Table of Contents
What makes this gigantic fish “the great white shark” a perfect agile hunter?
Do calling it man-eater and white-death justify its anatomy?
Important features of great white sharks
Great White sharks are cigar shaped gigantic fishes. They are the world’s largest known predatory fish. They possess sharply pointed conical snout after which it is named as white pointer. They possess huge pectoral and dorsal fins along with powerful sickle-shaped tail.
Habitat
White shark inhabits temperate coastal and offshore waters laden with fishes and marine mammals between temperature range of 54 and 75 °F and depths of up to 3900 ft. White sharks can be found in the waters of southern Africa, southern Australia, northeastern and western United States, northern Japan, Chile, New Zealand, and the Mediterranean.
Size
The largest fully grown white sharks are 15-20 feet long and weighs between 1500 and 4000 pounds usually. But some of them can be 21 feet long and 7000 pounds heavy. These figures show its massiveness due to which it is termed as Great in its name.
Females are larger than males in size, females are 11-13 feet in length and males are 15-16 feet in length. However scientific world knows it by the name of Carcharodon carcharias, genus name derived from greek word meaning “jagged tooth” and specie name derived from greek word meaning “shark”.
Coloration
Their white belly gave them the name of white shark. Otherwise they are not completely white. Rather they have bluish, grayish, or brownish contrasting pattern on its dorsal area. This coloration merges the shark’s outline when seen from the side and so helps them to hunt perfectly. The darker shade of dorsal side merges with the sea and from ventral side shows a slight etch against the sunlight.
Senses
They are incredible hunters equipped with great musculature, strong eyesight, and intense sense of smell. They can smell a colony of seals two miles away and even only one drop of blood in 100 litres of water. Their eyes are larger as compare to their body size with bluish iris rather than black. It has sensitive ampullae of lorenzini that can detect a change of half a billionth of a volt in electromagnetic radiations. They can even detect immobile organisms by sensing their heartbeat.
Jaws
They possess huge jaws provided with almost 300 big sharp saw-edged, coarse teeth arranged in seven rows; still it does not chew its food. Rather it tears its prey into mouth-sized pieces which are gulped as whole. They have extra rows of teeth behind the main row to replace the broken tooth immediately if any.
They shake their heads side to side while biting the prey to pierce the flesh, and crush and shatter the bones of its prey. Studies revealed that a 7000 pounds heavy great shark can bite with a force of 4000 pounds, and such intense bite force resolves problems of feeding competition. All these adaptations are responsible for its popularity as white death.
Feeding habits and predation
Newborn white sharks feed on relatively smaller and softer fish including cartilaginous fishes. Adult great sharks prey upon sea turtles, seals, sea lions, porpoises, dolphins, and small whales some of which are as big as great shark itself.
They attack their prey by ambush, attempting to flash the animal by surprise and bite it into pieces. Owing to its torpedo shaped body it cruises skillfully for long periods of time, and then suddenly bursts in high speed chasing its prey. Usually this initial flash reaches up to the speed of 25 mph which is so intense that the prey may be thrown out of the water or the shark itself into the air if it misses the target.
While hunting seals, great shark reaches surface water with high speeds of up to 25 miles per hour and their momentum cause them to jump out of water up to 10 ft high in air. This is breaching technique. In addition to being agile hunters Great white sharks are also opportunistic scavengers. They feed upon preys that contain high amounts of fat rich energy.
They are diurnal feeders and hunt preferably in first two hours of sunrise when light is dim with 55% success rate, falling to 40% in late morning after which hunting stops. Great White Sharks are thought to consume an average of 11 tons of food annually and, after a proper big meal, it may not feed properly again for up to 3 months.
Attacks on human beings
In the areas where they are most common, white sharks are responsible for numerous unprovoked, and sometimes fatal, attacks on swimmers, divers, surfers, kayakers, and even small boats with fatality rates of more than 20 percent. Fatality rates as high as 60 percent have been recorded from attacks in the waters of Australia.
Many researchers maintain that attacks on humans stem from the shark’s curiosity or shark mistaking humans for its natural prey, such as seals and sea lions as white sharks are likely to be color blind, or even when their natural prey may be scarce. This behavior earns it the name of man-eater.
Some other important facts about great white shark
Thermoregulation
Most fish are ectothermic, or cold-blooded, but unlike most fish great white shark is warm blooded. Great white sharks have complex circulatory system equipped with rete mirabile that is specialized at conserving heat generated through counter current flow mechanism. This heat is used to raise the body temperature of selective organs of great white shark higher than the temperature of the surrounding water.
Great shark has varied temperature throughout its body but it is internally regulated. This adaptation, called regional endothermy is responsible for keeping the animal active in water that is too cold for other species of predatory sharks. It all happens due to gigantic size of great white shark and this phenomenon is called gigantothermy.
Buoyancy and migration
Liver of the shark is responsible for controlling its buyoncy and migration patterns.
Self healing
Great shark shows astonishing ability of resisting heavy metal poisoning. They can self-heal and avoid age related ailments.
Reproduction and development
Mating has yet to be fully documented in white sharks, but it is supposed to be like internal fertilization in most sharks-that is, the male inserts his claspers into the cloaca of the female. Courtship behavior is unknown, if any.
Male white sharks reach sexual maturity at 10 years of age, whereas females reach sexual maturity at 14-16 years of age. It may reproduce every couple of years or even more infrequently. It is hypothesized that great white sharks mate in shallow water away from feeding areas. They continually roll belly to belly while copulating.
Great white sharks are ovoviviparous. Their eggs develop and hatch in the uterus and continue to develop in uterus until birth. Its gestation period is 11-months long. The fetuses feed on ova of their mother and so do oophagy. Delivery is in spring and summer and females are thought to give birth in warm temperate and subtropical waters.
The largest number of pups born to this species is 14 pups from a 15 ft. long single mother that was killed accidentally off Taiwan in 2019. Baby sharks are on their own right from the start. It swims away from its mother immediately after birth. Their mother may see them only as prey. The pup’s jaws begin to develop in the first month.
Lifespan
Great shark has a lifespan of maximum 73 years which can be counted from vertebral growth rings. But its average lifespan is 40 years of age.
Threats
Great white sharks are at top of marine food chain and have few natural enemies.
However, young white sharks can sometimes be eaten by larger sharks including other white sharks. Once it was documented that an adult killer whale (Orcinus orca) attacked and killed an adult white shark. Great sharks are threatened by orcas in areas where their preys are same or overlapping. Orcas can threaten white sharks to play death in combat and can sometimes kill white sharks.
Human beings are the most profound enemies of the white shark. In order to save humans from white sharks, governments are killing white sharks deliberately using nets and drum lines with baited hooks. This act is called shark culling and is considered cruel, ancient and unproductive. The overstated dangerous nature of this shark has encouraged trophy hunting for their jaws and teeth. Their teeth, jaws, and fins can reach huge prices as much as $50,000 on the Asian fin market.
Protection
The white shark was declared as vulnerable species by the International Union for Conservation of Nature IUCN since 1996. Its widespread distribution throughout ocean has made complete population surveys difficult. White sharks are legally protected in several places such as Australia, South Africa, and California despite their ferocity.
The protection of white sharks may even have economic benefits. For example, in waters that contain white sharks, boaters and dive operators earn tens of thousands of dollars yearly by featuring popular “shark dives” where guests can see white sharks from the safety of steel cages suspended in the water.
Conclusion
Great white Sharks are insightful, lustrous and totally misinterpreted. Great white sharks are the glorious ruler of temperate coastal and offshore waters. Human are afraid of them and they are also afraid of humans as human make their existence difficult. A change in its image from vicious killer to magnificent predator is needed to assure the future survival of white sharks.[1]https://www.britannica.com/animal/white-shark[2]https://en.wikipedia.org/wiki?curid=43619[3]https://eol.org/pages/46559751/articles[4]http://www.geocaching.com/track/details.aspx?guid=a271a958-d6c0-47cf-9b76-385a430b0b79
Reviewed by:
Dr. Muhammad Tahir Ph.D. (PU)
Post Doctorate
American Museum of Natural History, New York, USA