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Great White Sharks are greatly misinterpreted as vicious man-eaters because of the media, movies, and peoples imaginations, but they are actually large fish who mistake people for seals and other marine life. What is a great white shark? The great white, among the least understood of Earths creatures, is an apex predator, meaning that it is at the top of the food chain with no natural predators. This means great whites have their pick of food when it comes to selecting their prey (Klimley 15).
Carcharodon cercarias, better know as the great white shark, have existed as a group for over 350 million years (Long). Its name means ragged-toothed (Gorman 10). The largest white shark on record was 21 feet long and weighed 7302 pounds. Its ancestors, now extinct, were three times this size, with teeth that were six inches long (White Shark). Today sharks are represented by over 600 species (Long). Great whites are part of a grouping know as mackerel sharks, a grouping which includes the salmon, porbeagle, and maco shark (MacGregor 46).
Unlike the true fishes, sharks do not have internal bone, but instead have a cartilaginous skeleton (Long). This stiff flexible material is found in the ridge of your nose and in your earlobes. Because cartilage does not leave fossil remains like bones, there are no fossils of ancient sharks- just their teeth (Klimley 56). Little is known about great whites because they are enormous, bulky, and hard to handle.
And thats when theyre dead. Their body temperature is sometimes ten to fifteen degrees [Celsius] warmer than the surrounding water, which makes them efficient predators in cool water (Gorman 15). The back of the shark is a dull gray color and the underside is colored white. The tail is crescent shaped. There are five gill slits on great white sharks. Studying a live great white shark up close and in detail is, for obvious reasons, practically impossible (Sanders 31).
The great white is the only shark that can hold its head above water to see what is happening on the surface (MacGregor 47). It has been said that sharks do not swim through water as much as they fly through it with their torpedo like body (Gorman 25). The fins of a shark serve important roles in this action. As the shark moves the Caudal, back, fin to propel it forward, careful adjustment of the pectoral, side, and dorsal, top, fins keep the shark level and on course, much as the wings and tail of an airplane do. Great whites have a pair of nostrils near the tip of their snout.
Since breathing takes place in the gills, the nostrils of a shark are used solely for sniffing out their prey (Gorman 11). The nostrils can smell a drop of blood in 25 gallons of water (All About Sharks). Unusually large olfactory bulbs result in a keener sense of smell than that of nearly all other fish. The pores on the nose are tiny electrical field sensors, connected to nerves via canals filled with receptive jelly, which can detect heartbeats or movement of prey (Martin 55). Sharks are drawn to motors by their electrical signals, (on their snout), and have a habit of biting them to see if theyre edible, said Andy Hartman.
That is how they decide what and what not to eat- and sometimes theyll knock out a bunch of their teeth (Gorman 10). Much has been made of the infamous jaws of the great white. They have about 3000 teeth arranged in several rows. The first two rows of teeth are used for grabbing and cutting prey, while the teeth in the last rows rotate in place when front teeth are broken, worn down, or fallen out (All About Sharks). Each upper tooth is a marvel of compact engineering with hundreds of tiny serrations. This coupled with their enormous jaw strength enables the great white to cut through just about anything it feels needs cutting.
The bottom teeth are not as large as the top, but serve the purpose of skewing the sharks prey, holding it in place for the upper teeth to remove as much flesh from the victim as possible (Klimley 89). A white can tell the relative fat content of an animal by first mouthing it gently; if the tensile resistance associated with blubber is revealed, the shark goes for a full bite. If not it will save its energy for a more nutritious meal. Thats probably why most humans who are bitten are not killed, says Klimley. A human has too much muscle and not enough fat for a great white.
The same calculation may factor into the whites rejection of other potential prey. Great whites may favor fat because they burn prodigious amounts of calories (Martin 59). Sharks have excellent eyesight and see well in dim light. In fact, sharks corneas have been used as transplants for human corneas (MacGregor 45). The cone receptors in the eyes heighten the contrast between dark and light to help distinguish prey from greater distances under water (Martin 59). Great whites are predatory animals that begin life by feeding on fish, rays, and other sharks, and as they grow, switch to feeding on marine mammals and scavenging on large animal carcasses.
Their first mammalian prey are usually the small harbor seals, but as the shark increases in size, they become large enough to eat sea lions, elephant seals, and small toothed whales (Long). Great whites are picky eaters and their favorite prey are pinnipeds, a fancy name for seals and sea lions (Klimley 31). Large great whites will also scavenge on the carcasses of whale sharks, and on the fat-rich blubber layer of dead whales. They will occasionally feed on sea turtles and sea otters and are known to attack, but not eat humans (Long). An elephant seal rookery like Ano Nuevo Island is a supermarket for whites, says Burney Le Boeuf, a University of California at Santa Cruz behavioral ecologist and a leading expert on pinnipeds. Its stationary, its open 24 hours a day, and its full of things they like to eat.
Its difficult to come up with a statistic for the probability of attack because it is hard to estimate how many people go to the beach each day, how many actually enter the water and for how long. Studies indicate that 79 - 90 percent of all attacks on humans occur at the surface. Mainly because sharks prefer to attack animals at the surface or it may simply result from the fact that humans spend most of their time in the water on the surface (MacGregor 48). Great whites feed infrequently, although their exact time between meals is unknown one study showed that a 15 - foot shark can live for 45 days on 66 pounds of...
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