Sharks
Explore the World of Sharks
Dive into the fascinating world of these apex predators, from their unparalleled hunting prowess to their enigmatic migration patterns. Unravel the secrets of these ancient creatures, steeped in myth and mystique, within the underwater realm where they reign supreme.
Great White Shark
Of the estimated 350 plus shark species in the world, the iconic Great White has always fascinated mankind the most – for various reasons.
The Great White as we know it today is believed to have been around for 70 million years, but their very first ancestors might have appeared as early as 200 – 500 million years ago! Yet, it is shocking how little we know of these most adapted species that outlived even dinosaurs and the ice ages!
Marine research is a relatively new field that only got momentum in the 1950’s. Therefore, most of the gripping questions regarding the elusive Great white shark have as yet remained unanswered or have not been documented. One of these questions concerns their age. Many scientists estimate they can live up to 50-80 years of age, but the truth is that nobody is sure. Another question would be – how old would they normally grow if their biggest enemy – mankind – did not kill them off at a shocking rate for commercial and recreational purposes?
Underneath are some of the interesting information our Marine Biologists and researchers have been able to verify regarding these mysterious and misunderstood apex predators of the ocean.
Bronze Whaler (Copper) Shark
Bronze whaler sharks have become the new stars at Gansbaai’s shark cage diving boats.
Bronze whaler sharks (Carcharhinus brachyurus) otherwise known as the copper shark because of its distinctive colouration is the new star at the shark cage diving boats in Gansbaai. This species is found in temperate waters and usually seen in groups. Bronze whalers can grow up to 3.3m in length during its 25 to 30-year lifespan. Their copper/gold colour is distinctive, and this species is very active around the boats leaving nature lovers and divers enthralled. It is not known to be predatory to humans, but itself faces fishing pressures and is considered near threatened by IUCN – International Union for Conservation of Nature. Marine Dynamics, together with other operators, is working towards a no catch policy in the Kleinbaai area.
We first noticed bronze whalers at the shark boats in 2013 and it has been amazing to see how they have adapted to the area. The only other way that people are able to see bronze whalers is if scuba diving on the sardine run, which is limited to a few weeks in June and July.
Shark Facts
This question has reared its ugly head once or twice on Slashfin, so I thought I’d lay it to rest with this week’s shark fact blog! We’ll learn about gill slits, revisit ram ventilation, and show how two branches of evolution come up with two different solutions.
Have you ever pet a shark (not that we condone shark petting!)? Shark skin is smooth if you rub them from head to tail, but rough if you go tail to head. This is because shark skin is actually teeth and this shark blog explains all about it…
Have you ever wondered, when do white sharks go through puberty? This shark fact blog delivers the facts (of what we know) about white shark sexual maturity. Do they get acne and voice cracks too??
Did you know?
Precarious Population
It is believed that there are less than 5 000 Great White Sharks left on the planet, and recent estimates suggest that 2 000 of these are to be found in South African waters, emphasising just how special our ecosystem is.
South Africa’s Rich Marine Diversity
The presence of sharks is a key indicator of the health of a system. South Africa boasts one of the largest concentrations of Great Whites and other shark species thanks to our prolific and diverse marine life and contrasting oceans.
Rapid Recovery
Great whites may have some of the fastest healing rates known in the animal kingdom, with incredibly strong tolerance to injury and illness. Cases have been recorded of sharks making a full recovery after being severely injured by boats or encounters with other marine animals.
Anatomy and Predatory Prowess of the Great White
The Great white is one of the top predators in the world. They have one of the most developed sensory and visual systems of all fish species and are highly sensitive to vibrations and electrical impulses. These qualities, combined with their counter-shaded streamlined, torpedo-shaped bodies and powerful tails that enable them to slice through the water at speeds of up to 50 – 60 km per hour in short bursts, make them a most formidable hunter and an expert on surprise-attacks.
Adaptation to Diverse Environments
They are partially warm-blooded to adapt to contrasting and extreme water temperatures. This enables these migrating animals to be equally at home in the cold waters of the Atlantic Ocean, the warmer Indian Ocean and tropical waters.
Eyes of Midnight Blue
Great Whites do not have that cold, staring fish-like onyx black buttons for eyes that most people think. Contrary to popular belief, their eyes rotate in their sockets and they are actually a stunning midnight blue! In good light one can clearly distinguish the circular pupil and dark iris ringed with a spectral hint of bright blue. They have no eyelids and roll the eyeballs back in their sockets to protect the vital front part of the eye from being scratched. Their highly developed visual system – in certain aspects more advanced than our own! – enables them to see perfectly in day or night light and their retinas are particularly sensitive to contrast and motion.
Great Whites’ Vast Oceanic Journeys
They are migratory animals and can travel vast distances in short periods of time. One has been tracked swimming from Dyer Island to Australia’s north-west coast and back – a journey of 20 000 km – in 9 months! Despite this, experts are not sure why, when and where they travel.
Maturation and Reproduction of Great Whites
Great Whites only reach maturity between the ages of 15 – 20 years. Nobody has ever witnessed a Great White mating or giving birth in the wild, but we do know that they are born live and that the new born pup is self-sufficient at birth. They are ovoviparous, which means the eggs are fertilised in the female’s uterus, where they also develop and hatch while still in the womb. After a gestation period thought to be 12 – 18 months, the females may give live birth to 2-8 fully formed pups measuring between 1,2 and 1,6m.
Great Whites’ Teeth and Tooth Replacement
Great whites have up to 300 serrated, triangular teeth arranged in several rows. When they lose or damage a tooth, it is replaced by a new one throughout their life. It is believed that a Great white may use and lose up to 30 000 teeth in its lifetime.
The Hunter’s Diet
They are selective carnivorous feeders. They hunt and feed on a wide variety of fish, seals, sea lions and even dolphins.
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