55 Amazing Facts About Sharks
These beasts of the deep are far more interesting than you might have thought.
Is there any creature that inspires more fascination, fear, or awe than the shark? These animals have die-hard fans who tune into every annual Shark Week and have seen every movie in the Jaws franchise. But there are some fascinating facts that even the most shark-obsessed people might not know.
Whether it's their unique organs that them help detect motion or their cannibalistic babies, sharks are endlessly interesting and full of surprises. To satisfy your curiosity about everyone's favorite predator, we've rounded up the shark facts you've never heard before.
Their favorite sound is a faint buzz called a "yummy hum."
Blood in the water may be the most obvious signal that shark bait is lurking, but did you know that sharks also respond to sound? Sharks are able to pick up on super low frequencies that are undetectable to the human ear. For example, when dying fish give off low-pitched infrasound, sharks hear it and head off to finish the job. This low-frequency buzz, often referred to as a "yummy hum," is a useful hunting tool for predatory sharks, according to the Discovery Channel.
Swell sharks glow in the dark.
Blue light doesn't only come from screens. Nearly 1,700 feet beneath the ocean's surface, you'll find the swell shark to be another unlikely source of it. For reasons still unclear to scientists, these sharks emit a fluorescent glow that's only visible to other swell sharks. Scientists themselves have only been able to detect the glow using filters that block out yellow light. According to biologist David Gruber of the City University of New York, these creatures glow so they can communicate with their other swell shark pals.
Ghost sharks have sex organs on their heads.
These deep-sea creatures, also called chimera and ratfish, are mysterious, and not just because they lurk in the depths of the ocean. Among their most curious features is the male ghost shark's sex organ, which protrudes from its head and attaches to the female's pelvis during copulation, according to National Geographic. Female ghost sharks can hold onto this sperm and use it when they desire, sometimes up to three years later.
Sharks' only bones are their teeth.
Sharks have been on this planet for hundreds of millions of years, yet fossils show little record of their existence. That's because they're elasmobranches, or species that have cartilage instead of bones, meaning most shark carcasses decompose before a fossil has time to form. Other elasmobranches include rays, skates, and sawfish. The only bones you'll find in a shark's body are its teeth, which it has plenty of!
Sharks can't get cavities.
Imagine eating whatever you wanted and never getting a cavity. That's the reality for makos and tiger sharks, whose teeth are naturally coated in fluoride, according to 2012 research published in the Journal of Structural Biology. All the better for maintaining strong, healthy teeth that can bite into all kinds of flesh.
Sharks can go through up to 50,000 teeth in their lifetime.
Unlike human teeth, shark teeth don't have roots, making them liable to fall out. Considering that some species may have as many as 300 teeth in their mouth at a time, that's quite a lot of tooth loss. In fact, some sharks may only have a tooth for about a week before losing it.
And they can grow them back pretty much overnight.
Sharks are growing new teeth all the time, too. In fact, many sharks are able to replace a lost tooth in a matter of days or months. As long as the shark stays healthy, it will continue to be able to grow unlimited new teeth for the rest of its life.
Frilled sharks have 25 rows of teeth.
The frilled shark is the stuff of nightmares, and not just because it looks like a beady-eyed eel. This deep-dwelling species of shark also has 25 rows of razor-sharp teeth. Their 300 triangular teeth are good for locking down on their slippery prey—cephalopods, including octopus, cuttlefish, and squid. Because these sharks belong to a primitive species that has hardly evolved over millions of years, they're sometimes referred to as "living fossils."
Greenland sharks are the only sharks that can stand the Arctic cold.
Greenland sharks are unique for many reasons, one of which is that they are the only species of shark that can survive in Arctic temperatures, according to Fisheries and Oceans Canada. These sharks mostly live in polar regions in the North Atlantic Ocean but have also been sighted at extreme depths of lower latitude oceans.
As long as the water is chilly enough, the Greenland shark is happy. In the winter, they may come up to the surface, but by the time summer comes again, they make their home as deep as 2,400 feet below sea level.
And they can live up to 400 years.
Living in arctic conditions affects the Greenland shark in a number of remarkable ways. For one, they move incredibly slow, at an average speed of fewer than one mile per hour. But their movement isn't the only thing slow about them; they also grow slowly. Adult Greenland sharks may reach up to 16 feet, but will only grow about one centimeter each year. At that rate, it takes about 150 years for a female Greenland shark to reach maturity. With such a slow growth rate, it's only natural that these sharks would have exceptional longevity, often living up to 400 years.
Unborn sharks can protect themselves from predators.
Oviparous sharks are sharks that lay eggs rather than carrying the embryo until birth. In these species, mothers have a very limited role in pregnancy. As soon as they lay their eggs, they swim away forever, leaving the embryos to fend for themselves. And that's exactly what they do. When danger is afoot or a predator is nearby, shark embryos naturally freeze in their eggs to protect themselves. Researchers believe that this response is a sign that their electroreceptors develop at a very early stage.
Sharks carry their pups for up to two years.
Not all sharks carry their pups through gestation, but the ones that do hold on to them for a long time. In many cases, they may carry their pups for up to two years, such as in the case of the spiny dogfish shark. In the end, that bonding time means little to shark mothers, who disappear right after a pup is born, similar to egg-laying sharks.
Baby sharks swim away from their mothers after birth to avoid being eaten by them.
Baby sharks, called pups, are independent creatures from the moment they are born, complete with predatory and defensive instincts. One of their first instincts is to swim away from their mothers as soon as they are born. This is to protect themselves from being eaten, which may very well happen considering some mother sharks stop eating before giving birth, working up a hefty appetite. Even if they have evaded their hungry moms, they'll have many more predators to outmaneuver before they're fully grown.
Some shark pups eat each other in the womb.
It's a pup eat pup world in the womb of a shark, where embryos cannibalize each other regularly. This is common in many shark species, but most notably in sand tiger sharks (that's one of them, above). In a litter of up to eight pups, only one will be born. By that time, the strongest pup has eaten the others and is quite large at birth as a result. Because many litters include embryos from various fathers, some scientists believe that in utero cannibalization is a result of a paternity struggle.
Whale sharks can carry as many as 300 pups.
In 1995, a Taiwan fishery caught a pregnant whale shark. When she finally gave birth, they were surprised to find that she was carrying more than 300 pups. This particular shark was relatively small as far as whale sharks go, which suggests that whale sharks may even be able to carry more pups than that. Whale sharks' reproduction remains widely mysterious and scientists are still unsure whether this was a normal or a remarkable instance.
Male blue sharks get violent when mating.
Male blue sharks literally bite into female sharks between their two dorsal fins in order to keep them still during sex. As you can imagine, this is hardly pleasant for the females. Thankfully, their skin is much thicker than the male's, specifically to prevent too much damage during mating. Between nine and 12 months later, a female blue shark will give birth to between 20 and 50 pups.
But some sharks don't need males to breed.
It doesn't happen very often, but scientists have been documenting more and more virgin births among sharks, especially those in captivity. One recent example comes from the Reef HQ Aquarium of Townsville, Australia, where Leonie the tiger shark gave birth to three pups without any sperm from a male shark. Asexual reproduction, called parthenogenesis, also occurs in Komodo dragons, wild pit vipers, chickens, and turkeys.
Thresher sharks kill with their tails.
When it comes to thresher sharks, you need to look out for more than just their bite—their tails are just as dangerous. This doubly deadly animal has learned to take advantage of its large, muscular rear as a way to maim its prey. Just one whip of the thresher shark's tail and dinner is served. Once the tail whip has killed its prey, the shark just scoops it right into its mouth.
Sharks only eat about two percent of their body weight.
Sharks may be skilled killers, but that doesn't mean they're constantly killing. In fact, sharks may go entire months without eating and tend to feed only when they need more energy. Because they're cold-blooded animals, they burn energy slowly and only need to refuel when the oil in their liver gets low.
And they don't chew their food.
Sharks don't even chew their food; they swallow it whole. Those scary teeth are just used to trap and maim their prey.
Some sharks like to tan.
One of the few other species that is known to tan is the scalloped hammerhead shark, which develops a darker hue when exposed to solar radiation. Scientists suppose that these sharks may tan as a way to shield themselves from larger sharks that may prey on them.
Sharks possess unique organs that help them sense motion.
Sharks have the ability to detect slight movements nearby thanks to whisker-like protrusions in their "lateral lines." A shark's lateral lines are two tube-like organs that run along either side of the shark's body. The inside of these tubes is lined with "whiskers" that sway along with movement in the water, alerting the shark to whatever might be lurking nearby.
Sharks use body language to communicate.
The majority of shark-to-shark communication takes place through body language. For example, sharks that live in schools, like the gray reef shark, arch their backs to signal feeding time. Solitary sharks, like great whites, use body language too. When they lower their pectoral fins it means that they're scared, and when they pulse them back it means they're agitated. When they are anxious, they may also open and close their jaws.
Sharks have impressive panoramic vision.
The reason sharks are such keen predators is because they have ultra-heightened senses—and that includes their eyesight. Because sharks' eyes are on the sides of their heads, they are able to see nearly all around them. In general, their only blind spots are directly behind the head and right in front of their snout. The most perceptive sharks are hammerhead sharks, whose extended eyes provide nearly 360-degree vision.
The world's smallest shark can fit in the palm of your hand.
Though people often imagine sharks as massive predators, some are so tiny they can fit in your hand. The dwarf lanternshark, for example, only grows to about 6 inches and survives on a diet of tiny crustaceans, like krill. It's rare to come across one of these sharks, both because of their small size and the fact that they spend most of their time about 1,500 feet below the surface. As you might guess from their name, these sharks are bioluminescent. They use their glowing bellies to protect them from predators below.
Whale sharks are the biggest sharks in the world.
Whale sharks are the largest of all shark species. These massive fish can grow up to 65 feet long and weigh more than 75,000 pounds. That's larger than a school bus! But just because they're large doesn't mean they're dangerous—whale sharks are gentle giants who move very slowly and who don't even eat other sea animals!
And they only eat plankton.
When it comes to sharks, bigger may seem scarier, but in fact, the two largest shark species only eat plankton. The whale shark and the basking shark are both filter feeders, meaning that they take large gulps of water and filter out only the plankton to eat. Megamouth sharks, a smaller but still quite large species of shark, is another planktophagous shark. Baleen whales feed this way too.
Sharks can smell a drop of blood from hundreds of meters away.
Yet another sense that makes sharks excellent predators is their sense of smell. Sharks are able to pinpoint specific smells in even the tiniest quantities. For example, some sharks can detect a single drop of blood in an Olympic sized pool, according to the American Museum of Natural History.
Sharks are older than trees.
Nearly 100 million years before trees existed on Earth, sharks were already swimming the seas, making them one of the most ancient earthly organisms. The earliest trees arrived about 350 million years ago, while sharks arrived somewhere between 400 million and 420 million years ago. That makes them older than both dinosaurs and humans. What's even more impressive is that they've hardly changed, suggesting that sharks have always been the effective killing machines we know today.
And they are aged the same way as trees.
Since sharks have cartilage rather than bones, aging them is not always reliable. Still, analyzing their vertebrae remains an important step in studying the lives of these large animals. To do so, scientists take a single vertebra and cut it in half to examine its concentric bands, which are used to estimate the shark's age, just like the rings on a tree trunk. Each band pair represents approximately one year of life.
The ancient megalodon shark weighed as much as 140,000 pounds.
Whale sharks are nothing compared to the megalodon shark, which reached a mature weight of more than 140,000 pounds. The name megalodon literally translates to "big tooth," so-called because of their massive teeth and jaws. The megalodon's largest teeth were about 7 inches long—about three times the size of a modern great white's teeth. These massive, legendary beasts went extinct some 3.6 million years ago, according to a 2019 study published in the journal PeerJ.
Sharks are colorblind.
A 2011 study by Australian researchers published in the journal Naturwissenschaften found that sharks only possess one long wavelength sensitive cone, which is just a fancy way of saying they aren't receptive to most colors. If we've learned anything, though, it's that sharks don't need perfect vision to be good predators.
Sharks have three eyelids, but they never blink.
Have you ever seen a fish with its eyes closed? Probably not, since most fish don't have eyelids. Sharks, however, do. But that doesn't mean they use them often. In fact, many sharks have three eyelids: an upper and lower lid, as well as a clear membrane that shields the eye. The species that don't have the membrane prevent ocular impairment by rolling their eyes back into their heads in moments of danger. This is what great whites do when they attack.
They don't have vocal cords and they don't make sounds.
It's one of the reasons people call sharks "silent killers." Unlike many other underwater creatures that emit sounds and frequencies to communicate, sharks don't make any noise at all. The only known exception if the Draughtsboard shark, which is native to New Zealand. Local fishermen swear that this shark can bark like a dog, though no one seems to know how.
Sharks are covered with tooth-like scales.
Shark skin may look smooth from far away, but it's actually covered in tiny, microscopic scales. These sharp, tooth-like scales are called dermal denticles and help make sharks more efficient swimmers by reducing drag. Dermal denticles also serve to keep sharks quiet in the water, part of what makes them such stealthy predators.
Teeth aren't sharks' only sharp feature—they've also got sharp memories.
Fish are known for having short memories, but one study published in the journal Animal Cognition found that sharks can actually remember for up to 50 weeks. For the experiment, gray bamboo sharks were exposed to optical illusions that they had to see past to achieve a food reward. After they were shown how to solve the problem, the sharks were able to remember it for a period of up to 50 weeks, or almost a year.
They're not the only intimidating fish in the sea.
It's hard to imagine a great white shark afraid of any creature. After all, they're enormous and built to kill. For a long time, people have considered great whites to be at the top of the food chain, but recent studies show that there is actually another killer at the top: the killer whale. On multiple occasions, killer whales have been known to attack great whites that encroach on their feeding grounds.
Sharks can't sleep.
This is one of the more commonly known facts about sharks, though it's not always true. Most, but not all, sharks need to keep moving to avoid drowning. That's because some sharks need to continuously move new water into their gills to keep breathing. Other sharks are able to stop moving thanks to respiratory openings called spiracles that force water into their gills. In both cases, sharks never fully experience sleep.
Someone once stole a shark from the San Antonio Aquarium.
In one of the more bizarre heists of 2018, three criminals smuggled a live shark out of the San Antonio Aquarium using a baby stroller. The shark, named Miss Helen, was in an interactive exhibit where visitors could touch animals when the three fugitives snatched her out of the water and sped her back to one of their homes. When police arrived, they were shocked to find Miss Helen perfectly happy in a homemade aquarium along with various other marine animals. When asked why he did it, the homeowner said he was trying to save the shark from the aquarium.
The world's fastest shark is also the world's most fished shark.
The speedy shortfin mako can be found all across the world in temperate and tropical waters. Though it may be among the more common shark species, it is also the most commercially sought after. Mako sharks are prized game fish and are often hunted for food and vitamin harvesting. Their torpedo shape and hydrodynamic build may make them fast, but sadly, not fast enough to out swim the hunters.
They're being killed faster than they can reproduce.
Shark fin soup, a popular Chinese dish is traditionally prepared with the fins of shortfin mako sharks. But now that the demand for this fish is exceeding supply, other species are starting to take the hit. A process called finning is one of the primary culprits of shark deaths. It involves removing the shark's fins and throwing them back into the water, where they're left to die.
Sharks have inspired sports car designers.
Sharks are a magnificent example of natural engineering, so it's no wonder why sports car manufacturers would use them as inspiration. They're sleek, agile, and hydrodynamic, just like you would want a sports car to be. The most popular example would be the Corvette Mako Shark and the Corvette Mako Shark II, which even borrowed the coloring of the world's fastest shark. Corvettes have also been modeled after the stingray and the manta ray, which are relatives of the shark.
Only about five people die from shark attacks a year.
The truth is that sharks typically don't want anything to do with humans, but when confronted, they will defend themselves. In 2018, 34 of the 130 shark attacks in the world were considered "provoked," while 66 were considered "unprovoked," according to the International Shark Attack File. Only five of those 130 attacks were fatal.
But an estimated 150 people died in the worst shark attack in history.
Yes, shark attacks are far less common and even less fatal than many people imagine. Still, fatalities sometimes occur, such as in the case of a 1945 attack that may have killed as many as 150 people. According to Smithsonian, it happened when the U.S. naval ship, the USS Indianapolis, was struck by a Japanese torpedo in the middle of the Pacific, sinking immediately and leaving more than 1,000 men stranded in the open water. It was a buffet of shark bait. By the time help came, only 317 of the ship's initial 1,196-man crew were left alive. Some succumbed to the sharks, while others died of exposure and thirst.
Sharks play a crucial role in the food chain.
Sharks' only predators are killer whales and humans. Such limited competition for resources makes them apex predators. This means they're on top of the food chain and their behavior affects every single other living organism below them on the food chain. Even small changes in shark behavior can have drastic effects on marine life diversity and sustainability. With the overfishing of certain shark species leading to dwindling shark populations, you can only imagine the changes bound to strike today's oceans.
They respond to electromagnetic waves around them.
Sharks are highly attuned to electromagnetic waves. But what does electricity have to do with ocean life and what do sharks have to do with electroreceptors? Well, all muscle movements give off an electric signal which is transported by the salt in the ocean water. These electrical currents help sharks know where to find nearby prey. It also helps them navigate the ocean when it comes time to migrate.
Great white sharks travel up to 2,500 miles during migration.
No one really knows why sharks migrate. Sometimes their routes follow a pattern—for example, some pregnant female sharks return to the sites they were born to give birth. Other times, migration routes are shrouded in mystery, such as in a 2013 study that found great whites coming from the coasts of California and Hawaii to meet in a remote spot in the Pacific Ocean. Whatever the destination, one thing is for sure: Distance is not an issue.
Sharks and humans share a common ancestor.
Unbelievable, right? But it's true. The acanthodes bronni is actually the descendant of all jawed species. About 420 million years ago, this jawed fish branched into two different families, one of which would remain cartilaginous and go on to birth sharks as we know them. The other would become bony fish, which would eventually make way for the evolution of man.
Velvet belly lanternsharks have light-up spines.
A shark with a built-in lightsaber? Dive deep enough and you might see it for yourself. Velvet belly lanternsharks are a species of bioluminescent sharks that live far, far in the depths of the sea. Like other lanternsharks, it lights up its belly to camouflage itself from predators lurking below. What makes this species unique, though, is its ability to also light up its spine. Predators who spot this shiny-spined shark know to stay away.
Cookiecutter sharks bite but never kill.
No shark bite is pleasant, but the cookiecutter shark bite may be the worst of them all. These small but vicious sharks attach themselves to prey using suction, then scoop out a bite-sized hole of flesh from their victims (that's a seal with a scar from a cookiecutter shark, above). Their bites may be nasty, but they never kill their prey. Thankfully, cookiecutter sharks aren't too fond of human flesh. Still, the thought of its toothy hole punch bite is enough to make you paranoid while wading into the water.
Sharks are not so buoyant in freshwater.
As it turns out, (most) sharks are saltwater fish by necessity, not by choice. In fact, many sharks would actually sink in freshwater. This is because sharks lack an organ called a swim bladder, which most other fish have to keep them afloat. Instead, sharks have extra-large livers that help keep them buoyant in saltwater. Without the help of naturally buoyant saltwater, sharks would need a liver eight times as large just to keep them afloat.
Actually, they're not so buoyant in saltwater either.
Another side effect of missing a swim bladder is that sharks can never stop moving. This is not necessarily because they'll die, but because they'll sink. Even in the saline ocean water, sharks are bound to sink unless they make an effort not to. So, to stay afloat, sharks must constantly move their fins, alternating angles to create lift, while simultaneously moving their tails to maintain a forward motion.
Bull sharks have the unique ability to survive in fresh and saltwater.
If you think you're safe from sharks when swimming in freshwater, think again. It turns out that some ocean-dwelling sharks are able to survive in freshwater, too. Bull sharks (that's one of them, above), for example, have been spotted time and again along the Mississippi River, as far north as Michigan. They are able to survive through a process called osmoregulation, which allows sharks to maintain the salinity of water inside their bodies. Over time, they can habituate themselves to freshwater, allowing them to thrive in both environments.
Bonnethead sharks are the only omnivore sharks.
When most people think of sharks, they don't think of them as eating salads. So when researchers set out to study the bonnethead shark, they were surprised to learn that about 50 percent of its diet was made up of seagrass. According to Discover magazine, the bonnethead is the only omnivore shark ever discovered.
Nearly one-third of sharks are at risk of extinction.
Sharks may be scary to some, but they are vital to the ocean ecosystem. According to the IUCN Red List of Threatened Species, as many as 30 percent of sharks are at risk of extinction. Scalloped and great hammerhead sharks are at the greatest risk and are currently classified as endangered, mostly due to overfishing. Organizations like the World Wildlife Foundation are making an effort to establish sustainable management of shark fishing on a global scale in hopes of saving such species. And for more deep-sea knowledge, here are 33 Mind-Blowing Facts About the Earth's Oceans.
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