Sharks are amazing creatures with ancestral roots that extend back to 420 million years ago, and perhaps the most amazing shark fact of all is that these powerful beasts survived all five major mass extinctions that decimated 90 percent of the world’s animal species, and they came out the other side thriving! Pretty cool, huh?! You can learn even more about the history of sharks here.
While sharks get a very bad rap from the media and pop culture, they’re more harmless to humans than we’d like to believe. Hopefully, these fun shark facts will give you a renewed appreciation for these animals, which are absolutely essential for maintaining balance within the marine ecosystem.
From Teeny Tiny to Titanic
Considering the relatively small ranges in size of most animals of a single species, it’s pretty amazing that sharks can be as small as 6.5 inches long, in the case of the dwarf lantern shark, or as long as 40 feet, in the case of the whale shark. You’d have to line up 80 dwarf lanterns to reach the length of a whale shark, and it would take somewhere in the vicinity of 100,000 dwarf lantern sharks to add up to the weight of one whale shark!
Keeping the Tooth Fairy Busy
While pretty much every animal on land has one row of teeth on top and one row on the bottom, sharks have multiple rows of teeth, which aren’t attached to the gums. The average number of rows of teeth in various shark species is five, but the bull shark has a staggering 50 rows of teeth in both its upper jaw and lower jaw! These rows are like conveyor belts, and when one tooth is lost, the tooth behind it moves forward to replace it, which can be done within a day.
Sharks may go through as many as 20,000 teeth over the course of a lifetime. They don’t actually chew with their teeth, though, using them only to rip prey into manageable chunks, which they swallow whole.
Although finding shark teeth on the beach is exciting, you should never buy them in a tourist shop, which probably means they were extracted from a shark killed solely for its commercial value. And don’t even think about bringing shark teeth into the U.S. from another country, which is illegal under the Wild Life Protection Act of 1972.
Different shark species have different ways of reproducing. It all starts when a male shark inserts its claspers into the reproductive tract of a female shark, fertilizing the female’s eggs. Then, depending on the type of shark, the pups will be born in one of three ways.
Oviparous sharks lay eggs. The eggs are contained in a protective sac known as a “mermaid’s purse.” Sometimes those sacs wash ashore, but normally they attach to a hard surface under water, like a rock. When it’s time, the eggs hatch and the shark pups swim off to find food. About 40 percent of sharks are oviparous, including the bamboo shark and the bullhead shark.
Placental viviparous sharks reproduce similarly to humans. The yolk sac of the eggs becomes a placenta and nourishes the live shark pups until they’re born. This type of reproduction is more common among larger shark species, like blue sharks and hammerhead sharks. Only 10 percent of sharks give birth this way.
Ovoviviparous sharks are perhaps the most interesting. After fertilization, the eggs develop inside the mother. When the time to be born nears, the eggs hatch inside the shark, and exit the mother as live shark pups. Fifty percent of sharks give birth this way, including whale sharks and tiger sharks.
Shark pups are fully independent from the moment they’re born or hatch, and swim away immediately to find food and to avoid being eaten by their mother.
Sharks’ Seven Senses
In general, sharks have keen senses. With two-thirds of its brain devoted to controlling the sense of smell, a shark can smell a drop of blood in 25 gallons of water. They also have excellent eyesight. But perhaps the most interesting thing of all about sharks’ sensory abilities is that they have two additional senses above the usual five.
A sensory organ called the ampullae of Lorenzini, located on the snout, can detect electrical currents. This helps sharks navigate with the help of electrical fields on the ocean floor, and it also helps them detect electrical impulses made by prey when it moves.
Another sensory organ is called the lateral line, which extends along the length of the shark’s body on each side. The lateral lines are canals that are filled with water and sensory cells with tiny hairs growing from them. These allow sharks to detect even the tiniest of vibrations, which helps them to find prey more easily, even when it’s hidden in rock crevices or under the sand at the bottom of the ocean.
Humans Have Little Reason to Fear Sharks…
The fear of sharks is known as “galeophobia,” and it afflicts a large number of people, especially those who have seen movies like Jaws and Open Water. But the fact is, you’re more likely to be killed by a bee or injured by a toilet seat than by a shark. On average, less than 10 people are attacked by sharks annually worldwide, and most survive. Great white sharks are responsible for the most attacks on humans, followed by the tiger shark. And while great whites don’t like the taste of humans and rarely eat them, tiger sharks will eat just about anything, including us.
But Sharks Have a Good Reason to Fear Humans!
Researchers recently estimated that between 100 million and 273 million sharks are killed by humans each year, which is why over 30 species of sharks are on the endangered list. Humans kill sharks for their fins, which they sell to purveyors of shark fin soup, a delicacy in some Asian countries. They also kill them for their skin, which is made into fashion accessories, and for various other substances that are widely used in lotions, deodorants, and cosmetics.
Protecting sharks should be a major priority, because they help control populations of other species that could seriously compromise the balance of the marine ecosystem if their numbers grow out of control. Plus, they’re just really cool animals!