WhyReef - Lifestyle
| Common names: shark (English), tiburón (Espanol) |
Galeocerdo cuvier (Peron & Lesueur in Lesueur, 1822)
Head, and body stout but becoming very slender towards tail; snout very short, blunt and slightly rounded (its length 0.7-1.1 of distance between nostrils); long groove over top of mouth to under eye; spiracle a narrow slit behind large, round eye; mouth large, wide; characteristic cockscomb teeth (serrated, front edge convex, oblique tip with a deep notch on lower rear side); strong ridge on back between dorsal fins; origin of dorsal fin over posterior corner of pectoral fin; first dorsal fin not very large (height 7.5-9.3% of TL) tip pointed, rear edge concave; origin of second dorsal fin distinctly in front of anal fin origin; a low keel along each side of the narrow tail base; tail strongly asymmetric, with sharp pointed tip, large pointed lower lobe.
Adults grey with vertical bars on upper half of sides (sometimes faint or absent); young with large dark spots, some coalescing to form bars.
Size: attains > 550 cm (1 record to 740 cm).
Habitat: coastal pelagic, often in turbid areas, and estuaries, but also on reefs; retires to deeper water during the day, and feeds on shallow reefs at night.
Depth: 0-350 m.
Circumtropical; throughout our region.
WhyReef - Fun Facts
Global Endemism: All species, TEP non-endemic, Circumtropical ( Indian + Pacific + Atlantic Oceans), "Transpacific" (East + Central &/or West Pacific), All Pacific (West + Central + East), East Pacific + Atlantic (East +/or West), Transisthmian (East Pacific + Atlantic of Central America), East Pacific + all Atlantic (East+West)
Regional Endemism: All species, Eastern Pacific non-endemic, Tropical Eastern Pacific (TEP) non-endemic, Continent + Island (s), Continent, Island (s)
Climate Zone: North Temperate (Californian Province &/or Northern Gulf of California), Northern Subtropical (Cortez Province + Sinaloan Gap), Northern Tropical (Mexican Province to Nicaragua + Revillagigedos), Equatorial (Costa Rica to Ecuador + Galapagos, Clipperton, Cocos, Malpelo), South Temperate (Peruvian Province )
Tiger sharks are found in many subtropical and tropical waters, primarily from 45°N to 32°S. Tiger sharks have been sighted from the eastern coast of North America to the eastern coast of Brazil. This includes the coasts of southern North America, Mexico, and Latin America along the Gulf of Mexico. Tiger sharks also populate the coasts of China, India, Africa, Japan, and many islands of the Pacific Ocean.
Biogeographic Regions: nearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Native ); indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )
Other Geographic Terms: cosmopolitan
Little is known of the Tiger Shark's depth range. Clark and Kristof (1990) illustrate a female Tiger Shark of about 250 cm total length (TL) from a photograph taken from a submersible in 350 m of water off Grand Cayman. The species is also encountered in very shallow water.
Regularity: Regularly occurring
Type of Residency: Year-round
Tiger sharks are one of the largest carnivores in the ocean. Juveniles have tiger-like stripes, which fade as they grow older. Tiger sharks are blue or green in color with a light yellow or white under-belly. This speices has a large blunt nose on the end of a wedge-shaped head. Tiger sharks have serrated teeth, making it easy to tear flesh and crack the bones and shells of their prey. They have a heterocercal tail, meaning the dorsal lobe of the caudal fin is longer than the ventral lobe. Adults range from 3.25 to 4.25 m in length, although tiger sharks of 6 to 7.5 m in length have been documented. Female tiger sharks are on average 2.92 m in length and are smaller than males, which are on average 3.20 m in length. Adult tiger sharks typically weigh 385 to 635 kg, with largest sharks reaching 862 kg.
Range mass: 385 to 862 kg.
Range length: 3.25 to 7.5 m.
Average length: females 2.92 m; males 3.20 m.
Other Physical Features: ectothermic ; bilateral symmetry
Sexual Dimorphism: male larger
Catalog Number: USNM 231757
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Fishes
Locality: Java, Batavia, Java, Indonesia, Pacific
Inshore/Offshore: Inshore, Inshore Only
Water Column Position: Surface, Near Surface, Mid Water, Near Bottom, Bottom, Bottom + water column
Habitat: Reef (rock &/or coral), Reef and soft bottom, Reef associated (reef + edges-water column & soft bottom), Soft bottom (mud, sand,gravel, beach, estuary & mangrove), Estuary, Water column
FishBase Habitat: Pelagic
Tiger sharks are a saltwater species. Although they prefer the sea grass ecosystems of the costal areas, they occasionally inhabit other areas due to prey availability. Tiger sharks spend approximately 36 % of their time in shallow coastlne habitats (Heithaus et al., 2002), generally at depths of 2.5 to 145 m. This species, however, has been documented several kilometers from the shallow areas and at depths up to 350 m. Females are observed in shallow areas more often than males. Tiger sharks have also been documented in river estuaries and harbors
Range depth: 2.5 to 350 m.
Habitat Regions: temperate ; tropical ; saltwater or marine
Aquatic Biomes: pelagic ; reef ; coastal
Habitat and Ecology
The age and growth characteristics of Tiger Sharks have been investigated by a number of authors, most notably De Crosta et al. (1984) and Branstetter et al. (1987). Working in the north-west Hawaiian Islands De Crosta et al. (1984) estimated that a Tiger Shark with a precaudal length of 200 cm is about five years old and that one of 300 cm is about 15 years old. Branstetter et al. (1987) used similar techniques to De Crosta et al. (1984) to produce growth curves for Tiger Sharks from the coast of Virginia and the northern Gulf of Mexico. They estimated that initial growth was very fast, but that the rate of growth of very large animals is 5-10 cm year-1; thus, individuals of 400-450 cm TL would be 20-25 years of age. Branstetter et al. (1987) gave a maximum age of 45-50 years. Smith et al. (1998) estimated the intrinsic rate of increase of a tiger shark population at MSY to be 0.043 year-1. Randall (1992) summarised that the size at maturity of male Tiger Sharks is 226-290 cm TL and in females 250-350 cm TL.
The Tiger Shark is the only species of the family Carcharhinidae that is ovoviviparous. Litter sizes are large, with between 10-82 embryos reported from a single female. Mean litter sizes of 30-35 have been reported (Tester 1969, Bass et al. 1975, Simpfendorfer 1992). The size at birth is 51-90 cm TL (Randall 1992, Simpfendorfer 1992). Clark and von Schmidt (1965) gave the gestation period as 13-16 months. There have been few other estimates of gestation period. Mating is reported to take place in the Northern Hemisphere in spring, with pupping the following spring to summer. Mating occurs before full-term females have given birth to young, indicating that litters are produced every two years or less. In the Southern Hemisphere Stevens and McLoughlin (1991) and Simpfendorfer (1992) have reported pupping during summer. The young are very slender with a flexible body and caudal fin; they swim with an inefficient anguilliform motion. Branstetter et al. (1987) concluded that they are probably very vulnerable to predation at this stage, especially by sharks, including their own kind.
Tagging studies, particularly in the western Atlantic, have provided the best information on the movements of Tiger Sharks. Randall (1992) provided data from a range of studies that indicated that two patterns of movement are observed in tagging studies. The first of these is where the release and recapture positions are close together, suggesting that the individual may have remained in a relatively small area. The other pattern observed is where the individual is recaptured a long distance from the release site, often after a short period at liberty. The maximum reported distance between release and recapture for a Tiger Shark was approximately 3,430 km.
Habitat Type: Marine
Water temperature and chemistry ranges based on 604 samples.
Depth range (m): 0 - 8290
Temperature range (°C): 2.068 - 26.525
Nitrate (umol/L): 0.171 - 31.613
Salinity (PPS): 34.202 - 36.558
Oxygen (ml/l): 2.718 - 6.202
Phosphate (umol/l): 0.083 - 2.007
Silicate (umol/l): 0.777 - 59.370
Depth range (m): 0 - 8290
Temperature range (°C): 2.068 - 26.525
Nitrate (umol/L): 0.171 - 31.613
Salinity (PPS): 34.202 - 36.558
Oxygen (ml/l): 2.718 - 6.202
Phosphate (umol/l): 0.083 - 2.007
Silicate (umol/l): 0.777 - 59.370
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
Recorded at 350 meters.
Habitat: pelagic. Tiger shark. (Peron & Lesueur, 1822) Vivaparous 23 - 46 pups. Attains 4.1 metres in our area; pups born at about 70 cm. Scavenger / Predator noted for indiscriminate feeding habits. The fearsome teeth, enormous size ( up to 5.5 metres in some areas ) and powerful jaws make it a formidable predator easily able to bite through the bony shell of a turtle or cut a large shark in half. Their usual food is sharks, rays and various other fishes. They also consume sea birds, marine mammals and a variety of the miscellaneous rubbish that man dumps in the sea. May attack man and is greatly feared by men wrecked beyond the reefs, but is more likely to feed upon humans already dead from other causes. A tropical species found in all major oceans; ranges south to Natal ( chiefly juveniles and adolescents ) and rarely to the Cape. An embryo from a large female caught at Cape St. Francis is in the Natal museum. A great deal of excitement was caused when these sharks were discovered sleeping in caves on the east coast of Mexico as it was always maintained that most streamlined sharks had to keep swimming to pass water through their gills to allow the required oxygen to be extracted. As far as is known these sharks have not been found sleeping in any other area and there is a theory that fresh water seeps into these caves causing a narcotic effect on the sharks which makes them extremely docile and approachable by divers. It is further theorised that the high freshwater content may loosen or kill parasites on the body of the shark.
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Diet: mobile benthic crustacea (shrimps/crabs), mobile benthic gastropods/bivalves, octopus/squid/cuttlefish, bony fishes, sharks/rays, sea snakes/mammals/turtles/birds
The diet of tiger sharks includes mollusks, birds, snakes, crustaceans, sea turtles, and dugongs. Serrated teeth give this species the ability to penetrate the shells of sea turtles. Tiger sharks often scavenge dead or injured whales, and large tiger sharks can survive several weeks without feeding. This species most likely relies on stealth rather than strength and speed to catch prey. They are well camouflaged, allowing them to get within striking range of prey. If prey flee, tiger sharks may back off, not taking part in high-speed pursuits. However, tiger sharks are capable of short bursts of speed once their prey are within range.
Animal Foods: birds; mammals; reptiles; fish; carrion ; mollusks; other marine invertebrates
Primary Diet: carnivore (Eats non-insect arthropods, Molluscivore )
As top predators in their ecosystem, it is possible that tiger sharks control populations of prey species, although this has not been verified. Tiger sharks also serve as a host for remoras, which are small suckerfish. Tiger sharks and remoras share a commensal relationship: remoras attach to tiger sharks near the underbelly, and use the shark for transportation and protection. Remoras also feed on materials dropped by tiger sharks. Recently, copepods, specifically sea louse, have been discovered around the eyes of tiger sharks in Australia.
- Remoras Echeneidae
- Sea louse Caligus oculicola
Tiger sharks are some of the largest predators in the ocean and have few species feed on them. Some juvenile tiger sharks, however, fall prey to other sharks. Female tiger sharks gives birth in a nursery, which provides protection during the birthing process and to pups in the absence of parents. The coloration of tiger sharks provides camouflage against predators as well. Humans also fish for tiger sharks.
- humans Homo sapiens
Anti-predator Adaptations: cryptic
Known prey organisms
This list may not be complete but is based on published studies.
WhyReef - Menu
Life History and Behavior
Tiger sharks rely on electromagnetic receptors to perceive their environment and to hunt prey. Sensing organs called Ampullae of Lorenzini, located on the end of their nose, are filled with a jelly-like substance that reads electromagnetic signals. These signals are sent from the pores to the sensory nerve, and then to the brain. While hunting, tiger sharks uses this ability to detect electromagnetic signals given off by fish. Tiger sharks also use these organs to sense changes in water pressure and temperature (Plessis, 2010). Members of this species also have a lateral line on both sides of the body that runs from the gill line to the base of the tail. The lateral line reads the vibrations in the water from the movement of other animals nearby. Ampullae of Lorenzini and lateral lines also help detect electromagnetic signals from other sharks. While communally feeding on carcasses, sharks give off signals signifying dominance and thus the order in which they feed.
Communication Channels: visual ; electric
Perception Channels: tactile ; vibrations ; electric ; magnetic
Embryos of tiger sharks are fertilized internally. A yolk sac forms around the embryos to provide necessary nutrients during the 13 to 16 month gestation period. As the yolk begins to run out near the end of the gestation period, the embryo draws nutrients directly from the mother. At birth, tiger sharks are fully developed and independent. They are born with tiger-like stripes on their back and a lightly colored yellow or white belly which allows them to blend in with the environment. These stripes fade as the juveniles reach adulthood, which is around 6 to 8 years. Males reach maturity earlier than females.
The average lifespan of tiger sharks in the wild is 27 years, though some may live to 50 years of age. Tiger sharks in captivity do not live as long, a maximum of 17 to 20 years. In captivity, this species tends to die of starvation rather than old age, as food that is already dead is less appealing to tiger sharks.
Status: wild: 50 (high) years.
Status: captivity: 20 (high) years.
Status: wild: 27 years.
Status: captivity: 17 (high) years.
Lifespan, longevity, and ageing
Tiger sharks are polygynandrous, meaning males and females have multiple mates; they do not pair-bond at any time. Not much is known regarding the the behaviors of finding, attracting, and defending mates of tiger sharks.
Mating System: polygynandrous (promiscuous)
Male tiger sharks reach sexual maturity when they reach an average length of 292 cm, whereas females reach sexual maturity when 330 to 345 cm in length. Females mate once every three years. Breeding seasons differ in the northern and southern hemispheres. In the northern hemisphere, females delay fertilization until March or May in order to give birth between May and June of the following year. In the southern hemisphere, females delay mating until November or January in order to give birth between February and March of the following year. Tiger sharks are one of the few species that are ovoviviparous. Females give birth to 10 to 80 pups per litter after a gestation period of 16 months. Many of these pups will not survive to adulthood. Pups weigh 3 to 6 kg at birth.
Male tiger sharks have diametric testes, which are capable of synthesizing a larger amount of sperm than radial or compound testes. The females have external ovaries that appear on the epigonal organ, which is a primary lymphoid tissue in elasmobranchs.
Breeding interval: every three years
Breeding season: Northern Hemisphere: March-May to April-June of following year. Southern Hemisphere: November-December
Range number of offspring: 3 to 80.
Average number of offspring: 35-55.
Range gestation period: 13 to 16 months.
Range time to independence: 1 (low) minutes.
Average age at sexual or reproductive maturity (female): 8 years.
Average age at sexual or reproductive maturity (male): 7 years.
Key Reproductive Features: seasonal breeding ; sexual ; fertilization (Internal ); ovoviviparous ; delayed fertilization
Average age at sexual or reproductive maturity (male)
Sex: male: 1825 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 2555 days.
Female tiger sharks typically gives birth in a nursery, which provides protection during birth and to the young directly after birth. Tiger sharks are born independent, and mothers do not help their pups to find food, shelter or to survive. Males play no role in the lives of their offspring. Pups, however, are born with traits that help them survive without parents, including camouflage patterning, teeth to help capture prey, and speed to avoid predators.
Parental Investment: no parental involvement; pre-hatching/birth (Provisioning: Female, Protecting: Female)
Molecular Biology and Genetics
Barcode data: Galeocerdo cuvier
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
-- end --
Download FASTA File
Statistics of barcoding coverage: Galeocerdo cuvier
Public Records: 172
Specimens with Barcodes: 240
Species With Barcodes: 1
CITES: Not listed
Currently, the total number of tiger sharks worldwide is unknown. However, they are listed as near threatened on the IUCN Red List. One major initiative to protect this species has been the limitation of the number of sharks taken by fisherman (i.e., one per vessel with a specific license).
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: near threatened
IUCN Red List Assessment
Red List Category
Red List Criteria
This large (>550 cm), omnivorous shark is common world wide in tropical and warm-temperate coastal waters. It is a relatively fast growing and fecund species. The Tiger Shark (Galeocerdo cuvier) is caught regularly in target and non-target fisheries. There is evidence of declines for several populations where they have been heavily fished, but in general they do not face a high risk of extinction. However, continued demand, especially for fins, may result in further declines in the future.
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
NatureServe Conservation Status
Rounded Global Status Rank: GNR - Not Yet Ranked
In the US East Coast/Gulf of Mexico shark fishery tiger sharks are the third most common large, coastal species caught in the fishery, accounting for 12-20% of the catch (GSAFDF 1996). However, they account for only 5% of the landed weight as they are considered of limited value since finning is not allowed in this fishery. Most of the individuals caught in this fishery are juveniles less than 150 cm FL, although large animals are also taken (S. Branstetter pers. comm.).
In northern Australia gillnet fisheries catch Tiger Sharks, although the mesh sizes used have precluded the capture of significant numbers (Lyle et al. 1984). In northern West Australia a number of fishers have used heavy drumlines to fish for large sharks. Tiger Sharks have been a major target of these fishers, with catches reaching 116 t (live weight) in 1994/95 (Simpfendorfer and Lenanton 1995). All operators who have targeted Tiger Sharks in this area have now ceased fishing.
Tiger Sharks are taken as bycatch in a variety of fisheries including tuna and swordfish longline fisheries (e.g., Anderson 1985, Berkeley and Campos 1988), particularly those operating on, or close to, the continental and insular shelves. They are also taken in trawl fisheries (e.g., squid, fish and crustacean trawl fisheries), although normally in small numbers. There are few records of Tiger Shark catches for these fisheries. Tiger Sharks are undoubtedly caught in tropical and subtropical artisanal fisheries. However, gear limitations in these fisheries probably precludes the capture of large numbers, especially of larger individuals. There are few published data on artisanal fishery captures and it is not possible to quantify catches or the impact that these may have on Tiger Shark populations.
Tiger Sharks are caught by recreational fishers. The species is one that has International Game Fish Association (IGFA) status, the current record being 596 kg. Catches have been documented off the east coast of the United States, Australia and South Africa (e.g., Stevens 1984, Anderson 1985, Casey and Hoey 1985, Pepperell 1992, Anon. 1994). Estimates of total catches of shark by recreational anglers off the east coast of the United States (including the Gulf of Mexico) in 1978 are 10,300 t (Casey and Hoey 1985) and in 1980 over 15,000 t (Anderson 1985). Estimates of the species composition of the recreational catch indicates that Tiger Sharks represent 0.8-2.1% of the catch. Based on these estimates of species composition, the recreational Tiger Shark catches in 1978 and 1980 would have been approximately 10-20 t and 15-30 t, respectively. More recently recreational catches have declined, and tagging and release has become more common. In Australian waters Pepperell (1992) estimated that Tiger Sharks represented approximately 10% of the sharks captured by IGFA associated clubs off the New South Wales coast during the 1970s. This increased to approximately 20% during the 1980s, due to increased targeting. Size composition data provided by Pepperell (1992) indicate that the bulk of the catch was 80-130 kg. Stevens (1984) estimated that Tiger Sharks comprised 17% of the recreational catch by anglers off New South Wales between 1979 and 1982, based on catch sampling.
Tiger Sharks are undoubtedly caught by recreational fishers in many countries, and not only those documented above. Recreational fishing is likely to account for significant mortality in Tiger Shark populations in coastal waters of some countries.
The large size, and propensity to occasionally attack humans, makes Tiger Sharks a target of shark control programmes, particularly those operating in tropical areas (e.g., Queensland (Paterson 1990) and Hawaii (Wetherbee et al. 1994)). However, they are also taken in other programmes (e.g., South Africa (Dudley and Cliff 1993) and New SouthWales (Reid and Krough 1992)). These control programmes use either large mesh gillnets and/or heavy lines to capture large, dangerous sharks. The theory behind the programmes is that fishing reduces the abundance of the large, dangerous sharks and so reduces the probability of attacks in areas where there has previously been relatively high records of shark attacks. There is conflicting evidence as to whether these control programmes are effective in reducing the abundance of Tiger Sharks. Evidence from Paterson (1990), Simpfendorfer (1992) and Dudley and Cliff (1993) indicates that Tiger Shark abundance has either remained steady, or even increased in "meshed" areas. Catch rate data from Hawaii indicated that shark control programmes did reduce Tiger Shark abundance (Wetherbee et al. 1994). These data suggest that at best the use of shark control programmes to reduce population levels of Tiger Sharks may be of only limited value.
Tiger Shark populations face a variety of threats. These include not only a large range of directed and bycatch fisheries, but also problems such as the ingestion of human garbage. The high value of some products (especially fins) from Tiger Sharks has resulted in increased fishing pressures on this species in recent years. Musick et al. (1993) noted a precipitous decline in Tiger Sharks off Virginia, USA, due to both recreational and commercial harvesting between 1980 and 1992. There is anecdotal evidence that in areas where catches in commercial fisheries are high, abundance has been significantly reduced (e.g., Taiwan (POC) (Bonfil 1994)). There is some evidence from shark control programmes that localised catches of Tiger Sharks do not affect abundance.
The widespread distribution of this species increases the likelihood that it will survive increasing levels of exploitation in certain areas. Its growth and reproductive rates are also relatively high, making the levels of mortality that the Tiger Shark can survive higher than for many other species of shark. Additionally, juvenile survivorship increases where adult Tiger Shark populations have been depleted by fisheries and hence predation of young is lessened. However, the overall life history constraints to increased mortality applicable to all sharks must also be borne in mind when considering the conservation status of this species.
WhyReef - Threats
Relevance to Humans and Ecosystems
Although very unlikely, tiger sharks enter shallow, populated areas of coast and attack humans on rare occasions.
Negative Impacts: injures humans (bites or stings)
Tiger sharks are a popular gamefish, which are typically captured and released for sport. They are very strong, fast and perform aerial acts when hooked. Fishing for these sharks is tiring, as tiger sharks are not quickly or easily exhausted. In some states, permits such as a saltwater fishing license allow fishermen to collect the shark as a trophy.
Positive Impacts: food
The tiger shark (Galeocerdo cuvier) is a species of requiem shark and the only member of the genus Galeocerdo. Commonly known as the "Sea Tiger", the tiger shark is a relatively large macropredator, capable of attaining a length over 5 m (16 ft). It is found in many tropical and temperate waters, and it is especially common around central Pacific islands. Its name derives from the dark stripes down its body which resemble a tiger's pattern, which fade as the shark matures.
The tiger shark is a solitary, mostly nocturnal hunter, and is notable for having the widest food spectrum of all sharks, consuming a variety of prey ranging from crustaceans, fish, seals, birds, squid, turtles, and sea snakes to dolphins and even other smaller sharks. The tiger shark has been known to eat inedible manmade objects that linger in its stomach, and it has a reputation as a "garbage eater". The tiger shark is considered a near threatened species due to finning and fishing by humans.
The shark was first described by Peron and Lessueur in 1822, and was given the name Squalus cuvier. Müller and Henle in 1837 renamed it Galeocerdo tigrinus. The genus, Galeocerdo, is derived from the Greek galeos, which means shark, and the Latin cerdus, the word for the hard hairs of pigs. It is often colloquially called the man-eater shark.
The tiger shark is a member of the order Carcharhiniformes, the most species-rich order of sharks, with more than 270 species also including the small catsharks and hammerhead sharks. Members of this order are characterized by the presence of a nictitating membrane over the eyes, two dorsal fins, an anal fin, and five gill slits. It is the largest member of the Carcharhinidae family, commonly referred to as requiem sharks. This family consists of mostly slender but powerful mid- to large-sized sharks and includes some other well-known sharks, such as the blue shark (Prionace glauca), lemon shark (Negaprion brevirostris), and bull shark (Carcharhinus leucas).
Distribution and 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.
Tiger sharks can be seen in the Gulf of Mexico, North American beaches, and parts of South America. It is also commonly known in the Caribbean Sea. Other locations where tiger sharks are seen include off Africa, China, Hong Kong, India, Australia, and Indonesia.
Certain tiger sharks have been recorded at depths just shy of 900 m (3,000 ft), 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 (1,100 ft), 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 (10 ft) and regularly observed in coastal waters at depths of 6 to 12 m (20 to 40 ft).
Anatomy and appearance
Among the largest extant sharks, the tiger shark ranks in size only behind the whale shark (Rhincodon typus), the basking shark (Cetorhinus maximus), the great white shark (Carcharodon carcharias), and the great hammerhead (Sphyrna mokarran). Very large specimens of some other species such as megamouth sharks (Megachasma pelagios), Pacific sleeper sharks (Somniosus pacificus), Greenland sharks (Somniosus microcephalus), and bluntnose sixgill sharks (Hexanchus griseus) can attain similar sizes as tiger sharks. The tiger shark commonly attains a length of 3.25–4.25 m (10.7–13.9 ft) and weighs around 385–635 kg (849–1,400 lb). Sometimes, an exceptionally large male tiger shark can grow up to 4.5 m (15 ft). Females are larger, and exceptionally big ones can reportedly measure over 5 m (16 ft). According to Guinness World Records, one female specimen caught off Australia reportedly measured 5.5 m (18 ft) long and weighed an exceptional 1,524 kg (3,360 lb), 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.
The skin of a tiger shark can typically range from blue to light green with a white or light-yellow underbelly. The advantage of this is that when it is hunting for its prey, when prey looks at the shark from above, the shark will be camouflaged since the water below is darker. And when prey is below the shark and looks up, of course because of the sun, it is lighter so that the light underbelly will also camouflage the shark. This is known as countershading. Dark spots and stripes are most visible in young sharks and fade as the shark matures. Its head is somewhat wedge-shaped, which makes it easy to turn quickly to one side. They have small pits on the snout which hold electroreceptors called the ampullae of Lorenzini, which enable them to detect electric fields, including the weak electrical impulses generated by prey, which helps them to hunt. Tiger sharks also have a sensory organ called a lateral line which extends on their flanks down most of the length of their sides. The primary role of this structure is to detect minute vibrations in the water. These adaptations allow the tiger shark to hunt in darkness and detect hidden prey.
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, enhancing vision in low light conditions. 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. Tiger sharks normally swim using small body movements. Its high back and dorsal fin act as a pivot, allowing it to spin quickly on its axis, though the shark's dorsal fins are distinctively close to its tail.
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.
The tiger shark is an apex predator and has a reputation for eating anything. 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 (7.5 ft), 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 (e.g. bottlenose dolphins (Tursiops), common dolphins (Delphinus), spotted dolphins (Stenella), dugongs (Dugong dugon), seals and sea lions), and sea turtles (including the three largest species: the leatherback (Dermochelys coriacea), the loggerhead (Caretta caretta) and the green sea turtles (Chelonia mydas),) are regularly eaten by adult tiger sharks. The tiger shark also eats other sharks (including adult sandbar sharks (Carcharhinus plumbeus)), as well as rays, and will sometimes even eat other tiger sharks.
Due to high risk of predatory attacks, dolphins often avoid regions inhabited by tiger sharks. Tiger sharks may also attack injured or ailing whales and prey upon them. A group was documented attacking and killing an ailing humpback whale (Megaptera novaeangliae) 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 (Equus ferus caballus), goats (Capra aegagrus hircus), sheep (Ovis aries), dogs (Canis lupus familiaris), cats (Felis catus) and brown rats (Rattus norvegicus), are fairly common in the stomach contents of tiger sharks around the coasts of Hawaii. Because of its aggressive and indiscriminate feeding style, it often mistakenly eats inedible objects, such as automobile license plates, oil cans, tires, and baseballs.
Swimming efficiency and stealth
All tiger sharks generally swim slowly, which, combined with cryptic coloration, may make them difficult for prey to detect them in some habitats. They are especially well camouflaged against dark backgrounds. Despite their sluggish appearance, tiger sharks are one of the strongest swimmers of the carcharhinid sharks. Once the shark has come close, a speed burst allows it to reach the intended prey before it can escape.
Males reach sexual maturity at 2.3 to 2.9 m (7.5 to 9.5 ft) and females at 2.5 to 3.5 m (8.2 to 11.5 ft). Females mate once every three years. They breed by internal fertilization. The male inserts one of his claspers into the female's genital opening (cloaca), 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 for up to 16 months. Litters range from 10 to 80 pups. A newborn is generally 51 to 76 cm (20 to 30 in) long. This shark typically reaches maturity at lengths of 2 to 3 m (6.6 to 9.8 ft). It is unknown how long tiger sharks live, but they can live longer than 12 years.
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. Tiger sharks 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.
Relationship with humans
Although shark attacks are a relatively rare phenomenon, the tiger shark is responsible for a large percentage of fatal attacks and is regarded as one of the most dangerous shark species. They often visit shallow reefs, harbors, and canals, creating the potential for encounter with humans. The tiger shark also dwells in river mouths and other runoff-rich water. While the tiger shark is considered to be one of the sharks most dangerous to humans, its attack rate is low. The tiger is second on the list of number of recorded attacks on humans, with the great white shark being first. On average, three to four shark attacks occur per year in Hawaii, and most attacks are not fatal. This attack rate is surprisingly low considering thousands of people swim, surf, and dive in Hawaiian waters every day. Attacks by tiger sharks in Hawaiian waters have been shown to increase between September and November, when tiger shark females are believed to migrate to the islands to give birth.
Between 1959 and 2000, 4,668 tiger sharks were culled in an effort to protect the tourism industry. Despite these efforts, attacks did not decrease. It is illegal to feed sharks in Hawaii (except for traditional Hawaiian cultural or religious practices), and interaction with them, such as cage diving, is discouraged. South African shark behavioralist and shark diver Mark Addison demonstrated divers could interact and dive with them outside of a shark cage in a 2007 Discovery Channel special, and underwater photographer Fiona Ayerst swam with them in the Bahamas.
The tiger shark is considered to be sacred na ʻaumakua (ancestor spirits) by some native Hawaiians who think their eyeballs have special powers of visual perception. This aligns with the general known facts about sharks and their highly developed senses.
- For a topical guide to this subject, see Outline of sharks.
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