Shark attacks are still relatively rare occurrences even though humans should be easy prey compared to fast-moving fish and seals. But when they do happen, they can be devastating. So, why do sharks attack people? The crystal-clear water beneath 13-year-old Hannah Mighall darkened for a moment. She was sitting astride her surfboard, enjoying the warmth of the sun as she and her cousin waited for the next wave in Tasmania’s idyllic Bay of Fires. Behind them the brilliant-white sandy beach was largely deserted and the surfing had been good so far.
The sudden shadow below made Mighall instinctively lift her feet – balls of kelp often broke off nearby rocks and drifted in the surf. “They are really slimy so I hated touching them,” she says. But then something took hold of her leg. The water around Mighall exploded as a five-metre-long great white shark latched onto her right leg “It didn’t hurt at first, it was like something gently grabbed hold of me and then I was in the water,” says Mighall.
To those who witnessed what happened, however, it was anything but gentle. The water around Mighall exploded as a five-metre-long great white shark latched onto her right leg, lifted her off the surfboard and shook her in the air before disappearing underwater. “It took a few seconds for me to realise it was a shark,” she says. “When I popped back up from the water I was lying on my back but my leg was in its mouth. All I could see was my black wetsuit leg, its teeth, pink gums, teeth and the dark bit under its nose where it meets white. I thought I was having a nightmare and kept trying to blink my eyes open.”
Mighall’s cousin, 33-year-old Syb Mundy, who had been sitting on his own board just a few metres from her, raced over and began punching the shark in the side of its head. 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. Earlier that day Mighall had been practicing water rescues with another girl during training with her local Surf Life Saving association, repeatedly being carried into shore as the “victim”. Now she was doing it for real. The shark came with us all the way up to the beach – Hannah Mighall
“The shark was circling us underwater,” says Mighall. “Then this wave came in and Syb just said, ‘We have got to catch this as it is going to save our lives.’ I was just tapping the water as I was terrified but he was really paddling and the wave carried us to shore. 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. More than 10 years later, she still carries deep scars on her leg that trace the outline of the shark’s mouth. 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.
Mighall was one of roughly 83 people around the world to be attacked unprovoked by sharks in 2009. It is a figure that has remained around the same level over the past decade. The average number of unprovoked attacks between 2013-2017, for example, was 84. In 2023 there 69 unprovoked shark bites on humans and 22 provoked bites, according to the Florida Museum of Natural History’s International Shark Attack File. Fourteen of these attacks where fatal, with 10 considered to be unprovoked.
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?
“Shark bites are strongly correlated to the number of people and number of sharks in the water at the same time,” says Gavin Naylor, director of the Florida Program for Shark Research, which maintains the International Shark Attack File. “The more sharks and people there are in one place, the greater the chance of them bumping into each other.”
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.
Similarly, seal populations off Cape Cod on the coast of Massachusetts in the US have rebounded in recent years, largely thanks to protection by the US’s Marine Mammal Act introduced in 1972. 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, in autumn 2019, Massachusetts suffered its first fatal shark attack in 82 years and growing numbers of shark sightings have led to a string of beach closures.
New York also saw a record number of eight bites in 2022 – there had only been 12 reported unprovoked bites in total in the International Shark Attack File. The spike has coincided with the arrival of juvenile sand tiger sharks, which were confirmed in 2016 to have taken up residence in Great South Bay, between Long Island and Fire Island. Naylor believes the young and inexperienced sharks are being drawn into the surf zone by influxes of baitfish, making them more likely to encounter humans surfing and swimming there. We are like helpless little sausages floating around in the water – Gavin Naylor
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 1,000m (3,280ft) as they seek prey.
“We are like helpless little sausages floating around in the water,” says Naylor. But despite being potentially such an easy meal, sharks are really not that interested in hunting humans. “They generally just ignore people. 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 deeper at the statistics for the number of shark attacks can reveal some fascinating trends. In 2022, there were 57 confirmed, unprovoked attacks, below the most recent five-year average of 70 incidents annually and the joint lowest level for 10 years. Five of these attacks in 2022 were fatal according to the International Shark Attack File. Another database – the Global Shark Attack File – records 10 deaths. In 2023, it records 13 deaths from unprovoked shark attacks, compared to the 10 fatailities recorded by the International Shark Attack File. In the first three months of 2024, the Global Shark Attack File recorded eight unprovoked attacks, including two in Hawaii.
On 24 June 2024, professional surfer and actor Tamayo Perry, who appeared in Pirates of the Caribbean: On Stranger Tides film, Lost and Hawaii Five-0, was confirmed to have died after being attacked by a shark in Hawaii. Perry was also a lifeguard on the island of Oahu's North Shore, and had been surfing off the coast near Laie when the attack happened.
Although shark bites in Hawaii vary from year to year, there was a small increase from the average number of attacks in 2023 with eight shark attacks, including one incident that was fatal. The International Shark Attack File have said they will be closely monitoring the statistics in Hawaii for signs that may indicate changes in human encounters with sharks.
For decades, however, Florida has seen the most number of shark bites globally. The 16 cases it saw in 2023 represented 44% of the US total and 23% of all unprovoked bites worldwide. The overall global trend when looked at by decade shows a growing numbers of attacks, according to the International Shark Attack File's data. This, according to Naylor, is perhaps more of a reflection of the number of people now in the water where sharks live, and also increased reporting of bites due to social media and online news.
In recent years the number of unprovoked shark bites have varied greatly, and until recently had appeared to be in decline. In 2020, there were 57 unprovoked attacks on people reported globally and then 73 in 2021. In 2015, that number stood at 98. The recent spike in attacks bucks the overall trend for the past 10 years, which 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.
These statistics 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. Yet great whites – the species depicted in the film Jaws and demonised by Hollywood ever since – isn’t just a separate species, but an entirely different taxonomic order from the other two.
There are 530 different species of shark and there is so much diversity among them. You can’t just group them together,” says Blake Chapman, a marine biologist who has studied shark sensory systems and recently wrote a book on shark attacks on humans. “Different species have such a range in terms of their sensory biology, how they behave, their motivations and the habitats they live in.”
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 some evidence that shark teeth may also function as mechanosensory structures to help the animals learn more about what they are biting
“(Great) white sharks, which often hunt in very clear water use their vision a lot more and their eyesight is much better,” says Chapman. 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. Chapman believes there may be a complex set of reasons for why unprovoked attacks on humans appear to have risen in recent decades.
Aside from rising human populations along coastlines, the destruction of habitats, changing water quality, climate change and shifts in prey distribution are leading sharks to gather in greater numbers at certain hotspots around the world. Other factors, such as the time of day when humans use the oceans also play a role – attacks on nightby cookiecutter sharks in Hawaii, for example, tend to be more common on people swimming on moonless nights.
In 1992, for example, there was a sudden spate of shark bites off the coast of Recife, Brazil – an area that had no unprovoked attacks for the entire previous decade. Chapman believes that heavy commercial port construction in the area damaged large areas of reef and mangrove, potentially displacing species like bull sharks, which moved to new areas like Recife in search of prey.
R̩union Island in the Indian Ocean Рrenowned for its beautiful, unspoiled marine habitats Рhas seen a dramatic rise in tourism but in recent years it has also suffered a growing number of shark attacks by the bull and tiger sharks that live in the surrounding waters. Since 2011, there have been 11 fatal attacks on R̩union, mainly on surfers. Those who survive often lose limbs. Researchers have found that around two-thirds of the R̩union attacks have occurred in turbid water and swells of more than two metres Рthe favoured environment for bull sharks, which are thought to be responsible for most of the attacks.
Naylor believes that in most cases, sharks bites are a case of mistaken identity. “If these animals are chasing bait fish, the flash of the white sole of a foot from someone kicking on a board might cause them to dart at it,” he says. “When you have a large animal like a tiger or a white shark, which move quickly, a bite is far more likely to be fatal.” Great whites typically attack from below, delivering a massive catastrophic bite. In some cases they will withdraw while their prey bleeds to death before returning to eat.
“A great white in full predatory mode is quite a sight,” says Greg Skomal, a marine biologist with the Massachusetts Division of Marine Fisheries who has been tagging and tracking great white sharks since 2009. He should know – last year, as he was leaning over the pulpit on the bow of a research vessel while trying to tag a shark, a large great white breached directly underneath him with its jaws agape.
“It gave me some idea of what a seal feels like,” he says. “I’ve seen that behaviour a couple of times over the years we have been doing this. Most of the time we put a camera in the water and the sharks are completely complacent. We must have done it thousands of times. But on a handful of occasions they attack straight away, breaking the pole and the camera. It is like they are in a heightened predatory state where their senses lock onto any kind of stimuli. “I wonder if those strikes on people that are not merely investigative are the result of a person being in the wrong place at the wrong time with a shark in this kind of heightened state.”
But for every attack on a person, there are just as many stories of people who have managed to get up close to these giant predators without any harm. Take Ocean Ramsey for example, who swam alongside an enormous 20-feet-long great white off the coast of Hawaii and made headlines around the world. Skomal and his colleagues are now using new high-resolution tags that can give the researchers minute by minute and second by second data on what the sharks are doing. It is like they are in a heightened predatory state where their senses lock onto any kind of stimuli – Greg Skomal