In all the species I can think of, the nostrils of a nose are placed very close together. I was led to believe that the spacing of ears aids in locating the source of incoming sounds. Does that also apply to noses and odors?
Are there animals (or, for that matter, artificial devices) that can more precisely follow a scent trail due to the particular placement of their “nostrils”?
i only have one nose so it can’t be spaced farther apart.
odors are a diffuse stimuli so there is not the need to have strong stereo discrimination. animals do aim there nose to locate.
I meant nostrils :smack:
In order to locate the source of odors, animals, and humans too, move their noses about by turning the head and even moving the whole body, to see in which direction the scent is strongest. (It has been shown experimentally that blindfolded humans can actually follow a scent trail quite well, if they crawl with their noses close to the ground. We are not as good at it as dogs, but we are not as bad at it as it is often assumed we are.)
As a matter of fact, moving the sense organ (by moving the head) is the main mechanism by which we locate the source of sounds too, and much of how we locate the position of things by sight also depends on the movements of our heads and of our eyes within their sockets. The stereo effects of having eyes and ears spaced apart play a relatively minor role in humans, and even less in many animals. After all, most animals are smaller than humans, so their eyes and ears are not very far apart, even when they are on opposite sides of a tiny (for instance, mouse sized) head. They can all move about though, and, thanks to that fact, they can locate things by smell, hearing and sight quite well. So can we.
I believe this has been offered as a reason for the hammerhead shark’s shape, though I don’t know if that’s the current, predominant theory.
Perhaps I should add that having two separated nostrils does add something to the information we get from smell (as does having two, separated ears and eyes), but the advantages of having them more widely spaced are almost certainly very trivial, and clearly evolution has not found it worthwhile to move them very far apart in most (perhaps not in any) species. Presumably the trivial sensory advantages this might bring are outweighed by the problems it might raise for breathing. As I said above, the ability to turn the nose in different directions is much more important to its sensory role.
I understand that dog’s noses are wet in at least part to help them determine where a smell is coming from; apparently the sensation of air flowing over their wet nose lets them determine wind direction, and therefore the direction a scent is coming from. A dog with a dry nose isn’t as good at determining that direction.
I thought the hammerhead’s head shape was something to do with its electrical sense.
Snakes (and other reptiles) smell with their tongues, and the fork allows them to locate the direction of the smell in much the same way our ears locate the source of sound.
Dogs almost constantly are shaping, flaring, and directing their nostrils while sitting or standing still (outside predominantly, of course).
The other thing, though, is that a sound generally comes from a point source whereas smell might be something hours old, lingering on the ground or vegetation. So I can see where there would be a lot more bang for the buck to be able to locate a sound source vs an oder source.
From what I’ve read, the current theory is that it spreads out the electrical sensors (Ampullae of Lorenzini) and also gives the shark a much greater field of vision, both of which help with prey location.
I read recently that somebody discovered sharks use their noses differentially. Don’t know what particular kind and am now trying to figure out what a fish nostril would even mean…
Triangulating over what, 5 millimeters or so? Not much directional information there, let alone range information.
Snakes sense the direction of chemical stimuli the same way that we, and all other animals, do, by moving their heads and their tongues around to find out which orientation provides the strongest signal. Why do you think they dart their heads and tongues, around so much? Hold a snake’s head (or a human’s, or a dog’s) still, and they will be very poor at judging the direction of the source of a smell (or a sound, come to that). Perception is not something that happens independent of movement, they are a single, integrated system, as perceptual science has come to realize in recent years. For historical reasons, though, the obsolete paradigm that “real” perception is what happens when we keep perfectly still, passively absorbing inputs, and all the movement that occurs when people and animals actually perceive is just a distracting irrelevance, is still deeply entrenched in the way most people think about it.
I’ll second Napier on sharks. Source? Inside Natures Giants tv show, specifically the great white episode I just saw the other night. Of cource they’re always moving their head back and forth too, so I’m not sure how much stereo smelling would mean.
Is this really a “paradigm”? I don’t think I’ve ever thought to myself “hmm, I better not move my head or I’ll lose the signal”. Every time I want to locate the source of a sound, I move my head around… I thought it was instinctual?
Smell isn’t just for locating distant objects - it’s also for checking out objects close up. Having your smell sensing organs together let’s you hold things close up to your face and smell them - a useful trait for determining whether something’s poisonous or spoiled.
Why couldn’t you just smell it with one nostril? How does stereo smelling help up close?
It just needs to be bigger and easier to pick
The stereo part probably doesn’t help; but having your nostrils right over your mouth makes it more likely you’ll get a whiff of anything dangerous before you absentmindedly gobble it down.