Sharks aren't cute and cuddly but neither are they killing machines as so much of the media portrays. In fact little is known about sharks and as they become increasingly endangered this might be our last chance to learn more about them.
Scientists and people worldwide used to believe that sharks were merely scavengers, which lacked the ability to seriously injure humans due to the lack of pressure in their jaws. This can be seen reflected in Michael Capuzzo's 'Close to Shore'.
Although Peter Benchley 1 the author of
Jaws loosely based his novel on a series of attacks on humans, by a possible lone Great White in the summer of 1916 on the New Jersey resort shoreline, in which three adults and one child were killed. Peter Benchley primarily was inspired to write Jaws, after reading a newspaper story about a man who caught a two-ton great white off Long Island.
Benchley's novel and the film shocked the nation and made them feel threatened. Benchley was so horrified by what he’d done to the reputation of the shark species that he became a spokesman on their behalf.
Although, Jaws maybe seen as the most famous story to depict sharks, the Great White and other sharks of the big blue sea have also been characterised by television programmes such as Sharkie and George, Kenny the Shark and films such as Shark Tale and Deep Blue Sea.
- Kingdom: Animalia
- Phylum: Chordata
- Class: Chondrichthyes (rays, sharks, and relatives)
- SubClass: Elasmobranchs (sharks and rays)
- Superorder: Euselachii ( From the Greek Eu - true and selachos - shark)
- Order: Lamniformes (Mackerel sharks)
- Family: Lamnidae (mackerel sharks, porbeagles, and white sharks)
- Genus: Carcharodon (from the Greek, karcharos - sharpen and odous - teeth)
- Species: Carcharodon carcharias
The great whites family also contains the two species of Mako Shark, the Salmon Shark and the Porbeagle shark. All of which look more or less like small Great Whites and are probably often mistaken for them.
The great white is the only living species in the Carcharodon genus, the genus also used to contain the monstrous Carcharodon Megalodon2 that lived during the Neogene and Pliocene periods (24 to 1.67 million years ago). This time frame was when mammalian order Cetacea was at its highest diversity and abundance. So it is thought that the monstrous Megalodon used to eat whales! However we should be safe today as the last Megalodon fossil tooth (were about 12ft (3.5m) long) dates from around 3 million years ago.
The Great White is a very large species of shark. They are streamlined swimmers and have a torpedo-shaped body with a pointed snout. For decades the weight and measurements of the Great White Shark have been debated. However, after much consideration many academics now believe that the Great White Shark’s maximum length is 6 m (20 ft), new-born Great Whites measure only 47 inches (119 cm) long. It is believed that the Great White Shark weighs about 1900 kg (4200 lb.)and can absorb around 14 kg (30 lb.) of flesh, and can gorge on several hundred pounds or kilograms of food in just one bite.
They have about 3000 teeth, arranged in seven rows. The first two rows of teeth are used for grabbing and cutting prey, while the teeth in the last rows rotate into place when the front teeth are broken, worn down, or fall out. The teeth are triangular with serrations on the edges and they are retractable, moving into place only when the jaw is opened.
Their skin is rough as sandpaper and can cut fish as they swim past the shark.
Although named The Great White Shark, this particular species is in fact black, slate-grey and dun in colour, with only its ventral surfaces being white. These colours help the Great White Shark stay camouflaged from their prey. The Great White Shark has three main fins: the dorsal (on back) and two pectoral fins (on the sides). There is a distinct line of demarcation separating the dorsal and ventral surfaces. This marking which appears in the form of blotching is said to distinguish the sharks origin. Likewise the colour of the shark can be seen to reflect its origin; Californian sharks being very dark slate-grey, almost black. South African sharks (Cape Province) appear to be dun or olive, like Australian sharks, though it varies a great deal. Mediterranean sharks are usually slate-grey or dark olive-brown dorsally. Great White Sharks also exhibit a crescent shaped tail and have five-gill slits.
The Great White Shark is an incredible predator. Their keen senses make them an efficient killer. Great Whites have an acute sense of smell where they can sense a drop of blood in 100 litres (25 gallons) of water. They also have what appears to be a 'sixth sense' when it comes to detecting tiny electrical signals from other animals in the water and they can pick up electrical charges as small as 0.005 microvolts even if the prey is hiding.
It is debatable whether at all sharks' sleep or not. If they do then they are likely to
sleep during daylight and come awake during the night.
Overall the amount of Great White Sharks is unknown and even regional and localised estimates are sketchy. Annually, the number of Great White Sharks differs and can be very variable and unpredictable. It is not known why some years see more Great Whites being born than others. There is believed to be 200 Great Whites living in the Dangerous Reef area of South Australia. Another way the numbers of Great Whites is being reduced is through fishing.
Great White Sharks live in all coastal temperate waters, and have been known to occasionally make dives into the deep water of open oceans. They can be found in water as shallow as three feet deep, and as deep as 1,280 metres. They can be found on the following coastlines: California to Alaska, the east coast of the USA, most of the Gulf coast, Hawaii, most of South America, South Africa, Australia (except the north coast), New Zealand, Mediterranean Sea, West Africa to Scandinavia, Japan, and the eastern coastline of China to Russia.
Sharks are important predators in the marine ecosystem and the only known creatures (besides humans) which may eat them are Killer Whales. Sharks prey on seals, sea lions, turtles, sea birds and as youngsters feed off fish and rays. When they become fully grown they consume whales, seals, dolphins, large tuna fish, sea otters, and dead animals that they find floating on the surface. Sharks find their food by lurking at the bottom of the ocean and looking up to see the shapes of what is floating above them. If they spot what looks like food they are quick to pounce on it and stun and injure their prey by ramming it and biting at it in one quick motion. When a Great White believes the prey to be dead it rips it into shreds and swallows it. A big meal can last a shark up to two months and sharks can chase their prey at speeds of 25mph if needs be.
Unlike the shark in Jaws which was made out to be hungry for humans and lonely, the Great White Shark is actually quite a sociable character, with an abundance of complex behaviours. They have been known to exhibit pecking orders when it comes to feeding, with the largest Great White Sharks having priority over the smaller sharks. They hunt in packs. Great White Sharks are also known to have different swimming patterns which relate to keeping their own personal space, such as cautiously-timed 'turn-aways' between two animals coming into line with one another. Similarly, the 'parallel-swim' technique acts as a way of keeping distance from one another as well as personal space. When feeding the Great White Shark will also deflect competition by using their caudal fin 3 to 'tail slap' the competition away and they have also been known to shove or 'body-slam' other White Sharks (and boats) out the way. Many Great White Sharks also appear to have slash and puncture wounds made to their head and dorsum, which are inflicted by the rivals of the sharks in aggression, competition and in courtship.
Breeding and Life span
There is still much to learn about the Great White Shark as regards behaviour. For example, little is known about their mating rituals and the birth of this species of shark. What is known from examining the pregnant females is that Great Whites are ovoviviparous, which means that the eggs develop and hatch in the females uterus and continue developing until they are born, at which point they are perfectly capable predators. The Great White Shark is different to other sharks in this way because other species of shark lay eggs. The young fend for themselves; there is no placenta in which to feed, so they eat the unfertilised eggs and smaller siblings in the womb. Even when the young are born their mother does not help them; instead they swim away and live on their own. Great White Sharks appear to be born during spring to summer, with one single delivery containing as much as 14 young. Each of these baby sharks will measure about 1.5 m (5 ft) long when born, but will grow rapidly by 25cm (10inches) each year, reaching maturity at 10 years reaching 2 meters of length in the first year of life. A White Shark can reproduce when a male's length is around 3.8 meters and a female's length is around 4.5 to 5 meters. Their life span is not known, but is estimated to be 14 to 15 years.
Threats to the species
Scientists believe that sharks are in major danger because they appear to inhabit only 10% of the world's oceans. Although this has occurred their body plan has survived many traumas over the years including ice ages and warm spells. Their are also organisations being set up such as the Shark Trust which are helping to eradicate the threats below that the Great Whites are currently encountering.
Many reasons exist behind the act of shark fishing, such as their skin is used as leather, teeth and bone for ornaments, liver oil in cosmetics and aircraft industries, cartilage is used in cancer 'treatments' and their fins create food. Because sharks are at the top of the food chain, with as many as 100 million a year being slaughtered, there are severe repercussions for the whole marine ecosystem.
Source of Food
In some countries, such as the United States, Mexico and China (Hong Kong, China, Japan, Singapore, Thailand and South Korea), the Great White shark can be seen as a source of food. Ishark-fin soup is a delicacy comparable to caviar. Chefs extract the flavourless cartilage needles, which add a gelatinous texture to the soup. In China a bowl of shark soup can cost around £65, which at first only made it affordable for the rich, but due to the rise of a wealthy class in China shark fin soup is increasingly becoming affordable to all of China. Shark fin soup usually is eaten at special occasions such as birthdays and weddings and has even had an on screen debut featuring in the film Crouching Tiger, Hidden Dragon when the governor's daughter, Jen Yu, ordered shark-fin soup upon sitting down at a restaurant. There have been reports of fisherman cutting fins off live sharks and throwing the poor creatures back into the sea.
Sharks have also been known to be caught and killed in order to win competitions, before being abandoned.
Sharks are also accidentally caught up in the nets of commercial ships, which are out looking for fish. The accidental catches of shark well exceed those caught deliberately. While there are shark nets in place along the KwaZulu/Natal coast, which also trap sharks and stop them from moving. Consequently, the sharks are starved of fresh, oxygen-rich water for their gills, and die.
Cage Diving may be defined as a sport in which a human can stand within a 3mm cage of steel and see the shark up close in the water.
Although it has never been proven some people believe that Cage diving negatively effects sharks. This is because sharks and humans don't usually interact with one another and over time sharks will adapt their behaviour towards humans.
Seeing the Great White Shark is also a tourist attraction. The best places to see the Great White Shark in the wild are Farallon Islands4, Dyer Island (Shark Alley!) in South Africa and in the Southern Australian Ocean off Adelaide and Port Lincoln. As well as being great holiday destinations, these places enable holidaymakers to get close and personal with the sharks allowing for a memorable experience. This aside though Farallon Islands is not quite as Eco-friendly as it first thought it would be.
For centuries humans have been using the great oceans as a refuse site to dump their waste in. As a result all life in the oceans including sharks and their prey have been polluted. Like many other animals at the top of the food chain, sharks consume prey that has stored up so much toxic material in their tissues that they have actually become poisonous. The long-term effects of this type of pollution on sharks are unknown. Sharks are slow-growing animals. A single female shark produces only a few hundred pups or less in a lifetime. If the shark's population continues to suffer from the effects of pollution and other man-made problems like overfishing, it may take years to recover and certain species of sharks may disappear forever.
Usually Great Whites do not attack humans on purpose. Most attacks are test bites by sharks to recognise the creature; much like a dog sniffs a stranger to find out what they are like. Unfortunately, for the human bitten by a shark like the Great White (the pressure at the point of the Great White's teeth is some several tons), this could mean losing an arm.
Other attacks are due to a case of mistaken identity- from the bottom of the sea; a paddling surfer looks much like a seal (one of the Great White's target prey). Humans are certainly not ideal for the Great White shark to eat because they are not substantial food sources. Once the shark has taken a test bite and found the object is not edible they break off contact, thus it is believed that if any fatalities do occur from the shark it is because of the initial test bite. Many fatalities also occur in waters with low visibility, or other situations in which the shark's senses are impaired.