TIGER SHARK: CHARACTERISTICS, HABITAT, FEEDING, BEHAVIOR - BIOLOGY - 2024

The tiger shark (Galeocerdo cuvier) is an animal that is part of the Carcharhinidae family. The main characteristic of this shark is the pattern of stripes and dark spots that it has at the dorsal level, which stand out against the gray tone of the body. These are fading as the shark becomes an adult.

This species has a stocky body, with a robust head and large eyes. The muzzle is broad and blunt and the jaw is solid and strong. It has large teeth, with curved and serrated cusps. In addition, the edges have deep notches directed outward.

Tiger shark. Source: Albert Kok

The tiger shark's specialized teeth allow it to efficiently cut through the meat, cartilage, bones and even the shell of sea turtles.

Regarding the habitat, it is found in all the tropical and temperate marine waters of the world. It preferably lives in shallow coastal areas, but could also be found in the open sea. It could also be located in areas close to islands and continental shelves.

This shark is a solitary hunter, which goes out in search of its prey, mainly at night. Their diet is based on fish, seabirds, dolphins, seals and carrion.

characteristics

Source; Albert kok

Fins

The first dorsal fin is wide and originates from the area behind the pectoral axilla. In relation to the second dorsal fin, it is smaller and is born before the region where the anal fin originates. Along the entire length of the back is a ridge.

At the level of the caudal peduncle there is a keel and the anterior lobe of this fin is thin and long, with a subminal notch. The tiger shark's tail is heterocecal, because the dorsal lobe is longer than the ventral lobe.

Its fins are long, as they provide the necessary lift to perform maneuvers in the water. As for the broad tail, it offers the fish bursts of speed. Generally the swimming of this shark is done with small body movements.

Coloration

The dorsal surface of the tiger shark is dark gray or grayish brown, which contrasts with the white of the ventral area. The young have dark spots that, as they grow, some merge and form stripes, similar to those of a tiger.

These patterns fade and are less evident when the shark is adult. The color of the skin is a favorable element when the shark chases its prey. In this sense, when viewed from above, it goes unnoticed due to the darkness of the seabed.

On the contrary, if they see it from below, the white of the lower part serves as a camouflage against the luminosity, product of the solar rays.

Dentition

The teeth of the Galeocerdo cuvier have very particular characteristics. Their jaws have large teeth, with numerous curved cusps and serrated edges. In addition, each has a deep notch in the outer margin.

Also, the teeth have deep grooves and the point faces sideways. These specializations allow the animal to cut through meat, bones, and other hard surfaces, such as the shells of turtles.

Like the vast majority of sharks, the teeth are continually replaced by rows of new teeth. In relation to size, these diminish towards the back of the jaw.

Also, the tiger shark's teeth are considered smaller than those of the great white shark, but both are about the same width.

Size

The Galeocerdo cuvier is one of the largest sharks in the Carcharhinidae family. Their body length can be between 325 and 425 centimeters, with a weight that ranges from 385 to 635 kilograms. However, some species have reached a height of more than 5.5 meters and a body mass of approximately 900 kilograms.

At birth, they usually measure from 51 to 76 centimeters and when they reach sexual maturity, the male is 226 to 290 centimeters long and the female measures 250 to 325 centimeters.

Head

The head is wedge-shaped, allowing the animal to quickly turn it sideways. Electroreceptors, known as Lorenzini bullae, are found in the snout.

They detect electric fields, including those coming from dams. Also, they pick up vibrations in the water. In this way, the tiger shark can hunt in the dark and locate some hidden prey.

View

The tiger shark lacks lower or upper eyelids. However, it has a nictitating membrane, which covers the eye. This works like a mirror, reflecting light from the environment, allowing photoreceptors to pick up stimuli. In this way the shark can improve its vision in low light conditions.

Evolution

The ancestor of the Galeocerdo cuvier dates back to the early Eocene, around 56 million years ago. Research on the evolution of this unique species of the genus Galeocerdo is based on the analysis of isolated teeth and, in some cases, is based on a single tooth that represents a species.

Eocene

The oldest fossil records of the tiger shark date from the Eocene. There is some evidence on various species that inhabited at that time, among which are G. latides. This elasmobranch lived in North America, Europe, and Asia.

Another shark from that period is G. latidens, which, according to the evidence, was distributed in Europe, Africa and North America. Both species have teeth similar to those of the modern tiger shark, but smaller. Furthermore, they were simply sawn.

During the Middle Eocene, G. eaglesomei lived on the Arabian Peninsula, Africa, and in some regions of North America. The distal side of the teeth of this species does not have the notch that distinguishes Galeocerdo cuvier and the striations are thick. Likewise, the root lobe is rounded.

Oligocene, Miocene and Pliocene

G. mayumbensis developed in the Miocene, in West Africa. As for its teeth, it had characteristics very similar to those of the G. eaglesomi. Thus, it had teeth with complex serrations, typical of the modern tiger shark. However, it differs in that it had a higher crown.

As for the Galeocerdo aduncus, it lived during the Lower Oligocene and the Miocene in Europe. In the African continent, North and South America and in India it was found in the Miocene. It also populated Japan in the Pliocene. Its teeth are simply serrated. They are smaller and less robust in appearance than modern species.

In the United States, in the Miocene epoch, Physogaleus contortus was found. It was previously classified as a species of the genus Galeocerdo, however, it was reclassified and assigned to a different clade, Physogaleus. This early species had a thin, twisted tooth crown.

Taxonomy

Source: Albert kok

-Animal Kingdom.

-Subreino: Bilateria.

-Filum: Cordate.

-Subfilum: Vertebrate.

-Superclass: Chondrichthyes

-Class: Chondrichthyes.

-Subclass: Elasmobranchii.

-Order: Carcharhiniformes.

-Family: Carcharhinidae.

-Gender: Galeocerdo.

-Species: Galeocerdo cuvier.

Habitat and distribution

Distribution map of the Tiger Shark (Galeocerdo cuvier). Source: Chris_huh

Distribution

This shark is found in all temperate and tropical seas in the world. Thus, in the western Atlantic it is distributed from Massachusetts (United States) to Uruguay, including the Caribbean, the Bahamas and the Gulf of Mexico.

In the eastern Atlantic it lives in Iceland, in the Canary Islands, Morocco, from Senegal to the Ivory Coast. In relation to the Indo-Pacific, the Galeocerdo cuvier inhabits the Red Sea, the Persian Gulf and from East Africa to Tahiti and Hawaii. Also, he lives south of New Zealand and Japan.

In the eastern Pacific it is located south of California (United States) to Peru, encompassing the Galapagos, Revillagigedo and Los Cocos islands. This shark is found in the waters of the Indian Ocean, in Pakistan, Sri Lanka, Maldives, Vietnam, Thailand and from South Africa to the Red Sea.

Those living in the western Pacific are south of China, the Philippines, Japan, Indonesia, New Zealand, Australia, and New Caledonia. In the western central Pacific they inhabit Palau and the Marshall and Solomon Islands.

Habitat

The tiger shark shows a great tolerance to different marine habitats, however, they prefer those close to continental shelves and island territories, including coral atolls and lagoons. Occasionally, it may venture into pelagic areas.

This saltwater shark prefers shallow coastal areas, however, it could move to other waters if food is scarce. Although it is usually located at depths of 2.5 to 145 meters, it could submerge up to 350 meters.

The tiger shark is sometimes associated with coral reefs and occasionally takes longer excursions to the pelagic zone. They are also sighted in river estuaries and river ports.

The habitat of this species is generally associated with the abundance of prey. Thus, it could swim 30 to 40 miles daily in search of food.

Experts point out that they probably don't use a pattern when it comes to where they feed. The Galeocerdo cuvier usually visits these areas irregularly, being able to return to them in a period of time that can range from two weeks to 10 months.

Migrations

The tiger shark performs seasonal migrations, which may be associated with the temperature of the water or the availability of food. In this sense, studies have been carried out on their migratory behavior in the Atlantic Ocean.

Specialists point out that, during the winter, this shark is located in the Caribbean islands, Turks and Caicos Islands and in the Bahamas. In the summer, they inhabit the open waters of the North Atlantic. On these trips, the annual route is approximately 7,500 kilometers.

The Galeocerdo cuvier has adopted the same habitat that large sea turtles have, which are one of their main sources of food. However, migration for food reasons is unpredictable.

In a research work off the Australian coast, where sea turtles lay their eggs, only a few sharks remained in the area during the massive visit of the aquatic reptile.

With reference to this, probably the change in their strategies and patterns of movement in search of their food is due to the need to take advantage of the various types of prey that exist in the habitat.

State of conservation

Source: Taken May 2007 at Shark Reef Marine Preserve, Beqa Lagoon, Fiji, by Terry Goss.

The populations of this species have shown significant reductions, mainly motivated by poaching. Because of this, the IUCN has categorized the tiger shark within the group of animals that are close to being vulnerable to extinction.

Threats

Starting in the 1950s, the Galeocerdo cuvier is exploited by fisheries in an artisanal or commercial way. In addition to this, their capture is added incidentally. This species is highly valued for its skin, its fins and for the oil that is extracted from its liver. Their meat and cartilage are also widely traded.

In this sense, the tiger shark is hunted in various regions, including the western Atlantic. Thus, on the east coast of the United States and in the Gulf of Mexico, it is frequently caught in the bottom commercial longline, representing between 8 and 36% of the total catch in the area.

Relative to the west coast of India, it is caught in underwater longline fishing and gillnets. In northern Australia, on the high seas, net and line fishing is used, while in Western Australia the gillnet and longline fishery are used.

Also, the tiger shark is caught in artisanal fisheries in subtropical and tropical regions, as is the case in Brazil, Panama, Mexico and in some African countries.

Conservation actions

In general, there are no specific measures related to the management or conservation of this species. However, in some countries where it lives, such as Saudi Arabia, Kuwait, Maldives and Sudan, its fishing is prohibited. In others, such as the United Arab Emirates and Iran, the impediment to hunting is seasonal.

In the same vein, the Fisheries Management Program that is carried out in the Gulf of Mexico and in the United States contemplates quotas and seasons, where the capture of this coastal shark is regulated.

Reproduction

According to experts, a male tiger shark is sexually mature when it measures 2 to 3 meters, while the female is ready to reproduce when its body is approximately 3 to 4 meters long. This usually mates once every 3 years.

In terms of weight, a young man able to reproduce has a body mass between 80 and 130 kilograms. The mating period usually varies according to the geographical situation. Thus, those living in the northern hemisphere unite between the months of March and May and the calf will be born in April and June of the following year.

Those sharks that live in the southern hemisphere can copulate in November, December or early January, the young being born between February and March of the following year.

Mating

Tiger sharks do not mate, and the male can mate with several females during the same breeding season. During copulation, the male holds the female with his teeth, which generally leaves lesions on her body.

Fertilization is internal and occurs when the male introduces one of his hemipenis into the female's genital opening. The testes are diametric, which are protruding from the surface of the epigonal organ.

These have the ability to produce a higher number of sperm, compared to compound or radial testes. In relation to the females, the ovaries are oval and are in the superficial dorsal region of the epigonal organ.

The Galeocerdo cuvier is the only one within the Carcharhinidae family that is ovoviviparous. Because of this, the eggs hatch internally and the young are born alive when fully developed.

The eggs are retained within the female's body, in a brood chamber. In this the embryo develops, which is nourished by the yolk sac. As the yolk begins to be consumed, which occurs near the end of gestation, the embryo gets its nutrients from the mother.

In the following video you can see how two tiger sharks mate. Although it is a different species, it is similar in form in tiger sharks:

The babies

Gestation lasts about 15 to 16 months. After this time, between 10 and 80 young are born. The newborn measures 51 to 76 centimeters and has a weight that ranges from 3 to 6 kilograms. This is fully developed and is independent of the mother. Its body is striped on the back and its belly is white or light yellow.

This allows it to camouflage itself with its surroundings and thus escape the threat of predators. These stripes, similar to those of tigers, are fading as the shark matures.

Feeding

The tiger shark is a solitary hunter that feeds mainly at night. However, it can sometimes form groups, but these are associated with the availability of food and not with social behavior.

This predator swims near the surface at night, while in the day they are in deeper water. According to research, the young of this species eat small fish, jellyfish and mollusks, including cephalopods.

When its body reaches a length of 2.3 meters or in the stage before sexual maturity, its diet expands to larger animals. When the Galeocerdo cuvier is adult, it eats fish, seabirds, crustaceans, sea snakes, sea lions, seals and carrion.

Also, eat sea turtles, such as the leatherback turtle (Dermochelys coriacea), the green turtle (Chelonia mydas) and the loggerhead turtle (Caretta caretta). According to some studies, 21% of the diet of this shark may be made up of these reptiles.

As for marine mammals, it tends to hunt bottlenose dolphins (Tursiops), spotted dolphins (Stenella), common dolphins (Delphinus) and dugong (Dugong dugon). Likewise, it can eat rays and other sharks, such as the sandbar shark (Carcharhinus plumbeus).

Eating methods

The Galeocerdo cuvier has several adaptations that allow it to face large prey. Among these are its broad jaw, a nearly terminal mouth, and serrated teeth. These allow the shark to penetrate the shell of sea turtles.

In addition, it has highly developed eyesight and a keen sense of smell, which allows it to track the blood of an injured animal. Also, it has the ability to detect electric fields, which is why it captures variations in the marine current and the movement of some dams.

To hunt, the tiger shark swims slowly and surrounds its prey. When close enough, it swims faster and pounces on the animal before it can get away. When it bites, it shakes its head from side to side, allowing it to tear off large chunks of meat.

Behavior

The tiger shark is a solitary and nocturnal predator, except when mating or feeding in groups on a large carcass. In this communal feeding, a hierarchy is established, where the largest sharks eat first.

The smaller ones circulate around the carrion, until the big ones are full and retired. After this, they approach the remains of meat and devour them. During these behaviors, violent behaviors do not occur among group members.

The swim

In the Galeocerdo cuvier the tail fin is the main source of propulsion. This causes a downward impulse of water behind the equilibrium point. This should cause the animal's head to turn upward. However, because the tail has a side-to-side movement, it prevents the head from moving.

Because of this, the movement of the tiger shark while moving is described by experts as S-shaped.

Communication

To perceive the environment, this species uses electromagnetic receptors that are located at the end of its nose. The signals are transmitted to the brain, where they are interpreted.

In this way it can detect fish and changes in water temperature and pressure. Thus, it can be located more easily in the dark.

The tiger shark also has a lateral stripe on both sides of the body, starting from the gill line to the base of the tail fin. This line captures the vibrations produced in the water by the movement of animals.

References

1. 1. Craig Knickle (2019). Tiger shark. Recovered from floridamuseum.ufl.edu.
   2. Wikipedia (2019). Tiger shark. Recovered from en.wikipedia.org.
   3. Jim Bourdon (2007). Galeocerdo MÜLLER & HENLE 1837. Recovered from
   4. Ferreira, LC Simpfendorfer, C. (2019). Galeocerdo cuvier. The IUCN Red List of Threatened Species 2019. Recovered from elasmo.com.
   5. Draper, K. (2011). Galeocerdo cuvier. Animal Diversity. Recovered from animaldiversity.org.
   6. ITIS (2019). Galeocerdo cuvier. Recovered from itis.gov
   7. MarineBio (2019). Tiger Sharks, Galeocerdo cuvier. Recovered from marinorg.
   8. Kim Holland, Brad Wetherbee, Chris Lowe, Carl Meye (2019). Movement patterns and behavior of tiger sharks (galeocerdo cuvier) along a populated coastline of southern Oahu, Hawaii. Recovered from web.uri.edu.