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Great white shark: man-eater or misunderstood?

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Introduction to How Great White Sharks Work

Almost everyone has the occasional daydream of being a movie star. We think about the glamorous parts -- captivating audiences on the big screen, seeing ourselves on movie posters all over the world and raking in the dough and the adulation of our fans. And if we have to play a bad guy every now and then, so be it; those are the juicy parts that win awards.

For the star of "Jaws," though, fame had a flip side, and I'm not talking about Richard Dreyfuss. The great white shark got a taste of fame when it was cast as the villain in the 1975 Steven Spielberg film about a town terrorized by a shark, based on the book by Peter Benchley. But instead of Oscars, the great white got harpoons and hunters. Instead of fame and fortune, the great white became a symbol of fear, a monster. Heck, even its theme song is scary. This shark has been typecast as a crazed and indiscriminate killer.

Is this a fair reputation? Famed marine explorer (and occasional book critic) Jacques Cousteau didn't think so, and he publicly chastised Benchley for his "bad book" [source: Monsters and Critics]. For his part, Benchley expressed regret for writing a book that gave sharks such a bad name and spent his later years campaigning for marine conservation.

When "Jaws" was written, all that was known about great white sharks was based on rare sightings near the surface [source: Carey]. Yet the shark at the center of this scandal has released no public comment and has done remarkably little in the way of spin control. The great white shark is an elusive movie star. Compared to other sharks, we don't know much about the species, although would-be paparazzi have spent many hours in shark cages hoping to catch a glimpse. The great white's elusive nature has only fanned the public's fears, and when it does make the papers, it's usually for attacking people.

Has the great white shark been typecast unfairly? Did its one starring role doom it to an everlasting reputation as the hungry madman of the sea? Or did Hollywood get it right for once? We'll investigate this true Hollywood story by taking a look at shark attacks on the next page.

Let's hope this isn't the last thing you see.

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Great White Shark Attacks

The great white shark has been involved in some of the most chilling attacks on humans. In 1985, Australian Shirley Ann Durdin was torn in two and then devoured by a white shark. Rodney Fox had his lungs and stomach ripped open and required more than 360 stitches in a 1963 attack [source: Rodney Fox]. In 2008, Dave Martin was killed in California when a great white bit off his legs.

The great white shark does outrank all other sharks in the number of shark attacks. As of May 2008, the great white had racked up 238 unprovoked attacks and 95 boat attacks, resulting in 65 fatalities; this far outpaces the runner-up tiger shark (88 attacks and 28 deaths) and the third-place bull shark (77 attacks and 23 deaths) [source: International Shark Attack File].

Why are the numbers so high? One factor to keep in mind is that great whites are easily recognizable, particularly if they leave a tooth or two in their victims. This means that more attacks are specifically attributed to them than other, less identifiable species [source: Carey]. There may also be a mind-set that great white sharks are guilty in a shark attack until proven innocent. Whether this bias is fair or not, scientists are quick to remind us that the odds of actually being attacked by any shark are very small.

Are humans especially delicious to great white sharks? Probably not, according to scientists who've studied the stomach contents of these sharks. Humans, because of their muscle content, aren't a very good meal for great whites, who crave fatty blubber. Many shark attack victims live to tell their tale because the shark takes a bite, as if to taste it. While this will be small comfort to anyone ever trapped in the mouth of a shark, it may just be a case of mistaken identity. Think about someone lying on a surfboard, their arms and legs out to the side to paddle and kick. From below, this shape might resemble a seal.

The great white is no doubt dangerous, but if you're trying to decide whether to go swimming, it might be worth remembering that elephants are more deadly than great whites [source: Carey]. A common adage in the shark world now is that man is a much greater danger to sharks than sharks have ever been to man. These sharks are hunted for sport and also for their parts, including their teeth and their fins.

But what does the great white shark hunt, if not humans? Find out next.

Time for lunch

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What the Great White Shark Eats

Like some of us, the great white prefers a fatty meal to one with lots of protein. That's why its main prey item is the pinniped, an aquatic carnivore like a seal or a sea lion. As we mentioned, humans are generally too muscular and lean for a typical shark meal, but a seal might be 50 percent fat, representing a very efficient meal for great whites [source: Carey]. They'll also dine on other fishes and occasionally sea turtles. The great white shark consumes approximately 11 tons of food in one year (for comparison's sake, a 150-pound (68-kilogram) human being wolfs down about half a ton) [source: Parker].

While sharks are equipped with impressive noses and ears that help them to hunt their prey, the great white seems to rely most heavily on its sense of vision. It scopes out the water's surface for seals and then approaches them from underwater. One scientist conducted a study in which he presented a great white shark with a plywood seal-shaped board and a square board, and found that the great white made more passes at the seal-shaped board [source: Klimley].

That's a choice between an unfamiliar object (square) and a familiar one (seal), though. Whenever an object was presented by itself, the great white went to investigate -- one reason why swimmers are warned not to go into shark-infested waters alone [source: Martins, Knickle]. The white shark is known for its curiosity and may examine solitary and vulnerable objects to determine if they're edible.

Once the shark has spied something to try, it makes its approach. Scientists have identified several different ways the great white moves towards its prey:

  • An underwater approach is used most often. The shark swims under the surface until it's just a few feet away from its prey. Then it attacks quickly, moving its head up to the surface to grab the unlucky victim.
  • In a surface-charge approach, the shark swims partly above the surface until it makes its move.
  • The inverted method, when the shark swims on its back towards the prey, is used rarely.

[sources: Tricas and Martins, Knickle]

The first bite serves several important functions. Of course, it's designed to disable the prey. Seals are fast and don't give up without a fight, sometimes biting and clawing the shark. That bite starts the process of exsanguination, or bleeding to death, so that the shark doesn't suffer any injury in the course of hunting. Scientists have observed sharks taking that bite, waiting until the pinniped bleeds to death and then returning to feast on the carcass.

But that bite must also appeal to the shark's discerning palate because sharks sometimes reject the prey. Scientists don't know if the choice is based on taste, or if the shark is able to tell in that bite how fatty the meal is, and thus if it's worth the energy expenditure of the hunt.

Let's take a closer look at the great white's bite. On the next page, we'll go inside those fearsome jaws.

Great White Shark Anatomy

Any discussion of great white anatomy should start with the infamous jaws that gave Peter Benchley's tome a title. In fact, the great white shark's scientific name is Carcharodon carcharias, which means "ragged tooth" in Latin and shows that this shark's teeth have always been an important trait.

The great white has about 3,000 triangular teeth. When the shark moves in to bite its prey, its jaws extend forward as its head recedes back. The lower jaw strikes first, stabbing the prey with serrated blades. Then the upper jaw descends, and the teeth fit together perfectly so that whatever's inside is not going anywhere anytime soon. This whole process, from the head lifting to dropping back in place, takes about 0.99 seconds [source: Tricas].

The great white doesn't chew its food; instead, it holds the prey locked in those teeth and shakes its head from side to side, tearing off bits of flesh and blubber. The strength of the bite is estimated at 1 ton per square inch, with the great white able to consume about 20 to 30 pounds (9.1 to 13.6 kilograms) of flesh with one chomp. The great white's bite is about twice as strong as that of a lion [source: Parker].

To look at the great white's snout, you wouldn't think such impressive teeth were waiting -- the snout is fairly short and cone-shaped. The rest of the great white's body is torpedo-shaped and ends with a symmetrical caudal fin, or tail.

The great white takes its name from its white belly, but it's not white all over. On top, it's gray, or sometimes brown. This coloring aids the great white as it stalks its prey. From below, the white underside blends in with the sky above, while from the top of the water, the shark is indistinguishable from the ocean floor below. Most great whites also have a black spot near their pectoral fin.

The great white is the largest predatory fish in the sea, a fact that no doubt helps to drive humans' fear of being eaten by one. The maximum length for a great white appears to be about 20 feet (6 meters). While the great white isn't the biggest shark (an honor that belongs to the whale shark), the only sharks that are bigger eat plankton and small schools of fish. The great white tips the scales at 4,500 pounds (2,041 kilograms).

One thing that sets the great white apart from a lot of other sharks and other fish is that it's warm-bl­ooded. The blood vessels are aligned concurrently, with the vessels that run to the exterior of the body next to the ones that come back from outside. As the warm blood from the inside passes the cooler blood that is coming back from the exterior, it transfers its heat to the adjoining vessel, allowing the great white to keep its interior organs warm [source: Dingerkus]. This movement allows the great white shark to maintain a body temperature as much as 25 degrees Fahrenheit (14 degrees Celsius) warmer than the water [source: Martin].

Being warm-blooded means they can live in slightly colder waters than other sharks, but it also means they need to eat more. Find out what waters the great white swims in on the next page.

The Record-setting Shark

With advanced tagging methods, scientists are now better able to follow the great white shark's movements. In 2004, scientists tracking a great white found that they might have a record holder on their hands: A great white shark swam from South Africa to Western Australia and back in just nine months [source: Carey­]. That's a one-way journey of 6,800 miles (10,944 kilometers)! Scientists think that this is one of the fastest long-distance speeds for a fish. They're still working out why she took the trip -- her food source was already ample in South Africa, and she wasn't mature enough to mate. While most migrating animals use the ocean floor to navigate, this shark primarily swam near the surface, perhaps to use the moon or the sun.

Great White Shark Habitat

The warm-blooded great white lives in fairly temperate waters, and only occasionally in tropical waters because such temperatures might cause the shark to overheat [source: Dingerkus]. The great white shark makes its home all over these waters, from the coastline to the farther offshore locations. They can be seen near the surface or near the bottom of the sea, as far deep as 820 feet (250 meters), but they're rarely seen in the middle of those two extremes [source: Martins, Knickle].

One key element to where the great white makes its home is the abundance of the pinniped; these sharks are usually located near pinniped hangouts, swimming near elephant seals along the California coast or cape fur seals in South Africa.

One place you won't find great white sharks is at your local aquarium, or any aquarium for that matter. While aquarium managers would likely cater to the great white's every need like the finest maitre d's, great whites are nearly impossible to keep in captivity. The Monterey Bay Aquarium was able to keep a juvenile great white for 198 days, breaking the previous record of just 16 days in captivity [source: Carey]. Aquariums have yet to figure out the combination of food, water and tank type that will accommodate the great white, and that assumes that the great white survives the shock of capture and transport. One great white in Australia had to be released because he kept slamming his head into his tank's walls [source: Stevens].

Many biologists want a great white shark in captivity so that we can learn more a­bout them as a species, and of course people want to look in the eyes of the shark that has captivated so many imaginations and eaten so many legs. That's o­ne reason why shark cage diving has become popular recently. People seem to think that if you can't get the sharks to come to you, then it might be time to go to the sharks.

Shark attack survivor Rodney Fox developed the first shark cage, and since then, many adventure seekers have shelled out hundreds of dollars to get an up close glimpse of a great white. As might be expected, this practice has sent up red flags for conservationists and scientists. For example, in order to attract sharks, some companies have sweetened the bait by using cow or pig blood. Scientists worry that these practices will affect the great white's feeding patterns in ways that could eventually pose dangers to humans. Rules that limit the amount of bait and the type of bait used have developed among the diving companies, and there have been no deaths associated with this practice. Still, sharks have gotten their heads stuck between the cage bars, which could potentially break the cage [source: Thomas].

Want to get even more up close and personal with the great white? Turn the page to read about mating and reproduction.

This great white shark was accidentally caught in a fishing line and died.

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Great White Shark Reproduction and Conservation

There are several unknowns in the great white shark's reproductive process; biologists have only been able to dissect about 10 pregnant females [source: McGhee]. Because of the scars on their fins, great whites likely practice the typical courtship rituals of a shark, which involve the male biting the female to hold her in place during insemination.

The great white shark is ovoviviparous, which means that the shark grows in an egg, which is then hatched inside the mother. Shortly thereafter, the shark pup is born. While in the womb, great white shark embryos feast on unfertilized eggs, a practice known as oophagy. It doesn't appear that they eat the fertilized eggs, as a few other species of shark has been known to do, but they may swallow their own teeth when they lose them for the calcium [source: Martins, Knickle].

The gestation period is estimated to be 12 to 18 months, but this is largely speculative [sources: McGhee, Francis]. The litter size of the great white ranges from two to 10 pups, although litters of up to 17 pups have been documented [sources: MarineBio, McGhee]. At birth, great white shark pups measure 5 feet (1.5 meters) and weigh about 77 pounds (35 kilograms). The great white grows slowly: Males reach maturity at age 9 or 10, while females are mature at 14 to 16 years of age. Scientists believe that they live about 30 years [source: Martins, Knickle].

Because of the long gestation period, it's possible that female great whites give birth every other year, taking some time to rest after mating. This low reproductive rate and slow growth to maturity are concerns to great white conservationists. Scientists are interested in learning more about the shark's reproductive habits so that they will know better what conservation methods are needed. As we mentioned, great whites face numerous threats from humans, including fishing for fins and teeth and hunting for sport.

Marine biologists lack exact numbers on the great white population, but they're seen very rarely and are currently listed as vulnerable, according to the International Union for Conservation of Nature and Natural Resources. To those who didn't go swimming for a year after "Jaws," worrying about the great white's numbers may seem silly. Wouldn't the world just be better off if these man-eaters weren't around?

Conservationists and scientists stress that a lot of our fear of the great white is in our head, and that these creatures serve an important role in the ecosystem, one example being that they eat seals, which in turn eat salmon. An abundance of seals could lead to the elimination of salmon [source: Martin]. Currently, great white sharks have been afforded protected status in South Africa, Australia and the United States.

To find out more about the great white shark, see the links on the next page.

Lots More Information

Sources

  • "Carcharodon carcharias. Great White Shark." MarineBio.org. (May 5, 2008) http://marinebio.org
  • Carey, Bjorn. "Great White Shark Sets Ocean-Crossing Record." LiveScience. Oct. 6, 2005. (May 5, 2008) http://www.livescience.com/animals/051006_shark_migration.html
  • Carey, Bjorn. "The Truth about Great White Sharks, 30 Years After 'Jaws'." LiveScience. July 7, 2005. (May 5, 2008) http://www.livescience.com/animals/050707_jaws_anniv.html
  • Dingerkus, Guido. "The Shark Watchers' Guide." Wanderer Books. 1985.
  • Francis, Malcolm P. "Reproductive Strategy of White Sharks, Carcharodon carcharias." National Institute of Water and Atmospheric Research. (May 5, 2008) http://www.flmnh.ufl.edu/fish/organizations/ssg/sharknews/sn9/ shark9news8.htm
  • "Great White Shark." National Geographic. (May 5, 2008) http://animals.nationalgeographic.com/animals/printable/ great-white-shark.html
  • Grudowski, Mike. "The Shark Blotter." Outside. August 1998. (May 9, 2008) http://outside.away.com/outside/magazine/0898/9808sharkblot.html
  • "Guess Who's Coming to Dinner." The Bulletin. Feb. 16, 2005. (May 5, 2008) http://www.flmnh.ufl.edu/fish/sharks/innews/cage2005.html
  • Hammer, Joshua. "Going Nose-to-Nose with a Great White." New York Times. June 17, 2007. (May 5, 2008) http://travel.nytimes.com/2007/06/17/travel/17explore.html?sq= great%20white%20shark&st=nyt&scp=2&pagewanted=all
  • Harrison, Donald H. "What swallowed Jonah? Sea World educators identify the prime suspects." San Diego Jewish Press-Heritage. Sept. 13, 2002. (May 5, 2008)
  • Hoffman, Allison. "Fatal shark attack forces beach closures near San Diego." Washington Post. April 26, 2008.
  • "ISAF Statistics on Attacking Species of Shark." International Shark Attack File. Updated Jan. 29, 2008. (May 5, 2008) http://www.flmnh.ufl.edu/fish/sharks/statistics/species2.htm
  • Klimley, A. Peter. "The Predatory Behavior of the White Shark." American Scientist. March/April 1994.
  • Lineaweaver, Thomas H. and Richard H. Backus. "The Natural History of Sharks." Nick Lyons Books/Schocken Books. 1984.
  • Martin, Glen. "The Great White's Ways." Discover. June 1999.
  • Martin, R. Aidan and Anne. "Sociable Killers." National History Magazine. October 2006. (May 5, 2008) http://nhmag.com/master.html?http://nhmag.com/1006/1006_feature.html
  • Martins, Carol and Craig Knickle. "White Shark." Florida Museum of Natural History Ichthyology Department. (May 5, 2008) http://www.flmnh.ufl.edu/fish/Gallery/Descript/Whiteshark/whiteshark.html
  • McGhee, Karen. "Great White: Troubled Waters." Australian Geographic. January-March 2004.
  • Parker, Steve and Jane. "The Encyclopedia of Sharks." Firefly Books. 2002.
  • "Peter Benchley, author of Jaws, dies at 65." Monsters and Critics. Feb. 13, 2006. (May 5, 2008) http://www.monstersandcritics.com/books/news/article_1097132.php/ Peter_Benchley_author_of_Jaws_dies_at_65
  • Ragland, Jennifer. "Great White Hope." Los Angeles Times. July 10, 2003.
  • "Rodney Fox Biography." Rodney Fox Shark Experience. (May 9, 2008) http://www.rodneyfox.com.au/index.php?option=com_content&task= view&id=38&Itemid=51
  • Stevens, Jane E. "The Delicate Art of Shark Keeping." Sea Frontiers. Spring 1995.
  • Thomas, Pete. "Given a choice, they swim with the sharks." Los Angeles Times. Nov. 27, 2007.
  • Tricas, Timothy C. "Feeding Ethology of the White Shark, Carcharodon carcharias." Biology of the White Shark, a Symposium. May 24, 1985. (May 5, 2008) http://repositories.cdlib.org/sio/lib/3/
  • "White Shark." Monterey Bay Aquarium. (May 5, 2008) http://www.mbayaq.org/efc/living_species/print.asp?inhab=480

Great White Shark: Cheat Sheet

Stuff you need to know:

  • While the great white shark does outrank all other sharks in the number of shark attacks, humans are generally too muscular and lean for a typical shark meal. They tend to prefer fatty prey -- for instance, a seal might be 50 percent fat, representing a very efficient meal for great whites.
  • Great white sharks rely primarily on their sense of vision, though they are also equipped with strong senses of hearing and smelling.
  • Its jaws, filled with about 3,000 triangular teeth, are its most notable feature. The great white shark's scientific name is Carcharodon carcharias, which means "ragged tooth" in Latin.
  • Unlike many other fish and sharks, the great white shark is warm-blooded.
  • Great white sharks are nearly impossible to keep in captivity, so you likely won't find one at the aquarium. As a result, scientists and adventurers alike are always trying to find new ways to get a close look at these fascinating creatures.

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