As white sharks get bigger, between about two to three metres, they change their diet. They stop predominantly eating fish and start to include things like seals and sea lions in their diet.
From the deep: A shark will investigate and might just do an exploratory bite before leaving their victim alone, says Professor Hart. Water can often be murky, so that's a complicating factor, making it harder for a shark to detect and identify objects beyond a few metres. We also know that sharks are completely colour blind. They also have poor visual acuity — in other words, they can't see as much detail in an image as we can. If you imagine a black and white and slightly blurry image, that's what a shark sees compared to humans.
Obviously it's a bit chaotic when that type of event happens. Someone might start bleeding a lot. They may start panicking and thrashing around in the water. They may choose to fight back against the shark.
This assumption comes from analyzing several cases of white shark attacks on surfers, which concluded that looking a surfer from the bottom of the ocean resemble a seal. However, considering the visual capabilities of white sharks contradict this theory as white sharks have an exceptional vision system, making this explanation very unlikely. Even more, this premise does not explain many other attacks close to the shore and sometimes in very shallow waters.
There is another theory which states that the super sensitive senses of sharks, can detect electrical impulses characteristic of muscle moving and such signals make them interested in tasting. Some other theories introduced the idea that sharks are curious by nature and taking a small bite of a human is simply a way to satisfy their curiosity. This explanation came from the fact that most of the times that a shark attack, they give only a quick bite and then swimming away.
This behavior is very convenient for humans as sometimes people can survive the attack leaving the sea while the shark retreats. Attacks can be provoked and unprovoked.
The first ones happen when a person touches or hurts the animal so that it reacts to defend itself from what bothers or disturbs it. These are very rare cases, and their frequency is once a year. Unprovoked attacks are the most likely, and in these cases, sharks attack in three different ways:.
Hit and run. This modality takes place near the beaches if the shark is looking for food. The movements of people and confusion with their prey due to surfboards or activities cause the animal to approach, bite and walk away after verifying that the victim is not part of their diet. The person usually gets with minor limb injuries, and the chances of death are slim. Surprise attacks. The person and the shark are in deep waters, and the victim does not notice the presence of the animal. The shark confuses the person with a prey and bites it repeatedly before moving away or continue attacking.
These figures are blunt instruments, of course. They fail to account for the comparatively fewer numbers of people who actually use the water, and the fewer still who swim in water inhabited by dangerous sharks. But these statistics, however ridiculous or comforting they might seem, do little to dampen our fear of sharks. We learn that fear very quickly from a single story. People who have never seen a shark before fear them because we hear or watch stories about them. The focus on the risks that sharks pose to us also diverts attention from the far greater threat we pose to their survival due to over fishing and human-induced climate change.
But for those who are afraid and want to know how to protect themselves from a shark, some advise punching a biting shark in the gills or poking it in the eyes. Swimming in groups and staying close to the shore are known to reduce the risk of attacks. Getting into water where there are lots of bait fish that can attract sharks will increase your risk of being bitten Credit: Alamy. Read more about whether technology could reduce shark attacks.
In some areas, the local authorities themselves have taken action. Traditionally, some authorities have used shark nets to protect areas used by swimmers, but these are controversial due to the harm they do to other wildlife. Instead, smart drum lines — which use baited hooks attached to a system that sends out an alert when triggered — are now being trialled at several beach locations along the coast of western Australia.
When a shark takes the bait, an alert is sent to response teams who catch, tag and then release the shark in a safer location. Another approach being tested in Cape Town, South Africa, is an electromagnetic cable that aims to discourage sharks from approaching areas used by swimmers. Scientists have also been testing an electromagnetic barrier as an alternative to shark nets.
These could be important steps as the harm caused by shark attacks can extend far beyond their immediate victims. He himself was attacked by a bull shark while surfing eight years ago in south-west Australia, nearly losing his arm when the animal smashed into him, bit into his forearm to the bone and carried him underwater.
A spate of shark attacks on Reunion Island led to calls for the local authorities to take action beyond bans on swimming and surfing Credit: Getty Images. On a recent visit to Ballina, a surfing hotspot in New South Wales, Australia, he saw just what a shark attack can do to a town.
The area has suffered a spate of attacks, including two fatal ones on surfers in They were both thinking about closing. A similar story is unfolding in Reunion where the local authorities have banned surfing and swimming in the water at certain times of the year due to fears about further shark attacks.
The number of bites on humans have reduced as a result, but it has also taken its toll on the tourism industry. Forensic analysis of shark bite patterns is helping to reveal more about the species responsible for attacks and the reasons why they happen Credit: Alamy. The personal effect of her attack, however, has been long lasting.
Now I am scared of it. I used to think sharks were cool, but now I am terrified of them, although I still [have] respect for them. Her shark posters have gone, as has her enjoyment of the sea. Instead she tends to prefer swimming or kayaking on rivers. But she still has the occasional nightmare about sharks. I ended up seeing a psychiatrist to help me get over this. Mighall still has the surfboard she was riding on the day of her attack, a huge toothy bite missing from one side.
Like the scars on her leg, it is a reminder of what can happen on the rare occasions that sharks do choose to attack the humans who stray into their domain. They both entitle her to fear these animals.
For those who fear them without having had such a close encounter she has a sound piece of advice. Gavin Naylor and his colleagues at the Florida Program for Shark Research have come up with several tips to help people stay safe when in the water inhabited by sharks. You can get more tips from this entertaining, but informative video made using Lego by Naylor's children.
Join one million Future fans by liking us on Facebook , or follow us on Twitter or Instagram. If you liked this story, sign up for the weekly bbc. Worst Case Scenario Shark. The real reasons why sharks attack humans. Share using Email. By Richard Gray. Humans are like ungainly packets of meat when paddling in the ocean and should be easy prey compared to fast-moving fish and seals.
So, why are so few people attacked by sharks?
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