Why do sharks attack people?

The sharks are the main ones predators oceans, but although we often hear about it attacks on peoplethey do not attack us to prey on us but by mistake or defensebecause they never had to deal with organisms like us during their evolutionary history.

These animals have inhabited the sea since the Ordovician, i.e about 450 million years, retaining an almost unchanged appearance, testifying to the efficiency of their body construction, which did not require major modifications. There are sharks chondrichthyansor cartilaginous fish, such as stingrays and chimeras, and belong to the superorder Selachimorphawhich he understands well 500 species different, adapted to different marine environments.

On the contrary, the history of our species is relatively recent, considering that the occurrence is estimated Homo sapiens are about 300,000 years old and our oldest known ancestor today, Sahelanthropus tchadensis, appears to have split from other great apes more than 7 million years ago. Our species is not naturally adapted to aquatic life and the first basic canoe-like boats are estimated to be only 8,000 years old.

Specimen of the great white shark (Carcharodon carcharias), the most famous species thanks to the numerous films in which it is the main character

This assumption is intended to help us understand how many millions of evolution of sharks as marine predators took place before modern species had to – by sheer chance – deal with some specimens of our species. Human beings who do not live in the marine environment are not part of the natural prey of sharkswho, for their part, are unable to recognize us as they do other fish, molluscs and crustaceans with whom they have coexisted for millions of years.

Predators store a general picture of their prey in their genetic information who evolved to hunt and in the case of sharks there are also some marine mammals that vaguely resemble humans when they swim, which could confuse them. Or again like all animals sharks they attack when they feel threatened or cornered, so it’s important to know what to do when you encounter one of these predators.

Tiger shark (Galeocerdo cuvier)

Sharks attack us because they cause havoc

Since only a small minority of the 500 species of sharks currently known are actually dangerous to humans, it is useful to understand how their senses work in order to understand how they can mistake us for prey. Many species live in deep or turbid waterswhere sight proves to be a useless sense: in general, sharks’ eyesight is good, but it is debated whether it is really important for hunting, while they have a definitely developed sense of smell. They are able to perceive blood at long distances and in some species the olfactory organs are able to detect one millionth of the blood present in seawater.

However, several experiments have shown that it does it is more attracted to the blood of fish and other marine animals than to the blood of terrestrial vertebrates. It is certainly also among the most developed senses of sharks electroreception and lateral linecommon to all fish: thanks to these senses, they are able to pick up vibrations and strike accurately even in conditions of poor visibility.

Bull shark (Carcharhinus leucas) known in English as “bull shark”, but different from bull shark

Sharks they are not the merciless killing machines depicted in the movies, but carnivorous animals hunting out of necessity, which according to nature should not come into contact with humans in their environment. Several studies have attempted to explain why these predators occasionally attack swimmers and surfers, and the most popular hypothesis claims that they may have been mistaken for other animals: sharks bite people by accident, mistaking them for seals, sea lions and other pinnipeds. The hypothesis was then tested in a 2021 study.

Simply put, a shark, attracted by the vibrations we create when we skim the water to swimassociated with fish or other animals in difficulty, will approach and see a shape vaguely resembling that of a seal, especially if we are horizontal or on a small surfboard, and decide to “taste“. In fact, it often happens that after a bite, these predators move away, because they did not recognize the prey by taste, in a sense they recognize that they have made a mistake.

Bull shark (Carcharias taurus)

Sharks attack us because they feel threatened

Contrary to what one might think, sharks are afraid of humans: for these animals, we are the only predator. we knowingly kill 75 to 100 million a year, approximately 1 shark every 3 seconds. However, the probability of a person being attacked is only 1 in 3,750,000, which means that it is definitely more likely to be attacked by other animals such as snakes (which cause around 100,000 deaths per year), dogs (35,000 deaths per year) or cows (around 20 deaths per year), or even being killed by lightning or fireworks. Although, according to statistics, sharks are therefore often labeled as “dangerous”. it causes “only” 6 human deaths on average each year.

White tip or tip shark (Carcharhinus longimanus)

We must always remember that it is we who invade the territory of these animals and not the other way around: when a shark, like any other animal, finds itself face to face with something unknown, it can become intimidated and attack as an instinctive defensive reaction. The various behaviors we perform can be wrong and trigger an aggressive response in these predators. In fact, sharks should never be approached or chased, let alone touched or attracted to food that might activate their predatory instincts.

Blacktip shark (Carcharhinus limbatus)

What types of sharks attack humans?

According to data from the Florida Museum’s International Shark Attack Collection There are approximately 35 species of sharks that are potentially dangerous to humanscertainly a small number compared to the 500 currently known species. Out of a total of 949 attacks recorded over the years, only 142 were fatalcompared to the remaining 807 where the victim suffered only an injury.

In fact, there are only a few recorded attacks on most shark species, and most of them have been committed by three large species, called “the big three” (big three) which are great white shark (Carcharinus leucas) with 119 attacks, of which 26 were fatal, tiger shark (Galeocerdo cuvier) with 142 attacks, of which 39 were fatal and finally great white shark (Carcharodon carcharias) with 351 attacks, more than a third of the total, of which 59 were fatal.

Hammerhead shark (Sphyrna sp.)

These numbers give us an idea shark accidents are definitely rarer than commonly believed, because shark encounters are not that common and most species are not large or dangerous enough to pose a threat to an adult human. All of the shark attacks recorded by the Florida Museum are the result of years and years of reporting, and again, on average only 6 people die from shark attacks per year.

In addition to the three large species already mentioned, there are other potentially dangerous sharks: gray reef sharks (Carcharhinus spp.), blacktip reef shark (Carcharhinus limbatus), White shark or winged (Carcharhinus longimanus), great white shark (Carcharias taurus), hammerhead sharks (Sphyrna spp.), lemon shark (Negaprion brevirostris), shortfin mako (Isurus oxyrinchus) A the green one (Prionax glauca). Of these various species, the total number of recorded attacks is 219, of which only 13 were fatal.

Blue shark (Prionace glauca) accompanied by pilot fish

What should you do if you encounter a shark?

There are some measure which those who visit areas where there are sharks should always keep in mind and we have already talked about it several times on Kodami. Here are 10 useful rules if you encounter these animals:

  1. Do not swim if you have bleeding wounds. Sharks can smell blood from a great distance and will inevitably be drawn to it, even if your blood doesn’t match that of their typical prey.
  2. Avoid swimming near fishermen or where there is likely to be bait or dead fish that is sure to attract predators.
  3. Avoid rough and murky waters, as well as estuaries. The sharks here, who can’t see well, could easily mistake you for one of their natural prey. You won’t see them in these conditions either.
  4. Do not dive where many fish are gathered and always keep an eye on the sea.
  5. Avoid swimming towards the sun, which will limit your vision. Sharks use sunlight to avoid being seen, also thanks to their coloring.
  6. Do not swim at night. Most shark species hunt at night.
  7. Do not touch, provoke or feed sharks. The smell of food can cause them to react uncontrollably and they may feel the need to defend their territory if they feel threatened.
  8. Do not spray water on the surface. Sharks associate splashing with prey in trouble, and running with your back to a shark only reinforces the idea that you are food to be caught.
  9. If the shark gets too close, it’s best to do it cover your shoulders with a rock or a boat, stay upright into the water and facing the animal according to the so-called face-guide-push-move rules, i.e. guiding the shark in another direction with your hand on its snout or pushing it away without being too aggressive. If this movement is not enough, you can touch the shark’s gills, which are very delicate, because the sharks themselves point to them in situations of danger.
  10. However difficult avoid panic because sharks are sensitive to this emotion and will stay alert. These animals have no idea what a human is and can be as fascinated as they are frightened by your presence.

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