Why shark attacks

I thought I was having a nightmare and kept trying to blink my eyes open. The shark that attacked Hannah Mighall took an enormous bite out of her surfboard before it allowed her to bob back to the surface Credit: Malcolm Mighall. The shark pulled away from him and as it went underwater it let go of Mighall, lunging instead for her surfboard that was still attached by a rope to her leg.

With the board in its mouth, the shark pulled Mighall underwater for a second time. Moments later she popped back up to the surface with her damaged board. The animal had bitten clean through the fibreglass and foam. Mundy grabbed hold of his cousin, put her on his back and paddled frantically for the shore.

Now she was doing it for real. The shark came with us all the way up to the beach as there is a deep gutter running up to it. We could see its fin as it surfed in on the same wave. Luckily for Mighall, among the few people on the beach who witnessed what had happened that day were a doctor and a nurse. They gave her vital first aid while waiting for an ambulance to arrive.

Her right leg is noticeably weaker than her left — so much so that she has to lift it with her hands when she wants to kick-start the dirt bike she rides occasionally. Great white sharks typically attack their prey from below with great speed, delivering a single devastating bite Credit: Getty Images.

Mighall was one of roughly 83 people around the world to be attacked unprovoked by sharks in It is a figure that has remained around the same level over the past decade. The average number of unprovoked attacks between , for example, was But recent research indicates that shark attacks in some parts of the world appear to be on the rise. The eastern US and southern Australia have seen shark attack rates almost double in the past 20 years , while Hawaii has also seen a sharp increase.

But why? This seems like an obvious point, but when you look closer at where attacks are taking place there are some clues as to what might be going on. The large human populations along the southern coast of Australia and the eastern coast of the US mean large numbers of people enjoying the water. But southern Australia has also seen rising numbers of fur seals along its coastline, the favourite prey of great white sharks in the region. The resurgence in seal populations on Cape Cod on the east coast of the US has led to rising numbers of great white sharks in areas popular with people Credit: Getty Images.

This has led to increased numbers of great whites in the area too during the warm summer months as they look to feast on the seals that pull themselves out to bask on the beaches. Sadly, last autumn, Massachusetts suffered its first fatal shark attack in 82 years and growing numbers of shark sightings have led to a string of beach closures. But there is no real evidence that sharks are actively hunting humans, according to the scientists who study them. Great whites in the North Atlantic, for example, show seasonal movement patterns, migrating thousands of miles to warmer waters further south during the winter months.

Some mature adults will venture out into the open ocean for months at a time , covering tens of thousands of miles and diving to depths of 1,m as they seek prey. But despite being potentially such an easy meal, sharks are really not that interested in hunting humans.

I think if people knew how frequently they were in water with sharks, they would probably be surprised. However, Naylor believes that the official statistics on shark attacks are probably an underestimate. Most reports come from highly developed countries with large populations and highly active news media.

Attacks on remote islands or in less developed communities probably go unreported. Looking at the statistics for the number of shark attacks last year can reveal some fascinating trends. Just four of these were fatal according to the International Shark Attack File, although another database of shark attacks records seven deaths. So far in , there have been four fatal shark attacks.

Tiger sharks are one of the three main species responsible for attacks on humans but much of the time they ignore people in the ocean Credit: Getty Images. The reason for the fall — which bucks the overall trend of growing numbers of attacks — has been attributed to a sharp decline in the number of black-tipped sharks. These sharks account for many of the bites around the south-eastern US, migrating down the coast of Florida due to rising sea temperatures that have led their prey to become more dispersed.

The findings highlight one of the key challenges in understanding why sharks bite humans. There are dozens of different species responsible for bites , each with their own unique behaviour, hunting strategies, prey and preferred habitat — although in many cases the species can be misidentified or not identified at all.

The majority of unprovoked attacks on humans where a species is identified involve three large culprits: the great white, tiger and bull sharks. Great white sharks are considered to be the most dangerous species in the oceans today, but we still know very little about their life cycle and behaviour Credit: Getty Images.

Bull sharks, for example, tend to hunt in shallow, murky water that will require them to rely less on vision and more upon their sense of smell and electroreception, which allows them to detect minute electrical fields produced by their prey. There is also some evidence that shark teeth may also function as mechanosensory structures — similar to touch — to help the animals learn more about what they are biting.

In Hawaii, attacks by tiger sharks are the most common, whereas in California, white sharks also known as great white and white pointer are most likely to be involved. Globally, these species are involved in the majority of fatal attacks, contributing to their negative reputation in the media.

These species tend to be territorial and if they do attack people, they may be sending a warning: get out of my space. Smaller shark species contribute more attacks to the Atlantic Ocean tally. Currents in the Atlantic Ocean , like the Gulf Stream , can push warmer water closer to shore—with bait fish. These bait fish attract sharks, like blacktips, closer to shore. Blacktip sharks have bitten 28 people since the s the majority in Florida , though all but one have resulted in relatively minor, and non-fatal, bites.

The one exception to the Atlantic trend, says Naylor, is Massachusetts, where a few more attacks popped up in the last few years as the white shark population has rebounded since the Marine Mammal Protection Act in brought back their prey—seals.

Another factor in the distribution of shark incidents may be water temperature. Catherine Macdonald , a shark expert and director of the Field School in Miami, Florida, says more attacks do tend to occur in warmer waters, because more people spend more time playing or swimming in those waters, increasing the chances of bumping into a shark.

Most victims of attacks are swimmers or surfers. Even so, in recent years, the raw numbers of shark attacks—especially fatal attacks—have been on the decline. People reported only 66 unprovoked attacks in , down from a peak of 98 in Worldwide, 49 shark attacks have been reported—a pretty standard year, Naylor adds.

But they can get confused. If they are chasing after smaller fish, and a person is standing or swimming among the school, a confused shark may bite human flesh. Bowling notes that the shark is often just as freaked out as the human in any encounters, not being used to a human being in its environment.

She has never been bitten, though the risk exists. Experts say that, despite the news reports, people should not avoid going into the water out of fear of sharks. Statistically, your chances of getting struck by lightning are considerably higher than a shark attack.

In , 1. Fewer shark attacks were reported in and than deaths related to people taking selfies. For a fun time at the beach, you can take proactive measures to reduce your chances of having a negative shark encounter even further:. Sharks tend to follow these schools of fish towards the beach, and out of confusion, could bite you instead of a fish.

They also play important roles in the ocean ecosystem. Attacks are extremely rare and people are rarely consumed by sharks. 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.