Freedom, a beagle trained by Jeremy Ecker
STAN HONDA/AFP/Getty Images
If you’ve ever seen a dog, you know they like to sniff — the ground, people, each other’s butts. They like to smell just about everything. But why? We’re digging into the science of smell and how dogs are able to decode things we can’t even begin to imagine.
Right-click to download episode transcript.
We spoke with Dr. Anneke Lisberg, an ethologist at University of Wisconsin-Whitewater. Read more about some of her research here.
Dr. Anneke Lisberg and her dog Canyon.
Molly Bloom
We also paid a visit to PawPADs, an organization that trains service dogs for people with physical disabilities, diabetes and autism.
Linda Ball introduced us to Breezy, who’s training to be a diabetes assistance dog. Here they are:
To train Breezy, Linda uses samples (pictured below) collected from people with diabetes. The person will breathe onto a piece of gauze when his or her blood sugar level is low and they put the gauze into a small tube. Then, Breezy is trained to recognize the scent of a person’s breath when his or her blood sugar level is low or high.
Sample used in training Breezy, a diabetes assistance dog.
Molly Bloom
This episode was originally released on November 16, 2014. Listen to that version here:
Dogs: What's the secret of their sense of smell?
by Brains On!Audio Transcript
Download transcript (PDF)
MADISON MACDONALD: You're listening to Brains On, where we're serious about being curious.
SUBJECT 1: Brains On is supported in part by a grant from the National Science Foundation.
MOLLY BLOOM: If you have a dog--
MADISON MACDONALD: Or ever seen a dog.
MOLLY BLOOM: You'll know they like to sniff.
MADISON MACDONALD: They sniff the ground.
MOLLY BLOOM: They sniff trees.
MADISON MACDONALD: They smell you.
MOLLY BLOOM: And of course, they even smell each other's butts.
MADISON MACDONALD: Eww.
MOLLY BLOOM: Yeah, let's just say--
MADISON MACDONALD: They smell everything.
But why?
MOLLY BLOOM: We're going to find out right now. Keep listening.
SUBJECT 2: Brains On!
MOLLY BLOOM: You're listening to Brains On from American Public Media. I'm Molly Bloom, and my co-host today is 12-year-old Madison MacDonald. Hi, Madison.
MADISON MACDONALD: Hey, Molly.
MOLLY BLOOM: Now when we first started talking about what questions you had about dogs, you wanted to know about why dogs smell each other and us. So what got you thinking about that?
MADISON MACDONALD: Well, I have a dog of my own, and I been wondering, why does he smell the ground, why does he smell other dogs' butts, why does he smell trees.
MOLLY BLOOM: Right. There always smelling everything.
MADISON MACDONALD: Right.
MOLLY BLOOM: What's your dog's name?
MADISON MACDONALD: My dog's name is Cody.
MOLLY BLOOM: And what kind of dog is he?
MADISON MACDONALD: He's a Siberian husky.
MOLLY BLOOM: And why do you think he smells you?
MADISON MACDONALD: So he knows that we're part of his family, not just random strangers in his house.
MOLLY BLOOM: The first part of the answer to why dogs like to smell everything is that they can smell so much more than we can. It's hard for us to even understand it because it's so different than our sense of smell. First, we're going to dig into the hardware that makes that possible.
MADISON MACDONALD: Dog noses can be long.
MOLLY BLOOM: They can be short.
MADISON MACDONALD: They're usually wet.
MOLLY BLOOM: But not always.
MADISON MACDONALD: They're always cute, though.
MOLLY BLOOM: Yeah, they're pretty darn cute. But they're also amazing sniffing tools as our pal Sanden Totten explains.
SANDEN TOTTEN: Think about it this way. If noses were vehicles, dogs have a race car.
[RACE CAR]
And humans have a tricycle with a broken wheel. It's not just that dogs' noses tend to be longer. They also have a lot more scent receptors. These are cells in the nose that detect smells. Now those smells come in through the nose in the form of tiny molecules in the air. These could be bits of flowers, or food, or whatever. The scent receptors in the nose grab on to these molecules in the air.
SUBJECT 3: Gotcha.
SANDEN TOTTEN: They check them out.
SUBJECT 3: Let's see what we have here.
SANDEN TOTTEN: And then these scent receptors send a message to your brain, letting you know what it is that you're smelling.
SUBJECT 3: He's sniffing stinky cheese, everybody. Stinky cheese.
SUBJECT 4: Hmm.
SANDEN TOTTEN: All of that happens in your nose when you smell something. Cool stuff. But think about this. Madison, Molly, and all the rest of us humans, we have about five million scent receptors. Sounds like a lot, right? But dogs, dogs can have more than 200 million in their snouts. So humans, 5 million. Dogs, 200 million.
So what does this mean in real smelling terms? Let's take our pal, Bob.
BOB: Hello.
SANDEN TOTTEN: And a dog.
DOG: Woof, woof.
SANDEN TOTTEN: Now say we give Bob a cup of coffee.
BOB: Oh, thanks.
SANDEN TOTTEN: He might be able to smell if there's a teaspoon of brown sugar in the coffee.
[SNIFFS]
BOB: Smells like sweetener I think.
SANDEN TOTTEN: The dog could detect that teeny tiny teaspoon of brown sugar even if it was poured into a pool filled with 1 million gallons of water. For those of you doing the math at home, that's 16 million cups of water.
DOG: Yup. There's sugar in there.
SANDEN TOTTEN: Dogs can also control each nostril independently. And if a tiny trace of a smell enters one side of the nose but not the other, a dog can figure that out. So a dog theoretically could tell if the sugar was dropped into the left side of the pool or the right side of the pool.
DOG: It's to the left.
BOB: I just smell chlorine.
SANDEN TOTTEN: Cool fact, dogs also have front nostrils for breathing in and side nostrils for breathing out. That way the stuff they exhale doesn't blow away the stuff they're inhaling, which means a dog can sniff almost continuously.
DOG: I also smell sunscreen, bathing suits, snorkels, goggles.
BOB: Well, I can see all that.
DOG: Also I smell a little pee in the pool, just warning you.
BOB: Ehh.
SANDEN TOTTEN: One more thing, dogs have a really powerful second smelling tool called the vomeronasal organ.
BOB: Vomero-- numero-- what?
SANDEN TOTTEN: The vomeronasal organ is also called the Jacobson's organ which is much easier to remember. Humans don't really have a working version of this, but many other animals do like pigs, hamsters, and snakes. This bit of nose technology is designed especially to pick up body scents called pheromones.
Pheromones are smells animals give off to let others in their species know how they're feeling, like whether they're alarmed, angry, or in the mood for love. So while Bob might sniff princess the poodle here and say--
BOB: Well, that smells like a dog, all right. I definitely know that's a dog smell.
SANDEN TOTTEN: Our dog friend would whiff princess using his Jacobson's organ and think--
DOG: Oh my princess had a really good day. She's calm, happy, and oh, hey, up for date later maybe?
PRINCESS: A woof, woof.
DOG: Well, then I'll meet you at the dog park around 7:00.
[DOGS BARKING]
BOB: The dog smelled all that?
SANDEN TOTTEN: Yes, because dogs are awesome at smelling. They have more receptors, amazing nostrils skills, and a whole other organ just for sniffing pheromones. Back to you Molly and Madison.
[MUSIC PLAYING]
MOLLY BLOOM: All right, Madison. So what did you think of that? Was there anything in there that you found surprising or particularly interesting?
MADISON MACDONALD: I found like when dogs can smell their behavior, like how the dogs smell the other dog, how the first dog smelled like, hey, she's calm, hey, she's happy, hey.
[LAUGHS]
MOLLY BLOOM: Yeah. It's kind of amazing they can learn all that just by smelling. We can't tell that about humans by smelling them.
MADISON MACDONALD: No.
MOLLY BLOOM: At all. Kind of wish you could sometimes, though.
MADISON MACDONALD: Yeah.
MOLLY BLOOM: While we can sit and wish our sense of smell was just a little bit better, how about we put another sense to the test? Your sense of hearing. Are you ready?
MADISON MACDONALD: Yeah.
MOLLY BLOOM: It's time for the mystery sound.
[WEIRD SOUND]
SUBJECT 5: Mystery sound.
MOLLY BLOOM: Here it is.
[CLICKS]
That's a quick one. So let's hear it again.
[CLICKS]
Any guesses?
MADISON MACDONALD: It sounds like somebody is snapping their fingers to get something's attention, like a dog.
MOLLY BLOOM: That's a very good guess. We're going to give you and our listeners a little more time to think about it. But in the meantime, let's get down to why dogs are smelling each other.
MADISON MACDONALD: We talked with Anneke Lisberg from University of Wisconsin-Whitewater.
MOLLY BLOOM: She's an ethologist.
MADISON MACDONALD: That means she studies animal behavior.
MOLLY BLOOM: And we got right to the subject at hand.
MADISON MACDONALD: I asked, why did dogs smell each other's butts?
ANNEKE LISBERG: So the reason that the dogs are sniffing urine marks and sniffing each other's butts when they're getting to know each other is they're getting a lot of information about who that dog is, where they came from, what they're doing right now in a very little bit of time. And then they can use that information potentially to have a nice smooth social introduction with each other without major faux pas.
So I think it's a lot sort of scoping someone out online, and that you get not just one piece of information but a lot of really detailed information. And then you can use that to kind of decide what kind of relationship you want to have, or whether you want to have a relationship and how you might even want to approach somebody. We're really just at the very baby beginnings of figuring out what dogs actually can determine through smell. But everything we have so far suggests that they get a lot of information. And they're so social that it would be kind of foolish for them to have it and not use it.
The study I'm working on now is actually suggesting that part of the getting-to-know-you phase is pretty tense and pretty important and is probably a very important step to getting into a nice positive friendly relationship. But not all dogs are willing to get past that point to get there.
MOLLY BLOOM: So that process is called chemical communication. But do we actually know what the chemicals are that they're smelling?
ANNEKE LISBERG: No. Well, there are different ones. But they do not have names because we haven't figured out what they are yet. So I'm actually working with a chemist right now where we're just starting-- again, just starting to try to figure out if we can isolate them. But one of the challenges with smell is that we don't have-- there are a lot of smells that just seem to be more of like a whole group of signals that were interpreting all together.
And so there isn't always this 1 to 1 ratio of this chemical means this thing. And instead, a lot of what smell is there's this 60 different components. And if you have one of these 10 combinations, then it can mean this.
MADISON MACDONALD: Why do dogs smell human?
ANNEKE LISBERG: They're probably trying to get to know us the same way they'd get to know each other. And for all we know, they're just sitting there going, why and she's sniffing me back? What's wrong with her? We're the ones that are breaking the rules and that relationship.
MOLLY BLOOM: Before she studied dogs, Anneke actually studied insects. And she told us they have a better sense of smell than we do too. In fact, pretty much all animals have a better sense of smell than humans.
MADISON MACDONALD: Whether it's a shark--
MOLLY BLOOM: Or a silk moth.
MADISON MACDONALD: Or a polar bear.
MOLLY BLOOM: Lots of creatures do amazing things thanks to smell. Kind of makes you wonder what we're missing out on.
[MUSIC PLAYING]
SUBJECT 6: (SINGING) Well, the polar bear can smell the seal three feet under ice. When it's meal time, he smells his honey for 100 miles. They say the snake tastes the air with its tongue when it's wet. The elephant can smell rain when it ain't raining yet. It's a stinky, spinning world for every boy and girl.
And every bird that flies by smelling with his beak. The dog wags his tail because you stinky feet. Have you you met the [INAUDIBLE] falling deep in love. With pheromones and particle, he knows she's up above. But when he starts to stagger like a drunk man does, she ask why you love me? Well, he said just because. It's a stinky, spinning world for every boy and girl. And every birds flies by smelling with his beak. Your dog wags its tail 'cause you got stinky feet.
[MUSIC PLAYING]
Well, the great white shark with his big olfactory bulb in the big white water he can smell one drop of blood. With electrolocation, he knows when you're swimming, kid. That's why he's lived much longer there than dinosaurs did. It's a stinky, spinning world for every boy and girl. And every bird the flies by is smelling with its beak. Your dog wags its tail 'cause you get stinky feet.
MOLLY BLOOM: That was a song--
MADISON MACDONALD: Stinky, Spinning World.
MOLLY BLOOM: --by the Dust Bowl revival.
MADISON MACDONALD: Head to our website--
[MUSIC PLAYING] Brainson.org.
MADISON MACDONALD: --to hear it again.
MOLLY BLOOM: While you're there, you can listen to all our past episodes. And speaking of past episodes, we're about to reach our 100th episode. And to mark that occasion, we want to hear from you about your favorite fact you've learned from Brains On!
Was there a fact about elevators or ants or hiccups that stuck out to you? A fact you've shared with your friends or family or teachers or maybe your dog? If so, email it to us. We're at hello@brainson.org. We'll include some of your answers in our 100th episode. And you can send mystery sounds, drawings, and questions to that same email address any time. That's what Leah did when she sent us this question.
LEAH: How do bees make honey?
MOLLY BLOOM: We'll be back with an answer to that question during our Moment of Um at the end of the show. We'll also read the latest group of kids to be added to the Brain's honor roll. Stay tuned.
[MUSIC PLAYING]
I'm Molly Bloom.
MADISON MACDONALD: And I'm Madison McDonald.
MOLLY BLOOM: And you're listening to Brains On! from American Public Media.
MADISON MACDONALD: Today, we're sniffing out what makes dogs' noses so amazing?
MOLLY BLOOM: Now, back to the mystery sound. Maybe you already have a guess. But before we get to the answer, let's hear it again. Ready?
MADISON MACDONALD: Ready.
[CLICKING]
MOLLY BLOOM: Final guess?
MADISON MACDONALD: It still sounds like so many snapping their fingers.
MOLLY BLOOM: Ready for the answer?
MADISON MACDONALD: Yeah.
MOLLY BLOOM: All right, here it is.
LINDA BALL: That was the sound of a clicker. And what a clicker does is it helps us tell the dog that they've done a good job, and that they're going to get a reward. I'm Linda Ball, and I'm the director and founder of Positive Perspectives Assistance Dogs or Paw Pads for short. It's much easier.
And we train assistance dogs for people with physical disabilities, as well as diabetic alert dogs. We call it priming the clicker. And we don't have to do it very much, particularly when they're puppies.
What we do is we go-- where'd my dog go? Breezy. It would sound like this. [CLICKER] Good. Treat. [CLICKER] So we're having them make an association to click means treat. [CLICKER]
MOLLY BLOOM: So what does that have to do with the dog sense of smell? Well, not only can dogs use their noses to find out more about their fellow dogs and find treats they've hidden around the house, they can use their noses to help people.
MADISON MACDONALD: Linda introduce Molly to Breezy.
MOLLY BLOOM: Breezy is learning how to be a diabetes assist dog.
LINDA BALL: Breezy knows upwards of 100 different tasks and commands. Breezy, come. Sit. Sit pretty. Shake. Touch. Down. Roll. Yes, good girl.
MOLLY BLOOM: When someone has diabetes, it means his or her body can't regulate the amount of glucose in their blood very well.
MADISON MACDONALD: Basically, that means they have either too much sugar or too little sugar in their blood.
MOLLY BLOOM: So people with diabetes can put something called insulin into their blood, which helps their cells process the sugar.
MADISON MACDONALD: But since that level is constantly changing, they need to monitor their blood sugar levels.
MOLLY BLOOM: In addition to regular monitoring, diabetes assist dogs like Breezy can help people make sure their blood sugar level doesn't get too high or too low.
MADISON MACDONALD: How do they do that?
MOLLY BLOOM: Well, it turns out dogs can actually tell if someone's blood sugar is low just by the way their breath smells.
LINDA BALL: And then as far as the diabetic alert, I'm going to sneak over here and grab a scent. I just put a low sample. So a person with diabetes who had a blood sugar level of 56 gave us a donation, a sample.
MOLLY BLOOM: So the sample that Linda has is actually a piece of gauze that someone with diabetes has breathed on and then put in a small tube. She puts the sense sample in her pocket when Breezy isn't looking so she doesn't know that it's there.
LINDA BALL: Hi, Breeze.
MOLLY BLOOM: Breezy comes over to Linda immediately and starts sniffing her pocket.
LINDA BALL: Yes! Good girl. So what she did was she came right to me and then just started poking me. That's called the alert. And that's kind of the most important part.
MOLLY BLOOM: When a person's blood sugar is too low or too high, Breezy's been trained to nudge that person on the leg so they to check their blood sugar levels.
LINDA BALL: It's very specific that hey, you should check your blood sugar. Breezy, high or low? Yes.
MOLLY BLOOM: Linda puts her hand out when she asked this question. If the blood sugar level is too low, Breezy will put her paw on top of Linda's hand. If it's too high, she'll nudge the bottom of the palm of her hand with her nose.
LINDA BALL: So then she tells me that's a low sample. And then we also can do-- thank you. Good girl. So I'm going to pretend to pass out. Let's say my blood sugars just went down to too low, too fast. I'm going to pretend to pass out and not give her any feedback.
So we're building a really high-level skill where she has to think, wow, wake up, wake up, wake up. What's the matter? Something's the matter. I better go get help. So, oh, no, I've passed out
[POPPING]
Good girl. Good girl.
MOLLY BLOOM: That popping sound you hear is Breey's nose hitting the microphone as she comes to me for help.
[MUSIC PLAYING]
MADISON MACDONALD: Scientist Anneke Lisberg said that there's still a lot to learn about how dogs can sense things like blood sugar levels just by smelling.
ANNEKE LISBERG: They have a whole separate sense of smell than we do. Because they have a functional vomeronasal system, it's not even like they have a better sense of smell. They have another sense of smell and a better sense of smell.
Again, a lot of what we don't know is there because we haven't thought to ask. It seems like every time there's this big breakthrough. Like, oh, we can use dogs to smell termites in a house. And everyone's so amazed. But probably, if we had better noses, that would be an obvious thing. We just pay so little attention to it that we usually forget to ask.
MOLLY BLOOM: Anneke said part of the problem is since we can't smell any of these things, it's hard for us to understand what's possible. We don't even have the language for it. So let's think about it. If something smells bad, like what words can we use?
MADISON MACDONALD: Hmm. Gross?
MOLLY BLOOM: Yeah. Like, stinky.
MADISON MACDONALD: Yeah.
MOLLY BLOOM: But that's not a lot, and it's not very specific because like stinky eggs, stinky garbage, stinky feet. It's all the same thing. But those are all different smells. So what about if something smells good, what words can we use then?
MADISON MACDONALD: Hmm. I guess, beautiful? It smells beautiful?
MOLLY BLOOM: Yeah, it smells beautiful. It smells good. It smells delicious. But again, those aren't very specific. We don't have a word for how cake smells. We don't have those words. So we just don't have the language. So scientists have to start by looking for the actual chemical components of a scent so we can begin to understand what our noses can't.
ANNEKE LISBERG: It's usually kind of a fluky thing when we figure it out because anecdotally the dogs do something strange, and then we piece it together afterwards. Like, oh, it was probably smell. But it's usually like the last place that we think about. And so it's a whole area where there's just been very little that's been done. We're starting to crack it open enough to realize how little we know, and that's a pretty exciting place to be as a scientist because there's a million directions that you can head from here.
MOLLY BLOOM: So this is really a brand new area that scientists are trying to learn more about. In fact, recent research shows that dogs can sniff out some kinds of cancer. And scientists are trying to figure out how they do that. So they can develop new cancer screening tools.
MADISON MACDONALD: Dog noses are amazing.
MOLLY BLOOM: Compared to dogs, our noses are basically useless.
MADISON MACDONALD: They can breathe and smell at the same time.
MOLLY BLOOM: And they have a second smelling tool that we don't even have.
MADISON MACDONALD: Jacobson's organ.
MOLLY BLOOM: Plus, they can use their smell to find out how other dogs are feeling or where they've been.
MADISON MACDONALD: And scientists are just starting to figure out what we can learn from their amazing noses.
[MUSIC PLAYING]
This episode was produced by Mark Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: Special thanks to Jonathan Shifflett, Alexandra Horowitz, Katherine Bowers, Zach Lupton, Julianne Larson, Colin Campbell, Johnny Vine Evans, Eric [? Wrangham, ?] Marquita [? Fornoughf, ?] Sam Chou, Jen Miller, and April McDonald.
MADISON MACDONALD: Follow us on Instagram and Twitter @Brains_On. And you can find us on Facebook.
MOLLY BLOOM: Now, before we go, it's time for our moment of--
[RANDOM PEOPLE SAYING UM]
LEA HUANG: Hello, my name is Lea [? Huang ?] I'm from Irvine, California. How do bees make honey?
LILA HIGGINS: Bees make honey not for us, but for them. It's their food. My name is Lila Higgins, and I work at the Natural History Museum of Los Angeles County. And I studied bugs when I was in college.
Bees are foragers. They go out and about during the daytime to look for nectar. They bring the neck to back from the flower. They have a special stomach called a honey stomach.
In this honey stomach, they keep the nectar and bring it back to the hive. And they go inside the hive, and then they find one of the hexagonal cells that they're going to put the nectar into. And they regurgitate the nectar. It's kind of like throwing it up. And then they put that droplet of nectar inside the hexagonal cell.
[MUSIC PLAYING]
There's a lot of water in nectar. There's sugar, and there's water. When water is in nectar, it is easy to mold, and it could spoil. Could go bad. So they remove a lot of the water.
And to do that, it's very interesting how they do that. A whole bunch of bees around that cell will flap their wings to help get the air movement over it. And so it starts to evaporate the water out of the honey. And then it gets thicker and thicker.
[MUSIC PLAYING]
And so eventually, there's only about 18% water in honey. So it's gone from really liquidy to really gooey. And then is then stored for the bees to use over the winter and throughout the year when they're looking for a honey snack.
[RANDOM PEOPLE SAYING UM]
MOLLY BLOOM: Now, it's time for me to buzz through this list of names. It's time for the Brain's honor roll. This is how we thank the kids who help us out by sharing their questions, ideas, and mystery sounds with us. Here's the latest group.
[MUSIC PLAYING]
[LISTING HONOR ROLL]
We'll be back soon with more answers to your questions.
MADISON MACDONALD: Thanks for listening!
SUBJECT 4: (SINGING) Ba, ba, ba, ba, ba, ba, ba, ba, ba, ba, ba, brains on.
SUBJECT 1: Brains On is supported in part by a grant from the National Science Foundation.
MOLLY BLOOM: If you have a dog--
MADISON MACDONALD: Or ever seen a dog.
MOLLY BLOOM: You'll know they like to sniff.
MADISON MACDONALD: They sniff the ground.
MOLLY BLOOM: They sniff trees.
MADISON MACDONALD: They smell you.
MOLLY BLOOM: And of course, they even smell each other's butts.
MADISON MACDONALD: Eww.
MOLLY BLOOM: Yeah, let's just say--
MADISON MACDONALD: They smell everything.
But why?
MOLLY BLOOM: We're going to find out right now. Keep listening.
SUBJECT 2: Brains On!
MOLLY BLOOM: You're listening to Brains On from American Public Media. I'm Molly Bloom, and my co-host today is 12-year-old Madison MacDonald. Hi, Madison.
MADISON MACDONALD: Hey, Molly.
MOLLY BLOOM: Now when we first started talking about what questions you had about dogs, you wanted to know about why dogs smell each other and us. So what got you thinking about that?
MADISON MACDONALD: Well, I have a dog of my own, and I been wondering, why does he smell the ground, why does he smell other dogs' butts, why does he smell trees.
MOLLY BLOOM: Right. There always smelling everything.
MADISON MACDONALD: Right.
MOLLY BLOOM: What's your dog's name?
MADISON MACDONALD: My dog's name is Cody.
MOLLY BLOOM: And what kind of dog is he?
MADISON MACDONALD: He's a Siberian husky.
MOLLY BLOOM: And why do you think he smells you?
MADISON MACDONALD: So he knows that we're part of his family, not just random strangers in his house.
MOLLY BLOOM: The first part of the answer to why dogs like to smell everything is that they can smell so much more than we can. It's hard for us to even understand it because it's so different than our sense of smell. First, we're going to dig into the hardware that makes that possible.
MADISON MACDONALD: Dog noses can be long.
MOLLY BLOOM: They can be short.
MADISON MACDONALD: They're usually wet.
MOLLY BLOOM: But not always.
MADISON MACDONALD: They're always cute, though.
MOLLY BLOOM: Yeah, they're pretty darn cute. But they're also amazing sniffing tools as our pal Sanden Totten explains.
SANDEN TOTTEN: Think about it this way. If noses were vehicles, dogs have a race car.
[RACE CAR]
And humans have a tricycle with a broken wheel. It's not just that dogs' noses tend to be longer. They also have a lot more scent receptors. These are cells in the nose that detect smells. Now those smells come in through the nose in the form of tiny molecules in the air. These could be bits of flowers, or food, or whatever. The scent receptors in the nose grab on to these molecules in the air.
SUBJECT 3: Gotcha.
SANDEN TOTTEN: They check them out.
SUBJECT 3: Let's see what we have here.
SANDEN TOTTEN: And then these scent receptors send a message to your brain, letting you know what it is that you're smelling.
SUBJECT 3: He's sniffing stinky cheese, everybody. Stinky cheese.
SUBJECT 4: Hmm.
SANDEN TOTTEN: All of that happens in your nose when you smell something. Cool stuff. But think about this. Madison, Molly, and all the rest of us humans, we have about five million scent receptors. Sounds like a lot, right? But dogs, dogs can have more than 200 million in their snouts. So humans, 5 million. Dogs, 200 million.
So what does this mean in real smelling terms? Let's take our pal, Bob.
BOB: Hello.
SANDEN TOTTEN: And a dog.
DOG: Woof, woof.
SANDEN TOTTEN: Now say we give Bob a cup of coffee.
BOB: Oh, thanks.
SANDEN TOTTEN: He might be able to smell if there's a teaspoon of brown sugar in the coffee.
[SNIFFS]
BOB: Smells like sweetener I think.
SANDEN TOTTEN: The dog could detect that teeny tiny teaspoon of brown sugar even if it was poured into a pool filled with 1 million gallons of water. For those of you doing the math at home, that's 16 million cups of water.
DOG: Yup. There's sugar in there.
SANDEN TOTTEN: Dogs can also control each nostril independently. And if a tiny trace of a smell enters one side of the nose but not the other, a dog can figure that out. So a dog theoretically could tell if the sugar was dropped into the left side of the pool or the right side of the pool.
DOG: It's to the left.
BOB: I just smell chlorine.
SANDEN TOTTEN: Cool fact, dogs also have front nostrils for breathing in and side nostrils for breathing out. That way the stuff they exhale doesn't blow away the stuff they're inhaling, which means a dog can sniff almost continuously.
DOG: I also smell sunscreen, bathing suits, snorkels, goggles.
BOB: Well, I can see all that.
DOG: Also I smell a little pee in the pool, just warning you.
BOB: Ehh.
SANDEN TOTTEN: One more thing, dogs have a really powerful second smelling tool called the vomeronasal organ.
BOB: Vomero-- numero-- what?
SANDEN TOTTEN: The vomeronasal organ is also called the Jacobson's organ which is much easier to remember. Humans don't really have a working version of this, but many other animals do like pigs, hamsters, and snakes. This bit of nose technology is designed especially to pick up body scents called pheromones.
Pheromones are smells animals give off to let others in their species know how they're feeling, like whether they're alarmed, angry, or in the mood for love. So while Bob might sniff princess the poodle here and say--
BOB: Well, that smells like a dog, all right. I definitely know that's a dog smell.
SANDEN TOTTEN: Our dog friend would whiff princess using his Jacobson's organ and think--
DOG: Oh my princess had a really good day. She's calm, happy, and oh, hey, up for date later maybe?
PRINCESS: A woof, woof.
DOG: Well, then I'll meet you at the dog park around 7:00.
[DOGS BARKING]
BOB: The dog smelled all that?
SANDEN TOTTEN: Yes, because dogs are awesome at smelling. They have more receptors, amazing nostrils skills, and a whole other organ just for sniffing pheromones. Back to you Molly and Madison.
[MUSIC PLAYING]
MOLLY BLOOM: All right, Madison. So what did you think of that? Was there anything in there that you found surprising or particularly interesting?
MADISON MACDONALD: I found like when dogs can smell their behavior, like how the dogs smell the other dog, how the first dog smelled like, hey, she's calm, hey, she's happy, hey.
[LAUGHS]
MOLLY BLOOM: Yeah. It's kind of amazing they can learn all that just by smelling. We can't tell that about humans by smelling them.
MADISON MACDONALD: No.
MOLLY BLOOM: At all. Kind of wish you could sometimes, though.
MADISON MACDONALD: Yeah.
MOLLY BLOOM: While we can sit and wish our sense of smell was just a little bit better, how about we put another sense to the test? Your sense of hearing. Are you ready?
MADISON MACDONALD: Yeah.
MOLLY BLOOM: It's time for the mystery sound.
[WEIRD SOUND]
SUBJECT 5: Mystery sound.
MOLLY BLOOM: Here it is.
[CLICKS]
That's a quick one. So let's hear it again.
[CLICKS]
Any guesses?
MADISON MACDONALD: It sounds like somebody is snapping their fingers to get something's attention, like a dog.
MOLLY BLOOM: That's a very good guess. We're going to give you and our listeners a little more time to think about it. But in the meantime, let's get down to why dogs are smelling each other.
MADISON MACDONALD: We talked with Anneke Lisberg from University of Wisconsin-Whitewater.
MOLLY BLOOM: She's an ethologist.
MADISON MACDONALD: That means she studies animal behavior.
MOLLY BLOOM: And we got right to the subject at hand.
MADISON MACDONALD: I asked, why did dogs smell each other's butts?
ANNEKE LISBERG: So the reason that the dogs are sniffing urine marks and sniffing each other's butts when they're getting to know each other is they're getting a lot of information about who that dog is, where they came from, what they're doing right now in a very little bit of time. And then they can use that information potentially to have a nice smooth social introduction with each other without major faux pas.
So I think it's a lot sort of scoping someone out online, and that you get not just one piece of information but a lot of really detailed information. And then you can use that to kind of decide what kind of relationship you want to have, or whether you want to have a relationship and how you might even want to approach somebody. We're really just at the very baby beginnings of figuring out what dogs actually can determine through smell. But everything we have so far suggests that they get a lot of information. And they're so social that it would be kind of foolish for them to have it and not use it.
The study I'm working on now is actually suggesting that part of the getting-to-know-you phase is pretty tense and pretty important and is probably a very important step to getting into a nice positive friendly relationship. But not all dogs are willing to get past that point to get there.
MOLLY BLOOM: So that process is called chemical communication. But do we actually know what the chemicals are that they're smelling?
ANNEKE LISBERG: No. Well, there are different ones. But they do not have names because we haven't figured out what they are yet. So I'm actually working with a chemist right now where we're just starting-- again, just starting to try to figure out if we can isolate them. But one of the challenges with smell is that we don't have-- there are a lot of smells that just seem to be more of like a whole group of signals that were interpreting all together.
And so there isn't always this 1 to 1 ratio of this chemical means this thing. And instead, a lot of what smell is there's this 60 different components. And if you have one of these 10 combinations, then it can mean this.
MADISON MACDONALD: Why do dogs smell human?
ANNEKE LISBERG: They're probably trying to get to know us the same way they'd get to know each other. And for all we know, they're just sitting there going, why and she's sniffing me back? What's wrong with her? We're the ones that are breaking the rules and that relationship.
MOLLY BLOOM: Before she studied dogs, Anneke actually studied insects. And she told us they have a better sense of smell than we do too. In fact, pretty much all animals have a better sense of smell than humans.
MADISON MACDONALD: Whether it's a shark--
MOLLY BLOOM: Or a silk moth.
MADISON MACDONALD: Or a polar bear.
MOLLY BLOOM: Lots of creatures do amazing things thanks to smell. Kind of makes you wonder what we're missing out on.
[MUSIC PLAYING]
SUBJECT 6: (SINGING) Well, the polar bear can smell the seal three feet under ice. When it's meal time, he smells his honey for 100 miles. They say the snake tastes the air with its tongue when it's wet. The elephant can smell rain when it ain't raining yet. It's a stinky, spinning world for every boy and girl.
And every bird that flies by smelling with his beak. The dog wags his tail because you stinky feet. Have you you met the [INAUDIBLE] falling deep in love. With pheromones and particle, he knows she's up above. But when he starts to stagger like a drunk man does, she ask why you love me? Well, he said just because. It's a stinky, spinning world for every boy and girl. And every birds flies by smelling with his beak. Your dog wags its tail 'cause you got stinky feet.
[MUSIC PLAYING]
Well, the great white shark with his big olfactory bulb in the big white water he can smell one drop of blood. With electrolocation, he knows when you're swimming, kid. That's why he's lived much longer there than dinosaurs did. It's a stinky, spinning world for every boy and girl. And every bird the flies by is smelling with its beak. Your dog wags its tail 'cause you get stinky feet.
MOLLY BLOOM: That was a song--
MADISON MACDONALD: Stinky, Spinning World.
MOLLY BLOOM: --by the Dust Bowl revival.
MADISON MACDONALD: Head to our website--
[MUSIC PLAYING] Brainson.org.
MADISON MACDONALD: --to hear it again.
MOLLY BLOOM: While you're there, you can listen to all our past episodes. And speaking of past episodes, we're about to reach our 100th episode. And to mark that occasion, we want to hear from you about your favorite fact you've learned from Brains On!
Was there a fact about elevators or ants or hiccups that stuck out to you? A fact you've shared with your friends or family or teachers or maybe your dog? If so, email it to us. We're at hello@brainson.org. We'll include some of your answers in our 100th episode. And you can send mystery sounds, drawings, and questions to that same email address any time. That's what Leah did when she sent us this question.
LEAH: How do bees make honey?
MOLLY BLOOM: We'll be back with an answer to that question during our Moment of Um at the end of the show. We'll also read the latest group of kids to be added to the Brain's honor roll. Stay tuned.
[MUSIC PLAYING]
I'm Molly Bloom.
MADISON MACDONALD: And I'm Madison McDonald.
MOLLY BLOOM: And you're listening to Brains On! from American Public Media.
MADISON MACDONALD: Today, we're sniffing out what makes dogs' noses so amazing?
MOLLY BLOOM: Now, back to the mystery sound. Maybe you already have a guess. But before we get to the answer, let's hear it again. Ready?
MADISON MACDONALD: Ready.
[CLICKING]
MOLLY BLOOM: Final guess?
MADISON MACDONALD: It still sounds like so many snapping their fingers.
MOLLY BLOOM: Ready for the answer?
MADISON MACDONALD: Yeah.
MOLLY BLOOM: All right, here it is.
LINDA BALL: That was the sound of a clicker. And what a clicker does is it helps us tell the dog that they've done a good job, and that they're going to get a reward. I'm Linda Ball, and I'm the director and founder of Positive Perspectives Assistance Dogs or Paw Pads for short. It's much easier.
And we train assistance dogs for people with physical disabilities, as well as diabetic alert dogs. We call it priming the clicker. And we don't have to do it very much, particularly when they're puppies.
What we do is we go-- where'd my dog go? Breezy. It would sound like this. [CLICKER] Good. Treat. [CLICKER] So we're having them make an association to click means treat. [CLICKER]
MOLLY BLOOM: So what does that have to do with the dog sense of smell? Well, not only can dogs use their noses to find out more about their fellow dogs and find treats they've hidden around the house, they can use their noses to help people.
MADISON MACDONALD: Linda introduce Molly to Breezy.
MOLLY BLOOM: Breezy is learning how to be a diabetes assist dog.
LINDA BALL: Breezy knows upwards of 100 different tasks and commands. Breezy, come. Sit. Sit pretty. Shake. Touch. Down. Roll. Yes, good girl.
MOLLY BLOOM: When someone has diabetes, it means his or her body can't regulate the amount of glucose in their blood very well.
MADISON MACDONALD: Basically, that means they have either too much sugar or too little sugar in their blood.
MOLLY BLOOM: So people with diabetes can put something called insulin into their blood, which helps their cells process the sugar.
MADISON MACDONALD: But since that level is constantly changing, they need to monitor their blood sugar levels.
MOLLY BLOOM: In addition to regular monitoring, diabetes assist dogs like Breezy can help people make sure their blood sugar level doesn't get too high or too low.
MADISON MACDONALD: How do they do that?
MOLLY BLOOM: Well, it turns out dogs can actually tell if someone's blood sugar is low just by the way their breath smells.
LINDA BALL: And then as far as the diabetic alert, I'm going to sneak over here and grab a scent. I just put a low sample. So a person with diabetes who had a blood sugar level of 56 gave us a donation, a sample.
MOLLY BLOOM: So the sample that Linda has is actually a piece of gauze that someone with diabetes has breathed on and then put in a small tube. She puts the sense sample in her pocket when Breezy isn't looking so she doesn't know that it's there.
LINDA BALL: Hi, Breeze.
MOLLY BLOOM: Breezy comes over to Linda immediately and starts sniffing her pocket.
LINDA BALL: Yes! Good girl. So what she did was she came right to me and then just started poking me. That's called the alert. And that's kind of the most important part.
MOLLY BLOOM: When a person's blood sugar is too low or too high, Breezy's been trained to nudge that person on the leg so they to check their blood sugar levels.
LINDA BALL: It's very specific that hey, you should check your blood sugar. Breezy, high or low? Yes.
MOLLY BLOOM: Linda puts her hand out when she asked this question. If the blood sugar level is too low, Breezy will put her paw on top of Linda's hand. If it's too high, she'll nudge the bottom of the palm of her hand with her nose.
LINDA BALL: So then she tells me that's a low sample. And then we also can do-- thank you. Good girl. So I'm going to pretend to pass out. Let's say my blood sugars just went down to too low, too fast. I'm going to pretend to pass out and not give her any feedback.
So we're building a really high-level skill where she has to think, wow, wake up, wake up, wake up. What's the matter? Something's the matter. I better go get help. So, oh, no, I've passed out
[POPPING]
Good girl. Good girl.
MOLLY BLOOM: That popping sound you hear is Breey's nose hitting the microphone as she comes to me for help.
[MUSIC PLAYING]
MADISON MACDONALD: Scientist Anneke Lisberg said that there's still a lot to learn about how dogs can sense things like blood sugar levels just by smelling.
ANNEKE LISBERG: They have a whole separate sense of smell than we do. Because they have a functional vomeronasal system, it's not even like they have a better sense of smell. They have another sense of smell and a better sense of smell.
Again, a lot of what we don't know is there because we haven't thought to ask. It seems like every time there's this big breakthrough. Like, oh, we can use dogs to smell termites in a house. And everyone's so amazed. But probably, if we had better noses, that would be an obvious thing. We just pay so little attention to it that we usually forget to ask.
MOLLY BLOOM: Anneke said part of the problem is since we can't smell any of these things, it's hard for us to understand what's possible. We don't even have the language for it. So let's think about it. If something smells bad, like what words can we use?
MADISON MACDONALD: Hmm. Gross?
MOLLY BLOOM: Yeah. Like, stinky.
MADISON MACDONALD: Yeah.
MOLLY BLOOM: But that's not a lot, and it's not very specific because like stinky eggs, stinky garbage, stinky feet. It's all the same thing. But those are all different smells. So what about if something smells good, what words can we use then?
MADISON MACDONALD: Hmm. I guess, beautiful? It smells beautiful?
MOLLY BLOOM: Yeah, it smells beautiful. It smells good. It smells delicious. But again, those aren't very specific. We don't have a word for how cake smells. We don't have those words. So we just don't have the language. So scientists have to start by looking for the actual chemical components of a scent so we can begin to understand what our noses can't.
ANNEKE LISBERG: It's usually kind of a fluky thing when we figure it out because anecdotally the dogs do something strange, and then we piece it together afterwards. Like, oh, it was probably smell. But it's usually like the last place that we think about. And so it's a whole area where there's just been very little that's been done. We're starting to crack it open enough to realize how little we know, and that's a pretty exciting place to be as a scientist because there's a million directions that you can head from here.
MOLLY BLOOM: So this is really a brand new area that scientists are trying to learn more about. In fact, recent research shows that dogs can sniff out some kinds of cancer. And scientists are trying to figure out how they do that. So they can develop new cancer screening tools.
MADISON MACDONALD: Dog noses are amazing.
MOLLY BLOOM: Compared to dogs, our noses are basically useless.
MADISON MACDONALD: They can breathe and smell at the same time.
MOLLY BLOOM: And they have a second smelling tool that we don't even have.
MADISON MACDONALD: Jacobson's organ.
MOLLY BLOOM: Plus, they can use their smell to find out how other dogs are feeling or where they've been.
MADISON MACDONALD: And scientists are just starting to figure out what we can learn from their amazing noses.
[MUSIC PLAYING]
This episode was produced by Mark Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: Special thanks to Jonathan Shifflett, Alexandra Horowitz, Katherine Bowers, Zach Lupton, Julianne Larson, Colin Campbell, Johnny Vine Evans, Eric [? Wrangham, ?] Marquita [? Fornoughf, ?] Sam Chou, Jen Miller, and April McDonald.
MADISON MACDONALD: Follow us on Instagram and Twitter @Brains_On. And you can find us on Facebook.
MOLLY BLOOM: Now, before we go, it's time for our moment of--
[RANDOM PEOPLE SAYING UM]
LEA HUANG: Hello, my name is Lea [? Huang ?] I'm from Irvine, California. How do bees make honey?
LILA HIGGINS: Bees make honey not for us, but for them. It's their food. My name is Lila Higgins, and I work at the Natural History Museum of Los Angeles County. And I studied bugs when I was in college.
Bees are foragers. They go out and about during the daytime to look for nectar. They bring the neck to back from the flower. They have a special stomach called a honey stomach.
In this honey stomach, they keep the nectar and bring it back to the hive. And they go inside the hive, and then they find one of the hexagonal cells that they're going to put the nectar into. And they regurgitate the nectar. It's kind of like throwing it up. And then they put that droplet of nectar inside the hexagonal cell.
[MUSIC PLAYING]
There's a lot of water in nectar. There's sugar, and there's water. When water is in nectar, it is easy to mold, and it could spoil. Could go bad. So they remove a lot of the water.
And to do that, it's very interesting how they do that. A whole bunch of bees around that cell will flap their wings to help get the air movement over it. And so it starts to evaporate the water out of the honey. And then it gets thicker and thicker.
[MUSIC PLAYING]
And so eventually, there's only about 18% water in honey. So it's gone from really liquidy to really gooey. And then is then stored for the bees to use over the winter and throughout the year when they're looking for a honey snack.
[RANDOM PEOPLE SAYING UM]
MOLLY BLOOM: Now, it's time for me to buzz through this list of names. It's time for the Brain's honor roll. This is how we thank the kids who help us out by sharing their questions, ideas, and mystery sounds with us. Here's the latest group.
[MUSIC PLAYING]
[LISTING HONOR ROLL]
We'll be back soon with more answers to your questions.
MADISON MACDONALD: Thanks for listening!
SUBJECT 4: (SINGING) Ba, ba, ba, ba, ba, ba, ba, ba, ba, ba, ba, brains on.
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