Terrifying giant jaws, intimidating look and razor-sharp teeth. Sharks are predators that inspire fear. Year after year thousands of people are killed by sharks. Regardless, these fascinating creatures are unique in their behaviour and variety. Scientists spend years studying sharks, and every time we learn something new about them.
Here are ten surprising facts about sharks provided by National Geographic:
An average shark loses up to 30,000 teeth throughout its life
Usually sharks have 45 to 50 teeth, but those are only in the front row. Behind it, there are can be up to seven rows of teeth that can be put to use in an instant if teeth in the front row are damaged or lost. Some shark species constantly replace teeth throughout their lives – they can replace up to 30,000 teeth in a span of the whole life. There are sharks whose teeth are replaced every 8 – 10 days.
Some species of shark have no need for teeth
Even though sharks are usually associated with big and sharp teeth, some shark species really have no need for teeth. The whale shark and basking share – two of the largest species of shark – feed passively, by filtering half-decomposed remains of organisms and micro-organisms from water. They do have a lot of small teeth. For example, the whale shark can have up to 300 rows of teeth.
Sharks have a special body language
White sharks do not use sound to communicate. They use body language instead. Bent back, lowered pectoral fins, sharp zigzag movements and sudden movements backwards and forwards – all of these are powerful indicators that show a shark is anxious about something.
Shark lifespan varies from species to species
Some of the largest sharks in the world have longer lives than their smaller counterparts. For example, the whale shark, which can be 5.5 – 10 m in length, can live up to 100 years. The smooth lantern shark – which is 0.6 – 1.2 m in length – lives on average for 16 years.
Sharks vary in size dramatically
The whale shark is not only the largest shark, but also the largest fish in the world. The smallest sharks in the world are dwarf sharks – on average their length is only 17 cm.
Sharks have three different ways of reproduction
Approximately 30% of sharks lay eggs. Some sharks are viviparous. Most sharks carry eggs in a special egg chamber – Fallopian tube – which is filled with special secretions. The baby shark develops in that chamber until it is ready to be born. A single female shark can carry up to 48 offspring.
Sharks are a protected species
Statistics show that for every one shark that kills one human, 25 million sharks are killed by humans. This is mainly done to acquire shark fins, which are considered a delicacy in many parts of the world. More than 200 species of shark are included in the Red Book of Protected Species. Sharks are an important part of the oceanic ecosystem. This is why their dwindling numbers seriously worry ecologists. If sharks die out, the oceans of the world will soon follow.
Sharks can see yellow colour – a myth
Shark studies have helped disprove the myth that sharks are attracted by yellow colour. In truth, sharks cannot see any colours. Research has shown that sharks do not have eye cells that differentiate between different colours. They can differentiate between contrasts of colours, but not colours themselves.
Sharks inhabit freshwater environments as well
Sharks inhabit all seven of the world’s oceans. However, some sharks do inhabit freshwater environments. There are sharks that inhabit mixed environments, like estuaries and bodies of water connected to the ocean. Other species of shark feel absolutely fine in fresh water.
Sharks have been around for 400 million years
Sharks have been present on Earth since the age of dinosaurs. Scientists have found remains of 400-million-year old fossilized teeth and scales that may have belonged to ancestors of modern sharks. The so-called modern sharks first appeared around 100 million years ago. A rare species of shark is said to still inhabit the Earth. Apparently, it has not changed much over the past several million years. It is the so-called frilled shark – one of the best examples we have to imagine how ancient sharks might have looked like.