Sharks, with their powerful presence and streamlined efficiency, have long been considered the ocean’s ultimate predators. But beneath the surface lies a world of surprising facts that challenge our preconceptions about these magnificent animals.
Here are 15 lesser-known aspects of shark biology, behavior, and evolution, revealing information that will transform your understanding of these marine marvels.
1. Sharks Predate Dinosaurs
Sharks have been swimming in our oceans for an astonishingly long time. These ancient predators first appeared around 450 million years ago, long before dinosaurs roamed the Earth. (ref)
To put this into perspective, sharks have been around for nearly 200 million years longer than the oldest known dinosaur fossils.
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This longevity is a testament to the shark’s incredible adaptability and evolutionary success. Over the course of their existence, sharks have survived multiple mass extinction events, including the one that wiped out the dinosaurs 65 million years ago.
Their ability to thrive in various marine environments has allowed them to persist and diversify into the hundreds of species we know today.
2. Some Sharks Can Walk on Land
Believe it or not, there are sharks that can actually “walk” on land. (ref) The epaulette shark, found in the shallow waters around coral reefs in New Guinea and Australia, has the remarkable ability to use its fins to propel itself across exposed reef flats during low tide.
This unusual behavior allows them to move between tide pools in search of stranded prey.
These walking sharks can survive out of water for up to an hour, thanks to their ability to slow down their heart rate and breathing. Their unique adaptation demonstrates the incredible diversity of shark species and their ability to thrive in challenging environments.
It’s a reminder that sharks are not just confined to the deep seas but have evolved to exploit various ecological niches.
3. Sharks Have Electricity-Sensing Superpowers
Sharks possess a remarkable sixth sense that allows them to detect electrical impulses in the water. This extraordinary ability is made possible by special organs called the ampullae of Lorenzini, which are small pores filled with conductive jelly on the shark’s snout.
These organs are so sensitive that they can detect the faintest electrical fields produced by the muscle contractions of potential prey. (ref)
This electrical sense is particularly useful for sharks hunting in murky waters or when pursuing prey that might be hidden in the sand. Some shark species, like the hammerhead, have an especially large number of these electroreceptors, giving them an enhanced ability to locate prey.
This unique adaptation showcases the sophisticated sensory capabilities that have made sharks such successful predators over millions of years.
4. Greenland Sharks May Live for Centuries
The Greenland shark holds the title of the longest-living vertebrate known to science. These deep-sea dwellers have an estimated lifespan of up to 500 years (ref), with some individuals potentially living even longer.
This extraordinary longevity was discovered through radiocarbon dating of the sharks’ eye lenses, which revealed their incredible age.
What’s even more astounding is that Greenland sharks don’t reach sexual maturity until they’re around 150 years old. Their slow growth rate and late maturation contribute to their vulnerability to overfishing and other human activities.
The discovery of their extreme longevity has raised important questions about shark conservation and the need to protect these ancient mariners of the deep.
5. Some Sharks Glow in the Dark
In the inky depths of the ocean, some shark species have evolved the ability to produce their own light. This phenomenon, known as bioluminescence, is found in several deep-sea shark species, including the velvet belly lanternshark and the cookiecutter shark.
These sharks use specialized cells called photophores to produce a soft, blue-green glow.
The bioluminescence serves various purposes, from camouflage to communication. For some species, it helps them blend in with the faint light from above, making them less visible to predators below.
For others, it may aid in attracting prey or finding mates in the dark depths. This fascinating adaptation highlights the diverse strategies sharks have developed to thrive in different marine environments.
6. Sharks Can Go into a Trance-Like State
A peculiar phenomenon known as tonic immobility can occur in some shark species when they’re flipped upside down. This trance-like state causes the shark to become temporarily paralyzed and unresponsive.
Marine biologists have observed this behavior in various species, including great white sharks and tiger sharks.
While the exact purpose of tonic immobility is not fully understood, it’s thought to be a natural response that may have evolved as a defense mechanism against larger predators.
Interestingly, some researchers have used this technique to safely study sharks in the wild, allowing them to take measurements and attach tracking devices without harming the animals. However, the practice remains controversial due to potential stress on the sharks.
7. Thresher Sharks Use Their Tails as Weapons
The thresher shark is known for its extraordinarily long tail, which can be as long as its entire body. But this isn’t just for show – thresher sharks use their tails as powerful weapons to stun and kill their prey.
They’ve been observed whipping their tails at speeds of up to 80 mph, creating underwater shockwaves that disorient or outright kill small fish.
This unique hunting technique is a testament to the diverse adaptations sharks have developed over millions of years. The thresher shark’s tail-slapping method allows it to efficiently hunt schooling fish, demonstrating how different shark species have evolved specialized strategies to exploit various food sources in the ocean ecosystem.
8. Some Shark Embryos Cannibalize Their Siblings
In a startling display of survival of the fittest, some shark species practice intrauterine cannibalism. This occurs most famously in sand tiger sharks, where the largest embryo in each of the mother’s two uteruses consumes its siblings before birth.
This gruesome process ensures that only the strongest and most developed pups are born.
As a result of this prenatal battle royale, sand tiger sharks typically give birth to only two pups at a time, one from each uterus. While this may seem brutal, it’s an evolutionary strategy that ensures the survival of the fittest offspring.
This remarkable adaptation highlights the intense competition for resources that begins even before these sharks enter the world.
9. Sharks Have Replaceable Teeth
Unlike humans, sharks have the ability to continuously replace their teeth throughout their lives. A shark can lose and replace thousands of teeth in its lifetime, with some species going through up to 30,000 teeth (ref).
This constant renewal ensures that sharks always have sharp, functional teeth for hunting and feeding.
Shark teeth are arranged in multiple rows, with new teeth developing in the back and moving forward to replace lost or worn teeth. This conveyor belt-like system of tooth replacement is one of the reasons sharks have been such successful predators for millions of years.
It allows them to maintain their hunting efficiency even as their teeth are regularly lost or damaged during feeding.
10. Hammerhead Sharks Have 360-Degree Vision
The distinctive hammer-shaped head of hammerhead sharks isn’t just for show – it provides them with an extraordinary field of vision. The placement of their eyes at the ends of their hammer-shaped head allows them to see 360 degrees around them, including above and below.
This gives them a significant advantage in detecting prey and avoiding predators.
In addition to their enhanced vision, the shape of their head also increases the surface area for their electroreceptors, improving their ability to detect electrical impulses from prey.
This combination of sensory adaptations makes hammerhead sharks incredibly efficient hunters, able to locate prey hidden in the sand or camouflaged against the ocean floor.
11. Sharks Can Detect One Drop of Blood in an Olympic-size Pool
The oft-repeated claim that sharks can smell a drop of blood from a mile away is an exaggeration, but their sense of smell is still incredibly acute. In reality, sharks can detect one part of blood in 10 billion parts of water, which is roughly equivalent to a drop of blood in an Olympic-size swimming pool. (ref)
This remarkable olfactory ability is due to their highly developed nostrils and large olfactory bulbs in their brains.
However, it’s important to note that sharks don’t mindlessly attack at the slightest whiff of blood. Their feeding behavior is complex and influenced by various factors, including the type of blood, other environmental cues, and the shark’s own hunger level.
This sensory prowess is just one of the many adaptations that have made sharks such successful predators in the marine environment.
12. Some Sharks Give Birth to Live Young
While many people think of sharks laying eggs, not all species reproduce this way. This method of reproduction, known as viviparity, is found in species like great white sharks, bull sharks, and hammerhead sharks.
The mother shark carries her pups inside her body until they’re fully developed and ready to be born.
Interestingly, some shark species, like the tiger shark, exhibit a form of reproduction called ovoviviparity. In this case, the eggs hatch inside the mother’s body, and the pups continue to develop internally before being born live.
These diverse reproductive strategies showcase the adaptability of sharks and their ability to thrive in various marine environments.
13. Cookiecutter Sharks Leave Circular Bite Marks
The cookiecutter shark, despite its small size (usually less than 2 feet long), is known for its unique feeding habit. This deep-sea dweller attaches itself to larger marine animals and uses its strong jaws and razor-sharp teeth to carve out a circular chunk of flesh, leaving behind a distinctive cookie-cutter-like wound.
These bites have been found on a wide range of marine life, from large fish to whales and even submarines!
This unusual feeding strategy allows the cookiecutter shark to prey on animals much larger than itself. The circular wounds left behind by these sharks have long puzzled marine biologists and have even been mistaken for bites from other, larger predators.
The cookiecutter shark’s feeding behavior is a testament to the diverse and sometimes bizarre adaptations that have evolved in the shark world.
14. Sharks Can Go into a Sleep-Like State
While sharks need to keep moving to breathe, some species have been observed entering a sleep-like state. During this time, they appear to be in a restful condition while still swimming slowly to keep water moving over their gills.
This behavior has been observed in species like the nurse shark, which can lie motionless on the ocean floor for long periods.
However, the nature of shark sleep remains a topic of scientific debate. Unlike humans, sharks don’t have eyelids, so they can’t close their eyes.
Some researchers believe that sharks might be able to rest half of their brain at a time, similar to how dolphins sleep. This ability to rest while remaining vigilant is another example of how sharks have adapted to life in the constant motion of the ocean.
15. Basking Sharks Can Jump Completely out of the Water
Despite their massive size – they’re the second-largest fish in the sea after the whale shark – basking sharks have been observed jumping completely out of the water. This behavior, known as breaching, involves the shark launching its entire body out of the water and then crashing back down with a tremendous splash.
Some breaches have been recorded at heights of up to 13 feet above the water’s surface.
The reason for this spectacular behavior isn’t entirely clear. Some scientists speculate that it might be a way to remove parasites, while others suggest it could be related to courtship or communication.
Regardless of the reason, the sight of a 33-foot-long, several-ton shark leaping out of the water is a testament to these gentle giants’ power and agility.
These 15 unusual facts only scratch the surface of what makes sharks truly extraordinary. As we learn more about these diverse and often misunderstood animals, it becomes increasingly apparent that they play a crucial role in maintaining the health of our oceans.
Nancy has been a plant person from an early age. That interest blossomed into a bachelor’s in biology from Elmira College and a master’s degree in horticulture and communications from the University of Kentucky. Nancy worked in plant taxonomy at the University of Florida and the L. H. Bailey Hortorium at Cornell University, and wrote and edited gardening books at Rodale Press in Emmaus, PA. Her interests are plant identification, gardening, hiking, and reading.