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Biology - Behaviour - Research Biology of 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 sharks 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 animals 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 Natals 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 oceans top predator. If you have any questions about white shark biology, please contact us at mike@sharkdivingunlimited.com A phenomenon made famous in South Africa is the awe-inspiring breach. Launching themselves from the sea at great speeds, white sharks can easily clear the water in an attempt to attack and kill elusive pinniped prey. Michael Rutzen is a master at eliciting this behavior from the great white shark due to his intimate knowledge of the Dyer Island's aquatic topography and years of observing the complex relationship between shark and seal. In one day during 2000 he managed to elicit a staggering 15 breaches from great white sharks at Dyer Island, a feat that has never been matched. Open Mouth These type of images have traveled around the world and have even been illustrated in National Geographics. The Touch... Michael Rutzen has mastered the technique of triggering the White Shark to react to his touch. The shark arcs backwards and extends his jaws to a maximum out of the water. The reason behind this amazing behavior remains a mystery to all. But whatever the reason may be, the spectacular reaction of the shark to Michael's touch is one of awe and admiration. Shark Diving Unlimited offer their staff, resources like boat space and bait, and expertise to any bonifide research group. In South Africa, all White shark research is performed by Marine and Coastal Management, with an additional project run in Gansbaai by Michael Scholl (White Shark Trust). SDUs Mike Rutzen has dived many times for Marine and Coastal Management, placing and recovering white shark acoustic tag receivers in Mossel Bay, False Bay and Dyer Island. He was also a part of the team that placed Satellite tags on white sharks to study their large scale movements. This project, a collaboration between MCM and the Wildlife Conservation Society, was groundbreaking and resulted in white sharks receiving CITES Appendix II protection. SDU have supported the White Shark Trust for many years, providing boat space for both Michael Scholl and his research assistants. |