How blood can be smelled over distances in water by sharks when it would take the physical water that has the blood awhile to reach them?
In: Biology
The same way you can smell things that are not right next to you. The particles that are sensed by the olfactory nerves diffuse out into the air/water. In neither case is it instantaneous, and the scent gets weaker the further away you or the shark is from the source.
They can’t smell it until it gets there. But the blood isn’t just flowing in the water in a blob, it’s mixing in and fairly rapidly spreading out “diffusion”.
Pour milk in your tea or coffee and see how fast it mixes in…that’s basically what the blood is doing in the water. And sharks have *really* good sense of smell so it only takes a tiny tiny bit of blood for them to pick up.
It does take a while. But once they detect it, they just follow the direction the smell gets stronger. They can sense such an absurdly small amount which is why they can be so far away and still detect the blood.
As others said, sharks have highly sensitive olfactory glands, allowing them to detect blood in water at very low concentrations (1 part per 10 billion parts of water). This sensitivity enables them to sense blood from miles away. So when blood enters the water, its molecules disperse through the movement of the water (currents, waves). Sharks detect these molecules as they spread, not needing the physical water with the original blood to reach them. Their ability to follow the scent gradient—concentrations of blood molecules—helps them locate the source of the blood.
The stats about a shark’s olfactory sensitivity seem to be somewhat well known at this point, but I’m curious if that number was achieved using fish blood or human blood, and if the difference even matters…
To add to your question, since many fish eat other fish, and the smell of blood takes time to go to the shark, wouldn’t the shark go there to see nothing in most situations as the fish would have already consumed the other fish?
Latest Answers