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False Bay wildlife – Great white sharks

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Great white shark. 
Great white sharks, as featured in the 70s blockbuster movie Jaws, are not monstrous man eating sharks but instead great predators of the sea that hunt marine life. Known for their great size and as the largest predatory fish on Earth, males reach an average of up to 5.2 m (17 ft) in length while females generally grow larger in size. Great white sharks have been recorded to reach a remarkable length of 6.4 m (21 ft).

Being cartilaginous fish, sharks are made up of cartilage and have a streamlined body designed to cruise easily through water with little effort. Their snouts are large and conical in shape with a strong jaw lined with rows of teeth making a total of up to 300 triangular, serrated and razor sharp teeth. Great whites have an outstanding sense of smell and organs that can sense electromagnetic fields generated by animals and humans alike. These sharks, along with mako and whale sharks, will die from lack of oxygen obtained through their gills if they stopped swimming.

Their colouration helps with camouflage in the sea, with slate-grey upper bodies and white underbellies (hence the name great white sharks). Due to the white underside and grey dorsal area that break up the outline of the shark, it can be difficult to spot the shark from the side, below and above.

These ferocious predators of the sea have no natural predators other than the killer whale and are legally protected in South Africa. Great whites live on average up to 70 years or more, making them the longest living of all cartilaginous fish.
Shark spotters

The Shark Spotting Programme was founded in 2004 due to the increase in number of great white shark sightings along the shores of Cape Town and thus the fear of beach goers, predominantly in False Bay. Shark spotters are employed and plotted along the coast, seven days a week during daylight hours, in high platforms to scan seashore waters for sharks, and once sighted the alarm is raised.

Shark spotters flag meanings

·         No flag = no spotter on duty
·         White Flag (with a solid black shark) = shark has been spotted, sires have been sounded, or after serious shark incident at the beach.
·         Red Flag (with solid white shark) = high shark alarm, 1 hour after shark seen, high risk of shark activity.
·         Black Flag (with shark outline) = poor spotting conditions, no shark seen.
·         Green Flag (with shark outline) = spotting conditions good, no shark seen.
Shark spotting flags. 
Habitat

Great whites establish their cruising waters in all major oceans that fall in the temperature range from 12 through to 24 °C (54 to 75 °F). They swim along coastal countries such as the United States, Japan, Chile, Australia and South Africa and are found in the Mediterranean seas.

One of the highest numbers of great white shark populations are found swimming between Dyer Island and Geyser Rock off the coast of the Gansbaai coastline, dubbed Shark Alley. Seal Island is situated in the middle of False Bay, some 30km out to sea from Cape Town, and is home to about 64 000 seals, three species of cormorants among other sea birds and even some penguins. Between February and May great white sharks make a return to Seal Island to hunt seals, often drawn to the northern tip where sick or wounded seals are found.
Great white breaching. 
Behaviour

In South Africa, great whites follow a dominance hierarchy that is determined by the size, sex and rights of the resident: females are dominate over males, while larger sharks dominate smaller sharks and residents of the area dominate newcomers.

During hunting, these sharks tend to resolve conflicts with other sharks using rituals and displays instead of taking on one another in combat. Great white sharks are one of the few sharks known to engage in spy-hopping, which entails the lifting of their heads above the surface of water to gaze as other objects such as potential prey. These magnificent sharks propel themselves out of the water into the air by travelling up to speeds of 40km/h under water, which is known as breaching.

According to scientists, great white sharks behave differently in False Bay at Seal Island than anywhere else along the South African coastline.
Diet

Great white sharks are carnivorous predators of the sea who prey on and eat fish, seals, sea lions, sea turtles, sea otters and sea birds. Ambush hunters by nature, they take on their prey by means of surprise attacking from below.  When the shark bites, it shakes its head side-to-side, helping the sharp teeth cut off large chunks of flesh.
The jaws of a great white shark.
Reproduction

Not much knowledge is known about the reproduction and mating of the colossal great whites. Male great white sharks are believed to reach sexual maturity between 9 and 12 years of age while females are ready for mating between 13 to 16 years old.

Great whites are ovoviviparous, meaning eggs develop and hatch in the uterus and then continue to grow for between 14 to 18 months until birth. The youngsters are then delivered during spring and summer.
Did you know

Great white sharks are responsible for the highest number of reported and identified unprovoked yet fatal shark attacks on human. 

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