Distribution : Sometimes called the white death, the Man-eater, the White Pointer (in Australia) or the Blue Pointer (in South Africa), the shark is found, now in decreasing numbers, in all tropical, subtropical and temperate seas. It is most often recorded in relatively shallow offshore waters. It may well occur in deeper waters but has not been noticed there. It appears to prefer subtropical waters to temperate waters. The Great White shark has been recorded within the Mediterranean Sea, and there are reliable records of it's occurrence around the coasts of Britain up to about the middle of the last century, especially around the Cornish peninsula and in the Bristol Channel. Whether as a result of climatic changes, pollution or a lack of food, none has been seen last century or this in British coastal waters.
Colour : Despite the common names the Great White shark is not white. A large specimen is slaty grey, dun, blue or very dark grey on the back and top of the sides. This darker colour changes abruptly to a cream or dirty white to pale grey on the lower part of the sides and belly
Size : Although the Great White is the largest of carnivorous sharks, it does not reach the size alleged in popular literature and in the films. The largest accurately measured specimen, caught of Cuba in 1945, was 6.4m (21ft) long and weighed just over 3 tons. Of moderate reliability is an unsubstantiated report of a specimen 9m (29ft) long caught off the Azores in 1978. in a slightly less reliable category still is the report of an 11.3m (37ft) long fish from New Brunswick, Canada, in the 1930's. Perhaps more interesting is that small specimens are practically unknown.
General Biology : Very little is known about the biology of the Great White shark. It is not evenly distributed throughout it's range, nor necessarily throughout the year at any one locality. There is some evidence that this species may show some territoriality, returning to the same coastal area year after year. The age of the mother at sexual maturity is unknown, as is the life expectancy of the species although ages of 10 years and 40-50 years have been suggested. Neither the mating or pupping areas are unknown. The relative frequency of small specimens in one part of the western North Atlantic has led to postulations that the waters off Montauk Point, Long Island may be a pupping region. If, as is like that of other lamnid sharks, it will give birth to a few, well formed young, possibly only every alternate year. Like all other sharks, the Great White has an electroreceptive sense. It is thought that some attacks on small boats (right) are the result of the sharks being attracted by the electric field set up between the metal of the boat and the sea water and so mistaking the boat for a prey item.
Jaws : The sharks jaws exhibit characteristics unique in the animal world, no terrestrial predator has jaws that come anywhere near matching them for perfection. The ancestors of modern sharks were equipped with an upper jaw fixed to the skull (as in man) and with a mouth located at the extremity of the head. Since the age of these fossil sharks, the mouth has moved underneath the head, and the upper jaw, disengaged from the skull, has become mobile. The shark is therefore equipped with two mobile and independent jaws, enabling it to swallow much larger prey and to tear off enormous pieces of flesh. The spectacular distance these jaws can open would be nothing were they not subtended by muscles of exceptional power The shutting force of a sharks jaws was measured a few years ago using an apparatus tested by J.N Snodgrass which he called the "gnathodynamometer" . With the help of Dr Perry Gilbert he measured the dentitional strength of the Tiger Shark, the Lemon shark and the Dusky shark. The maximum force recorded for a single tooth of a dusky shark was 600 kilos per 2mm square, or 3 tonnes per cm square. Even then it should be noted that their specimens were not more than 3m long, so doubtless this enormous force must be doubled for animals (Great Whites) 5-6m in length. As an indication, the strength exerted by a human jaw is 220 kilos per cm square for a man weighing 70 kilos (11 stone). It must be remembered that, in addition to cutting, these jaws are capable of crushing bones|
Teeth : Besides it's extensibility and its Herculean strength, the jaw of the shark possesses a third formidable feature : a set of teeth whose anatomy and manner of replacement are also unique in the animal kingdom. The sharks teeth can be renewed indefinitely as fast as they are lost either at the time of an attack or when they fall out spontaneously. Several sets of reserve teeth exist behind the set that is functional at the time, i.e. the one that sits on the ridge of the jawbone (middle left). There are thus 5 sets, covered to varying degrees with buccal mucous membrane depending on whether they are number five, four, three or two in line. If one or more teeth in the functional row are exposed at the root, broken or torn out, the corresponding tooth or teeth of the next row will move up and become functional. Furthermore, the teeth are held fast on a very strong fibrous tissue, allowing them to be erected when the mouth is opened. The opening movement makes them turn forwards and outwards, enabling the shark to bite firmly and to hold on to what it bites. Taking into account the fact that each one of these teeth itself bears smaller teeth, making it a veritable saw (left), and that it's concavity at the rear gives it the qualities of a hook, one can understand why the wounds left by such a formidable jaw are always dramatic if not fatal |
