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 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.

Links to other pages in this site

What Is A Whale Shark?
How Do Sharks Breed?
What Is The Largest Shark In The World?
Where Does A Whale Shark Live?
Why The Great White Shark Is Endangered?

Tiger Sharks in South Africa

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.