great white

The great white shark, Carcharodon carcharias, also known as white pointer, white shark, or white death, is an exceptionally large lamniforme shark found in coastal surface waters in all major oceans. Reaching lengths of about 6 metres (20 ft) and weighing almost 2,000 kilograms (4,400 lb), the great white shark is the world's largest known predatory fish. It is the only known surviving species of its genus, Carcharodon. They are also regarded as an apex predator with its only real threats from humans and occasionally Killer Whales have been known to feed on great whites.Distribution and habitatGreat white sharks live in almost all coastal and offshore waters which have a water temperature of between 12 and 30° C (54° to 75° F), with greater concentrations off the southern coasts of Australia, off South Africa, California, Mexico's Isla Guadalupe and to a degree in the Central Mediterranean and Adriatic Seas. The densest known population is found around Dyer Island, South Africa where up to 31 different white sharks have been documented by Michael Scholl of the White Shark Trust in a single day. It can be also found in tropical waters like those of the Caribbean and has been recorded off Mauritius.It is a pelagic fish, but recorded or observed mostly in coastal waters in the presence of rich game like fur seals, sealions, cetaceans, other sharks and large bony fish species. It is considered an open-ocean dweller and is recorded from the surface down to depths of 1,280 metres(4,200 ft), but is most often found close to the surface. In a recent study white sharks from California were shown to migrate to an area between Baja California and Hawaii, where they spend at least 100 days of the year before they migrate back to Baja. On the journey out, they swim slowly and dive to up to 900 metres (3,000 ft). After they arrive, they change behaviour and do short dives to about 300 m (1,000 ft) for up to 10 minutes. It is still unknown why they migrate and what they do there; it might be seasonal feeding or possibly a mating area. In a similar study a white shark from South Africa was tracked swimming to the northwestern coast of Australia and back to the same location in South Africa, a journey of 20,000 kilometres in under 9 months.Anatomy and appearanceThe great white shark has a robust large conical-shaped snout. It has almost the same size upper and lower lobes on the tail fin (like most mackerel sharks, but unlike most other sharks). It is pale to dark grey and has a white stomach.Great whites, like many other sharks, have rows of teeth behind the main ones, allowing any that break off to be rapidly replaced. Their teeth are unattached to the jaw and are retractable, like a cat's claws, moving into place when the jaw is opened. Their teeth also rotate on their own axis (outward when the jaw is opened, inward when closed). The teeth are linked to pressure and tension-sensing nerve cells. This arrangement seems to give their teeth high tactile sensitivity. A great white's teeth are serrated and when the shark bites it will shake its head side to side and the teeth will act as a saw and tear off large chunks of flesh. Great whites often swallow their own broken off teeth along with chunks of their prey's flesh. These teeth frequently cause damage to the great white's digestive tract. However great whites often feed on stingrays and swallow the 'sting' as well, the barbed sting often getting stuck in the shark's intestines. There are anecdotal reports of the sting working its way out through the shark's side. Correspondingly, a tooth causes the shark no major harm.SizeThe average length of a full grown great white is 4 to 4.8 metres (13.3 to 15.8 ft), with a weight of 680 to 1,100 kilograms (1,500 to 2,450 lbs), females generally being larger than males. But the question of the maximum size of a great white shark has been subject to much debate, conjecture, and misinformation. Richard Ellis and John E. McCosker, both academic shark experts, devote a full chapter in their book The Great White Shark (1991) to analysis of various accounts of extreme size. Today, most experts contend that the great white's "normal" maximum size is about 6 metres (20 ft), with a maximum weight of about 1,900 kilograms (4,200 lb). Any claims much beyond these limits are generally regarded as doubtful, and are closely scrutinized.For some decades many ichthyological works, as well as the Guinness Book of World Records, listed two great whites as the largest individuals caught: an 11 metre (36 ft) great white captured in south Australian waters near Port Fairy in the 1870s, and an 11.3 metre (37.6 ft) shark trapped in a herring wier in New Brunswick, Canada in the 1930s. While this was the commonly accepted maximum size, reports of 7.5 to 10 metre (25 to 33.3 ft) great whites were common and often deemed credible.Some researchers questioned the reliability of both measurements, noting they were much larger than any other accurately-reported great white. The New Brunswick shark may have been a wrongly-identified basking shark, as both sharks have similar body shapes. The question of the Port Fairy shark was settled in the 1970s, when J.E. Reynolds examined the shark's jaws and "found that the Port Fairy shark was of the order of 5 m (17 feet) in length and suggested that a mistake had been made in the original record, in 1870, of the shark's length.[3]Ellis and McCosker write that "the largest white sharks accurately measured range between 19 and 21 ft [about 5.8 to 6.4 m], and there are some questionable 23-footers [about 7 m] in the popular — but not the scientific — literature". Furthermore, they add that "these giants seem to disappear when a responsible observer approaches with a tape measure." (For more about legendary exaggerated shark measurements, see the submarine). The largest specimen Ellis and McCosker endorse as reliably measured was 6.4 metres (21.3 ft) long, caught in Cuban waters in 1945 (though confident in their opinion, Ellis and McCosker note, however, that other experts have argued this individual might have been a few feet shorter). There have since been claims of larger great whites...