Do snails have noses?

by / Jun 01, 2022



This post is edited from an episode of the Is That True? Podcast, where host Arionne fact-checks different kid questions. Today’s episode is a question about how many noses snails have by Leo. 

Arionne: Our fact we’ll be investigating is a really cool one. And honestly, it’s about something I don’t really know anything about: SNAILS and how they smell.


Leo: Hi. My name is Leo and I am 8 years old and I live in Pasadena, California. 


A fact that I learned is that, this is kinda funny, snails have 4 noses. And I learned that from my class.


Arionne: Wow, Leo. That’s such a cool fact. And I have no idea if that’s true! So, we’ll have to investigate it.


But first, let’s talk a little bit about what a snail is and how I found someone to help us figure things out.


You might have seen a snail in your yard or while you were on a walk outside. Those are land snails. But there are also snails that live in freshwater like lakes and rivers plus sea snails that live in oceans. They are generally small and have shells that they can completely hide inside.


To learn more about snails, I wanted to visit a museum that studies them. I live in Chicago, Illinois, and we have a really cool museum called the Field Museum. I always loved visiting it when I was a kid because they do a lot of research on how we can better support the things we see in nature — things like snails! 


I went to their website to learn more. I found that there was a guide that explained the types of snails I could find here where I lived. But I still wasn’t sure about how many noses these snails had. 


So my next step was an easy one: I emailed them to ask! That’s how I met a scientist who could help us find out more.


And it turns out, the answer is not a simple yes or no. We’re going to test out this fact by asking questions with someone who has devoted his whole career to studying snails and other animals.  



Dr. Gerber: Hi, my name is Jochen Gerber. I'm a malacologist. Malacologists [are] scientists who research animals like snails, clams, squid, and they are relatives. And I work at the Field Museum, where I oversee the collection that we have of these animals.


So I'm a collections manager there. 


Arionne: Just like our friend Leo, Dr. Gerber has been interested in snails for a LONG time. 


If there’s anyone who would know about our fact, it would be Dr. Gerber. So I asked him: is it true that snails have four noses? I know that this is actually a much more complicated answer than just a yes or no. So I'm excited to chat with you about it. 


Dr. Gerber: Okay. So to make it complicated, it all depends on how you define [a] snail and how do you define [a] nose?


If you define nose as the organ that we have, that we call nose, then snails have no noses at all because our nose has different functions. We breathe through the nose, but we also smell with the nose. Snails don’t breathe through noses. So if they have noses, they are different from our noses.


Arionne: Dr. Gerber explained that there are different kinds of snails and they all smell in different kinds of ways. So to answer if snails have four noses, we’re going to talk specifically about the typical land snail. 


Dr. Gerber: If I answered the question in that way, then I have to say, yes, these snails have four noses. Each one of these four tentacles has a sense of smell. Now they are two pairs, the lower ones and the upper ones, the lower ones obviously are closer to the ground and they are apt to smell things nearby by, on the ground, just before the snail, by the upper tentacles are usually straight out into the air. 


And so they can perceive smells that come from a bit further away. And smelling is important for the snails because other senses that work at a distance for us, for example, like sight or hearing, do not work well or not work at all for snails. Snails have no sense of hearing. And their sense of sight is very limited. 



Arionne: And that very limited sight comes from two of the SAME tentacles that they use for smell.


Dr. Gerber: So in our example with the land snail with four tentacles, the upper two tentacles in addition to the smell sensors also have two eyes. I mean, each tentacle obviously has one eye. Um, so those tentacles, the upper ones, are not only noses, but they're also eyes or they have the eyes at the tip of them.


Arionne: So if we're talking about a land snail, then we have four tentacles that some people might say are noses, even though they're different than human noses—two are above, two are lower down. And the reason why is because the ones that are higher up can smell different things compared to the ones that are lower. And also the ones that are higher you can also see out of. 


Arionne: To summarize, would you say that their sense of smell is their strongest sense? 


Dr. Gerber: That is probably, you could say that. I mean, how much do we really know about the world of a snail as it perceives it? Not that much. We have a really hard time [understanding] these animals. But from what we know, you can say probably that the sense of smell is the most important and strongest developed sense in the snail. 


Arionne: Yeah, I guess that's true. They can't tell us so.