| Great white shark | |||
|---|---|---|---|
| |||
| General information | |||
| Universe | Real Life | ||
| Aliases | Great white White pointer White shark | ||
| Classification | Carcharodon carcharias | ||
| Species type | Shark | ||
| Homeworld | Earth | ||
| Environment | Ocean | ||
| Intelligence | Non-sapient | ||
| Biochemistry | Carbon-based | ||
| Biological information | |||
| Lifespan | Wild: 30-70 years Captivity: 6 months | ||
| Reproduction | Sexual, viviparous | ||
| Average weight | ♂: 522–771 kg (1,151–1,700 lb) ♀: 680–1,110 kg (1,500–2,450 lb) | ||
| Average length | ♂: 3.4 to 4.0 m (11 to 13 ft) ♀: 4.6 to 4.9 m (15 to 16 ft) | ||
| Locomotion | Powered swimming | ||
| Feeding behavior | Carnivorous | ||
| Prey | Earless seals Sea otters Tuna Rays Dolphins Porpoises Whales Fur seals Sea lions Sea turtles Seabirds | ||
| Predators | Orcas | ||
| Lineage information | |||
| Related species | Carcharodon caifassii† Carcharodon hubbelli† | ||
| Cultural information | |||
| Sociocultral characteristics | |||
| Scientific taxonomy | |||
| Planet | Earth | ||
| Domain | Eukaryota | ||
| Kingdom | Animalia | ||
| Subkingdom | Bilateria | ||
| Infrakingdom | Deuterostomia | ||
| Phylum | Chordata | ||
| Subphylum | Vertebrata | ||
| Infraphylum | Gnathostomata | ||
| Class | Chondricthyes (Cartilaginous fishes) | ||
| Subclass | Elasmobranchii | ||
| Infraclass | Euselachii | ||
| Superorder | Selachimorpha (Sharks) | ||
| Order | Lamniformes (Mackerel sharks) | ||
| Family | Lamnidae | ||
| Genus | Carcharodon | ||
| Species | C. carcharias | ||
| Other information | |||
| Status | Vulnerable | ||
| Creator | God (debated) | ||
The great white shark (Carcharodon carcharias) is one of the most well-known sharks alive today.
Anatomy and appearance[]
The great white shark has a robust, large, conical snout. The upper and lower lobes on the tail fin are approximately the same size which is similar to some mackerel sharks. A great white displays countershading, by having a white underside and a grey dorsal area (sometimes in a brown or blue shade) that gives an overall mottled appearance. The coloration makes it difficult for prey to spot the shark because it breaks up the shark's outline when seen from the side. From above, the darker shade blends with the sea and from below it exposes a minimal silhouette against the sunlight. Leucism is extremely rare in this species, but has been documented in one great white shark (a pup that washed ashore in Australia and died). Great white sharks, like many other sharks, have rows of serrated teeth behind the main ones, ready to replace any that break off. When the shark bites, it shakes its head side-to-side, helping the teeth saw off large chunks of flesh. Great white sharks, like other mackerel sharks, have larger eyes than other shark species in proportion to their body size. The iris of the eye is a deep blue instead of black.
Size[]
In great white sharks, sexual dimorphism is present, and females are generally larger than males. Male great whites on average measure 3.4 to 4.0 m (11 to 13 ft) long, while females at 4.6 to 4.9 m (15 to 16 ft). Adults of this species weigh 522–771 kg (1,151–1,700 lb) on average; however, mature females can have an average mass of 680–1,110 kg (1,500–2,450 lb). The largest females have been verified up to 6.1 m (20 ft) in length and an estimated 1,905 kg (4,200 lb) in weight, perhaps up to 2,268 kg (5,000 lb). The maximum size is subject to debate because some reports are rough estimations or speculations performed under questionable circumstances. Among living cartilaginous fish, only the whale shark (Rhincodon typus), the basking shark (Cetorhinus maximus) and the giant manta ray (Manta birostris), in that order, are on average larger and heavier. These three species are generally quite docile in disposition and given to passively filter-feeding on very small organisms. This makes the great white shark the largest extant macropredatory fish. Great white sharks are at around 1.2 m (3.9 ft) when born, and grow about 25 cm (9.8 in) each year.
According to J. E. Randall, the largest white shark reliably measured was a 5.94 m (19.5 ft) individual reported from Ledge Point, Western Australia in 1987. Another great white specimen of similar size has been verified by the Canadian Shark Research Center: A female caught by David McKendrick of Alberton, Prince Edward Island, in August 1988 in the Gulf of St. Lawrence off Prince Edward Island. This female great white was 6.1 m (20 ft) long. However, there was a report considered reliable by some experts in the past, of a larger great white shark specimen from Cuba in 1945. This specimen was reportedly 6.4 m (21 ft) long and had a body mass estimated at 3,324 kg (7,328 lb). However, later studies also revealed that this particular specimen was actually around 4.9 m (16 ft) in length, a specimen in the average maximum size range.
The largest great white recognized by the International Game Fish Association (IGFA) is one caught by Alf Dean in south Australian waters in 1959, weighing 1,208 kg (2,663 lb). Several larger great whites caught by anglers have since been verified, but were later disallowed from formal recognition by IGFA monitors for rules violations.
Examples of large unconfirmed great whites[]
A number of very large unconfirmed great white shark specimens have been recorded. For decades, many ichthyological works, as well as the Guinness Book of World Records, listed two great white sharks as the largest individuals: In the 1870s, a 10.9 m (36 ft) great white captured in southern Australian waters, near Port Fairy, and an 11.3 m (37 ft) shark trapped in a herring weir in New Brunswick, Canada, in the 1930s. However, these measurements were not obtained in a rigorous, scientifically valid manner, and researchers have questioned the reliability of these measurements for a long time, noting they were much larger than any other accurately reported sighting. Later studies proved these doubts to be well-founded. This New Brunswick shark may have been a misidentified basking shark, as the two have similar body shapes. The question of the Port Fairy shark was settled in the 1970s when J. E. Randall examined the shark's jaws and "found that the Port Fairy shark was of the order of 5 m (16 ft) in length and suggested that a mistake had been made in the original record, in 1870, of the shark's length". These wrong measurements would make the alleged shark more than five times heavier than it really was.
While these measurements have not been confirmed, some great white sharks caught in modern times have been estimated to be more than 7 m (23 ft) long, but these claims have received some criticism. However, J. E. Randall believed that great white shark may have exceeded 6.1 m (20 ft) in length. A great white shark was captured near Kangaroo Island in Australia on 1 April 1987. This shark was estimated to be more than 6.9 m (23 ft) long by Peter Resiley, and has been designated as KANGA. Another great white shark was caught in Malta by Alfredo Cutajar on 16 April 1987. This shark was also estimated to be around 7.13 m (23.4 ft) long by John Abela and has been designated as MALTA. However, Cappo drew criticism because he used shark size estimation methods proposed by J. E. Randall to suggest that the KANGA specimen was 5.8–6.4 m (19–21 ft) long. In a similar fashion, I. K. Fergusson also used shark size estimation methods proposed by J. E. Randall to suggest that the MALTA specimen was 5.3–5.7 m (17–19 ft) long. However, photographic evidence suggested that these specimens were larger than the size estimations yielded through Randall's methods. Thus, a team of scientists—H. F. Mollet, G. M. Cailliet, A. P. Klimley, D. A. Ebert, A. D. Testi, and L. J. V. Compagno—reviewed the cases of the KANGA and MALTA specimens in 1996 to resolve the dispute by conducting a comprehensive morphometric analysis of the remains of these sharks and re-examination of photographic evidence in an attempt to validate the original size estimations and their findings were consistent with them. The findings indicated that estimations by P. Resiley and J. Abela are reasonable and could not be ruled out. A particularly large female great white nicknamed "Deep Blue", estimated measuring at 6.1 m (20 ft) was filmed off Guadalupe during shooting for the 2014 episode of Shark Week "Jaws Strikes Back". Deep Blue would also later gain significant attention when she was filmed interacting with researcher Mauricio Hoyas Pallida in a viral video that Mauricio posted on Facebook on 11 June 2015. Deep Blue was later seen off Oahu in January 2019 while scavenging a sperm whale carcass, whereupon she was filmed swimming beside divers including dive tourism operator and model Ocean Ramsey in open water. In July 2019, a fisherman, J. B. Currell, was on a trip to Cape Cod from Bermuda with Tom Brownell when they saw a large shark about 40 mi (64 km) southeast of Martha's Vineyard. Recording it on video, he said that it weighed about 5,000 lb (2,300 kg), and measured 25–30 ft (7.6–9.1 m), evoking a comparison with the fictional shark Jaws. The video was shared with the page "Troy Dando Fishing" on Facebook. A particularly infamous great white shark, supposedly of record proportions, once patrolled the area that comprises False Bay, South Africa, was said to be well over 7 m (23 ft) during the early 1980s. This shark, known locally as the "Submarine", had a legendary reputation that was supposedly well-founded. Though rumours have stated this shark was exaggerated in size or non-existent altogether, witness accounts by the then young Craig Anthony Ferreira, a notable shark expert in South Africa, and his father indicate an unusually large animal of considerable size and power (though it remains uncertain just how massive the shark was as it escaped capture each time it was hooked). Ferreira describes the four encounters with the giant shark he participated in with great detail in his book "Great White Sharks On Their Best Behavior".
One contender in maximum size among the predatory sharks is the tiger shark (Galeocerdo cuvier). While tiger sharks which are typically both a few feet smaller and have a leaner, less heavy body structure than white sharks, have been confirmed to reach at least 5.5 m (18 ft) in the length, an unverified specimen was reported to have measured 7.4 m (24 ft) in length and weighed 3,110 kg (6,860 lb), more than two times heavier than the largest confirmed specimen at 1,524 kg (3,360 lb). Some other macropredatory sharks such as the Greenland shark (Somniosus microcephalus) and the Pacific sleeper shark (S. pacificus) are also reported to rival these sharks in length (but probably weigh a bit less since they are more slender in build than a great white) in exceptional cases. The question of maximum weight is complicated by the unresolved question of whether or not to include the shark's stomach contents when weighing the shark. With a single bite a great white can take in up to 14 kg (31 lb) of flesh and can also consume several hundred kilograms of food.
Adaptations[]
Great white sharks, like all other sharks, have an extra sense given by the ampullae of Lorenzini which enables them to detect the electromagnetic field emitted by the movement of living animals. Great whites are so sensitive they can detect variations of half a billionth of a volt[citation needed]. At close range, this allows the shark to locate even immobile animals by detecting their heartbeat[citation needed]. Most fish have a less-developed but similar sense using their body's lateral line.
To more successfully hunt fast and agile prey such as sea lions, the great white has adapted to maintain a body temperature warmer than the surrounding water. One of these adaptations is a "rete mirabile" (Latin for "wonderful net"). This close web-like structure of veins and arteries, located along each lateral side of the shark, conserves heat by warming the cooler arterial blood with the venous blood that has been warmed by the working muscles. This keeps certain parts of the body (particularly the stomach) at temperatures up to 14 °C (25 °F) above that of the surrounding water, while the heart and gills remain at sea temperature. When conserving energy, the core body temperature can drop to match the surroundings. A great white shark's success in raising its core temperature is an example of gigantothermy. Therefore, the great white shark can be considered an endothermic poikilotherm or mesotherm because its body temperature is not constant but is internally regulated. Great whites also rely on the fat and oils stored within their livers for long-distance migrations across nutrient-poor areas of the oceans. Studies by Stanford University and the Monterey Bay Aquarium published on 17 July 2013 revealed that in addition to controlling the sharks' buoyancy, the liver of great whites is essential in migration patterns. Sharks that sink faster during drift dives were revealed to use up their internal stores of energy quicker than those which sink in a dive at more leisurely rates.
Toxicity from heavy metals seems to have little negative effects on great white sharks. Blood samples taken from forty-three individuals of varying size, age and sex off the South African coast led by biologists from the University of Miami in 2012 indicates that despite high levels of mercury, lead, and arsenic, there was no sign of raised white blood cell count and granulate to lymphocyte ratios, indicating the sharks had healthy immune systems. This discovery suggests a previously unknown physiological defence against heavy metal poisoning. Great whites are known to have a propensity for "self-healing and avoiding age-related ailments".
Bite force[]
A 2007 study from the University of New South Wales in Sydney, Australia, used CT scans of a shark's skull and computer models to measure the shark's maximum bite force. The study reveals the forces and behaviours its skull is adapted to handle and resolves competing theories about its feeding behaviour. In 2008, a team of scientists led by Stephen Wroe conducted an experiment to determine the great white shark's jaw power and findings indicated that a specimen massing 3,324 kg (7,328 lb) could exert a bite force of 18,216 newtons (4,095 lbf).
Ecology and behavior[]
This shark's behaviour and social structure are complex. In South Africa, white sharks have a dominance hierarchy depending on the size, sex and squatter's rights: Females dominate males, larger sharks dominate smaller sharks, and residents dominate newcomers. When hunting, great whites tend to separate and resolve conflicts with rituals and displays. White sharks rarely resort to combat although some individuals have been found with bite marks that match those of other white sharks. This suggests that when a great white approaches too closely to another, they react with a warning bite. Another possibility is that white sharks bite to show their dominance.
The great white shark is one of only a few sharks known to regularly lift its head above the sea surface to gaze at other objects such as prey. This is known as spy-hopping. This behaviour has also been seen in at least one group of blacktip reef sharks, but this might be learned from interaction with humans (it is theorized that the shark may also be able to smell better this way because smell travels through air faster than through water). White sharks are generally very curious animals, display intelligence and may also turn to socializing if the situation demands it. At Seal Island, white sharks have been observed arriving and departing in stable "clans" of two to six individuals on a yearly basis. Whether clan members are related is unknown, but they get along peacefully enough. In fact, the social structure of a clan is probably most aptly compared to that of a wolf pack; in that each member has a clearly established rank and each clan has an alpha leader. When members of different clans meet, they establish social rank nonviolently through any of a variety of interactions.
Diet[]
Great white sharks are carnivorous and prey upon fish (e.g. tuna, rays, other sharks), cetaceans (i.e., dolphins, porpoises, whales), pinnipeds (e.g. seals, fur seals, and sea lions), sea turtles, sea otters (Enhydra lutris) and seabirds. Great whites have also been known to eat objects that they are unable to digest. Juvenile white sharks predominantly prey on fish, including other elasmobranchs, as their jaws are not strong enough to withstand the forces required to attack larger prey such as pinnipeds and cetaceans until they reach a length of 3 m (9.8 ft) or more, at which point their jaw cartilage mineralizes enough to withstand the impact of biting into larger prey species. Upon approaching a length of nearly 4 m (13 ft), great white sharks begin to target predominantly marine mammals for food, though individual sharks seem to specialize in different types of prey depending on their preferences. They seem to be highly opportunistic. These sharks prefer prey with a high content of energy-rich fat. Shark expert Peter Klimley used a rod-and-reel rig and trolled carcasses of a seal, a pig, and a sheep from his boat in the South Farallons. The sharks attacked all three baits but rejected the sheep carcass.
Off of Seal Island, False Bay in South Africa, the sharks ambush brown fur seals (Arctocephalus pusillus) from below at high speeds, hitting the seal mid-body. They achieve high speeds that allow them to completely breach the surface of the water. The peak burst speed is estimated to be above 40 km/h (25 mph). They have also been observed chasing prey after a missed attack. Prey is usually attacked at the surface. Shark attacks occur most often in the morning, within two hours of sunrise, when visibility is poor. Their success rate is 55% in the first two hours, falling to 40% in late morning after which hunting stops.
Off California, sharks immobilize northern elephant seals (Mirounga angustirostris) with a large bite to the hindquarters (which is the main source of the seal's mobility) and wait for the seal to bleed to death. This technique is especially used on adult male elephant seals, which are typically larger than the shark, ranging between 1,500 and 2,000 kg (3,300 and 4,400 lb), and are potentially dangerous adversaries. Most commonly though, juvenile elephant seals are the most frequently eaten at elephant seal colonies. Prey is normally attacked sub-surface. Harbor seals (Phoca vitulina) are taken from the surface and dragged down until they stop struggling. They are then eaten near the bottom. California sea lions (Zalophus californianus) are ambushed from below and struck mid-body before being dragged and eaten.
In the Northwest Atlantic mature great whites are known to feed on both harbor and grey seals. Unlike adults, juvenile white sharks in the area feed on smaller fish species until they are large enough to prey on marine mammals such as seals.
White sharks also attack dolphins and porpoises from above, behind or below to avoid being detected by their echolocation. Targeted species include dusky dolphins (Sagmatias obscurus), Risso's dolphins (Grampus griseus), bottlenose dolphins (Tursiops ssp.), humpback dolphins (Sousa ssp.), harbour porpoises (Phocoena phocoena), and Dall's porpoises (Phocoenoides dalli). Groups of dolphins have occasionally been observed defending themselves from sharks with mobbing behaviour. White shark predation on other species of small cetacean has also been observed. In August 1989, a 1.8 m (5.9 ft) juvenile male pygmy sperm whale (Kogia breviceps) was found stranded in central California with a bite mark on its caudal peduncle from a great white shark. In addition, white sharks attack and prey upon beaked whales. Cases where an adult Stejneger's beaked whale (Mesoplodon stejnegeri), with a mean mass of around 1,100 kg (2,400 lb), and a juvenile Cuvier's beaked whale (Ziphius cavirostris), an individual estimated at 3 m (9.8 ft), were hunted and killed by great white sharks have also been observed. When hunting sea turtles, they appear to simply bite through the carapace around a flipper, immobilizing the turtle. The heaviest species of bony fish, the oceanic sunfish (Mola mola), has been found in great white shark stomachs.
Whale carcasses comprise an important part of the diet of white sharks. However, this has rarely been observed due to whales dying in remote areas. It has been estimated that 30 kg (66 lb) of whale blubber could feed a 4.5 m (15 ft) white shark for 1.5 months. Detailed observations were made of four whale carcasses in False Bay between 2000 and 2010. Sharks were drawn to the carcass by chemical and odour detection, spread by strong winds. After initially feeding on the whale caudal peduncle and fluke, the sharks would investigate the carcass by slowly swimming around it and mouthing several parts before selecting a blubber-rich area. During feeding bouts of 15–20 seconds the sharks removed flesh with lateral headshakes, without the protective ocular rotation they employ when attacking live prey. The sharks were frequently observed regurgitating chunks of blubber and immediately returning to feed, possibly in order to replace low energy yield pieces with high energy yield pieces, using their teeth as mechanoreceptors to distinguish them. After feeding for several hours, the sharks appeared to become lethargic, no longer swimming to the surface; they were observed mouthing the carcass but apparently unable to bite hard enough to remove flesh, they would instead bounce off and slowly sink. Up to eight sharks were observed feeding simultaneously, bumping into each other without showing any signs of aggression; on one occasion a shark accidentally bit the head of a neighbouring shark, leaving two teeth embedded, but both continued to feed unperturbed. Smaller individuals hovered around the carcass eating chunks that drifted away. Unusually for the area, large numbers of sharks over five metres long were observed, suggesting that the largest sharks change their behaviour to search for whales as they lose the manoeuvrability required to hunt seals. The investigating team concluded that the importance of whale carcasses, particularly for the largest white sharks, has been underestimated.
In another documented incident, white sharks were observed scavenging on a whale carcass alongside tiger sharks. In 2020, marine biologists Sasha Dines and Enrico Gennari published a documented incident in the journal Marine and Freshwater Research of a group of great white sharks exhibiting pack-like behaviour, successfully attacking and killing a live juvenile 7 m (23 ft) humpback whale. The sharks utilized the classic attack strategy used on pinnipeds when attacking the whale, even utilizing the bite-and-spit tactic they employ on smaller prey items. The whale was an entangled individual, heavily emaciated and thus more vulnerable to the sharks' attacks. The incident is the first known documentation of great whites actively killing a large baleen whale. A second incident regarding great white sharks killing humpback whales involving a single large female great white nicknamed Helen was documented off the coast of South Africa. Working alone, the shark attacked a 33 ft (10 m) emaciated and entangled humpback whale by attacking the whale's tail to cripple it before she managed to drown the whale by biting onto its head and pulling it underwater. The attack was witnessed via aerial drone by marine biologist Ryan Johnson, who said the attack went on for roughly 50 minutes before the shark successfully killed the whale. Johnson suggested that the shark may have strategized its attack in order to kill such a large animal.
Stomach contents of great whites also indicates that whale sharks both juvenile and adult may also be included on the animal's menu, though whether this is active hunting or scavenging is not known at present.
Reproduction[]
Great white sharks were previously thought to reach sexual maturity at around 15 years of age, but are now believed to take far longer; male great white sharks reach sexual maturity at age 26, while females take 33 years to reach sexual maturity. Maximum life span was originally believed to be more than 30 years, but a study by the Woods Hole Oceanographic Institution placed it at upwards of 70 years. Examinations of vertebral growth ring count gave a maximum male age of 73 years and a maximum female age of 40 years for the specimens studied. The shark's late sexual maturity, low reproductive rate, long gestation period of 11 months and slow growth make it vulnerable to pressures such as overfishing and environmental change.
Little is known about the great white shark's mating habits, and mating behaviour had not been observed in this species until 1997 and properly documented in 2020. It was assumed previously to be possible that whale carcasses are an important location for sexually mature sharks to meet for mating. According to the testimony of fisherman Dick Ledgerwood, who observed two great white sharks mating in the area near Port Chalmers and Otago Harbor, in New Zealand, it is theorized that great white sharks mate in shallow water away from feeding areas and continually roll belly to belly during copulation. Birth has never been observed, but pregnant females have been examined. Great white sharks are ovoviviparous, which means eggs develop and hatch in the uterus and continue to develop until birth. The great white has an 11-month gestation period. The shark pup's powerful jaws begin to develop in the first month. The unborn sharks participate in oophagy, in which they feed on ova produced by the mother. Delivery is in spring and summer. The largest number of pups recorded for this species is 14 pups from a single mother measuring 4.5 m (15 ft) that was killed incidentally off Taiwan in 2019. The Northern Pacific population of great whites is suspected to breed off the Sea of Cortez, as evidenced by local fisherman who have said to have caught them and evidenced by teeth found at dump sites for discarded parts from their catches.
Breaching behavior[]
A breach is the result of a high-speed approach to the surface with the resulting momentum taking the shark partially or completely clear of the water. This is a hunting technique employed by great white sharks whilst hunting seals. This technique is often used on cape fur seals at Seal Island in False Bay, South Africa. Because the behaviour is unpredictable, it is very hard to document. It was first photographed by Chris Fallows and Rob Lawrence who developed the technique of towing a slow-moving seal decoy to trick the sharks to breach. Between April and September, scientists may observe around 600 breaches. The seals swim on the surface and the great white sharks launch their predatory attack from the deeper water below. They can reach speeds of up to 40 km/h (25 mph) and can at times launch themselves more than 3 m (10 ft) into the air. Just under half of observed breach attacks are successful. In 2011, a 3-m-long shark jumped onto a seven-person research vessel off Seal Island in Mossel Bay. The crew were undertaking a population study using sardines as bait, and the incident was judged not to be an attack on the boat but an accident.
Natural threats[]
Interspecific competition between the great white shark and the killer whale is probable in regions where dietary preferences of both species may overlap. An incident was documented on 4 October 1997, in the Farallon Islands off California in the United States. An estimated 4.7–5.3 m (15–17 ft) female killer whale immobilized an estimated 3–4 m (9.8–13.1 ft) great white shark. The killer whale held the shark upside down to induce tonic immobility and kept the shark still for fifteen minutes, causing it to suffocate. The killer whale then proceeded to eat the dead shark's liver. It is believed that the scent of the slain shark's carcass caused all the great whites in the region to flee, forfeiting an opportunity for a great seasonal feed. Another similar attack apparently occurred there in 2000, but its outcome is not clear. After both attacks, the local population of about 100 great whites vanished. Following the 2000 incident, a great white with a satellite tag was found to have immediately submerged to a depth of 500 m (1,600 ft) and swum to Hawaii.
In 2015, a pod of killer whales was recorded to have killed a great white shark off South Australia. In 2017, three great whites were found washed ashore near Gansbaai, South Africa, with their body cavities torn open and the livers removed by what is likely to have been killer whales. Killer whales also generally impact great white distribution. Studies published in 2019 of killer whale and great white shark distribution and interactions around the Farallon Islands indicate that the cetaceans impact the sharks negatively, with brief appearances by killer whales causing the sharks to seek out new feeding areas until the next season. Occasionally, however, some great whites have been seen to swim near killer whales without fear.