Animal Encounters XI
The great white shark is a streamlined swimmer and a ferocious predator with 3,000 teeth at any one time. This much-feared fish has a torpedo-shaped body, a pointed snout, a crescent-shaped tail, 5 gill slits, no fin spines, an anal fin, and 3 main fins: the dorsal fin (on its back) and 2 pectoral fins (on its sides). When the shark is near the surface, the dorsal fin and part of the tail are visible above the water.
Only the underbelly of the great white shark is actually white; its top surface is gray to blue gray. This is useful in hunting its prey. The great white usually strikes from below and its grayish top coloration blends in with the dark water, enabling it to approach the prey unobserved. Great whites average 12-16 feet long (3.7-4.9 m) long. The biggest great white shark on record was 23 feet (7 m) long, weighing about 7,000 pounds (3200 kg). Females are larger than males, as with most sharks. Shark pups can be over 5 feet (1.5 m) long at birth. Young great white sharks eat fish, rays, and other sharks. Adults eat larger prey, including pinnipeds (sea lions and seals), small toothed whales (like belugas), otters, and sea turtles. They also eat carrion (dead animals that they have found floating dead in the water). Great whites do not chew their food. Their teeth rip prey into mouth-sized pieces which are swallowed whole. A big meal can satisfy a great white for up to 2 months.
The great white shark has 3,000 teeth at any one time. They are triangular, serrated (saw-edged), razor-sharp, and up to 3 inches (7.5 cm) long. The teeth are located in rows which rotate into use as needed. The first two rows are used in obtaining prey, the other rows rotate into place as they are needed. As teeth are lost, broken, or worn down, they are replaced by new teeth that rotate into place. Great whites are propelled through the water by their powerful tails. The fins are only used for balance. Their movement is more like an aircraft's flight than other fishes swimming. They can swim 30 miles per hour in short bursts. They swim constantly or they will sink since, like other sharks, they have no gas filled swim bladder to keep them afloat like bony fish do. Like other sharks, their large, oily liver provides some buoyancy, but they are still heavier than water and will sink unless they are propelling themselves through the water. Also like other sharks, they cannot swim backwards or even come to an abrupt stop, because their fins are not flexible like other fish. In order to go backwards, they must stop swimming and fall backwards, using gravity to propel themselves backwards. Great white sharks can also jump out of the water (called breaching). They jump into the air from deep water in order to catch fast-swimming seals.
The organisation I work with (White Shark Projects) undertakes much cage diving with sharks. This was originally thought of as a bad idea, as it was believed that by baiting humans in cages, sharks would associate humans as food, through the process of conditioning. However, this is disputed as sharks are highly nomadic animals, their territory ranging over vast areas, even across continents. Recently a female great white that was tagged in South Africa was found swimming of the coast of Southern Australia. And a couple of months later, she was back in South African waters. Personally, I see a different shark every time I go out on the boat. We get about 6-9 different sharks a day approaching our boat. Hence this and other research show that a shark would never stay in a place long enough to become conditioned. The organisation also disagree that cage diving is a dangerous on the basis that a shark cannot mentally seperate the human diver from the cage.
Note: Many thanks to Dean for his wonderful underwater camera and photography tips !
Update: There was a shark attack on a swimmer off False Bay, Cape Town, yesterday. He lost a foot.