Despite misleading media reports suggesting that shark attacks are on the rise, such assaults on humans are exceedingly rare and even more rarely are fatal. While the
number of recorded shark attacks has risen in recent years, the rate per capita has not. Our species is simply undergoing a massive population explosion, so there are more people spending time in the water, especially as aquatic recreation opportunities expand, and thus more of us being exposed to the risk of an elasmobranch encounter. We are also developing far more effective methods of documenting and cataloging these encounters, which may have been underreported in the pastБand, maybe most important, we are gaining a greater understanding of why run-ins with sharks, as infrequent as they are, occur in the first place. The oversimplified prevailing wisdom, until recently, attributed shark attacks on humans to misdirected feeding attempts. That is, we thought that sharks took a bite or two out of humans because they looked like food and, in most cases, decided that they werenБt, to the sometimes fatal detriment of the bather in question. That is not, as it turns out, entirely inaccurate. However, a constellation of other factors accounting for shark attacks have emerged in the wake of intensive study of shark behavior. The image of surfers, arms dangling off their boards, being perceived as seals from below by sharks has largely been discarded. Sharks have extremely powerful vision and are unlikely to mistake a surfer for a seal. However, in turbid waters, the erratic motion of humans and the contrast between their skin and their attire can confuse sharks. It is thought that especially in shallower waters near shore, where smaller species such as blacktip and spinner sharks may go to feed on schools of smaller fish, many shark encounters occur out of simple confusion. The shark, hardwired to snap at anything looking remotely like a thrashing fishБsuch as a foot with a tanned top and paler bottomБmay accidentally bite a human in the churned-up surf of a crowded beach. In most cases, these types of encounters consist of a single bite, after which the shark flees. Why, though, are surfers and other swimmers in deeper water attacked if sharks do not perceive them as food? In the case of, which, along with and sharks, are the largest and most dangerous species known to attack humans, there is compelling evidence from survivors of attacks suggesting that the sharks may simply have been investigating what they considered to be foreign objects in the water.
Certainly, most attacks have not resembled the spectacular hunting techniques employed when white sharks are in the mood for seal. When is on the menu, the white shark will approach from below at great speed, often breaching the surface and knocking the animal into the air before moving in to feed. In contrast, most encounters with humans are far less explosive. In fact, one surfer did not even notice a shark until it was nibbling on his surfboard. ThatБs right: nibbling. Not devouring. Even fatal attacks most often result in the sharkБs leaving after a bite or two, uninterested in consuming the unfortunate swimmer. Considering the force with which these creatures are capable of attacking, another explanation has been suggested: the sharks are simply curious, and, because they are the dominant predators in most ocean ecosystems, they arenБt afraid. Their mouths also function as finely tuned sensory organs, leading sharks to БmouthБ unfamiliar objects as a means of examining them and determining their possible food value. (Their gums and slightly mobile teeth are so sensitive that it has been proposed that they can gauge the probable fat content of a potential prey item. Humans fall far short of the blubbery BMIs of seals and sea lions. ) So, at worst, such encounters likely result from sharksБ actively assessing whether itБs worth eating a human, not actually trying to eat one. The distinction is an important one: sharks arenБt making БmistakesБ during such attacks. TheyБre exhibiting purposeful, goal-driven behavior (that may or may not have damaging consequences for the human subject of curiosity). Another factor that may be in play is shark territoriality. Though they do not necessarily have territories in the sense that terrestrial predators do, there is a discernible dominance hierarchy among sharks. The system is simple: the largest sharks get the best hunting spots. Incursions by smaller sharks are frowned upon, and intruders are evicted, violently if necessary. Some shark encounters may be a result of the sharkБs natural instinct to defend its food source against all comers. Whatever the ultimate cause of shark attacks, we are a far greater threat to them than they are to us.
We have decimated their populations, with some 100 million taken each year both on purpose and as bycatch. Several theories have been put forward by experts as to why white sharks sometimes bite people. In this article we examine three of the most prominent theories and look at why most of these incidents are non-fatal. Firstly it is important to realise that shark attacks are far more rare than many people might expect. According to the International Shark Attack File there have been an average of just over 60 shark attacks per year worldwide over the last decade. However, on average, less than 5 people per year die from these attacks so the overwhelming majority of shark attacks are non-fatal. Considering the amount of people who use beaches every year these numbers represent a relatively small risk to the average beach-goer, compared to say driving a car, where according to the World Health Organisation 1. 2 million people are killed annually in road accidents. Sharks have wandered our oceans for the past 400 million years, at least 200 million years earlier than the dinosaurs and 396 million years before the first hominids evolved. At the beginning of the Jurassic period, about 200 million years ago, the first БmodernБ sharks developed. Smaller sharks and other fish as well as marine mammals joined great white sharks on their journey through time and as these evolved in the water beside them they became their natural prey. Though we humans may be fascinated by the ocean and endeavor to extend our natural limits in or on it through the use of modern technology, it is not our natural habitat. We did not evolve alongside sharks and hence they do not recognize us as their natural prey or part of their diet. So why do sharks bite people and why are most of the attacks non-fatal? Here are some of the main theories put forward to explain what might be happening. 1: Investigatory theory White sharks are intelligent and curious apex predators with complex behaviour patterns. They sit at the top of the marine food chain, and although they are hunted by man, they have no natural predators. As a result white sharks, especially the larger individuals, are confident in nature and extremely curious. They are much more likely than other marine species to investigate unknown objects in or on the water. Unfortunately, when they are unable to identify an object they rely on an investigatory bite to gather more information.
White sharks donБt have arms like we humans do and so their mouths are their best exploratory tool when it comes to up-close investigations. White sharks are known to have БtastedБ a variety of animals and objects, including seabirds, kayaks, boats, plastic bags, and paddle skis. 2: Mistaken identity theory A shark is able to sense a person in the ocean long before that person can detect a shark. White sharks have excellent senses. They can detect sound and pick up smells from hundreds of metres away. They can sense moving objects through their lateral line, which consists of pressure-sensitive receptors along their body, and their vision underwater is far better than ours. However, these senses, impressive as they are, are not perfect. A large number of attacks occur when water conditions are poor leading many scientists to believe that bad visibility, background noise from heavy surf, and other conditions can cause white sharks to mistake humans for their normal prey. 3: Social / defensive theory White sharks defend their Бpersonal spaceБ by communicating through body posturing and biting, and the less dominant shark is normally forced to give way to the more dominant. A surfer or swimmer at the surface, totally unaware of a sharkБs presence below the water, would be unaware of a shark defending its space until bitten. A shark could even view a person as a competitor when fish or other prey is in the water. So we see that there are a number of reasons why a white shark might БattackБ a person, although these seem less like attacks and a lot more like accidents. Especially when most of the incidents tend to be non-fatal. Some researchers believe that in the initial bite a shark can detect the calorific value of its potential prey, informing the shark through the ratio of fat to bone or muscle whether its mouthful is worth eating or not. This could explain why in many cases the white shark has bitten lightly and let go, as the initial contact with its taste buds sends clear signals that a human is not prey, particularly if the swimmer or surfer is wearing a wetsuit. It is extremely rare that a white shark bites a human and continues feeding. Most of these incidents involve bites of minimal force and this could account for why there are so many more non-fatal shark БaccidentsБ than fatal ones.