How to Smell like a Dog, with Ed Yong

0:00I did get hit by a mantis shrimp, which has the most powerful punch in nature. This was a very, very small mantis shrimp, and it still hurt. Do-do-do, science chats with our favourite nerds. Yeah. Hi, I'm Wendy Zukerman, and you're listening to Science Versus. today on the show, the amazing superpowers of animals. Some animals can see things that we can't see. They can hear things that we can't hear, touch things that we will never feel. And so today on the show, we are diving into their world to talk about the groundbreaking science of how animals perceive. And to go on this journey, we'll be chatting to Ed Young.

0:53He's a Pulitzer Prize winning science writer. And we'll be talking about his book, An Immense World, How Animal Senses Reveal the Hidden Realms Around It. And I think you're going to love this chat. You are going to look at your dog in a totally different light by the end of this chat. You're going to appreciate how eyes have literally painted the world. And you may even feel sorry for the humble cockroach. If you are listening to this on Spotify, you can also be watching it because it's on video. Hello. My interview with Ed Young is coming up just after the break.

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2:47welcome back today on the show the wonderful ed young hi ed welcome to the show hello yeah thanks for having me in your book you you say that sort of regardless of our technology or intellect we are really perceiving only a thin fraction of all there is to perceive our sense of the world is an illusion. So tell me more about that. Every creature has its own particular ways of sensing the world, its own set of sights and sounds and smells and textures that it has access to. So we're all trapped in our own little sensory bubbles. And there is a wonderful word for such a bubble. That word is Umwelt.

3:32It's just German for environment, but it has a very special meaning in this context. And it's one of my favourite ideas in all of biology, because it tells us that no matter where we are, and no matter which kind of living thing we are, we really are only experiencing a tiny fraction of all there is to experience. It's such a lovely idea as we're walking around in the world to think about what else is there? What else could I be seeing or perceiving if I was a different animal? Yeah, I agree. I think it means that there's so much wonder to be had everywhere. If you dive into water, depending on the part of the world you're in, You might be surrounded by the electric fields generated by fish that can make their own electricity.

4:32You'll be surrounded by turbulent currents that are left behind by swimming animals that you won't be able to feel. You'll be suffused by the magnetic field of the Earth itself, which you won't be able to detect. There's all of this stuff, all these signals around us that we don't perceive and that other animals do. Electric fish can detect each other's signals. Seals can detect the tracks left behind by swimming fish. Sea turtles can detect the magnetic fields of the Earth itself. Yeah. And now I want to move through some of the senses. And one of the things that perhaps we get wrong about ourselves, which is the sense of smell.

5:16I think we have this idea that humans don't have a great sense of smell. I think this sort of evolutionary chit-chat that you hear, this sort of story I guess I've heard since primary school is like, now we are visual creatures and we don't really use our smell. It's been thrown off to the side. But is that entirely true? How bad is a human's sense of smell? Yeah, it's actually all right. I'm not going to tell you that our sense of smell is as good as, say, an elephant's or a dog's. They have hardware that we don't have. Humans really aren't too bad at it. Like we have decent noses. We can smell a lot of different kinds of chemicals.

6:02We can detect some of them at concentrations that rival championships like dogs. And in your book, you did a fun experiment involving getting on all fours. Tell me about it. Yes. So I went to see a woman named Alexandra Horowitz who studies dogs, dog cognition, a dog's sense of smell. She got a length of string that had been scented with chocolate and she laid it on the floor. And my task was to, with a blindfold on, follow the path of the string. so i got down in all fours and i sniffed at the string and i did basically what a dog does which is to swing your head left and right while you're sniffing um and by doing this you can follow the path of the string and i did but um two things first it took a long time uh and second i was hyperventilating as i was doing it because i am not like we are not used to just going right because our the the way our noses work um every time you blow every time you exhale you lose that perception of whatever you're smelling right so you have to just repeatedly if you're doing that many times in a row you start it's not good a dog you know and then why doesn't that happen to dogs why could dogs keep going So dogs can do it for a bunch of different reasons.

7:39And Alexandra's dog Finn did the same task, followed the string much more accurately, much more quickly. He was doing it in fractions of a second in what took me many minutes and with no effort. He does that for a couple of reasons. So when a dog breathes in, that airstream is cleaved into two by structures inside its skull. So there's a large stream of air that goes down into the lungs and is for breathing. And then there is another smaller stream that goes to a chamber in the back of a snout that is dedicated for smell and smell alone. So there's this constant influx of scented air into the part of the dog's head that is responsible for processing smell.

8:23That's not what happens in us. The dog, it's just getting this constant conveyor belt of scented air going into its nose, whether it's on the inhale or the exhale. And again, that means that its experience of smell is not this strobing, flickering thing that I am having to fight against. It's continuous. I like to think of it as closer to our experience of vision, where we have, even though we're blinking all the time, our view of the world doesn't black out. It's smooth, it's continuous. And why do they love the smell of a human crotch?

9:05What? I think, so I think that is also related to how dogs interact with each other, right? So what happens when two dogs meet? They sniff each other, right? And they sniff each other usually in the groin. They'll do that like cool yin-yang thing where they're both sniffing each other's groins. And that's because all animals, to various degree, are just leaking sacks of chemicals, right? We are just like spewing chemicals into the world around us all the time, whether we like it or not. And we do it especially, you know, from like moist membranes more than other places. So like our breath, our groins, armpits.

9:59And for us, as we've said, we don't go around sniffing each other in any of these areas. Dogs do, because to them, smell provides many clues about the individual that they're meeting. Right. Smell provides clues about identity, but also about things like age, health, diet. Now, tell me about this remarkable chemical that gives a sea smell, like the smell of the sea. Yeah. So this chemical is called dimethyl sulfide or DMS. It smells kind of seaweed-y, a little oyster-y. It's the smell of the sea. um we've talked about how there's been this long standing myth that human sense of smell is terrible equally there has been this very long standing myth that birds uh do not smell at all um it's a lie um birds do smell uh many of them smell very very well and seabirds like arbitroses are some of them um dms is one of the things that they are paying attention to So when there's a ton of creole munching down on a ton of plankton under the surface of the water, when there's just a lot of life out there, that releases a ton of DMS.

11:16It's so cool. It's like an oven with cookies baking. Yes, exactly like that. Exactly like that. And to a bird with a right nose, like an albatross, the scent of DMS reveals the parts of the ocean that are richest in life and so richest in food. What I love about this is that the ocean seems completely featureless to us. The open ocean is just this flat landscape. It's two-dimensional. It looks kind of boring. That is what it looks like to our eyes. But to the nose of an albatross foraging over the ocean, it's very three-dimensional. It has these mountains and valleys of DMS and other scents that give the bird an idea of what's going on beneath the surface of the water.

12:15It's not flat. It's not featureless. And it only is that way to our umbelt, but not those of a bird like an albatross. From smell to sight. So the amazingness of the human eye is often used by creationists to say that God must have created the world because evolution can't create such a complex structure. And as you write in the book, Darwin himself wasn't sure how complicated human eyes could have evolved. And writing in The Origin of Species that to suppose the eye had been formed, quote, by natural selection seems, I freely confess, absurd in the highest possible degree. But he did say as well that if we could find other versions of the eye, like sort of crappier gradations, Like if we could see the sort of beginnings of the human eye and then in other animals, maybe that would suggest it was evolution, which is sort of funny because that's how the pyramids are.

13:18People see the beautiful pyramids of Giza, but there's crappier ones down the road. They see the pyramids and they're like, aliens must have done it. And it's like, well, it's because you didn't see the crappier ones that they went before they perfected it. That's right. Like the beta test pyramids before we landed on this deluxe model. Yeah, right. Right. So when you look through the animal queendom, do you see variations of what might become the human eye? Yeah, you absolutely do. And Darwin can relax. We have it sorted. So yeah, there are actually animals with every possible degree of eye. The simplest eye really is just a single photoreceptor.

14:06So it's a single cell that is sensitive to light where light triggers a chemical change in the cell which leads to an electrical signal being sent. And that cell can detect the presence of light. Once you're sensitive to light, once you can detect it, then you can add things like a little bit of pigment. If you have pigment on one side, it creates shade. And now you can not only detect light, but work out where it's coming from. When you have lots of those clustered together, then not only can you detect where light is coming from, but you now start to have the very rudimentary image, like with very few pixels, but an image nonetheless.

14:47Then you can add an element on top of that, a lens that helps to focus the light to give you extra acuity. The point is that you can actually very easily see how an eye can build up over time from something that is really unlike an eye at all, that doesn't take a lot of generations to actually happen. And we have organisms that have every possible step along the way. And I think it also, actually, animals get the kinds of sense organs they need. And eyes that are, you know, quote unquote, worse than ours, exist because their owners don't need to do anything fancier. An eagle has an incredible eye because an eagle is soaring at great heights and trying to detect rabbits at large distances.

15:43A starfish has a considerably worse eye because a starfish is not doing that. All a starfish needs to do is to find the shady shelter of a reef and scuttle into some crevice somewhere. I don't want to fall into that trap of to say that we are at the top of some evolutionary pinnacle. It's all just a beautiful rainbow. Sure, yeah. And then when we, just to really land the point that, you know, humans are not at the pinnacle of the eye evolutionary story, when we think of colour, humans can, you know, most humans can see the colours of the rainbow, but lots of animals can see an ultraviolet light, So beyond the purple or violet.

16:28Right. Can you help us imagine the world of ultraviolet light, whether it's how our world would look different for birds and flowers? Yeah, so flowers are a great place to start. So many flowers have evolved to attract animals like bees and hummingbirds and other pollinators, almost all of which can see ultraviolet. And if you can see ultraviolet, you can see many signals on flowers that humanize mists. So sunflowers, for example, just look yellow to us, but they have this beautiful ultraviolet halo in the middle of them. Many other flowers have things like this, these like bull's eyes and like landing strips.

17:14I think of them as signs that attract pollinators to the flower. Birds also, you know, all birds can see ultraviolet to a different extent. And if you can see ultraviolet, you can see patterns on the feathers of birds that, again, our eyes miss. um here in the u.s the american robin has a famously red um breast uh males and females both have red breasts the sexes are a little bit hard to tell apart um in this bird uh but to us the birds have no problem because the male's breast blazes with ultraviolet as well as red the females does not so robins can easily tell them apart tell each other apart and then um that's just you know ultraviolet as color in and of itself um you can also blend ultraviolet with other colors so um our most most people have eyes with three kinds of color color sensing cells let's call them um they're called cone cells and they're the ones responsible for our our color vision um and uh my dog has only two um so his rainbow is much more limited than mine birds have four um so their rainbows are are just so much more expansive um a typical bird can probably see about a hundred times more colors than what we can perceive um which is just stunning to me because so many birds are already just shockingly colorful and beautiful like take the most colorful bird that you can imagine and now try and imagine that that bird has you know maybe a hundred times more colors on it that to another bird than what you are currently seeing it's amazing it's like stop it at that point you're like stop it you know i know Oh, right, like enough, please.

19:14Yeah. Did you have to wear that to the Met Gala? Like did you, you know. So now let's look at sounds and hearing. In the 1960s, researchers got hold of this amazing recording of an animal that ultimately became this huge cultural phenomenon inspiring a Star Trek movie, also an entire animal rights movement. Can you tell me about this? Yeah, so we're talking about whales.

19:52And we're talking about the really big whales too. So things like blue whales, fin whales, the largest animals that exist and have ever existed. They communicate with each other with infrasound. So that's sound that's too low for the human ear to detect and sound that travels over very, very, very large distances. In the ocean, a blue whale's call could conceivably traverse the entire span of, say, the Atlantic. Which is crazy to think about. It is absolutely crazy. So there were definitely cases where you could have a whale calling off the coast of Europe and detect that call with a hydrophone, an underwater microphone, off the coast of the US.

20:43When the Navy first picked up these kinds of sounds, they were, you know, they didn't know what to make of them. and eventually they tracked the sounds to their sources which were very large whales like blue and fin whales i think it's still an open question of whether whales are really communicating over those kinds of distances right so you know is a whale off the coast of europe having a chat with a whale off the coast of the u.s it seems like implausible right those messages would take maybe half an hour or so to move across that distance um but maybe another animal superpower that you talk about is echolocation which is this amazing ability of bats and dolphins to use echo to find their way and their prey but in the book you met a person who can echolocate tell us about that Yeah, so his name is Daniel Kish.

21:50He is one of several human echolocators. So he is blind and he has been blind since very close to his first birthday. And he navigates through the world with a cane, as many blind people do, but also by making these very loud clicks with his tongue. so if I try to click with my tongue the noise is kind of pathetic and wet and muffled his is like much closer to me snapping with my fingers it's sharp, it's loud produces a very strong echo he does this as he moves about his neighbourhood and I went on a walk with him and Daniel is incredibly independent the cane helps of course but with his echolocation he can tell when we're walking past a house, a car a lawn You know, whether there's a fence next to us.

22:43A lawn? How would he just from, it sounds a little different. The texture of the grass is different from the texture of concrete or texture of pavement. He can tell, you know, when there's a tree, a branch blocking his path. You know, a fence, he can tell whether it's like chain link or slatted. Were you walking with him and testing him? No, no, no, he's just narrating. Like, you know, I'm just walking along, he's narrating. At some point, there's a branch across our path and I duck and I forget to say, hey, Daniel, there's a branch. And he gets it, like he knows. The word echolocation was actually defined in a paper that was about bats and humans.

23:30And everyone kind of forgot the human bits and the human bits. And, you know, a lot of people know that bats can do this. So what bats are doing is that they are releasing very, very high-pitched ultrasonic calls, too high for us to hear. They're doing it at often incredible speeds, up to a couple of hundred times a second. And they're listening for those echoes bouncing off objects in the world around them. And by timing how long it takes for the sound to go out and to return, the bat can translate that time into distance. Amazing. Daniel is basically doing exactly the same thing. His clicks are not ultrasonic like those of a bat.

24:13So they provide a little less information to him. But it's basically the same thing. He is using the timing of rebounding sound to map the world around him. How did it feel to be walking with him? So it felt amazing. it is very easy to watch Daniel and to think of this as some kind of superpower but like every way of sensing the world it has some strengths and it has drawbacks too it's really bad for anything that involves a small thing against a large thing so if I wanted to hide from Daniel I would stand right up against a wall and the thing is bats also suffer from this problem bats really can easily detect a moth in air.

25:06But if the moth is sitting on a leaf, most bats will really struggle to find it. So one of my favourite stories that Daniel told me is that he was once asked to try and tell the difference between two objects that to him sounded exactly the same. One was a stuffed bear, like a teddy bear, and the other was a champagne bottle. and those obviously look different to us but they both distort and muffle echoes in different ways. So the champagne bottle has all these curves to it which send the sound bouncing off in random directions. The teddy bear is very soft and fluffy so it's absorbing and like doing the same kinds of things to the sound.

25:51So both of those are returning very bad, uninformative echoes. So they basically sound kind of the same. After the break, how an impeccable sense of touch can help turn a cockroach into a zombie.

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28:32Welcome back. I'm here with Pulitzer Prize winning science writer Ed Yong. Then on to touch. So animals use touch and vibrations in all sorts of exciting ways. But I think one of my favorites from your book was the emerald jewel wasp, which when I saw a picture of it, it's a gorgeous wasp. Oh, it's stunning. Inch long, metallic turquoise body. It looks like it's wearing orange bike shorts, kind of. Yes, yes, it does. I mean, the metallic green and orange combo is really working for us. I also want that combo. It's a combo I'm not sure I could get away with, but it's, yeah. No, right. So tell us how she uses touch.

29:18The emerald cockroach wasp is a parasite that lays eggs inside the bodies of still living cockroaches. The young wasp hatches from those eggs and then basically eats the cockroach alive. Right. So nom, nom, nom. It turns into an adult wasp. It bursts out. It flies away. It finds its own cockroach. The horrible cycle repeats. it's it's a special kind of parasite because it also manipulates the mind and the behavior of its host so the wasp's sting not only lays an egg but it also delivers venom to the cockroach's brain that changes its behavior it makes it very docile um and uh you know we all know when cockroaches are threatened they run away very easily but um once stung the cockroach becomes very very amenable um so the wasp actually grabs it by its antennae and leads it to its nest like a person walking a dog it really does we actually have a video and it really does look like it's just walking this cockroach is meant it's a lot bigger than the wasp like a dog it's It's crazy.

30:31It's wild. It really does. Now, where touch comes in is how do you, how does the wasp know where to inject venom, right? So it's got, it's stung the cockroach. The tip of the sting is full of touch sensors. So the sting not only is an egg laying tube and a drill, but it's also kind of like a hand, right? It's an organ of touch. And the wasp can detect the texture, the shape maybe, of a cockroach brain and uses that as a cue. So it'll go in, like it sees the head, goes in through the carapace. That's right, yeah. But then it has to feel for the little brain, right, because it has to sting the brain.

31:28Yeah, yeah. Yeah, you know, and there have been some great experiments showing that it's doing this by replacing a cockroach brain with like stuff that feels very different, stuff that feels like a fake brain and seeing what the wasps do. So, yeah, the wasp is absolutely using its sense of touch to feel for the distinctive feel of a cockroach brain. And then one of the last senses I want to look at is pain that you talk about in your book and you sort of asking this question of whether all other animals feel pain. Writing, caterpillars will continue munching on a leaf while parasitic wasp larvae eat them from the inside out, suggesting that perhaps they're not bothered by what's going on.

32:22What have you come to conclude here? Do you think that all animals in the Queendom feel some semblance of pain? Yeah, I think it's a really, really tough question. You know, pain is unusual in that it's like the unwanted sense, right? It's the thing that we definitely don't want to feel. It is helpful, though, because it does stop us from watching, you know, Star Wars Revenge of the Sith a second time. so that's right that's more of a kind of emotional pain than the uh than the more sensory pain that i'm talking about but sure i i i agree um the the um um now i'm thinking about that movie so i'm reliving the pain now why okay um much of the discussion around animal pain has um has revolved around a very, very simple question, which is, can this group of animals feel it?

33:24Yes or no? There have been, you know, there was a time when some people believed that no other animals besides humans could feel pain. And then that ability was extended to things that are very similar to us, other mammals, birds, maybe. And then there were a lot of these edge cases, right? So there's been for a long time this idea that fish don't feel pain. I think that that has been refuted by a number of very good studies showing that they very much do. But here's the thing. I think that there are probably many different kinds of ways of feeling and experiencing pain. So we might look to the cephalopods, so octopuses and squid, which are very distant from us clearly very intelligent animals do they have the ability to feel pain so if you damage the arm of a squid like if you just cut off the tip of an arm this is something that happens very often in nature the animal does react as if it's in pain is some of the indicators, but crucially, it doesn't seem to behave as if, it doesn't seem to act as if this arm has been injured, right?

34:49The whole body becomes hypersensitive to stimuli. It's as if, like, I stubbed my toe and suddenly, like, my elbow feels sore or, like, my neck kind of hurts. And it sort of makes sense with the biology of a squid, right? Here is an animal that the arms are actually relatively short and cannot explore most of the body. So, you know, maybe it's useful for the squid to just behave as if the whole, you know, something is wrong, right? Octopuses behave in a very different way. Octopuses have very dexterous long arms that can reach all around the body, including inside themselves. And if you damage the arm of an octopus, it very much knows that this arm is hurt.