What is your opinion of sharks? You may love them or the thought of that apex silhouette in some opaque surrounding may send shivers down your spine, but one thing is for certain, they are fascinating creatures. Sharks fall under the scientific heading of Selachimorpha and are further divided into 13 sub-orders, 4 of which are now extinct. The first reference of the word ‘shark’ was found in a letter written in the 1500s, but the species, in different forms, has been around for about 420 million years. This article will explore their history and unusual behaviour, while also providing a profile on some of the most well know sharks found in the ocean today.
According to scientists, the sharks that we see in our oceans today evolved into their present form about 100 million years ago. They were contemporaries of the dinosaurs. The Hammerhead shark is one of the most modern forms and has been around for between 33-53 million years. Fossils of the (Great) White shark have been dated at 60-66 million years old. It is difficult to get a precise picture of ancient sharks because their bodies were mainly made up of cartilage, which tends to disintegrate quickly and doesn’t leave many fossilised remains. Their development era has been named the Devonian Period after the English county of Devon where thousands of ancient fish fossils were found in its red sandstone.
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Where do sharks live?
Sharks can be found all over the globe from the icy waters of the Arctic and Antarctic to tropical waters. Although sharks aren’t territorial, the different species tend to broadly cling to climate zones. There are sharks that are habitually found in the polar, temperate, or tropical regions. Most stay within their climate zones, but there are also a few that will migrate to others.
Sharks can be found in the deep oceans and at such depths as 6,600 ft. (2,000 meters) beneath the sea, or in the open oceans, but most are encountered closer to land. The reason for this is because of the abundance of food resources. These include such places as coral reefs, which are breeding grounds for other fish.
There are also some sharks that can survive in both sea and freshwater. The most famous is the Bull shark. It flourishes in Lake Managua in Nicaragua and has been seen in the Mississippi, Amazon and the Brisbane River in Australia. They have been seen in the Ganges in India and also the Tigris in Iraq. In addition, the River shark, a little known species, frequently inhabits the major rivers in the Far East.
Sharks and mating
Mating and reproduction are varied among the many species of sharks, but it involves physical contact. The male inserts what is called a clasper into the female. Unfortunately, not much is known about shark reproduction. Most sharks reproduce like mammals, meaning they produce their young in the womb. Some species only mate once every 2-3 years, but others, the smaller species reproduce every year. The amount of offspring can vary wildly between 2-80, depending on the species. Gestation periods can last from as little as 3 months to 2 years.
What do sharks eat?
Most sharks are constantly on the move, looking for prey. Depending on the species, most have their habitual diets. Some filter their food, like Whale or Basking sharks that feed on plankton or krill. Others swallow their prey whole. Still others, like the larger hunters, bite or tear their victims. The hunters usually circle and draw nearer, then attack from below.
Sharks usually eat fish or other sea creatures smaller than themselves. The more aggressive and bigger predators will prey on crustaceans, squid, octopuses, sea turtles, seals, sea lions, penguins, dolphins and other sharks.
How do they catch their prey? Well, they have a variety of senses. They have an acute sense of smell, very developed hearing, based mainly on sound vibration and (some have) much better eyesight than humans. Their greatest weapon is electroreception. This acts like a kind of sonar. With sensitive organs in their snouts, sharks can pick up minuscule electrical emissions from other fish and sea mammals.
Shark attacks (humans….)
Given the number of sharks and the number of people that use the oceans for recreation and commerce the likelihood of you being attacked is very small. Sharks don’t see humans as part of their diet. In 2019, there were 64 recorded shark attacks, a reduction on previous years.
On the other hand, sharks are under threat from humanity. Sharks get caught in commercial fishing nets or are hunted specifically for human use. Humans eat shark meat, use their skin for apparel items such as boots, luggage, bags, or suits. Some of their internal organs are used for medicinal purposes, plus humans extract oils from their bodies. Probably the worse threat to sharks is the popularity of shark fin soup in South East Asia.
Why are sharks misunderstood?
Most of us know virtually nothing about sharks. Our perception of these creatures has come mostly from horror books and films portraying them as ravaging monsters on the lookout for humans to devour. When someone says the word ‘shark’ we immediately think of the more aggressive types that we have seen on our screens, but that isn’t the reality. Even the larger sharks such as the Great White has its gentler side and doesn’t attack unless frightened or provoked. Even marine biologists and other researchers admit that very little is known about sharks, but that is changing. Slowly, they are learning the habits, behaviour and etiquette of these giant predators.
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Extra Trivia: Great White Shark vs Killer Whale
These two are the heavy hitters of the oceans. They are both apex predators, both carnivores and both massive in size. What are the differences? Believe it or not, the Killer Whale or Orca belongs to the dolphin scientific family, not the shark family. Great Whites are grey and white, whereas the Orca has distinctive pitch black and pure white colouring. The Great Whites are found off the coasts of North America, Japan and South Africa. Orcas can be found anywhere between the Polar Regions and the equator. The Whites feed on fish mostly (they do also eat sea mammals), while the Orcas hunt sea mammals. An adult Great White can weigh in at around 5,000 lbs, but an adult Orca can weigh double that. Great Whites measure between 15-20 ft., but Killer Whales grow to between 23-32 ft. in length. The lifespan of a Great White is around 70 years and the Orca is up to 80 years.
Three Well-known Sharks
The Great White
- The Great White is mostly grey on top and white underneath, with a conical snout and large eyes.
- Speed: 25 mph (40 kph)
- Location: North America, South Africa and Japan, but not exclusively
- Fun Fact: Females are larger than the males
- The Hammerhead shark is light grey on top and white underneath with a distinctive double hammer-shaped head.
- Speed: 12 mph (20 kph)
- Location: tropical waters
- Fun Fact: There are nine species of hammerheads
The White Tip
- White Tip sharks are also known by various other names. They have large fins with white tips. Their lower teeth are different from their upper set.
- Speed: No one has bothered to record their speed because they are slow-moving creatures
- Location: Prefers open ocean and warm waters
- Fun Fact: They hunt both day and night
Our fear of sharks is unwarranted as very few people actually get attacked by sharks. They are a beautiful misunderstood species and as a result, they should be respected and protected. Their history is considerably longer than the history of Homo sapiens. If we too want to experience that tenureship on this planet, we must learn to live with sharks and encourage them to prosper and thrive as they are vital to the ecosystem of our oceans which we to depend on.