Marine Biology

Eating Habits of Great White Sharks



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Carcharodon carcharias, otherwise known as the Great White', is probably the world's most instantly recognisable shark. However, its fearsome appearance with rows of serrated white teeth and soulless black eyes, have unfairly led to its notoriety as a man-eater.




This couldn't be further from the truth. Statistics show that shark attacks are far more likely to be perpetrated by species such as Tiger sharks (Galeocerdo cuvier) and Bull sharks (Carcharhinus leucas).




So far from being mindless killing machines, the eating habits of Great Whites, are primarily concerned with finding enough food to survive. They are the product of millions of years of evolution, and during this time their appearance has changed little since they swam with prehistoric Ichthyosaurs, some 65 million years ago.




Physiology:




Also known as the White Pointer', due to the distinctive white tip on the underside of its nose, the Great White weighs around two tonnes and can measure up to twenty-six feet in length.

It is a powerful swimmer and can reach speeds in excess of 45mph, by utilising its powerful sickle-shaped pectoral fins, and distinctive crescent-shaped tail.




Geographical distribution:




Great Whites are mainly found in a lateral band across the globe, from the coast off California, to the coral reefs off Western Australia, and anywhere in between within a temperature range of 54-75 degrees Fahrenheit.

Hotspots also include the Cape of South Africa, where the shark plays its part in the eternal predator-prey relationship with Cape Fur Seals (Arctocephalus pusillus).




Eating Habits:




When one thinks of a shark, they usually summon the image of Carcharodon carcharias, thanks to the insidious use of its image in film and advertising. However, there is no getting away from the fact that the Great White looks the way it does because it has evolved to do so.




Rows of razor-sharp, serrated triangular teeth, each the size of a silver dollar, are perpetually replaced throughout the shark's lifetime. He or she will never require dentures, as it is estimated an adult will go through 400 completely new sets by the end of their life.




Great Whites use these awesome weapons, combined with incredible acceleration, to target their favourite prey, Pinnipeds', or Fin-footed animals (Bowling, 2008); namely Seals and Sea Lions. Lacking the ability to chew its food, the shark will clamp on with these teeth, which are arranged to form a vice-like grip around the prey. Once it has hold, the shark will make familiar threshing movements, tossing its head from side to side as pieces are torn off it prey (Server, 1990).




Interestingly, the strategy of attack will depend on the particular species the shark is hunting.




For example, when attacking Cape Fur Seals (Arctocephalus pusillus), the Great White will search for a silhouette of what it recognises as a seal shape'. This being the familiar elongated, streamlined body, with large developed hind fins and a blunt head (which go some way to explaining why divers are occasionally mistaken for seals by the shark, as their swim fins or flippers look like seal's hind fins).




Once it has identified and selected its target, a Great White will accelerate at speeds of up to 45mph, and strike from an acute angle of between 45 and 90 degrees, perpendicular to the target (Burnie, 2001). This is thought to reduce the attack profile of the shark, and make it harder to spot for the seal until it is too late. Rather like a fighter pilot in a dogfight prefers to target an adversaries 6'o'clock.




After the ferocity of the initial attack, the shark will sensibly retreat, whilst the poor trashing seal or Sealion bleeds to death. Despite its ability to replace teeth, a Great White cannot replace an eye, and if one were to be damaged in the last death throws of a prey's life, it could limit the sharks capacity to hunt.




Once the unfortunate quarry is deceased, the shark will close in and feed in safety, targeting the easily accessible parts of the carcass and avoiding the blubber-coated hindquarters.




Opportunistic feeders:




Whilst Pinnipeds are the meat and two veg' staples of the Carcharodon carcharias diet, they will often take large fish species, dolphins and occasionally, even other sharks.




Shark attacks on Humans:




Despite the mass hysteria of the media, especially after the 1975 release of Jaws', and the myths it perpetrated about the risk of sharks to humans, statistics show that one is more likely to be killed by a Donkey than a Great White shark (Server, 1990).




Humans are not the intended prey of the Great White, as reports of attacks on humans have shown that when caught, people are usually quickly released.




Killer Whales (Orcinus orca) are actually the biggest and most voracious predator of the oceans, shared by the Great White, and it is the latter which is often the prey of the former.




Due to their frightening appearance, and especially when compared to the somewhat loveable antics of Orcas, Great White's have received an unfair reputation as the top man-eater in our seas and oceans.

Contrary to popular belief, swimmers, surfers, canoeists and other aquatic adventurers, are more at risk from being overturned by Orcas, or attacked by Tiger sharks (Galeocerdo cuvier) and Bull sharks (Carcharhinus leucas).




While many people suffer from Selachophobia (a phobia of sharks), most of them have never been near the ocean. Due to hunting and over fishing, the Great White Shark has more to fear from us than we do of it.

Sources:




Benchley, P. (1975). Jaws.




Bowling, S. (2008). Great White Shark, predator of the deep. from http://www.greatwhite.org (accessed 11/08/08).




Burnie, D. (2001). Animals. Dorling Kindersley, London.




Server, L. (1990). The World of Nature: Sharks. Gallery books.

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