A lemon shark showing its nares. The nares help figure out how far away can sharks smell blood.
A curious lemon shark showing off its' powerful nares. Photo courtesy of Paddy / Peach Snaps

Sharks have a strong sense of smell. They have this ability thanks to their nostrils or nares, which are found beneath their snouts. The nares exist only for smelling, not for breathing. Thanks to the nares, sharks can detect tiny amounts of various substances in the water. But how far away can sharks smell blood? 

Even when the chance of getting killed by sharks is only 1 in 3,7 million, the fear of the predator is still growing. People believe sharks can smell a tiny drop of blood from miles away, thanks to the movie industry and popular culture. Sorry to blow your bubble, but this ‘fact’ is simply not true. Sharks have a strong sense of smell, indeed, but the common information about it is exaggerated.

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How Far Away Can Sharks Smell Blood? 

The smelling ability of each shark depends on its type. Some sharks can detect a scent of a substance that is several hundred meters away, but most sharks don’t. If a shark is found more than a quarter-mile away, they won’t smell your blood and suddenly decide to eat you as a snack.

Some sharks can smell your blood from a quarter-mile away, but the smell doesn’t reach them instantly. Scents reach a shark through the currents, and it would take time for the scent to reach the shark’s nostrils. It also depends on the motion of the ocean. The faster it is, the quicker the scent will travel either closer or away to the shark. 

If you get injured and bleed while swimming in the ocean, you still have plenty of time to swim to the beach safely before any shark decides to attack. But if you are still worried about getting attacked by the predator, you may need to know that contrary to common beliefs. Sharks don’t actually like human flesh that much; they are, in fact, picky eaters. For example, lemon sharks love to eat bony fish, crustaceans, and mollusks. Sometimes they also enjoy seabirds and small sharks. But humans are not even on their menu. 

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Do Sharks go Crazy When They Smell Blood?

No. This is just another example of misconceptions built by the dramatic movies about sharks losing their minds and attacking humans just because they smell a drop of blood. This fact is backed up by an experiment by Skylar Thomas from the White Shark Studio Company. Thomas made a video of himself cutting his wrist while being surrounded by blacktip sharks. 

The experiment’s point was to prove that sharks don’t go crazy just because of a drop of blood. They can smell the blood for sure, especially when the blood source is so close to them, but due to their strong sense of smell, they smell not only blood but also everything else in the water. So, it is unlikely for them to drop whatever they are doing to go after the blood. 

Some critics of the experiment challenge Thomas to perform the same experiment again, but around a more aggressive species of sharks, but it hasn’t been done yet.

Are Sharks Attracted to Blood?

Yes. Not necessarily just human blood, but sharks can be attracted to blood. A former NASA engineer Mark Rober experimented to find what sharks prefer: human blood or fish blood. The experiment is performed using cow blood instead of human blood because all mammal blood practically smells the same to sharks, says Rober. Rober then releases the cow blood and the fish blood in the same area but at a distance to see which one attracts sharks the most. Based on the experiment, the predator prefers fish blood over cow’s blood, so one point for fish and zero points but a bonus life for mammals. 

Do Sharks Attack When They Smell Blood?

Sharks use a different sensory system when they are hunting for prey. Blood can be one indicator that leads sharks to their prey, so if it’s the smell of the prey they’ve been hunting, they will attack for sure. On the other hand, human blood is not as interesting for sharks. Just because they can smell you and your blood doesn’t mean they correlated the smell with food and want to eat you. 

So why do sharks attack humans? There are multiple theories for this phenomenon. The most popular one is linked to the environmental damage caused by humans that forced sharks to gather in a larger group in a spot where humans’ appearance is common. Sharks can also attack humans because they have mistaken humans’ bodies as their prey. For example, they hunt for a fish and see the tip of someone’s fin and think it’s a fish. The third is that juvenile sharks tend to experiment to increase their hunting ability. So, they can attack people out of curiosity. Other than that, sharks are usually ignoring humans even when they can smell us. Apparently, we are not as tasty to them.

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How Can a Shark Smell Blood in Water?

Sharks have nostrils that work only for smelling. They are called nares. The nares contain a lot of sensory cells named olfactory lamellae. The cells interact with the particles in the ocean water to detect even low concentrations of odors, indicating the presence of prey. This includes the smell of blood and other kinds of organic molecules. 

So, sharks can smell blood for sure, but it is not the only thing they smell. The smell of blood is just one odor among every other odor in the ocean, including the one that belongs to their favorite prey. Their ability is not limited only to the capability of sensing a smell but also to finding the source of the scent so it will be easier for them to hunt down their prey. 

The smell of the blood also needs some time to reach the sharks because they need to travel in the water. So, this also depends on the species of the shark and how far away they can smell blood. Some sharks are sharper at sensing smells, while other’s abilities are just average, just like any other fish. 

Can Sharks Smell Fear?

No, they can’t. The sense of smell of a shark is strong, and they can smell everything that interacts with their sensory cell on their nares, but this doesn’t include feelings such as fear. But you need to remember that sharks don’t rely only on just their sense of smell. They have other abilities, too, such as an electro sensing ability. By using this ability, sharks can detect movement and heartbeats of their prey. This way, they can feel if their prey is scared of them, and it will be easier for them to attack the prey based on their movement. 

How to Avoid Sharks Attacks?

Even after we learn that humans are not sharks’ favorite meal, we still need to be careful because shark attacks do occur on a regular basis. Shark attacks have cost many people’s lives, and for those who do survive, the loss of limbs, the creation of scars, and trauma are all possible. 

Below are a few things you can try to avoid a shark attack:

  • Swim in groups. This can help you avoid getting attacked by a shark because sharks like to attack lone prey. 
  • Stay close to the shore. 
  • Avoid swimming at night, dawn, and dusk. 
  • Don’t wear shiny jewelry.
  • Avoid water with lots of bait fishes because they will attract sharks. 
  • Leave the water immediately once you notice the presence of a shark. 
  • Avoid bright-colored clothing because sharks are sensitive to high contrasting colors. 
  • Reduce water splashing because it can attract a sharks’ attention. 
  • Keep pets out of the water. 
  • Don’t try to touch a shark if you see one. 
  • If you do get attacked, do whatever you can to get away from the shark. 

One thing we can do to remain safe from any shark is to stay away from them. But this doesn’t necessarily mean that we have to hate them. The way movies portray sharks as evil predators makes people fear them, and therefore hate them. Sharks are predators indeed, but so are we as humans. We eat other animals as well. We can be cautious and be careful when we are in the water, but there is no need to hate the predator. 

Now we know how far away can sharks smell blood and that blood is not the only thing matters for sharks. We can learn so many things about them, and better knowledge will lead us to understand them better.