How far can sharks smell blood?

sharks have long been feared and one of the main reasons is that we often see them as dangerous and bloodthirsty killers – something not helped by movies like jaws. Besides, we’ve all heard the myth about sharks and blood — that chilling rumor that sharks can smell blood from several miles away and detect even the tiniest drop in the ocean. But is that really true? Join us as we discover how far sharks can smell blood and learn how to detect their prey differently.

How do sharks detect prey?

Smell is just one of many methods sharks use to detect their prey. The other methods they use are vision, hearing, lateral line and electroreception. They also use taste and touch, but we’ll get to those two later. One of the first senses sharks use to detect their prey is sound, and they hear sounds from great distances — long before their prey comes into view. Sharks are especially attracted to low-frequency sounds, especially those of injured prey.

In addition to sound, sharks use the lateral line system to detect their prey. This system is a series of fluid-filled channels located under the skin along the sides of the body and head. There are small pores in the skin that allow water to flow into the channels where the sensory cells are located. These sensory cells allow the shark to detect water movements, such as currents and movements or vibrations caused by struggling prey.

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The other unusual way sharks detect their prey is electroreception. Electroreception is when sharks detect the electrical impulses given off by any living thing. Sharks can detect these impulses because they have many tiny pores in their skin around their snouts — known as Lorenzi’s ampullae. These pores help sharks detect their prey at close range, even when hidden under the sand.

How do sharks detect odors?

Before exploring how far sharks can smell blood, we need to understand exactly how they can detect odors underwater. Sharks have two nostril-like openings known as “nares” which are located on the underside of their snouts. However, unlike mammals, they do not use them for breathing. Their nostrils are not even connected to their throats or lungs as they breathe through their gills. Instead, sharks only use their nostrils to detect scents.

Fragrances are carried in the water by the currents that spread and transport molecules of, for example, blood. Sharks’ nostrils are lined with sensory cells called “olfactory epithelium.” These cells can detect the tiny odor particles carried in the water. The water enters the shark’s nostrils and flows over the sensory cells, allowing the particles to be detected. Once a scent is detected, a signal is sent to the shark’s brain, where the scent is interpreted. More than half of a shark’s brain is made up of olfactory lobes. These olfactory lobes interpret the scent and help the shark detect whether it is predator, prey or a potential mate they can smell. Then it’s up to the shark to decide what action to take.

Amazingly, shark nose holes work independently of each other. There is sometimes a delay between the two nostrils detecting a scent, especially if the scent particles hit the shark at an angle. Because of this, sharks always turn their heads in the direction of the nostril that first perceived the scent – even if the delay is only a fraction of a second. This means that sharks always turn in the direction of the scent.

How far can sharks really smell blood?

As we just learned, sharks rely on tiny particles entering their nostrils to detect scents. Sharks have extremely sensitive nostrils and can sense scents from afar, but how far they can detect these scents depends on a few things. Particles of different odors spread differently in the water. However, depending on what it is, they can detect things in the water between 1 part in 25 million and 1 part in 10 billion. To put the latter in perspective, that’s about one drop in an Olympic-sized pool.

However, it’s not just the number of particles that determines how far sharks can smell blood, it’s the water currents as well. This is because the odor particles spread (spread) through the water. The only way a shark can pick up on the scent is through the water carrying those tiny particles to it (or the shark swims in it). So because these particles are carried along by the current, the main factor determining how far a shark can detect blood is the direction and speed of the water. As a rule, it takes a long time for particles to move in the water once they are dispersed. However, faster currents mean that the scent will travel faster and further.

Under optimal conditions, sharks can smell blood from a quarter of a mile away, but it takes a while for the scent to get to them. However, that distance depends on the kind of shark (some can smell much better than others), and on the direction and speed of the water. So while it’s still a pretty good distance, it’s probably a lot less than we expected.

Do sharks go crazy when they smell blood?

In addition to the myth that sharks can smell blood from miles away, there is also the myth that sharks go crazy if they smell even a drop of blood. This myth has led many people to be terrified of getting even a small cut while in the water. However, the truth is that sharks don’t go crazy once they smell blood. We’ve already established that sharks can only smell blood a quarter of a mile away, and how long it takes them to detect it depends on the direction and speed of the waterberries. Therefore, even if they smell blood, they will not immediately descend on it.

But what if the blood is near them? A few experiments have been done by brave individuals to prove that the myth is false. Former NASA engineer Mark Rober and marine biologist Luke Tipple conducted an experiment in 2019 as part of Shark Week to find out. They used devices attached to surfboards to pump out cows blood, seawater, urine and fish oil for an hour to see which attracted the most sharks in an area already infested by sharks. Four went to the fish oil, none to the seawater or urine. However, after 45 minutes about 40 lemon and tiger sharks examined the cow’s blood. The result of the experiment showed that sharks, even when they are almost on top of it, do not go crazy from a single drop.

However, they went further and donated blood so they could see how interested sharks were in human blood. This experiment involved a control, one that pumped out blood quickly and one that pumped it out slowly. The result: no sharks were interested in human blood.

Why do sharks attack?

So, if sharks can’t smell blood from miles away, and can’t go crazy when they smell it, why do they still attack humans? As we mentioned above, taste and touch are both methods sharks use to detect their prey. Many scientists believe that many shark attacks are actually the result of the “bump and bite” action. When sharks are curious about something and want to know what it is, they touch it. However, since they have no hands, they have to touch it with their nose. This is known as the hump. The bite is when the shark then takes a bite to see if something (or someone) is edible. So some shark attacks are simply a result of the shark being curious and doing a “taste test”. But unfortunately for us, that taste test is often fatal.

So what all this tells us is that: sharks have a very good sense of smell, especially when it comes to blood, but anything more than a quarter of a mile away probably won’t reach them. Also, a little bit of blood is unlikely to attract a feeding frenzy of sharks to you. However, if someone comes up to you and punches you with their nose, you might have a problem.