Shark facts
Short facts, and straight answers to things people say about sharks. Every one lists where we found it.
Short facts, and straight answers to things people say about sharks. Every one lists where we found it.
Myth or fact?
Most sharks are harmless to people, and only a few kinds cause most attacks.
There are more than 500 kinds of sharks. The Florida Museum's records name the great white, tiger and bull sharks as the three behind the most recorded attacks. Even so, it is wise to treat any big shark with respect.
Myth or fact?
Only some sharks lay eggs, and most give birth to live pups.
There are more than 500 kinds of sharks. Most give birth to live young, and the rest, like the horn shark, lay tough egg cases.
Sources: Natural History Museum: Do sharks lay eggs?, NOAA Fisheries: 12 shark facts that may surprise you
Myth or fact?
Sharks probably can't see colour the way we do, so yellow isn't a magnet for them.
In a study at the University of Queensland, the sharks tested had only one kind of colour-sensing cell in their eyes, where people have three. That means they probably can't tell colours apart the way we can, so a colour like yellow is unlikely to be special to them.
Sources: University of Queensland: Sharks may be colour blind
Myth or fact?
The whale shark is the biggest shark, and the great white is much smaller.
NOAA Fisheries calls the whale shark the largest shark, at about 12 metres (40 feet). The biggest great whites measured reliably are about 6 metres. The great white is the biggest shark that hunts large animals, while the whale shark eats tiny plankton.
Sources: NOAA Fisheries: Fun facts about shocking sharks, Florida Museum: Sharks FAQ
Myth or fact?
Megalodon died out millions of years ago, and there is no evidence it is still alive.
The Natural History Museum says megalodon teeth are only found in rocks from between about 20 million and 3.6 million years ago. Nobody has ever found younger ones, and there are no confirmed sightings.
Myth or fact?
Sharks smell very well, but not well enough to find one drop of blood miles away.
Scientists tested five kinds of sharks and rays and found they can pick up a smell at about one part in a billion. That is excellent, but no better than ordinary fish. How far a smell travels also depends on the ocean currents.
Sources: Practical Fishkeeping, reporting a 2010 study in the Journal of Experimental Biology
Myth or fact?
Most sharks live in the sea, but a few, like the bull shark, also swim far up rivers.
The Florida Museum says bull sharks live in both salt water and fresh water, and have been found hundreds of miles up rivers. Most sharks do stay in the sea, though.
Sources: Florida Museum: Bull shark
Myth or fact?
Sharks see well in dim light, and many are probably colour blind, though scientists are not completely sure.
A 2011 study of 17 shark species found no colour-sensing cells in 10 of them and only one type in the other 7, so they probably cannot tell colours apart. They are far from blind, though: a mirror-like layer at the back of the eye helps them see in dark water. Scientists still disagree about how much colour some sharks can see.
Sources: NOAA Fisheries: 12 shark facts that may surprise you, ScienceDaily: Sharks may be colour blind, National Geographic: Sharks are colour blind, study suggests
Myth or fact?
Sharks don't eat constantly, and some can go weeks between meals.
NOAA Fisheries says sharks can go up to about six weeks without feeding. Big, active hunters do eat more often than that, but they do not need to eat all the time.
Myth or fact?
Sharks have no true bones, but they do have a skeleton.
A shark's skeleton is made of cartilage, the bendy material in your nose and ears. It is much lighter than bone. Many sharks add hard calcium to their cartilage as they get older, so it becomes stiff, but it is still not bone.
Sources: NOAA Fisheries: 12 shark facts that may surprise you, Wikipedia: Shark
Myth or fact?
Sharks do not hunt people as food, and bites on people are rare.
Researchers at the Florida Museum say many quick "hit and run" bites are probably mistaken identity in murky water. The shark soon finds out a person is not its usual prey, lets go, and does not come back.
Sources: Florida Museum, International Shark Attack File: How, Where and When Sharks Attack
Myth or fact?
Yes, it feels rough when you rub it from tail to head, and smooth the other way.
A shark's skin is covered in tiny tooth-like scales called dermal denticles, which point toward the tail. Please never touch a wild shark, though.
Sources: NOAA Fisheries: 12 shark facts that may surprise you, Wikipedia: Dermal denticle
Myth or fact?
Some sharks must keep swimming to breathe, but many can rest on the seafloor.
Sharks like great whites and makos breathe by swimming, which pushes water over their gills. Sharks that live on the bottom, such as nurse sharks, can lie still because they pull water in through an opening just behind each eye.
Sources: NOAA Fisheries: 12 shark facts that may surprise you, Hakai Magazine: Rock-a-bye Shark-y
Myth or fact?
Sharks can get sick, and they can get cancer too.
Scientists have found both harmless and cancerous tumours in sharks and their relatives. The idea that sharks are cancer-proof led people to sell shark cartilage as a cancer treatment, but the evidence does not show that it works.
Sources: Cancer Research (2004): Shark Cartilage, Cancer and the Growing Threat of Pseudoscience
Myth or fact?
Sharks do rest, and at least some of them sleep.
In a 2022 study, scientists measured draughtsboard sharks, small sharks that rest on the seafloor. Their bodies used less energy while resting, which is a sign of sleep. Fast swimmers like great whites have not been tested yet.
Sources: Biology Letters (2022): Energy conservation characterizes sleep in sharks, Hakai Magazine: Rock-a-bye Shark-y
Myth or fact?
Yes. Sharks go back about 450 million years, and the first trees came roughly 60 to 70 million years later.
The first trees appeared around 385 million years ago. The oldest shark evidence is a few tiny scales, so scientists still debate exactly when true sharks began, but sharks were around well before any forest.
Sources: Discover Wildlife: Are sharks older than trees?, NOAA Fisheries: 12 shark facts that may surprise you
Myth or fact?
Shark teeth are hard like bone, but they are made of something different.
The Natural History Museum says shark teeth are made of a very hard coating called enameloid over a core of dentine. A shark's skeleton is made of cartilage, so sharks have no true bones at all.
Sources: Natural History Museum: What can shark teeth tell us?, Florida Museum: Fossil shark teeth