Love them or hate them, you can’t deny that sharks are some of the most fascinating and oldest species on the planet. They’re certainly a hot topic when it comes to Google searches. So, in this blog, we’re answering some of the most asked (and a couple of the strangest) shark questions. How many different types of sharks are there? Is a shark a mammal? Read on for the answers and prepare to learn some fun facts about sharks.

A great white, like all kinds of sharks, is a fish and breathes through gills, answering the question 'are sharks mammals?'

Is a shark a mammal?

No, a shark is not a mammal. Despite names like ‘whale shark’, all sharks are fish and differ in many ways from mammals. For example, mammals breathe air through lungs, feed their young with milk and are warm-blooded. Sharks pass water over gills to breathe, don’t have mammary glands and (with the exception of mackerel sharks) are cold-blooded.

Can sharks swim backwards?

No. Sharks’ pectoral fins can’t bend upwards like other fish, limiting them to forward movement only. However, that’s a good thing since going backwards can cause water to enter their gills and interfere with respiration (answering another popular question, ‘Can sharks drown?’).

Do sharks sleep?

This one’s a topic of scientific debate, linked to whether sharks can stop swimming or not. Video evidence and recent research suggest sharks do sleep, based on indicators such as metabolic rate, activity levels and posture.

A shark egg casing attached to coral, which is also known as a mermaid's purse and an unusual subject of shark photography

Do sharks lay eggs?

It depends on the species! Many, including hammerheads, are viviparous and give birth to live pups (which may be why people ask, ‘Is a shark a mammal?’). Ovoviviparous sharks (like whale sharks) hatch eggs internally before giving birth to live young, while oviparous species (such as catsharks) lay external eggs in protective cases known as mermaid’s purses.

Why are sharks called sharks?

The exact etymology is unknown, but one theory is that it comes from the German word schurke (meaning villain, rogue) because of the fish’s predatory characteristics.

A closer view of a hammerhead shark in the Caribbean, which is one of the most popular scuba destinations for shark sightings

Are sharks blind?

No, sharks have excellent vision. They have similar eye anatomy to humans, but they can see 10 times better than us — especially in low light. However, sharks do have one recently discovered weakness: color-blindness.

Do sharks fart?

In a sense, yes. The sand tiger shark swallows air at the surface to help maintain its buoyancy before expelling it in a fart-like fashion to sink again. Sharks lack a swim bladder, so this action is like having a natural BCD!

The Greenland shark, one of the oldest species of sharks and one which has been known to live for around five hundred years

Do sharks live forever?

No, but the Greenland shark might live for nearly 500 years! The average whale shark lifespan is 70 years, while several other species may only live for around 20 years. The only known biologically immortal creature is a jellyfish.

What language do sharks speak?

Sharks are not capable of making sounds. So, how do sharks communicate? With body language! Arched backs, lowered pectoral fins, inflated gills and open jaws are all non-verbal forms of ‘shark speak’.

Do sharks have bones?

Believe it or not, sharks don’t have a single bone in their bodies! Instead, their skeleton is made from strong cartilaginous tissue, which is lighter and more flexible than bone. This allows them to swim faster, turn quickly and open their jaws extra wide for a more powerful bite.

Can you swim with sharks?

Absolutely! There are many destinations and dive sites where you can go scuba diving with sharks and see these magnificent creatures close up. But for the question ‘how to ride a shark’, there’s only one answer: never! Riding a shark or even touching them is a massive no-no.

Are sharks bulletproof?

Sharks don’t possess Kevlar armor or ballistic superpowers, no. But if you’re going to consider any animal to be bulletproof, it should be the whale shark. Not only the largest fish in the world, they also have the thickest skin of any living creature — around 10cm (4 inches) on average.

A large pod of dolphins, which could easily outnumber a solitary shark and is why sharks are often thought to fear dolphins

Are sharks scared of dolphins?

It’s not so much that sharks fear dolphins. In fact, larger species prey on them. But dolphins stick together to fight off threats, and with some ‘super pods’ reaching over 1,000 individuals, a solitary shark would prefer to swim elsewhere than find themselves outnumbered.

Are sharks dangerous?

Sharks generally pose no threat to us — we’re not part of their diet. Indeed, when shark attacks happen, it’s usually from confusion or curiosity. It’s surprising what’s more likely to hurt you than a shark attack — like hippos or ladders. How many people die from sharks each year? An average of five, according to the International Shark Attack File. But how many sharks are killed each year? 100 million. Indeed, sharks have more to fear from us!

A scuba diver and whale shark, a popular shark diving sighting and the name of which makes people ask 'is a shark a mammal'

Bite-sized answers…

  • How many species of sharks are there? There are over 500 species of sharks.
  • How fast can a shark swim? Mako sharks can reach bursts of 46mph (74kph).
  • Is a shark a carnivore? Strictly yes, but some (like basking sharks) are filter-feeding planktivores.
  • What is the biggest shark in the ocean? A whale shark — the record being 18.8m long (61.7ft).
  • How deep can sharks swim? Scientists have found sharks as deep as 1.8 miles (3km).
  • Are sharks endangered? Sadly, more than a third of shark species are threatened with extinction.
  • What shark am I? Take our shark quiz to find out!

So, now you know the answer to, ‘Is a shark a mammal?’ and many of the other most Googled questions about sharks. Learn more cool shark facts (as well as how to help sharks) by taking the PADI AWARE Shark Conservation Diver course, and find out how to protect their ocean habitat as a PADI Torchbearer.

Related Reading:

Sharks Should be Respected, Not Feared
Can I Dive with Sharks While Menstruating?
10 Incredible Sharks Every Diver Should See
How to Overcome a Fear of Sharks

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