I mean like, if no blood particles have traveled to them in the water, how can they possibly know that it is there? Is it just a myth?
In: Biology
If no particles are in the water the shark can’t sense it.
The smell has to travel to the nose. So that depends on so many things in the water. It depends on currents. It depends on how turbid the water is, so how much movement is there, and where the shark is facing
The thing is: it’s a myth that sharks are the best “blood hounds” of the oceans.
Sharks can smell one molecule of a scent in a billion molecules of water. But sharks actually have the same smelling ability as any other fish because sharks are fish, and they can smell just as good as just any other fish (there have been studies done on this).
But sharks have very capable electro receptors on their body which allows them to quickly locate their pray.
Sharks can indeed sense blood, but only when there is actually blood in the water.
However, the myth that a shark can sense blood in the water from several miles away is exactly that: a myth. In reality, they can sense blood in water from about half a mile away (Great white shark), tops. Which is still impressive, and also pant-shittingly terrifying.
So, if you’re having an especially shitty day and you’re being hunted by a shark (great white, tiger, bull or hammerhead, typically) and you’re not bleeding in the water, how do they find you?
Well, sharks have a fascinating organ called Lorenzini ampulae in their noses that can detect electrical activity. As you can imagine, electrical activity will be especially high in panicking or frightened prey, as a human would likely do in shark-infested waters.
Said electrical activity is generated by your heart, which emits electrical activity with every heartbeat, and the more you panic, the higher the electrical activity and thus the more detectable you become to the shark.
These haywire electrical signals allows the shark to home in on their prey in the absence of blood in the water or in complete darkness, as sharks have poor eyesight.
Blood particles **have** reached them. A very, very small amount of blood, in a very very large amount of water…but there’s blood in the water just the same.
Imagine getting a big bucket of water, and a bottle of food colouring. Put one drop of food dye in the bucket. There’s not a lot to see when it’s just one drop in an entire bucket. If you got a glass of water out of the bucketful, you probably wouldn’t notice anything different about the colour. But you definitely put the colour in, didn’t you?
The shark’s nose Is sensitive enough to find the one drop in the bucket. Even if you can’t.
You’re right that the idea of sharks smelling a single drop of blood from miles away is a myth. Sharks have an incredible sense of smell, but it’s not quite that superhuman.
Sharks can detect blood in the water from impressive distances, but it’s more like a quarter mile than a mile. They have a special superpower that helps them achieve this feat: electroreception.
Electroreception allows sharks to pick up on the weak electrical fields emitted by living organisms. When a fish gets injured, the electrical fields it gives off change. Sharks can sense these changes and home in on the source, which might be a wounded prey animal.
So, it’s a combination of their super-smeller ability and electroreception that makes sharks such efficient hunters.
It hasn’t got anything to do with distance. That’s kind of statement is somewhat misleading. It’s really a statement of how good of a detector of blood they are.
The further you get from the source of something the more dispersed it is and the better detector you need to detect there’s anything there at all.
Sharks can detect such a trace amount of blood in water that’s the concentration is somewhat similar to how dispersed something gets after it has travelled that distance from the source.
Once they detect it they simply swim in the direction where they detect an increasing amount of it.
Latest Answers