has led to them being known as the "garbage can of the sea."
Reproduction
Regarding reproduction, females mate every three years and give birth to litters of up to 80 pups.
During mating, the male tiger shark uses his teeth to hold onto the female, which can result in considerable discomfort for her. In the northern hemisphere, this process typically occurs between March and May, with the birth of the pups taking place between April and June of the following year. In contrast, in the southern hemisphere, mating occurs between November, December, or early January.
It is unique within its Carcharhinidae family in being ovoviviparous; this means that the eggs are incubated internally, and the pups are born alive when fully developed. Additionally, they employ embryotrophy, a unique process in which they receive nutrients through fluid-filled sacs within the uterus, allowing them to grow significantly, although they are not connected to the mother through a placenta. Once born, the pups measure between 51 and 76 centimeters long and begin their independent life in the ocean.
The gestation period of the pups within the mother's body lasts approximately 16 months, and litters can range from 10 to 80 pups. At birth, the newborn tiger sharks generally measure between 51 and 76 cm (20 to 30 inches) in length. It is estimated that the lifespan of tiger sharks is greater than 12 years.
Ontogeny
The ontogeny of the tiger shark has been the subject of recent studies that reveal significant changes as they mature. One of these changes is the symmetrization of their tails, which becomes more evident with age. Additionally, it has been observed that the heads of juvenile tiger sharks are more conical and similar to those of other requiem sharks, while adults have a relatively broader head. This morphological difference is believed to be related to adaptations for hunting and evading predators.
Species Conservation
The tiger shark faces significant threats due to indiscriminate capture for its fins, meat, and liver. The ongoing demand for shark fins has led to the decline of several populations, and it is considered a near-threatened species by the International Union for Conservation of Nature, but it is not currently endangered. However, there are risks of significantly reducing the worldwide population of these sharks.
Relationship with Humans: Is It Dangerous?
Regarding its relationship with humans, the tiger shark has been responsible for a notable proportion of fatal shark attacks. Although these incidents are rare, their presence in coastal waters and their habit of dwelling near areas frequented by humans increases the potential for encounters. However, it is important to note that interactions between humans and tiger sharks are rare, and most attacks are not fatal.
Mythology
In Hawaiian mythology, tiger sharks are considered 'aumākua, sacred ancestral spirits. They are attributed a special significance as guardians of the family and messengers between the human and divine. This perspective reflects the spiritual connection and reverence for nature in Hawaiian culture, highlighting the importance of coexisting harmoniously with the natural world.