There is not substantial evidence on how sharks communicate, however, there is a great belief that the extraordinary senses developed by sharks are involved in some kind of communication between sharks if there is any.

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How Big Is The Shark Brain?
How Many Teeth Do Sharks Have?
What Kind Of Skin Do Sharks Have?
How High Can A Shark Jump Out Of The Water?
How Many Teeth Does A Great White Shark Have?

Most sharks live from 20 to 30 years.

The life span of the great white shark is still unknown. Some scientist think that it could be up to 40 years, but it has not been proved.

The tiger shark could be between 12 and 30 years.

Some well known shark species like the mako shark, the lemon shark and the bull shark are still unknown.

The whale shark can live up to 70-100 years.

The nurse shark can live about 25 years in captivity.

Scientifically there is no way to determine the age and life span of sharks.

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Where Do Sharks Live?
What Is The Age Span Of A Shark?
What Is The Largest Shark In The World?
How Do Sharks Reproduce?
How To Get Over The Fear Of Sharks?

Sharks skeleton is made of cartilage instead of bones to have a lighter weight which allows them to go up and down quickly in the ocean without a lot of effort to stay afloat.

Cartilage is robust but not as dense as bone which gives them a great flexibility that allows them bending much easier than bony fishes. Such elasticity also gives them more speed as tails can move faster to propel them through the water.

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Why Are People Afraid Of Sharks?
What Color Is The Hammerhead Shark?
How Many Species Of Sharks?
Why Do The Great White Sharks Attack Humans?
Why Is Mako Shark Endangered?

Sharks have several extraordinary senses that help them find prey.

Usually, they use their ampullae of Lorenzini and electricity detection sense to find prey from long distances.

When approaching their smelling, hearing, and visual capabilities are essential to verify that the prey is edible.

Probably these developed and sharp senses have made them very successful for 420 million years.

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Where Do Sharks Live?
How Long Do Sharks Live?
How Many Years Does A Shark Live For?
Why Sharks Attack Humans?
What Kind Of Shark Can Live In Fresh Water?

Some research has proved that 70% of the ocean waters are shark free.

The great white shark habitat is along the U.S. west coast sometimes moving down to the Pacific coast of Mexico and the west reaching the coast of Hawaii.

The Mako shark habitat is from the US-Mexico border to Washington. It also dwells waters of Argentina and Canada.

The blue shark habitat is from the west coast of Mexico to Canada. Blue Sharks inhabit the coasts of every continent, except Antarctica.

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What Do Blue Sharks Eat?
How Many Species Of Sharks?
What Are The Tiger Shark Enemies?
Why Sharks Attack Humans?
How Does Great White Shark Attack?

However, humans are likely to be the target of a shark attack as long as they are in shark territory, which is water from all oceans, seas and even rivers and lakes.

About 100 shark attacks are reported each year in various regions of the world, of which approximately 5-15 cases are fatal. Although not a small number, compared with other causes of death at sea it turns out that deaths from shark attacks are not as frequent as we think.

THE ORIGIN OF THE ATTACKS

Many of the attacks occur in areas near the coasts, between sandbanks and in places of steep seabed because the sharks congregate there. Now, these do not attack for fun or because humans are very appetizing. Sharks have no particular liking for human flesh as it contains a lower level of fat than they need. Therefore, they are not man-eaters by nature.

Most of the attacks do not show unnatural aggression. An attack can occur when people are in an area that sharks consider their territory, and if it belongs to them, they will look for food in anything that seems an attractive meal. Naturally, this increases the chances of biting people in this area to check if it is their typical meal.

Fundamentally, the shark confuses a person with a natural prey. This kind of attacks also explain why many surfers are victims of shark attacks: when the shark looks from below, the silhouette of the man with his arms extended on the surfboard resembles a turtle, a sea lion or other common prey, so they see this shape and prepare to attack.

Why Sharks Attack People?

Some scientists think that sharks confuse humans with some other marine animals like seals or sea lions as sharks do not seek humans as prey. 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.

TYPES OF ATTACKS

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. The unfortunate subject gets critical injuries that can be fatal.

Hit and bite.
In this case, the shark surrounds the person and strikes with the head or the body before snapping him. The victim is seriously injured and sometimes killed.

SPECIES OF CARE

Among the hundreds of species of sharks that exist only a few represent a real danger to the humans. Incident reports show that only between 25 and 32 species are the perpetrators of attacks.

Whether for its strength, its size, its aggressiveness or its feeding habits, the following species are the ones that have most frequently attacked humans:

White shark (Carcharodon carcharias).
Tiger shark (Galeocerdo cuvier).
Bull shark (Carcharhinus leucas).
Shortfin Mako shark (Isurus oxyrinchus).
Oceanic whitetip shark (Carcharhinus longimanus).
Blue shark (Prionace glauca).

HOW TO PREVENT AN ATTACK

If you do not want to be the victim of a shark attack, it is essential to follow the recommendations of the Coast Guard and to heed possible warnings about shark sightings on the beaches. Additionally, you can avoid attacks if you avoid murky waters or close to sewage, places near sandbanks, or to swim during the twilight or the night wearing bright clothes and jewels as the reflected light can be confused with the brightness of the fish’s scales.

Another important recommendation is not to enter the water if you have a bleeding open wound since the smell of the shark is very sharp and detect blood from miles away. Finally, it is preferable to swim along with several people since sharks tend to attack individuals who swim alone.

Although they are not waiting for a man at sea, it is advisable to follow the recommendations to avoid an unfortunate situation.

Humans have tried to find the way to avoid shark attacks for a long time. During this quest, we have tried many things to avoid shark attacks unsuccessfully.

Sources:

https://www.flmnh.ufl.edu/fish/isaf/home/

www.discovery.com/tv-shows/shark-week/about-this-show/why-do-sharks-attack/

http://news.nationalgeographic.com/2015/06/150615-north-carolina-shark-attacks-science/

http://www.cbsnews.com/pictures/five-most-dangerous-sharks-to-humans/

BioExpedition Publishing © 2017.

Studies have proved that shark senses are responsible for shark hunting.

They commonly use their electro sense for the location of prey, even at long distances.

The lateral line sense detects water vibrations usual to most living things.

The smell and hearing are also used for confirmation, leaving to the sight the last check if a prey is edible.

After all these sensorial scannings, sharks sometimes test their food if they are not familiar with it.

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How Many Teeth Does A Great White Shark Have?
Why Do Sharks Have Cartilage?
What Are The Tiger Shark Enemies?
How Much Do Sharks Weight?
How Many Layers Of Teeth Do Sharks Have?

The biggest shark in the world is the whale shark.

According to records, the largest whale shark ever caught was 12.6 meters long and it was catch off the coast of Pakistan in the Baba Island.

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How Does Great White Shark Attack?
Why Does A Shark Grow New Teeth?
What To Do If A Shark Of The Atlantic Attack?
What Do Blue Sharks Eat?
Why Is Mako Shark Endangered?

Although the great white shark is known as the most ferocious and aggressive shark, this shark typically does not target humans as prey. This fact does not mean that you can swim without worries besides this species.

There are some regions in the world with very few shark attacks on humans like the Mediterranean sea which has only 31 confirmed attacks in the last centuries and a fewer number of dead people.

Those attacks could be the result of mistaken identity, or merely curiosity.

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What Are The Tiger Shark Enemies?
What Is The Largest Shark In The World?
Why Are People Afraid Of Sharks?
How Many Species Of Sharks?
What Is The Age Span Of A Shark?

There are three different ways in which every shark species reproduce.

While mating in sharks has been rarely observed, most species do it while they swim parallel to each other and the male inserts a clasper into female’s oviduct.

Oviparity
Sharks lay eggs in the ocean.

Viviparity
Very much like mammals, sharks have placental links with developing pups, nourish them and keep them until pups born fully functional.

Ovoviviparity
This is the most common reproduction method among sharks.

Eggs develop inside the oviduct of the mother and then hatch inside the oviduct where they finish their development using the remaining egg content to make pups born fully functional.

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How High Can A Shark Jump Out Of The Water?
How Much Do Sharks Weight?
What To Do If A Shark Of The Atlantic Attack?
How Do Sharks Use Static Electricity?