Lessons with Dad: Sharks

Hello my curious readers,

I’m back with another interesting story! This time we are going to talk about an animal that existed way before the dinosaurs and as long ago as 400 years. They are known to be the fastest predator of the oceans. There are several species of this animal, around 500; they are all nondescript in colour, varying from grey to cream, brown, yellow, slate, or blue and often patterned with spots, bands or protuberances. This animal is often feared as the monster of the oceans and many of this fame actually comes from films, which have used these predators to create horror and fear in people and bears like me! In particular, the film JAWS, a must-see of my generation, which I have not allowed my children to watch, so by now I can imagine you all know who this animal is?

And yes! You are correct it is the Shark! 

Most sharks live in oceans in the mild or warm parts of the Earth. We can find Tiger sharks on tropical and subtropical waters; Blacktip Reef sharks in tropical coral reefs of the Indian and Pacific Oceans. Bull sharks in all coastal waters even in freshwater rivers like the Mississippi and Amazon rivers, Hammerhead sharks can be found in the offshore and near the shoreline of template tropical waters around the world. However, some species have special habitats. The Greenland shark lives in the cold Arctic waters, the Sand sharks spend most of their time at the bottom of shallow water and the Portuguese shark lives in the deepest parts of the ocean.

 

Contrary to humans and many animals like me, sharks have skeletons made from cartilages instead of bones like us, that’s why they belong in a subclass of fish called elasmobranchii. Cartilage is strong and dense but not as dense and certainly not as heavy as bones. The cartilage gives sharks the advantage of greater flexibility in bending compared to other bony fish. This flexibility also makes their tail move faster, this is why sharks are able to swim so fast!

Like other fish, sharks use their gills to gain oxygen from the water. Sharks have five to seven gill slits on each side of their heads, while the majority of the fish only have one gill on each side.

 

At first glance, sharks seem to have one row of very sharp teeth along their top and lower jaw, but if we could look closely inside, which I am sure none of us feel like doing, we could actually see that sharks have multiple rows of teeth behind that first front row. Sharks are amongst the few animals that can regrow their teeth constantly. That explains why behind each row of the front functional teeth, we find multiple rows of replacement teeth, so when a shark loses a tooth over prey, it will soon be replaced by a new one moving forward. Some sharks can have more than 30,000 teeth over their live span, that’s a great number of teeth, don’t you think? 

 

The largest amongst all of the predatory species is the voracious White shark. Their average length is around 15 feet long but they can grow up to 20 feet and can weight up to 50,000 pounds, although their average weight varies from 1,500 to 4,000 pounds. The White shark is grey on its upper body, so why is it called a “White” shark? This is because they all have white underbellies. This species is characterised also by their torpedo shape and powerful tail. They have an exceptional sense of smell that helps them identify their prey even if it is far away, and by their huge and very scary jaw with triangle teeth of up to 300 in a row. The White sharks usual prey are Sea lions, Sea turtles, some small Whales, Seals and Carrion.

Like whales, White sharks can jump completely out of the water when attacking their prey from underneath.

However, not all sharks are predators, the largest fish in the water is actually another shark but totally harmless. The Whale shark is patterned with white spots and stripes and is the largest living fish. Its length varies from 18 to 40 feet long, and it can weigh from 40,000 to 50,000 pounds. So, in other words a Whale shark is as long as your school bus and as heavy as three of your school buses put together.

Whale sharks also have a great number of teeth but they are very tiny and they do not need them to eat, as they are filter feeders. What does it mean by whale sharks being filter feeders? It means that they eat by straining tiny plankton and small fish from the water while swimming with their 1.5 meter wide mouth open.

 

Do you know how small the smallest shark is? It’s as small as a pencil and is called the Dwarf Lanternshark, which can reach a maximum size of 20cm. It is practically impossible to see this shark. It is known to be found only on the upper continental slopes of Colombia and Venezuela and at the very deep depth of 283/430 meters

 

Do you know which is the faster shark? The faster shark is called the Mako shark and when hunting for its prey it can swim as fast as 60mph (97 km/h). In other words Mako sharks swim as fast as the speed limit of cars on a main single-carriageway road in the UK. The slowest shark is the Greenland shark it swims at a speed of 0.76mph (1.22km/h) and when swimming fast it can reach 1.6 mph|(2.6 km/h). Grown up humans walk and at an average speed of 3.1 mph (5 km/h), so humans walk practically twice as fast as the Greenland shark can swim in full speed!

  

Shark skin is made up of placoid scales or dermal denticles which are like tiny teeth in structure that feel like sandpaper. These scales face the tail and help to reduce friction from the water when the sharks are swimming.

 

 

Most Sharks are carnivores; they eat fish, shellfish, mollusks and crustaceans. The larger species eat mammals like dolphins, seals, turtles, sea lions, tunas and even small sharks. Some sharks also eat sea birds and whales.

Sharks have a very sharp sense of smell, which is hundreds of times higher than humans. From hundreds of meters away they can smell one part of blood for every one million parts of water. This is like you being able to smell in the water of the swimming pool, a teaspoon of hot chocolate your friend dropped in by mistake, impossible right? Well a shark would be able to smell the chocolate in the swimming pool even if it is at the other side of the big swimming pool.

 

And now comes probably the most expected question, why do sharks attack and eat human beings?

Shark can attacks humans if the shark is very hungry, disturbed, or they are defending their territory, though many interactions with humans appear more likely to be due to mistaken identity. Indeed, the kicking and thrashing vibrations people make in the water, to sharks resemble the irregular movements of a wounded fish. Sometimes sharks can also attack due to curiosity, examining if the unfamiliar object could be of food value for them or not. But in general humans are not on the food list of a shark and sharks are not hunting for humans. The possibility of being attacked by a shark is 24 times less probable than being in a fatal train crash.

Well, my little friends, I hope you enjoyed learning about sharks today and I hope you understood that the shark is a beautiful and mysterious animal and not just a predator! Below you can find the quiz to refresh your mind. Stay safe and stay tuned for the next amazing story! A big bear hug from me, Dad Cashmirino, and from all of my family! Feel free to leave a comment here below to let us know what you think and how to improve the blog.

 

  • Sources: Live Science
  • Encyclopedia britanica
  • com
  • National wildlife federation
  • Ocean conservancy
  • I outdoors
  • Wikipedia
  • co.uk
  • Enc
  • FLORIDA MUSEUM

Quiz

All sharks are dangerous and predators. True / False

Answer: False. The Whale shark is harmless

 

Sharks are all characterised by a grey skin colour. True / False

Answer: False. Sharks can be brown, black, cream, white…

 

Sharks have multiple rows of teeth. True / False

Answer: True

 

What is the special thing about the skeleton of a shark?

Answer: The skeleton of a shark is made from cartilage and not bones.

  

What’s the fastest shark? How fast can it go?

Answer: The fastest shark is the Mako shark, which can swim at 60 miles per hour

 

Why do sharks attack humans?

Answer: Attacks on humans occur when sharks are very hungry, disturbed, or to defend their territory, though many interactions with humans appear more likely to be due to mistaken identity.


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