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Great White Shark
Published: 07/01/2010
Reaching lengths of about 6 meters (20 feet) and weighing almost 2,000 kilograms (4,000 pounds), the Great White is the world's largest predatory fish. The Sixth Sense: Great Whites have a sixth sense given by the Ampullae of Lorenzini, which enables them to detect the electromagnetic field emitted by the movement of living animals. A Great White's sense of sight is useful, but the shark does not depend on it. A shark primarily uses its extra senses (i.e, Electrosense and Mechanosense) to locate prey from far off. Then, the shark uses smell and hearing to further verify that its target is food. At close range, the shark utilizes sight for the attack. Ambush Predator: The shark will often in ambush deliver a massive disabling bite and then back off to allow the prey to expire. This tactic allows the animal to avoid combat with dangerous prey, such as sea lions. It also has allowed occasional rescue of humans bitten by the animal, though it appears to attack humans mostly in error. Bad Reputation: White sharks' reputation as ferocious predators is well-earned, yet they are not (as was once believed) indiscriminate "eating machines". They typically hunt using an "ambush" technique, taking their prey by surprise from the bottom. This is the only shark known to lift its head above the sea surface to gaze at other objects such as prey; this is known as "spy-hopping". It is theorized that the shark may also be able to smell better this way, since smells travel through air faster than through water. On the Menu: Great White sharks primarily eat fish, smaller sharks, turtles, dolphins, and pinnipeds such as seals and sea lions. They are apex predators; the only animals known to attack them are other Great Whites, sperm whales and orcas. Rows and Rows of Teeth: 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 tensor-sensing nerve cells. This arrangement seems to give their teeth high tactile sensitivity. Sizes and Scales: While the average length of a Great White is 4 to 5 meters (females generally being larger than males), the question of the maximum size of Great White sharks has been subject to much debate, conjecture, and misinformation. Today, most experts contend that the Great White's "normal" maximum size is about 6 m (20 ft), with a maximum weight of about 1900 kg (4200 lb). Any claims much beyond these limits are generally regarded as doubtful, and are closely scrutinized. Shark Life-cycle: A White Shark can reproduce when a male's length is around 3.8 m and a female's length is around 4.5 to 5 meters. Their lifespan has not been definitively established, though many sources estimate 30–40 years. It would not be unreasonable to expect such a large marine animal to live longer however. Mysterious Mating: There is still a great deal that is unknown about Great White behavior, such as mating habits. Birth has never been observed, but several pregnant females have been examined. Great Whites are ovoviviparous, the eggs developing in the female's uterus, hatching there and continuing to develop until they are born, at which point they are perfectly capable predators. The embryos can feed off unfecundated eggs. The delivery takes place in the period transitioning spring and summer. Almost nothing is known about how and where the Great White mates.
Great White Shark
