1. In its lifetime, a shark can have up to 30,000 teeth. They are continuously being replaced and shifted within the mouth.
Sharks can lose dozens of teeth every month. Compared to humans — who grow 20 baby teeth, which are then replaced by 32 adult teeth — the difference is shocking!
3. Sharks have been in existence for over 400 million years.
There's actually fossil evidence that dates back to 450 million years ago — but only scales have been found, not teeth. If the scales did happen to come from an early shark, then those sharks could have been toothless.
4. Sharks have no bones in their bodies.
Instead, they are made of a rubbery tissue called cartilage. That's made it more difficult for scientists to study ancient sharks, since cartilage typically doesn't preserve as well as bones do — early shark fossil records are mostly based on scales and teeth.
5. The bull shark is able to survive in freshwater.
They've even been found in the Mississippi and Amazon Rivers.
8. Sharks have a sense called electrosense, which is the ability to sense electric signals. This gives them an advantage when searching for prey.
9. Sharks are hypersensitive to pressure changes in the water. They can notice the slightest changes via specialized cells with tiny hairs in them.
11. Tiger sharks, aka the "garbage cans" of the sea, will literally eat anything, which makes them particularly dangerous to humans.
13. A shark's skin is tough and thick because it is made of a protein called collagen. The whale shark's skin can be up to 10 centimeters thick!
14. The female shark pregnancy can range from 5 months to 3.5 years, depending on the specific species.
15. If a shark embryo develops teeth, it will partake in intrauterine cannibalism, meaning it will eat its siblings inside the womb.
19. The thresher shark has a tail that can grow to about half its body length. The tail serves as a sword.
20. Sharks have a highly evolved sense of hearing, which allows them to hear low-frequency sounds from up to a quarter-mile away.
25. Most female sharks have much thicker skin than males because male sharks often bite during mating.
26. The Greenland shark is the slowest-moving fish in history, but reindeer, polar bears, and extremely fast seals have been found in its stomach.
28. Sharks can be introverts or extroverts.
A study was done that proved sharks have individual personalities. More social sharks will band together and communicate with a group, while more introverted sharks will hide away on their own and camouflage.
31. A Great White named Lydia swam across the entire Atlantic Ocean, from one side to the other, while being tagged and tracked by scientists.
33. Shark teeth are covered in fluoride, so in a way, they kind of have their own built-in toothpaste.
34. Nurse sharks are extremely lazy. They spend most of their time resting on the sea floor and even stack up on top of each other.
35. Great white sharks found off the coast of Seal Island in South Africa will jump 10 feet out of the water to attack unsuspecting seals.
37. Sharks don't have scales covering their skin; they have tiny teeth.
Sharks don't have regular scales; they have dermal denticles, which are much more similar to teeth than regular fish scales. The enamel crown, i.e. the toothy part, anchors the dermal denticle to the skin. These tooth-shaped scales allow them to move swiftly through water without collecting barnacles and algae.
38. Great whites can also detect one drop of blood in 25 gallons of water and can sense tiny amounts of blood in the water from three miles away.
41. Some female sharks retain sperm in their bodies after mating and will use it to reproduce later on.
42. Sharks can live in freshwater by absorbing extra water and then urinating it into the streams around them.
43. Some female sharks can reproduce without any contact from a male, which is known as parthenogenesis.
44. When gray nurse sharks are born, the first baby shark to develop consumes its siblings as they hatch.
45. Despite its massive size, the whale shark is a filter feeder, subsisting on tiny, microscopic plankton.
46. The goblin shark lives along outer continental shelves and underwater mountain ranges in areas too deep for human exploration.
49. Hammerhead sharks can easily adapt to a change in water temperature and can be found from polar regions to the Florida coast.
50. The hammerhead shark's odd-shaped head not only allows for a better visual range than other sharks, but also spreads its sensory organs, allowing it to better detect prey.
51. The basking shark, which is a filter-feeder like the whale shark, can grow up to 33 feet long and can weigh as much as a four-passenger airplane.
53. In 1978, archaeologists uncovered remnants of shark bodies under the ruins of the Aztec Great Temple.
54. Great white sharks eat around 11 tons of food each year. In comparison, an adult human eats around half a ton.
56. Some female sharks use sperm from several different males to reproduce. Pups are half-siblings even though they are born in the same litter.
57. Despite being so big, the whale shark is a sneaky little thing.
The female whale sharks are especially sneaky. Sightings of whale sharks are 70% male, and no one has ever seen a female give birth.