What most people know–or think they know–about sharks is that they are predatory animals with a taste for human flesh. But, there are some things about these creatures that just might surprise you. Here are ten things you probably didn’t know about sharks.
10. They Don’t Have Bones
Shark skeletons are made out of cartilage and connective tissue. According to the weekly international journal Nature, sharks are missing a gene, which reduces their ability to form bone. They do, however, make bones in their teeth and fin spines.
-Sharks’ cartilaginous skeletons lend to their buoyancy.
-Despite not having any bones, sharks can still fossilize. This is due to the calcium salts they deposit in their skeletons as they age. Their teeth show up in fossil records as well.
9. They Have Very Keen Senses
Most sharks can see well in the dark. This is due to a reflective layer of tissue on the back of their eyes. Additionally, some sharks make their own light through a process called bioluminescence (NOTE: Fireflies also do this).
Sharks also have extremely acute hearing. Studies have shown that sharks can respond to low-frequency sounds a quarter of a mile away.
Great white sharks have a strong sense of smell. So strong, in fact, that they can smell a drop of blood in 100 liters of water and a colony of seals two miles away.
Lastly, sharks have electroreceptor organs which help them detect electrical fields and temperature changes in the ocean.
8. They Can’t Stop Swimming
At least some of them can’t anyway. Tiger, mako and great white sharks need to keep moving in order to breathe. Perhaps that’s why great white sharks are travelers. In 2005, a great white shark named Nicole swam 12,000+ miles in nine months.
Some species of sharks, particularly bottom dwelling species like angel sharks and nurse sharks, have a respiratory organ known as a spiracle that lets them pull water in while resting and eating. The spiracle is located just behind the eyes and supplies oxygen to the eyes and brain.
7. They’re the Garbage Cans of the Sea
That’s the nickname given to tiger sharks because they’ll eat just about anything. In fact, researchers have found some rather odd objects in the stomachs of tiger sharks. These include balls, bottles, cats, clothing, dogs, explosives, gasoline tanks, goats, horses, license plates, nails, rats, sheep, and tires. And get this, these items were found INTACT! Perhaps they should be nicknamed “Mikey” instead, since it’s obvious they’ll eat anything, lol!
NOTE: For those of you wondering who Mikey is, check out this YouTube video.
FUN FACT: There’s a robotic in-ground pool cleaner called TigerShark. It cleans “virtually every area of your pool” and is described as the “workhorse of the industry.” Coincidence? We think not.
6. They Come in All Different Sizes
Contrary to what we see in the movies, not all sharks are big. In fact, dwarf lantern sharks, found in the Caribbean off the shore of Colombia and Venezuela, are small enough to fit into your palm. And, the deepwater dogfish grows to just eight inches long.
The largest shark species–and the largest fish in the world–is the whale shark. It can grow to about 40 feet long and weigh more than 20 tons. It’s twice the size of most great white sharks.
The megalodon, sharks’ prehistoric ancestor, was the biggest shark that ever lived. Judging by the size of its teeth, some believe that the megalodon grew up to 60 feet long. Others believe it grew to about 80 feet long. By the way, its scientific name is Carcharocles megalodon, which means “giant tooth.”
DID YOU KNOW?
Female sharks are often larger than males, with the exception of the male snaggletooth, which is twice the size of the female.
5. They Reproduce in Different Ways
Some shark species lay eggs while others deliver their young through live birth. Some females use sperm from several males to reproduce, resulting in a litter of half-siblings all born at the same time.
-Shark youngsters are called “pups.”
-Blue sharks can give birth to up to 135 pups at one time.
-The spiny dogfish shark has the longest gestation period of any animal, ranging from 5 to 24 months.
-Not only does the great white shark not care for her offspring after birth (they swim off into the ocean immediately after they’re born), she may even try to eat them.
4. They’re Intelligent
According to researchers at Rheinische Friedrich-Wilhelms-University in Bonn, Germany, sharks can be taught to recognize shapes and even optical illusions, and can remember them for at least a year.
They’re also very cunning when it comes to catching their prey. They like to sneak up on them before leaping out of the water and grabbing them in their mouths. According to marine biologist Alison Kock, great white sharks are very clever when it comes to capturing seals off the coast of South Africa. “Cape fur seals are really smart and agile, and catching an experienced adult is hard work and difficult. But white sharks avoid this by targeting the naive seals each year,” Kock told Reader’s Digest.
3. They Live a Long Time
Great white sharks live up to 70 years, and Greenland sharks live up to 400 years. Scientists determine how old a shark is by the number of rings on its vertebrae. For example, if the vertebrae has ten band pairs, then the shark is assumed to be 10 years old. However, studies show that this methodology is not always accurate since sharks don’t have otoliths (a.k.a. earstones)–lumps of calcium carbonate structures in the inner ear that build layers over time in bony fish. NOTE: Scientists use otoliths to gather age data.
FUN FACT: Researchers believe that sharks first appeared on Earth about 455 million years ago.
2. They’re Important to the Ecosystem
Because sharks are predators, they play an important role in the balance of marine life. They eat other animals, which means they help keep animal populations under control. They also sometimes prey on sick and weak animals, which helps populations stay healthy. In fact, many of these populations are fish species that humans consume. Removing the sharks “may cause a domino effect that can impact other species, even down to corals and algae,” Dr. Nick Whitney, senior scientist at the Anderson Cabot Center for Ocean Life at the New England Aquarium, told Reader’s Digest.
1. We’re More Harmful to Them Than They are to Us
According to the Florida Museum of Natural History, humans kill about 1,000,000 sharks annually. Compare that to the six people killed in unprovoked shark attacks each year and you can see how we are more dangerous to them than they could ever be to us.
One reason for so many sharks deaths is the practice of overfishing–cutting off their fins (to make shark fin soup) and then releasing them back into the water to drown. Another reason is that many sharks get caught in nets meant for other fish.
DID YOU KNOW?
-Only three shark species are responsible for most human bites and fatalities: bull sharks, tiger sharks, and great white sharks.
-The U.S. sees the most shark attacks, but very few fatalities. Most bites in the U.S. happen in Florida.
Now that you know a little more about sharks, perhaps you’ll look at these majestic creatures a bit differently from now on. Thanks for reading!