Aug 2, 2009
The Great White Shark is the largest known predatory fish in the sea, at the top of its food chain with no natural predators. They’re equipped with two of the most powerful sensing mechanisms in Nature, a highly developed sense of smell, and the ability to sense the electrical fields radiating from living creatures. Also known as the white shark, white pointer, blue pointer, man-eater, and manila shark, this killing machine averages a length up to 20 feet (6 meters) and 5,000 pounds (2,270 kilos).
Great White Sharks bear a set of nostrils near the tip of their conical snout, used solely for olfactory purposes to sniff out their prey, while breathing through their gills. The nostrils are divided by a small flap of skin separating the water into 2 flows, one incoming and one outgoing. The flow passes through a section with countless small sensory organs called lamellae, shaped like tiny flower petals covered with millions of olfactory cells. These cells are linked directly to the center of the brain responsible for detecting odors.
But the secret weapon in the Great White’s arsenal are ampullae — small pore-like markings on the snout — which provide the shark with the ability to sense the electrical fields of their prey. Each is a minute capsule filled with a gel like substance the shark excretes, sensitive to electrical discharges as low as .005 micro volts. This remarkable sensitivity is due to both the large number of ampullae, and their numerous sensory cells in each to pick up the signal which is also directly linked to the brain.
Every living creature in the sea discharges a small electrical field. Mucous membranes that coat the mouth and gills of fish also create steady current fields affected by their breathing patterns. A wounded bleeding animal produces yet another set of electrical information.
By their ability to discern these sets of information, Great Whites can detect and distinguish between prey swimming peacefully, those moving quickly in panic, and those which might be bleeding and debilitated. Recent research on interactions between great whites and various species of seals and sea lions suggests that great whites also hunt their prey visually.
These 2 sensory mechanisms make for an inescapable and formidable predator.Food and Feeding BehaviorWhile young, White sharks feed on fish, rays, and other sharks, and as they begin to mature they’ll feed on marine mammals and forage for large animal carcasses. Progressing to small harbor seals, they hunt sea lions, elephant seals, and small toothed whales as they increase in size. Occasionally feeding on sea turtles and sea otters, they’ve been known to attack but not eat humans.
Camouflaging themselves near rocky bottoms, they’ll watch for unsuspecting prey near the surface. Once an animal is sighted, they accelerate quickly to the surface and ram into their kill from beneath, simultaneously stunning it and inflicting a large, potentially fatal bite. They then return to feed on the carcass.
World Range & HabitatGreat Whites have one of the widest geographic ranges of any marine animal, found in all cold temperate and tropical waters from 60°N latitude to 60°S latitude. Recent satellite tracking studies reveal that they migrate long distances, sometimes crossing entire oceans.
They can be found along the central California coast hunting near elephant seal haul-out areas from October through March, and off the western cape of South Africa near cape fur seal haul-outs from May to September. In North American waters, they’ve been reported from Newfoundland to Florida, and from the Aleutian Islands, Alaska to southern Mexico. Nowhere in its range is the white shark very common, and are becoming increasingly rare.
Great White Shark AttackThe cunning Great White appears almost to be toying with this sealprior to its ferocious attack.