how can sharks smell blood?
Discussion
you will often see people in wildlife films chucking blood and whatnot over the side of boats to attract sharks, it is said that they can sense blood over a quarter of a mile away.
My question is thus, how do they sense it so quickly? surely they need a bit of the original blood to sense and it would surely take days for that microscopic bit of blood to make its way over that sort of distance, not minutes or maybe an hour as is often portrayed in the programmes in question. and the chances of a shark being in the exact bit of water as a microscopic bit of blood over 400metres away from source is surely infinitesimally small, yet they are usually on the scene within moments, how come?
Greg
My question is thus, how do they sense it so quickly? surely they need a bit of the original blood to sense and it would surely take days for that microscopic bit of blood to make its way over that sort of distance, not minutes or maybe an hour as is often portrayed in the programmes in question. and the chances of a shark being in the exact bit of water as a microscopic bit of blood over 400metres away from source is surely infinitesimally small, yet they are usually on the scene within moments, how come?
Greg
You're right; sharks do need a 'bit' of the blood in the water to smell it - how soon they can detect it depends on the speed and direction that the local current can disperse the blood and its odour, which is very strong.
Ocean currents near the surface (where our injured swimmer would be) can easily cover over 100m in a minute, so it would easily take less than 4 mins for the blood to cover a quarter of a mile. Say the shark moves at 20kts, it could close down that quarter mile in less than a minute, so the prospect of sharks being on the scene in minutes is very, very real.
Sweet dreams.
Ocean currents near the surface (where our injured swimmer would be) can easily cover over 100m in a minute, so it would easily take less than 4 mins for the blood to cover a quarter of a mile. Say the shark moves at 20kts, it could close down that quarter mile in less than a minute, so the prospect of sharks being on the scene in minutes is very, very real.
Sweet dreams.
Taffer said:
You're right; sharks do need a 'bit' of the blood in the water to smell it - how soon they can detect it depends on the speed and direction that the local current can disperse the blood and its odour, which is very strong.
Ocean currents near the surface (where our injured swimmer would be) can easily cover over 100m in a minute, so it would easily take less than 4 mins for the blood to cover a quarter of a mile. Say the shark moves at 20kts, it could close down that quarter mile in less than a minute, so the prospect of sharks being on the scene in minutes is very, very real.
Sweet dreams.
And I was going to say "they have very big noses" Ocean currents near the surface (where our injured swimmer would be) can easily cover over 100m in a minute, so it would easily take less than 4 mins for the blood to cover a quarter of a mile. Say the shark moves at 20kts, it could close down that quarter mile in less than a minute, so the prospect of sharks being on the scene in minutes is very, very real.
Sweet dreams.
I'm often told that i give out useless information on a regular basis so heres a couple.
If you are ever in shark infested water and need a wee do NOT wee as wee wee contains blood cells.
another uselss piece of info would be this:-
If you're in a dingy/life raft and need to take a wee, do it in a bag and throw it as far away as possible.
Think I watch the discovery channel a little too much these days.
Paul
If you are ever in shark infested water and need a wee do NOT wee as wee wee contains blood cells.
another uselss piece of info would be this:-
If you're in a dingy/life raft and need to take a wee, do it in a bag and throw it as far away as possible.
Think I watch the discovery channel a little too much these days.
Paul
Interesting question that there seems to be some debate about.
Needless to say sharks have very sensitive senses, they are the ultimate predator. They dont just go after blood in the water but also many other signs that something is in the water in distress (Vibrations, shadows, light reflection etc)
You'd be very unlucky if a shark traveled miles to eat you. lol
Needless to say sharks have very sensitive senses, they are the ultimate predator. They dont just go after blood in the water but also many other signs that something is in the water in distress (Vibrations, shadows, light reflection etc)
You'd be very unlucky if a shark traveled miles to eat you. lol
They smell it the same way you smell anything.
For us humans, our medium is air. You breath a molecule of Julius Caesar's last breath several times a day (or anyone else you care to think of). But we aren't as predatory, at least not these days, so we don't detect as accurately, and we don't head automatically for the 'victim'.
The 'old' wisdom that dogs/others have a better sense of smell than us is increasngly questioned. It doesn't seem to be true. It is our actions that differ...
For us humans, our medium is air. You breath a molecule of Julius Caesar's last breath several times a day (or anyone else you care to think of). But we aren't as predatory, at least not these days, so we don't detect as accurately, and we don't head automatically for the 'victim'.
The 'old' wisdom that dogs/others have a better sense of smell than us is increasngly questioned. It doesn't seem to be true. It is our actions that differ...
I got this sent in an email the other day 
'YOU HAVE TO READ THIS FIRST BEFORE LOOKING AT THE PICTURE..
Family on holiday in Australia for a week and a half when husband, wife and their 15 year old son decided to go scuba diving. The husband is in the navy and has had some scuba experience. His son wanted a picture of his mum and dad in all their gear so he got the under water camera ready to go. When it came to taking the picture the dad realized that the son looked like he was panicking as he took it and gave the 'OK' hand sign to see if he was all right.
The son took the picture and swam to the surface and back to the boat as quick as he could so the mum and dad followed to see if he was OK. When they got back to him he was scrambling onto the boat and absolutely panicking. When the parents asked why he said 'there was a shark behind you.' The dad thought he was joking but the skipper of the boat said it was true but they wouldn't believe him. As soon as they got back to the hotel they loaded the picture onto the laptop and this is what they saw.'
'YOU HAVE TO READ THIS FIRST BEFORE LOOKING AT THE PICTURE..
Family on holiday in Australia for a week and a half when husband, wife and their 15 year old son decided to go scuba diving. The husband is in the navy and has had some scuba experience. His son wanted a picture of his mum and dad in all their gear so he got the under water camera ready to go. When it came to taking the picture the dad realized that the son looked like he was panicking as he took it and gave the 'OK' hand sign to see if he was all right.
The son took the picture and swam to the surface and back to the boat as quick as he could so the mum and dad followed to see if he was OK. When they got back to him he was scrambling onto the boat and absolutely panicking. When the parents asked why he said 'there was a shark behind you.' The dad thought he was joking but the skipper of the boat said it was true but they wouldn't believe him. As soon as they got back to the hotel they loaded the picture onto the laptop and this is what they saw.'
http://www.cartoonstock.com/directory/s/sharks.asp
Couldn't find the one with the scuba diver, and the comment from the shark something like
"Don't eat those with yellow things (SCUBA TANKS), they make you fart".
Couldn't find the one with the scuba diver, and the comment from the shark something like
"Don't eat those with yellow things (SCUBA TANKS), they make you fart".
http://www.snopes.com/photos/animals/scubashark.as...
I had heard about the wee wee thing. Luckily I'm a land lubber and won't be venturing much further into the sea than my knees.
I had heard about the wee wee thing. Luckily I'm a land lubber and won't be venturing much further into the sea than my knees.
mattviatura said:
julian64 said:
The wee thing is tosh too.
There are no red blood cells in wee. Or at least not unless you have a problem.
I regularly send urine samples for microscopy to check for exactly this.
Are you taking the piss?There are no red blood cells in wee. Or at least not unless you have a problem.
I regularly send urine samples for microscopy to check for exactly this.
grumbledoak said:
They smell it the same way you smell anything.
For us humans, our medium is air. You breath a molecule of Julius Caesar's last breath several times a day (or anyone else you care to think of). But we aren't as predatory, at least not these days, so we don't detect as accurately, and we don't head automatically for the 'victim'.
The 'old' wisdom that dogs/others have a better sense of smell than us is increasngly questioned. It doesn't seem to be true. It is our actions that differ...
I doubt it, the air is filtered by trees and stuff, so JCs last breath is long goneFor us humans, our medium is air. You breath a molecule of Julius Caesar's last breath several times a day (or anyone else you care to think of). But we aren't as predatory, at least not these days, so we don't detect as accurately, and we don't head automatically for the 'victim'.
The 'old' wisdom that dogs/others have a better sense of smell than us is increasngly questioned. It doesn't seem to be true. It is our actions that differ...
julian64 said:
mattviatura said:
julian64 said:
The wee thing is tosh too.
There are no red blood cells in wee. Or at least not unless you have a problem.
I regularly send urine samples for microscopy to check for exactly this.
Are you taking the piss?There are no red blood cells in wee. Or at least not unless you have a problem.
I regularly send urine samples for microscopy to check for exactly this.
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