Introduction

The legendary great white shark is a cartilaginous fish that has caused fear and admiration for many years. It is considered one of the biggest predators of the oceans and the fiercest, but there is more imagination than truth in this sentence. His reputation as a “man-eater” is also far from reality.

The white shark is a member of the class Chondrichthyes, the subclass Elasmobranchii, the order Lamniformes, the family Lamnidae and the genus Carcharodon.

DESCRIPTION

The body of the white shark is robust and fusiform, about 4-7 meters in length but the average is 6 meters. Its weight is between 3,000 and 3,400 kilograms. Adult females reach dimensions greater than males, which are usually 2 meters smaller.

Their sense of smell is very sensitive, which facilitates the detection of prey at a great distance.

It has a narrow pointed snout, two pectoral fins and a first dorsal fin with a triangle shape. The caudal fin is crescent-shaped, and its upper and lower lobe are long and of very similar size, almost symmetrical. The mouth measures 0.9 to 1.2 meters wide; Is provided with several rows of sharp and serrated triangular teeth, that the shark changes several times throughout his life. It has small onyx eyes and nostrils towards the end of the snout.

It exhibits discoloration of the body, because while the back is gray or blue, the lower area is lighter. This characteristic gives an advantage when hunting because preys do not notice the figure of the shark, which is confused with the bottom of the ocean.

Their sense of smell is very sensitive, which facilitates the detection of prey at a great distance, and together with the Lorenzini ampoules which detect electric fields of moving animals make them efficient predators.

Facts on video

DISTRIBUTION AND HABITAT.

The distribution area of the great white shark is very extended; It ranges from the latitudes 60 ° north to 60 ° south and can be found in tropical coastal waters as well as temperate and even cold. In general, the temperature of the water that inhabits oscillates between 12 ° and 24 ° Celsius.

It is commonly found on the coasts of North America from Newfoundland to southern Mexico in the Atlantic Ocean and from Alaska to southern Mexico in the Pacific. Outside of the American continent, the great white shark dwells mainly the waters of South Africa, the Mediterranean Sea, Japan, and Oceania. There is a substantial population in the Dyer Island in South Africa, and that is why there is a common place for research about their life.

Their habitats include coasts and continental and insular platforms whose waters do not surpass 1,875 meters of depth. In the open ocean, it inhabits to depths of up to 1,200 meters. It is an epipelagic shark that has been seen close to the shore on many occasions, but it is not an eminently coastal species.

Great White Shark – Carcharodon carcharias.

FEEDING

The diet of this shark species is, of course, carnivorous. However, it does not usually feed on large species, but on smaller animals such as squids, rays, and other fish. Adult individuals also include other sharks, seals, sea lions, dolphins and whale corpses. They sometimes catch turtles and seabirds to feed on them. They have a clear preference for fat-rich prey.

They have different hunting strategies depending on the target victim and the size of the species. The most usual approach is that, once they detect by electroreception their possible food, they locate below and then stealthily swim vertically. Once closer, they inflict a deadly bite and wait for the animal to bleed and die and then eat it. If the prey survives that, they try to hold it with their lower teeth while the upper tear the tissues. The most common forms to die of their preys are decapitation, mutilation, and bleeding.

BEHAVIOR

The great white shark is a fish mostly solitary although it can reunite with others of its same species. He has been seen a few times accompanied by a female or a male and even in small groups. In their groups, it is likely that there is hierarchical dominance, and the females are in the lead, but among all, large individuals dominate the small ones, and the residents of the group for a long time dominate the newcomers.

This shark is active both day and night. Interestingly, they jump out of the water sometimes to look the surrounding and look for prey. They are not aggressive with their own species, but if they feel threatened, they may bite his antagonist as a warning.

Most people expressly fear the great white shark and consider it a man-eater predator. Definitively, it is a powerful, aggressive and efficient predator, but it has no preference for humans. The attacks usually happen because of the shark confusion of a person with prey, and as a consequence, they give a “test bite,” but it is unlikely that it keeps eating once it finds that it is not its usual food.

REPRODUCTIVE HABITS

Males sexually mature about nine years old, but females mature between 14 and 16 years. This species is slow growing, late maturing and relatively long life.

Their reproduction is ovoviviparous. Bites on the flanks, backs and pectoral fins of females indicate that males exert “soft” aggression before and during mating. Males fertilize the eggs internally, inserting their claspers into the female oviduct so that eggs develop inside their body. Before birth, developed embryos presumably practice oophagy.

The gestation period lasts between 12 and 18 months, after which the female gives birth between 2 to 10 live offspring measuring more than 1 meter long. Female gives birth every 2 or 3 years.

THREATS AND CONSERVATION

The great white shark is at the top of the food chain, and except for killer whales, whales, and humans, it does not have predators. However, the Red List of the International Union for Conservation of Nature (IUCN) has classified it as a “Vulnerable” species, since overfishing and by-catch have led to a decrease in the number of individuals, as they have a low reproduction rate.

Some countries such as the United States, South Africa, Namibia, Malta and Australia protect the great white shark within their oceans, but it is still a feared and misunderstood fish. Therefore the conservation efforts do not have enough reach and impact.

Great White Shark Infographic!

(Click for expand)

Sources:

https://en.wikipedia.org/wiki/Great_white_shark

http://www.iucnredlist.org/details/3855/0

World of Animals Magazine. Issue 1. Imagine publishing.

World of Animals, Book of Predators. Imagine publishing. 2014

http://www.arkive.org/great-white-shark/carcharodon-carcharias/

http://sharkopedia.discovery.com/types-of-sharks/great-white-shark/#top-10-greatest-great-white-videos

BioExpedition Publishing © 2017.

Great White Shark Attacks Inside Cage

Great white sharks start their attack using their extraordinary senses like the electrosense, which allow them to detect prey from long distances.

Later great white sharks use their smell and hearing to further verify that the prey is eatable.

At the end, great white sharks will visually verify their food and in some occasions they will even test it.

This kind of sharks usually surprise their prey from below with a quick and lethal single attack.

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They have many rows of teeth in each jaw.

Shark teeth quickly fall as they are not firmly attached to the jaws. Therefore they replace the falling teeth with the ones in the row behind.

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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.

New teeth grow continuously inside shark’s mouth discarding the old ones and renewing them immediately.

Therefore, sharks do not have a particular reason to grow new teeth, but they do it all their life going through thousands of teeth during their lifetime.

Some guess that sharks produce up to 30,000 teeth during their entire life.

Usually, their mouth has several rows of teeth, therefore when they lose one because of struggling with prey or just because they are renewing it, the correspondent tooth from the row behind it goes forward to fill the space in the jaw.

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Scientists think that most of the shark attacks on humans are due to mistaken identity.

Observations proved that surfers on surfboards resemble the image of a sea lion a sea turtle or a seal when seen from the bottom of the ocean, making sharks curious to test the prey.

Other times, sharks attack humans as result of provocations by human activity like fishing, water activities or splashing.

Other occasions, colors used by people or shiny jewelry can attract the attention of sharks.

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Shark attacks are not as frequent as everybody thinks. During 2004 only 61 confirmed unprovoked attacks to humans worldwide were confirmed.

If attacked, avoid excessive splashing and leave the water immediately calmly as soon as you see a shark.

Do not harass or provoke the shark in any way as they will strike back.
If bitten, you will probably feel something like a brush against you. Several shark victims do not feel any pain when snapped.

Leave the water and check for injuries. Do not stay in the water, especially if you are bleeding.

If you are diving and a shark approaches you, stay as still as possible and drop any dead fish that you carry and that could be attracting sharks.

If an attack is imminent, aim shark eyes as they are the weakest point in shark’s body. The gill rakers are also a vulnerable area as well as the snout.

Playing dead, does not work with sharks, if bitten defend yourself as aggressive as you can.

Finally, if bleeding, try to stop blood while leaving the water.

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The bull shark is also known as the zambezi shark. It should not be confused with the sand tiger shark (Carcharhinus taurus), which is also called bull shark in other languages.

Many people consider the bull shark one of the most dangerous sharks in the world since this species has many attacks on humans registered, and according to the Internation Shark Attack File, it is the third species with most attacks on humans, only after the great white shark and the tiger shark. Besides, its aggressiveness and its ability to live in saltwater as well as freshwater, add further concern.

It is a member of the order Carcharhiniformes, Carcharhinidae, and Carcharhinus.

DESCRIPTION

The reason why it is called “bull shark” refers to the short, sturdy form of its body that resembles a bull, and perhaps it is also due to its hostile behavior. It has a blunt snout, rounded and wide but not very long. It has two dorsal fins with a triangular shape, of which the second is visibly smaller but the tips of both are dark in young specimens. They do not have an interdorsal ridge.

The reason why it is called “bull shark” refers to the short, sturdy form of its body.

Their eyes are quite small, which gives a clue about their limited visual sense and their preference for waters near the coasts where the prey are abundant. Instead, its movable jaws contain several triangular teeth that measure about 3 inches long.

The color of its skin is light gray, and its belly is white. There is sexual dimorphism: the female is larger than the male, as the male commonly has a length of 2.13 meters and weighs 90-95 kilograms, while the female reaches a length of 2.3-3.4 meters and weighs 129-230 kilograms.

DISTRIBUTION AND HABITAT

Bull shark distribution is along the coastal waters of tropical and subtropical seas around the world. In the Atlantic Ocean, it is located from the United States to Brazil and from Morocco to Angola. In the Indian Ocean, it is present in waters ranging from South Africa to Kenya and from India and Vietnam to Australia.

It is one of the few species of sharks prepared to inhabit saltwater and freshwater, in the latter for a long time. It dwells in waters ranging from 150 to 30 meters deep of oceans, seas, bays and harbors and even ventures into lakes and rivers.

Bull Shark – Carcharhinus leucas.

FEEDING

The bull shark is an opportunistic carnivorous predator but can eat almost anything it finds in its way including fish, rays, sea turtles, mollusks, echinoderms, young sharks (including the same species), mammals and seabirds. In the stomachs of some individuals have been found remains of hippos and humans but these are not a regular part of their diet. Their favorite fish are chelons, mullets, mackerels, and snappers. However, their food consumption adapts when they dwell in freshwater areas, and then feeds on turtles, shrimp and other species of that habitat.

It hunts only in murky waters and compensates its limited sense of sight with a keen sense of smell. If they find a suitable prey, they swim directly toward it reaching speeds of up to 19 kilometers per hour; it hits the victim, and then sink their sharp teeth into the flesh. The rest is already known.

REPRODUCTIVE HABITS

The bull shark is viviparous, and the age to reach sexual maturity depends on the geographic region in which it is located but usually the age is ten years old for males and 10.9 years old for females. Some individuals can mature when reaching eight years of age.

Mating occurs in late spring and the summer. The mating scars on the females’ body indicate that during the process, the male bites his mate.

The gestation period lasts 10 to 11 months. The female has between 1 and 13 offspring, often in brackish water or in freshwater lakes.

Probably their most notable behavior is that they can tolerate freshwater.

BEHAVIOR

The bull shark prefers loneliness than the company of other sharks of its species, so it hunts by itself. It is not migratory, but some individuals from South America travel thousands of kilometers to the Atlantic Ocean, and many often go to fresh and brackish waters to give birth.

Probably their most notable behavior is that they can tolerate freshwater. While their body adapts to this change (it reduces the amount of salt and urea to suit different salinities), it is surprising that they are not afraid of water systems that are less salty and more shallow than their natural habitat. They avoid regions with low temperatures.

It shows certain aggressiveness and tendency to live near populated areas, a fact that makes it an animal of care.

THREATS AND CONSERVATION

Commercial fishing usually does not try to catch bull sharks, but this species is classified as “Near Threatened” on the IUCN Red List without compelling reasons.

Over time it has been captured to obtain its meat, its skin and its oil for several purposes. Recreational or sports fishing is also responsible for the situation. In current times many aquariums demand the presence of the bull shark in their facilities since it is a species that adapts well to life in a closed environment and catches people’s attention. This practice still does not seriously harm shark populations but is a potential danger if demand increases.

On the other hand, roaming areas close to human populations makes it an animal more vulnerable to the effects of civilization, such as pollution and incidental fishing.

At the moment there are no specific programs, plans or actions for the conservation of the bull shark.

Sources:

http://www.iucnredlist.org/details/39372/0

https://en.wikipedia.org/wiki/Bull_shark

http://www.arkive.org/bull-shark/carcharhinus-leucas/

https://www.flmnh.ufl.edu/fish/discover/species-profiles/carcharhinus-leucas

http://animaldiversity.org/accounts/Carcharhinus_leucas/

BioExpedition Publishing © 2017.

The amount of teeth that sharks have vary according to the species, from 5 to 15 rows of teeth in each jaw.

Sharks teeth take about one week to fall, as they do not have roots to hold them as human teeth.

When they fall, the tooth behind moves up to replace them.

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What Are The Tiger Shark Enemies?
What Is A Whale Shark?
How To Get Over The Fear Of Sharks?
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