21 Things You Didn't Know About Sharks

There is so much more to sharks than the popular image of them as cold-blooded, man-eating killing machines. Sure they’re some of the most evolved and capable hunters in the animal kingdom, but there are plenty of shark facts that can better our understanding of these creatures and have you captivated by more than just their impressive teeth.  

Sharks have been known to curiously investigate humans and other objects in their environment that are strange to them. So indulge your curiosity for facts about sharks. Get to know their evolutionary history and their biology. Learn what makes them so impressive with the shark information collected in the list below!
Megalodons Are Amazing!
The picture is a to scale restoration, but many of the teeth in the sculpture were real fossilized teeth. The giant C. Megalodon sharks are now extinct but scientists believe that they could grow as long as 60 feet! “Megalodon” actually means “big tooth” in Ancient Greek.
Sharks Can Sense You from Your Body's Electricity
Sort of. Sharks have an array of electroreceptors in the pores around their mouths. These receptors can detect tiny electromagnetic fields made by things as seemingly inconsequential as muscle contractions or movements in living organisms. In the conductive environment of sea water, sharks have been measured detecting electric fields as weak as 5/1,000,000,000 of a volt per centimeter of receptor tissue.
There is no hiding from a shark – this is almost as conductive as the most high-tech man-made materials.
Hammerheads Have a 360 Degree View of the World Around Them
One of the most distinctive looking types of sharks, it is believed that the shape of the shark’s head and positioning of its eyes is an evolutionary adaptation to give it superior views of its surroundings. Hammerheads have a virtually 360 degree view at all times, letting them  efficiently sweep for prey.
Until the 16th Century They Were Called "Sea Dogs"
Until the 16th century, mariners called sharks “sea dogs.” Why? If you squint, a hairless teeth-lined maw with fins and no legs looks kind of like a dog, probably. The etymology of the word “shark” is not quite clear but it may have its origins in the Dutch words for predator or scoundrel.
Orcas Eat Great White Sharks
If you ever saw Jaws, you could be forgiven for thinking that those cold blooded eating machines were at the top of the food chain. But in fact there is a species that feeds on them:  killer whales, or orcas. Orcas are the true apex predators of their ecosystems, which means that no other animals prey on them.
Sharks Are 420 Million Years Old
The earliest recorded fossil records of sharks date back to 420 million years ago. This means that sharks were terrorizing the waters for hundreds of millions of years concurrently with dinosaurs.
Do They Really Have to Keep Swimming to Survive?
A lot of sharks do, in a manner of speaking. Sharks use gills to breathe and the only way they can extract oxygen from the water is to be continuously on the move so that water is always passing over their gills. Thus, they need to keep moving or they will asphyxiate, though most sharks are able to pump water over their gills while they are at rest.
There Are Over 500 Species of Sharks
They are found in oceans all over the world. They usually inhabit depths up to 2,000 meters below sea level and there are very few fresh water sharks.
Tiger Sharks Have Been Called "The Garbage Cans of the Sea"
Tiger sharks are probably the most widely carnivorous of all shark species. Not only do they prey on everything from crustaceans to fish, sea turtles, birds, squids, and dolphins, they’re the type of shark known to ingest all those man-made objects. This tendency has even earned them the nickname the garbage cansof the sea. Their common name comes from the tiger-like stripes they have along their sides.
Sharks Will Eat Anything, Even a Fur Coat or Suit of Armor
This cannot be emphasized enough – they will eat anything at all. Hungry for some examples? How about license plates, tires, a fur coat, a horse’s head, video cameras, a cannonball, and even a full set of steel armor –  helmet and all. You name it, it’s been found in the belly of a shark.
Some Sharks Are Tiny and Adorable
The smallest known species of sharks is the dwarf lanternshark, found only in the underwater continental slopes of Colombia and Venezuela. These little sharks only grow as long as eight inches. Yes, inches.
There's a "Cookiecutter" Shark and It Will Mess You Up
Yes, cookiecutter sharks. Perhaps one of the silliest named sharks, these little pests are parasitic and only grow up to about 20 inches in length. For their size, they still have enormous sets of teeth that open into a round patter, like a cookie cutter. They latch their teeth onto practically any kind of prey, from whales to other sharks to bony fish to the hulls of ships, then they wriggle their bodies to wrench flesh away. They can leave ” crater wounds” up to five inches wide and seven inches deep.
Great Whites Are Speedy Quick
They can reach speeds of up to 35 miles per hour in the water and can grow as long as 21 feet. While the movie Jaws popularized the idea of man-eating great whites, actual great white shark attacks on humans are incredibly rare.
Sharks Are Part of the Same Subclass as Rays
Like sharks, rays have cartilaginous skeletons, five to seven gills, and dorsal fins. Rays distinguish themselves with generally flattened bodies and enlarged pectoral fins. They both fall under the subclass Elasmobranchii but rays are in their own separate order called Batoidea.
Sharks Go Through Thousands of Teeth in Their Lifetimes
Sharks go through teeth like humans go through fingernails. Scientists believe that sharks will grow and losethousands of teeth over the course of their lives. This is mostly because teeth make up the abundant majority of all shark fossils found.
Whale Sharks Average Around 40 Feet Long
The largest species of shark that hasn’t gone extinct is the whale shark, averaging upwards of  40 feet long. Despite being the biggest fish in the sea, these sharks are gentle giants that filter feed on tiny plankton, so there’s no need to worry about a Jaws situation with a whale shark.
Sharks Have Intense Senses of Smell
You’ve likely heard how sensitive sharks are to blood in the water. Predatory evolution has turned these sea dwellers into impressive smelling machines. Tests of olfactory reception and stimulation in some species have shown that they can detect as little as 1 part per million of blood in sea water. In terms of volume, that’s like sniffing out a golf ball in the Loch Ness.
Sharks CAN Get Cancer
You could probably blame the myth of their immunity and use of shark cartilage as a cancer treatment on the god-like fear and reverence that Jaws still inspires towards sharks. There are much more reliable cancer treatments than extracting shark cartilage.
They Have Cartilaginous Skeletons
Cartilage is an anatomical substance found in the skeletons of many vertebrate species, but shark skeletons are made entirely of cartilage. As such, they are part of an order of animals called Chondrichthyes. These skeletons make them more adapted to their aquatic lives and environments.
Shark Week Hasn't Been Without Controversy
The week-long extravaganza of shark themed TV programming has been hosted by the Discovery Channel every summer since 1988. It’s become quite memetic and famous for celebrity hosts and crossovers with programs like Mythbusters. Discovery Channel and Shark Week programming came under fire for airing sensationalized docudramas using pseudoscience, but Discovery President Rich Ross (who joined the network in 2014) vowed to remove the so-called ” docufiction” from future Shark Week lineups.
There Are Nine Suborders of Sharks
All sharks are a part of the superorder Selachimorpha which is broken up into nine suborders. The different species are assigned to each order based on the arrangement of their fins, gills, and their proportional shapes.
Omnivorous Sharks Exist
In August 2018, Samantha C. Leigh, Yannis P. Papastamantiou, and Donovan P. German published a study revealing that the bonnethead shark doesn’t just eat fish – it munches on seagrass as well. Up to 60% of the hammerhead’s diet consists of seagrass, while the rest is bony fish, snails, shrimp, and bony fish.
“It’s the first known omnivorous species of shark,” Leigh said. Before the study, researchers knew bonnetheads occasionally chewed on seagrass, but Leigh says “it has been assumed by most that this consumption was incidental and that it provided no nutritional value.” Leigh and co. learned that this shark was better at digesting plant material than pandas and that the seagrass has nutritional value for the shark.