00:00Sharks have a scary reputation in part thanks to Steven Spielberg's Jaws, 1,975, which hit screens 50 years ago
00:08and has been inspiring a fear of sharks in people ever since.
00:11But while they may look threatening with their mouths full of hundreds of razor-sharp teeth, sharks don't actually attack
00:17humans all that often.
00:18Shark defenders are commonly correcting that misconception, but there are plenty of other shark facts that aren't nearly as well
00:25known.
00:25Here are 10 wild things that you might not know about the fearsome fish.
00:2910. Almost All Greenland Sharks Go Blind
00:32Greenland sharks, which swim the freezing waters of the North Atlantic and Arctic Oceans, have a reputation for being a
00:38bit slow and clumsy in comparison to other shark species.
00:42But in fairness to them, almost all of them go completely blind during adulthood.
00:47While Greenland sharks are born with fully functioning eyes, parasitic crustaceans called Omatacoida elongata often quickly embed themselves in the
00:55shark's eyes.
00:55Typically, each eye is home to an adult female and several larvae, which eat away at the shark's cornea over
01:01time.
01:02Most Greenland sharks are left only with enough vision to make out light and darkness.
01:07Although not being able to see isn't exactly ideal, they have an excellent sense of smell with which to track
01:12down their prey.
01:139. Swell sharks can double their size
01:16Swell sharks aren't particularly aggressive or large, usually measuring a little less than 3 feet – 0.9 meters –
01:23from nose to tail as sharks go.
01:25So instead of lashing out at predators, including larger sharks and seals, they employ a unique defensive strategy, which is
01:33their namesake – swelling.
01:34Swell sharks will swim into a rocky crevice and then swallow large amounts of water to double their size.
01:41This allows them to get lodged between the rocks, making it harder for a predator to prize them free and
01:46take a bite.
01:47Once safe, the shark expels the water in their stomach with a dog-like bark.
01:51Swell sharks can also perform this expanding trick with air if they're brought to the surface, but it works less
01:56well for evading humans who have plucked them from the water.
01:598. Great Whites Might Have Helped Drive the Megalodon to Extinction
02:04The Megalodon went extinct around 2.6 million years ago and is the largest shark ever known to have swum
02:09the oceans.
02:10While the Great White is roughly 20 feet 6 meters in length and weighs under 4,400 pounds 2 metric
02:18tons, the Megalodon is thought to have stretched to almost 60 feet 18 meters and weighed 110,000 pounds 50
02:25metric tons.
02:26But despite being so much bigger, it's thought that the Meg went extinct thanks, in part, to the Great White.
02:32In 2022, a scientific paper was published that looked at the zinc isotopes in the teeth of both Megalodon and
02:39Great Whites.
02:40While additional research is needed, our results appear to support the possibility for dietary competition of Megalodon with early Pliocene
02:48Great White sharks, explained Professor Kenshu Shimada.
02:51Both sharks are thought to have competed for the same prey, and the Meg's massive size worked against it in
02:56this regard because it needed more food to sustain itself.
02:59Along with being out-competed for prey, cooling oceans also led to a more restricted habitat for the Meg.
03:05Both of these factors are likely what sent the huge shark to its watery grave.
03:097. Some Sharks Lay Spiral-Shaped Eggs
03:12Most sharks give birth to live pups, some of which, incidentally, cannibalize each other in the womb, but some species
03:19lay eggs instead.
03:20While bird eggs tend to be oval-shaped, shark eggs come in a variety of odd but practical shapes.
03:26The Port Jackson shark lays spiral-shaped eggs, for instance.
03:30Mark McGrother, collection manager of ichthyology at the Australian Museum, explains that this is so that the mother shark can
03:37pick it up in her mouth and screw it into rocks and crevices to anchor it so that they don't
03:41wash away.
03:42The crested horn shark lays a similarly spiral-shaped egg, but with the addition of tightly spiraling tendrils attached to
03:48the bottom.
03:49The tendrils provide another opportunity for the egg to anchor itself by getting caught up in seaweed or algae.
03:55Other alien-esque shark eggs include those of the draft board shark and the Australian ghost shark.
03:59The draft board's eggs are a bright orange-yellow color and also feature spiral tendrils.
04:04In contrast, the ribbed edges of the ghost shark's eggs make them look like a stage of the xenomorph's life
04:11cycle.
04:116. Cookie-cutter Sharks
04:13Have Taken Bites Out of Submarines
04:15In the 1,970 seconds, the U.S. Navy noticed strange circular holes in the rubber covers of the sonar
04:23domes on their submarines.
04:25They initially attributed the damage to a new enemy weapon, but after investigating,
04:29they found out that the holes were created by a previously misunderstood type of shark.
04:34The cookie-cutter shark is named for its distinctive bite mark,
04:37although the spherical shape actually more accurately resembles an ice cream scoop or a melon baller than a cookie cutter.
04:43Although cookie-cutter sharks are fairly small, the biggest ones reach just under 2 feet, 56 centimeters.
04:48They have the largest teeth-to-body ratio of all shark species.
04:52They use their lips to suction onto their chosen prey, whether it be a submarine, whale, dolphin, or, in rare
04:59cases, a human.
05:00Once locked in place, they twist their body around to shear off a chunk of flesh with their teeth, leaving
05:05a distinctive hole behind.
05:073. Sharks Don't Have Any Bones
05:10Most people have seen a shark skeleton in a film, book, or museum, but what you're looking at isn't actually
05:15a bone structure.
05:16It's cartilage.
05:17There isn't a single bone in the body of any shark species, well, aside from any bones that they've eaten,
05:23with their frames instead being comprised of the same material that forms human ears and noses.
05:29The only hard part of their skeleton is their teeth, which are comprised of enamelloid and dentine.
05:34Being light and more flexible than bone, cartilage means sharks can typically swim faster than bony fish,
05:40explains Emma Bernard, curator of fossil fish at the Natural History Museum in London.
05:45As well as enabling sharks to swim faster, it also makes their bite more powerful,
05:49because they're able to open their mouths wider, thanks to the upper jaw not being fused to the skull.
05:54The areas of their skeleton that need a bit more support, the jaws, spine, and skull,
05:59are strengthened thanks to calcium salts, which come from their diet.
06:034. Some Sharks Can Turn Their Stomachs Inside Out
06:07Some shark species have a reputation for being garbage bins of the sea.
06:12Tiger sharks in particular will make a meal of anything, including rubber tires and metal license plates.
06:17While sharks have highly acidic stomachs that can break down many substances,
06:20they aren't able to digest absolutely everything.
06:23Some species have an odd way of dealing with this, by literally vomiting their stomachs.
06:29Known as stomach or gastric aversion, this process sees a shark expel its stomach out of its mouth
06:34to rinse it out in the water and then suck it back in.
06:38There are several reasons that sharks throw up, beyond getting rid of objects that can't pass into their intestines.
06:44In many cases, it's thought to be a stress response,
06:47possibly because it's easier to escape a stressful situation on an empty stomach.
06:51Sharks have also been observed throwing food up before returning for more likely,
06:55because they've deemed a particular bite of meat to be substandard and want to make room for tastier morsels.
07:013. Shark Skin Is Made Up Of Tiny Teeth
07:04If you thought a shark's mouth was full of teeth, just wait until you learn about their skin.
07:09On a microscopic level, a shark's skin looks like it's covered in tiny, razor-sharp teeth,
07:15and that's because it basically is.
07:17These toothy scales are called dermal denticles and are comprised of dentine,
07:22the same material that coats their teeth.
07:23If you stroke a shark one way, it'll feel smooth, but the other way,
07:27it'll feel like sandpaper because of the jagged points of their dermal denticles.
07:32The shape and size of the denticles vary from species to species,
07:36but for all sharks, they serve the same two very practical functions.
07:40Firstly, the scales streamline the shark's body, which means that it can swim faster.
07:44Secondly, they provide a layer of protection, not only from other sharks taking a bite,
07:49this can happen accidentally while feeding or can be a deliberate attack,
07:53but also from smaller creatures that might want to latch on, such as parasites and barnacles.
07:592. Sharks Existed Before Trees
08:01You may have heard the fact that sharks outdate dinosaurs, they're often called living fossils,
08:05having managed to survive multiple extinction events, but did you know that they also outdate trees?
08:10In 2019, the oldest known fossilized trees were discovered in a quarry in New York,
08:15dating back 386 million years.
08:19But the oldest evidence of sharks, or rather, the ancestors of sharks,
08:23has been dated to 450 million years ago.
08:26Shark-like scales from the late Ordovician have been found, but no teeth.
08:31If these were from sharks, it would suggest that the earliest forms could have been toothless.
08:35Scientists are still debating if these were true sharks or shark-like animals,
08:39explains Emma Bernard, the Natural History Museum's fossil fish curator.
08:44The earliest shark-like teeth to have been found belonging to a fish called Doleotis problematicus
08:49date back 410 million years, which remain significantly older than the oldest known trees.
08:551. Epaulette Sharks Can Walk On Land
08:58Although the idea of a shark that can walk on land may sound scary,
09:02the epaulette shark is relatively small, around 3 feet, or 0.9 meters in length,
09:08and doesn't look all that threatening.
09:10Epaulette sharks live in the waters around Australia and Papua New Guinea,
09:14and their ability to walk on land is a skill that no other shark has mastered.
09:18When an epaulette finds itself beached, it slows its heart rate and breath to conserve oxygen.
09:23Then it uses its pelvic and pectoral fins as proto-legs to propel itself forward.
09:29Although the shark doesn't move very fast, it's able to shuffle itself back into the water.
09:34Other sharks are thankfully unlikely to develop this trait anytime soon.
09:38Epaulettes often forage for food in coral reefs and tide pools,
09:42habitats that can be covered by water during high tide but left open to the air during low tide.
09:47It's only because epaulettes find themselves beached so often that they have evolved to walk on land.
09:53It's only because of its own sea.
09:54It's only because of its own sea.
09:54It's only because of its own sea.
09:55It's only because of its own sea.
09:55It's only because of its own sea.
09:55It's only because of its own sea.
09:55You
