Great White Sharks
(Carcharodon carcharias)
White sharks belong to the Lamnidae group, alongside species such as
Porbeagle and Mako sharks.
There are a few known white shark ‘areas’: South Africa, South Australia,
West and East coast USA, Japan, and the Mediterranean. These populations are
not believed to be isolated – it is probable that white sharks make large
migrations and trans-oceanic movements in search of food and/or mates.
Hunting
White sharks are supreme hunters, and are dominant in their ecosystem. Their
diet is made up of large fish like tuna, and other types of shark and rays.
Part of the diet is made up of mammals. In most cases that is seal. However,
in some areas, white sharks are known to hunt dolphins. And certainly,
should a shark come across a whale carcass, it will feed until full, and may
even stay with the carcass to get as much as possible. Blubber is an
incredibly rich food source.
When hunting fast prey like fish and seal, white sharks use mainly vision
and smell. Both of these senses are well developed in white sharks. They
also have a good and fast sense of taste. The white shark’s sense of touch
and hearing are also good, but not extra-ordinary. Like other elasmobranchs,
white sharks use special sensory pits around their snout and head (ampullae
of Lorenzini) to detect electro-magnetic pulses. Every living thing produces
these faint pulses, and sharks can use that to hunt.
Along with all other fish, white sharks also possess a lateral line. This
chain of sensory pits runs the length of the animal’s body, and is good for
detecting water vibrations. Using the lateral line, a shark can tell from a
distance whether an animal is injured or disorientated, and even how large
it is.
White sharks use ambush attacks and stealth to hunt prey. They do not
partake in prolonged high-speed chases. Instead, they use short bursts of
speed to catch prey, and conserve their energy when they are not hunting.
White sharks hunt around underwater reefs and kelp beds. They also hunt in
the surf zone and can enter water just a metre deep in search of fish and
possibly dolphins too. Sharks hunting around underwater drop offs can even
breach clear of the water in high-speed attacks on prey passing above them.
Reproduction
White shark reproduction is still not fully understood. It is believed that
females only become sexually mature at around 4m in length (which equates to
almost 20 years old). Females give birth to litters of pups (between 4 and
14), and pups are born fully functional.
Dangers
One thing that is clear is that white sharks are hugely at risk. White
sharks are not protected everywhere yet, and are freely hunted and killed by
some countries. Even here in South Africa, where they are protected,
anything up to 50 are killed annually by Kwa-Zulu Natal’s shark nets.
Although these nets can be replaced by an electrical alternative, the South
African government will not do so because the public will not accept the
changes. In addition, white sharks jaws and teeth are still sold as curios
and sickening mementos, and their fins are still sought after by the
Japanese for shark fin soup. This disgusting waste of such an awesome animal
should no longer be condoned. Please do not buy shark teeth, jaws, or any
shark leather products (or any other animal products). Please do not eat
shark fin soup, and walk out of any restaurant selling shark fin soup.
Please help save the ocean’s top predator.
If you have any questions about white shark biology, please contact Jenna at
sharkdivingunlimited@maxitec.co.za