My comment is I have heard that many animals (especially desert-dwellers) can “smell” water. Are they really smelling H[sub]2[/sub]O? Or, are they smelling chemicals associated with water?
Humans can’t smell water, yet I can recognize the odor of the ocean, or the scent of a freshly-watered lawn. Streams often have a pleasant odor about them. I expect that I’m smelling chemicals associated with wet plants or wet soil.
Just because humans can’t smell water doesn’t mean other animals couldn’t have evolved the necessary olfactory receptors for it. Have any scientific studies been done?
If animals could smell water itself, instead of smelling the effects of water (e.g. streams, rain) the way humans do, i’d image that the would be constantly overwhelmed by the scent of water.
We smell things because molecules of that substance have become a gas and traveled to out noses. Solids, such as cheese, sublime, and we smell the cheese vapor. The concentrations necessary to trigger our olfactory sense are usually very small, on the order of a few parts per billion, or even parts per trillion. Water exists in even the driest air in concentrations of a few percent, huge when compared to a part per billion.
So if you could smell water (actual H2O molecules), it would be all you could smell. That’s most likely the evolutionary reason why most common naturally occurring gases are odorless…because we are naturally faced with reasonably high concentrations of them, and the ability to smell them is pointless.
Odor is not a real quality of the material, it’s a measure of how perceive it with one of our five senses. Just like radio waves aren’t any more invisible than normal light, we’re just not equipped to detect them.
If ethanol were commonly found in the natural atmosphere, it would probably happen to be odorless to us. If nitrogen didn’t make up 80% of our atmosphere, we might have evolved a means to smell it, and it would have made it on our list of “gases with an odor.”
I have a dog who cannot only recognize water, he knows where to find it. When I have him loose in the woods he knows to go down ravines to find water. He isn’t always successful, but he knows what kind of terrain will likely have a stream.
Thanks for the respones, audiolover especially. I think you’re right for the most part, for animals living in non-desert environments. But what if water vapor detection only occured at much higher thresholds? For a desert animal, what if detection occured at say 40% humidity? That’d be high enough to avoid being overwhelmed usually, but sensitive enough know if water were near.
Does my hypothesis of smelling wetness by-products make any sense?
I think the wetness by-products theory does make sense.
I was told once, at summer camp many moons ago, that if I wanted to smell all the woodsy smells better, that I should stick a wet finger up my nose. The increased moisture is supposed to increase olfactory sensitivity… and it does. You smell more stuff with a wet nose.
Ever notice how you can smell rain coming? Maybe what you are smelling is an increase in “smelly” molecules because of a sudden increase in humidity, i.e. sudden increase in smell medium.
I think we do have some kind of specific sensitivity for water, though, and we’ve just lost it in our safe modern lives. I’d imagine wild humans are just as good at sniffing out water as other animals are. And the “detection level” idea makes sense too - water is too important for us to not be able to smell it. So maybe - increase in ambient level of humidity = “water smell” = water source nearby.