The study of shark attacks

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Posted by on November 24, 2004 at 01:42:08:

Near Cape Town, on the Southwest tip of South Africa, the coastline pounded by the planet's most violent sea. Here, the Indian Ocean meets the Atlantic, creating the notorious Cape of Good Hope feared by mariners worldwide. But beneath the waves, lies a greater danger. There are over 350 different species of shark that patrol our seas, but three are especially dangerous to man. The Bull, the Tiger and perhaps the most feared of all the Great White. Growing to over 20 feet in length and weighing over 3 tones- Great Whites have few enemies.

33-year-old local, Craig Ferreira, has been fascinated with the behaviour of the Great White for nearly all of his life.

"If we can really learn enough about the white shark's interaction with humans, we can provide positive input or really substantial information to the general public that use the ocean."

Craig hunts for Great Whites in a stretch of sea known as 'shark alley', 10 miles off the southerly tip of Cape Town. Already a veteran of cage diving, Craig now pushes the envelope even further. He dives with the Great White unprotected to study how they react to humans in open water. It is a high-risk experiment. Great White's are intelligent hunters and pick their prey carefully - they do not get to grow to 20 feet in length by being reckless…or too timid.

"What you've got to remember when diving with them is that these animals take out huge seals, they take out other large sharks, they eat and kill big sharks, so if that shark decides to do something, you've got absolutely no chance at all, and obviously as a result you do have close encounters."

On the other side of the world on the west coast of Australia, a group of swimmers confrontation with a Great White revealed how selective a shark can be when choosing its prey. In Perth there is a local swimming group called the Pod. One of their members was businessman Ken Crew. The morning of November 6th 2000 started like any other. The 'pod' met on the beach for their usual 6.30am swim. At the end of the swim over a dozen of the members stood chest deep water. Then suddenly someone yelled 'Shark! Get out of the water!' The swimmers fled for their lives. The Great White caught Ken in its massive jaws. The shark had bitten off his right leg, slicing through a major artery. He had bled to death in seconds. But how and why did the shark single out Ken Crew, in the middle of such a large group of swimmers?

Something about the movement and position of Ken Crew made him more vulnerable then the other swimmers. The Great White has better colour vision than any other shark - it is this hunter's greatest asset. It may have watched him from several hundred yards offshore. It can stalk its prey with one eye above the water's surface, picking the moment to close in and strike. As it approaches, a Great White rolls its eyes back into their sockets. Now attacking blind the Great White switches to electro detection. The human body is full of electrolytes and our breathing creates electrical fields that the shark can home in on. Sensitive capillaries on the snout can detect currents as low as one 5 billionth of a volt. In the attack on Ken Crew, the electrical activity from his beating heart may have been enough for the shark to home in on.

But Australia and South Africa are not the only place with a treacherous coastline. Around the world there are 14 shark attack hot spots. Danger zones where people are at greatest risk. As our fascination with using the sea for leisure increases, so do the number of attacks. 98 of them have happened in the warm tropical waters of Hawaii.

Three years ago housewife Laurie Boyette decided to take the long trip from Rhode Island to Kona, Hawaii for a family vacation. She went swimming in the sea with her nephew; both were strong swimmers.

"I actually had a premonition that if there was a shark this is where it would be and at that point I was a little bit past a raft which was maybe a 150 yards out. And I thought that was a very strange thought to have but it did not scare me I just wondered where it came from."

As Laurie approached the buoys, her premonition became a reality. She was hit from the backside and knocked out of the water.

"The actual bite itself was excruciating, and the only way I can describe it is to say that when you have a piece of glass in your finger it is, it, you are very uncomfortable. Well you can imagine having a thousand pieces of glass in your backside."

As she struggled to push the Tiger shark away, her hands tore against the razor sharp serrated teeth.

"I raised my hands up in front of my face and I saw pieces of flesh hanging down to my palms."

Although Laurie's hands had only been in contact with the teeth for a second, the damage was enormous. Flesh was torn from the bone. Nerves and tendons were shredded. But nothing could prepare the surgeons for the full extent of her injuries. They found the entire right buttock missing. The teeth had bitten a hole 16 inches in diameter. Saving Laurie's life was a race against time. The shark's teeth had sliced through arteries and she needed over 20 pints of blood just to keep her alive. Three years on Laurie has made a full recovery, but like others who have come face to face with oceans greatest killer - she still bears the scars.

But why did the shark attack her? Was it because she was swimming on the surface or that women are at greater risk then men? It seems highly unlikely that sharks can distinguish women from men and there is certainly no statistical evidence to back this up. It is far more likely that she was attacked because she was thrashing about on the surface. Surfers get attacked the most. One reason why surfers might get attacked so often is that they spend more time in the water than any other user group. They spend more time in than bathers, divers and windsurfers together - they spend a huge amount of time in the water.

Like many teenagers who live on the island of Hawaii, Jesse Spencer spends hours in the ocean waiting for that next big breaker. On the afternoon of October 1st 1999, he was at his favourite surf beach paddling into deep water. He was about to learn of a shark's attraction to movement on the surface and their readiness to have a quick taste. Like most shark attacks, Jesse's strike came out of the blue.

"I just felt a big bump. As I was turning my head I was thinking maybe a turtle another surfer. I do not think a turtle could bump me that hard. So then I turned and sort of saw the shark pop up and went over my arm and I went under water. I could feel the tips of the teeth pretty sharply. They first touched my skin and then went through, and I could not feel anything."

The shark that attacked Jesse was a Tiger and like most species its teeth are perfectly adapted for cutting through tough skin and muscle. Jesse was bitten and let go - the shark clearly did not want to make a meal of him. So why was he attacked? Was it a case of mistaken identity? Some scientists believe that if the animal's motivated to feed then what is the risk in going up and taking a little taste. Jesse's attack took place in open deep water. He had no defence against the shark that struck him silently from below. The bite left Jesse's arm so badly mutilated it's still on the road to recovery. After 2 years, he still does not have full mobility.

With over to 100 attacks and 10 deaths a year, protecting ourselves from shark attacks is becoming ever more important. Over the last few years the largest increase in shark attacks has been along the eastern coast of America. The summer of 2001 witnessed sharks moving in to shallow waters and striking swimmers near the shoreline. In just 3 weeks there were 20 attacks and 2 deaths - often in water no more than 3 feet deep. Everyone wants to know if it was because there were more people in the water or because the sharks were becoming more aggressive?

We may never know the answer but scientists from State Longbeach believe we could reduce the number of attacks if we knew more about their feeding habits. Their research could help us judge what times of the day it is most dangerous to get in to shark-infested waters. The scientists are not convinced by the popular theory that sharks only feed at the beginning and end of the day. The sharks' stomach contains acid that varies in concentration depending on how hungry they are. The weaker the strength, the bigger their appetite. Using a metal probe, packed with microelectronics, they plan to look into the digestive habits of a shark.

They plan to feed the probe to a shark and record the times of the day when stomach acid levels are at their weakest. Then they will know when the shark is hungriest and most dangerous. By gutting a squid and hiding the probe inside, they hope to fool the shark into swallowing it whole. Then by tracking and down loading data remotely, they will be able to pin point exact feeding times on any shark.

There is still much to learn about the science of shark attacks. Those who have lived through the nightmare have drawn their own conclusions about when it is safe to swim. Science and technology may be able to help us - but one fact is certain. As more and more of us take to water, the number of shark attacks is going to increase.

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