Instant Genius - Animal senses, with Ed Yong

Episode Date: June 26, 2022

Science writer Ed Yong tells us about the staggering diversity of animal senses, from dogs’ powerful sense of smell to birds’ incredible colour vision. Once you’ve mastered the basics with Instant Genius, dive deeper with Instant Genius Extra, where you’ll find longer, richer discussions about the most exciting ideas in the world of science and technology. Only available on Apple Podcasts. Produced by the team behind BBC Science Focus Magazine. Visit our website: sciencefocus.com Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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a bite-sized masterclass in podcast form. I'm Sarah Rigby, online staff writer at sciencefocus.com. In this week's episode, I'm talking to science writer Ed Yol. He's the author of An Immense World, how animal senses reveal the hidden realms around us.

He tells me about the staggering diversity of animal senses, from dog's powerful sense of smell to birds' incredible color vision, First of all, could you just tell us a bit about what your book's about, please? Yeah, an immense world is about the sensory worlds of other animals, so how other species from bats to elephants to manatees to snakes perceive the world around them, the way they smell, the way they see,

the way they hear, the way they feel. And the core of this book is a concept called Umwelt. It was pioneered by a German zoologist named Jakuban Uxkel in the early 20th century. And Umbelt comes from the word for the German word for environment. But Bonozykul wasn't using it to refer to an animal's physical environment. He meant its sensory world, its perceptual bubble. He recognized that each species, whether human or otherwise, had its own unique blend of sights and sounds and smells and textures that it could perceive. but that many other creatures could not,

and that we all experience the world in radically different ways, even if we are sharing the same physical space. And why do you think it's important for us to consider how other species see the world, or I guess experience the world rather than see? Yeah, many reasons. I think, firstly, it's just fascinating. The experiences of other creatures are so different from ours. There are animals that can sense the Earth's magnetic field and use it to navigate over long

migrations. There are a fish that can create and sense electric fields and use those to navigate through dark water or to communicate with each other. Even more familiar senses can have kind of extraordinary applications. So bats and dolphins can navigate the world by using a kind of sonar, by producing hyper high-pitched calls and then listening for the echoes that rebound to them. You know, just even vision can be extraordinary. Like a duck sitting on a pond can see the entirety of the sky without having to turn its head,

something that obviously we cannot do. So I think for a start, understanding the sensory worlds of other animals makes them seem more magical. It reveals sides to their lives that we haven't contemplated. It reveals abilities that seem incredible to us. But I think there's, I think in considering their umbelton, in considering their senses, we also see our world in a new and more profound way. So things that seem familiar or boring or flat take on completely new characters when you

think about them through the senses of other animals. So like an ocean surface, which seems flat and feet. featureless through the nose of an albatross is actually full of landmarks, full of odors and smells that reveal the presence of food. To the nose of my dog, the same streets that I walk along every day, many times a day, change almost constantly. They abound with new scents and smells, and every walk for him is an act of exploration. So an immense world is really about both of these facets together. It's about trying to understand the lives of animals better, but it's also about using animals to get a wider and richer understanding of the world around us.

So I think probably the example of another animal's senses that most of us would have some familiarity with would be dogs. We have a kind of rough idea, rough. idea. We have a kind of rough idea of what a dog's senses are like. So yeah, I'd like to talk about those first. So is it true that a dog's sense of smell is really that much better than ours? It is. So there is, if you do like kind of artificial lab experiments, humans actually perform pretty well at some basic tasks, like discriminating between different odors. You know, it's, it's often said that we are poor smellers. People for many centuries have argued that humans have an impoverished sense of smell compared to other senses such as vision. But it turns out not to be true,

our sense of smell is actually pretty decent. But then again, it doesn't quite compare to dogs to that of a dog for several reasons. Firstly, the hardware is just different. So a dog has structures in its nose that split the incoming air into two streams, one of which goes into its lungs and is for breathing, and another of which goes into the back of the snout, and is almost entirely used for smell. And it means that when the dog exhales, it doesn't wash away that air-filled stream of odors. It constantly replenishes its scent without getting this sort of flickering olfactory view of the world like we get when we inhale and exhale. A dog also, like the next time you look at a dog's nose, you might also notice that the nostrils taper off to the sides.

So it's got these little sideslits. What that does, when a dog sniffs on the ground, you would think that every exhale would actually blow away molecules of scent that lie on the ground. But those sideslits create small vortices, like little turbulent flows of air that actually waft odors into the nose. So regardless of whether the dog is inhaling or exhaling, it's getting this constant conveyor belt of smell going into its snout. So it has the hardware. It's also much more practiced at it. Humans aren't going around sniffing each other for the most part.

And we don't use our noses in the same way. A dog absolutely does. When I take my dog typo for a walk, he spends most of his time sniffing and exploring. He uses his nose very actively. And every walk becomes an adventure for him. And because of that, they pick up a lot more, you know, they're just more skilled at using their nose for things that we can't use our nose for support, like navigation, like social connections. Right. Okay. And then when it comes to dog's vision, it's something that's often said that dogs can only see in black and white. Is that true? It isn't. It is a really common misconception. But in fact, dogs do.

see color, they do, they just see a much narrower range of colors than we do. In our eyes, we have three kinds of color sensing cells, and that gives us a visual spectrum that runs from red to violet. Now, I shouldn't really say us, like this is true of the average human, but millions of people have colorblindness, which means that one of those classes of color sensing cells either is missing or doesn't quite work in the usual, typical. way. For a lot of those people, their visual, especially if they have a red, green color blindness, their visual spectrum just goes from yellow to blues with whites and grays in the middle. That actually is exactly what a dog's vision is like. It's also what the vision of a lot of

other mammals, like horses, is like. So yeah, they very much do see colour, but for example, like when Typo looks at his bright red chew toy, that's going to look like a dark and muddy yellow to him. When he looks at one of his violet toys, that's going to look more like a deep blue. Right, I see. And there's sort of an almost a meme going around the internet about this idea that there are some like extra colours out there that humans can't see, but other species like the mantis shrimp can see. So are there extra colours? So there are extra colours? This answer is a little complicated. So firstly, there are extra colours. Absolutely. Birds, for example, are tetragrammatic.

So they have four kinds of colour-sensitive cells in their eyes, red-green, so mostly that are maximally sensitive to red, green, blue, like ours, but also to ultraviolet. That doesn't just extend their visual spectrum into the margins. It unlocks an entire new dimension of colours that they can see and that we can't see. It means that things like their own feathers are going to look very different to a bird than to us. It means that there's this huge range of what are called non-spectral colors that are the equivalent of purple for us, right? Purple is a mix of red and blue. For birds, there might be

colors that are like red plus ultraviolets or blue plus ultraviolet and all the shades thereof, this whole world of colors to which we are completely oblivious. You mentioned the mantis shrimp. So that's complicated. There is this, so for people, Most people don't know. Most people don't know what mantis shrimps are. They are a group of crustaceans, you know, a distant relatives of crabs and lobsters and shrimp that are famed for a few things. One is punching things incredibly hard and another is having this crazy color vision system in their eyes. You know, we have three kinds of color sensing cells. Birds have four. Mantis shrimps have 12, possibly more. And so people have assumed like maybe it's that maybe they have. have, you know, if birds are unlocking a new dimension of colors, then what are mantishrum's doing, right? Like, they must have this incredibly rich kaleidoscopic rainbow that which they perceive the world. Turns out to not be the case. Mantis shrimps are actually substantially worse at discriminating between different colors than humans or basically any other animal that's been

studied. And it seems that their style of color vision is just radically different from that of any other animal. Like, rather than, like, you know, like, you know, like turning the rainbow into like tiny, tiny chunks and discriminating between them, it seems to actually turn it into like the equivalent of a children's coloring book. Like everything gets collapsed down into one of these 12 basic hues, and all that information is sent directly to their brain without a lot of processing. So their color vision seems to be actually very simple, but also very fast. the closest analogy that we have to it is actually what satellites do rather than what other

animals do. What do you mean by what satellites do? Okay, so, right. So we have three kinds of color sensing cells in our eyes, right? But we can discriminate between like a million different kinds of colors. And the reason we can do that is the signals from those cells don't just go directly to the brain. The nervous system adds and subtracts them and compares the signals against each other and then sends that to the brain. And that kind of processing is called opponentancy.

It's how we go from three types of cells to millions of colors that we perceive. A mantis shrimp doesn't seem to do any of that. It just sends the data straight to the brain. And then, like all the information from its 12 color sensing cells, seem to just, the idea is that it maybe just gets compared to like a lookup table of colours. So maybe if cells like one, five, six and seven go off, that's yellow. Or, you know, if it's like three, seven and eight, then maybe that counts as blue. It's a very different, but much faster way of sensing colour, which suits an animal that is noted for extreme speed.

Right. Okay, I see. So now back to dogs and their vision, I've noticed that my dog sometimes can't even see a biscuit that's on the floor right in front of him. So why is that? Does he just have particularly bad vision or do dogs in general have worse vision than us? This is a great question. So one of my caveats to this book is I can't explain why your pet does the weird thing that it does. Right, but like all of us who live with animals know that they sometimes do weird things that are very hard to explain. So it could be a visual thing. Dogs and actually most other animals except for birds of prey have less sharp vision than humans do.

Humans are notable in the animal kingdom for having exceptionally sharp eyesight. So it's possible that he doesn't see the biscuit. it's possible that he doesn't recognize it as something. It's sometimes I've noticed that Typo, so Typo is very, very good at finding treats with his nose. Like we play sniff games with him where we'll hide bits of kibble like around the living room, often like, you know, under a bit of carpet or, you know,

behind one of his favourite toys or something like that. And he'll find it very quickly. there are some moments when he just seems to struggle in ways that are inexplicable given how good his nose normally is. And often it's usually, like I find it's when the food is like right next to something, like when it's like next to the leg of a piece of furniture. And I wonder if there's something about the ways in which the presence of like a solid object like changes the way, changes like airflow patterns or like somehow masks the smell of the food. But I don't know.

I think these are the kinds of questions that I think are always worth asking. And like when you start thinking about the umwelt of another animal, I think you can, you know, you start like coming up with really interesting hypotheses for why your pets are behaving in a strange way. So you mentioned that human's vision is quite exceptional. in the animal kingdom. So what about our other senses? Do we have any other senses that are quite exceptional or are we just otherwise kind of normal? No, I mean, we are very good in a lot of respect. So the sharp, the acuity of our vision is certainly an obvious one. Our sense of touch is very good.

You know, our fingertips are exquisitely sensitive. You know, even turn to the nanoscale. People have done amazing experiments where humans have been able to, you know, detect the difference between two synthetic surfaces whose roughness differs by tiny, tiny amounts. So, yeah, we have very sensitive fingers. Our hearing is decent, our sight is sharp. Our color vision is not as wide as that of a bird, but it's wider than that of a lot of other mammals.

So what animals do you think have the most amazing senses? Gosh, it's extremely hard to choose. And, you know, I do want to clarify that I think, say early on in the introduction that an immense world is not a book about superiority. It's a book about diversity. And often, like, I think we become fascinated by the senses of other animals only when they surpass ours. So when a creature hears better than we can or smells more things than we can, this book is about the ways in which animals differ.

In some cases, in some cases, their senses can be much simpler than ours. In some cases, they're amazing, I think, just because they're incredibly different. So, you know, I write about jumping spiders, for example, animals with four pairs of eyes and that track, and hunt their prey using vision. The two central eyes on a jumping spider are the largest and the sharpest. They do color vision and they do detail. But the eyes on the side of those

are what the spider uses to track movement. So it has done this weird division of labor between its sets of eyes so that tasks that exist within our one set of eyes get split between different pairs, which is just wild to me. If you block the two side pairs of eyes on a jumping spider, it can't track movement, even though it can see very well. And it's that sort of thing that blows my mind, just the very different ways in which

a sense like vision, even one that's familiar like that, can operate in a different creature. And so far we've talked about most of the sort of obvious senses like vision and sound and smell. But obviously there's more senses as well that don't come under the sort of traditional five senses. And one of these is pain. I was surprised to read that there's a lot of controversy about which animals feel pain. So why is that? Why isn't it sort of obvious? Yeah.

As one scientist who works in this field told me, and people are pretty strong opinions about this. A lot of people either feel that... Some people think that animals just don't feel pain in the same way that humans do, and others are convinced that all animals feel pain in exactly the same way that humans do, and very few people are sort of agnostic in the middle.

I think that pain, the experience of pain varies across the animal kingdom, just as the experience of hearing or vision does. I think a lot of the controversies around weather, for example, fish feel pain or crustaceans feel pain or insects feel pain, stems from the fact that pain, unlike the other senses, is unwanted. You know, it's one of the only senses we try to avoid. It's a sense that we try and stop ourselves or other creatures from experiencing. And it comes with a huge amount of moral and ethical. and often economic baggage to it. So, like, the stakes are very high. And I think for a long time, a lot of people have argued that, for example, fish don't feel pain, that the wriggling of hooked fish is more of a reflex than anything else.

I think that's not true. I think there's a lot of evidence now showing that they do have some experience of pain, that they behave in ways that are analogous to a human when we, when we have injured parts of ourselves. But I don't expect that experience to be the same as ours. You know, I think there are going to be differences. So one example I write about in the book, squid and octopuses are part of the same group of animals called cephalopods.

They are related to one another, but their experience of pain seems to be really different. For a squid, when it gets injured in a specific body part, like the equivalent to say you stubbing your toe, it seems to feel pain across its entire body. Its entire body seems to be hypersensitized to further stimuli. It's as if you stub your toe and then suddenly your shoulder became really sore. And that might be because a squid has short arms.

It can't reach most of its body parts. Even if it knew where it was injured, it couldn't really do that much about it, bar better for the entire animal to act as if it was in peril and take like protective measures accordingly. me. An octopus, having longer arms and being much more dexterous, absolutely can inspect and careful parts of its body, and therefore does seem to know which parts of its body have been injured when they are. You know, if one of its arms loses a tip, the octopus will cradle that arm and groom it and care for it, much like I would if I burn my finger. So even here,

across like in two creatures that we think of as being quite close related, their experience of pain is going to be very, very different. And I think that this question of, do animals feel pain or not, that's asked as if the answer was just a simple yes or no, aligns a lot of the complicated reality, that, you know, that diversity that this book is all about. So on the basis of animals' senses as a whole, so pain, but also, you know, smell, vision, that sort of thing, are there any animals that you think that we should be treating better? Honestly, I think we should be treating them all better.

Regardless of whether, you know, how people feel about the debates around animal pain or not, I think there are good moral reasons to treat them well and to treat them ethically and to try and minimize any harm that occurs to them. The last chapter of this book is about one of the ways in which we're harming animals without really recognizing it. And that's by flooding the environment with sensory pollution, with light and with noise, that disrupts, waylays, and disturbs animals, often with fatal results. So light at night can deter pollinating insects away from flowers.

It can lure hatchling sea turtles away from the sea and up a beach onto a road. Noise can push birds and many other animals away from habitats that they were quite happily live in. It can drown out alarm calls and mating calls. all the other noises that animals need to hear in their environment. We don't really think of these things as problematic, but they are. And they are causing severe harmful consequences for much of the world's wildlife. And they're disconnecting us from the wilderness around us and that might exist even in our own

backyards. I hope that in reading about this book and in thinking about the unbelt of other animals, we also come away with a deeper appreciation of the ways in which we're forcing them to live in our own belt to their detriment. And just finally, what three things do you think we all should know about animals' senses? I think firstly, just that they are so different from ours. It's so easy to anthropomorphise animals and to believe that their experience of the world is the same as ours. It's not. It's not for, you know, for things that we think are obvious like vision, pain, our feeling of what is hot and what is cold. All of these things differ across the animal kingdom. I think we should understand that our experience of the world is constrained by our biology. We exist in this powerful illusion that our senses create in which we feel like our experience of the world is complete. It's all that we have. So we have. think that's all we get to have. And that's not true either. You know, what we experience is just a

thin sliver of the fullness of reality. And I think only by really contemplating the lives of other creatures do we get a sense of the true immensity of the world around us. And I think just finally that all of this stuff is worth knowing on its own terms. A lot of people study animals to learn more about, you know, as inspiration for tech. or to get lessons about our own lives, I think they are worth learning about it for their own sakes. And I think they're worth preserving and saving their own sakes. Every time a species goes extinct, it's not just that we lose the creature. It's that we lose a way of understanding the world. And that's truly tragic. It means that our reality becomes a little bit thinner and a little bit narrower.

And I'm hoping that by showing people the sort of magnificence lurking even in creatures that we're very familiar with, it will motivate them to more impetus to care about and to protect those creatures. Thank you for listening to this episode of Instant Genius. That was Ed Yong. If you want to know more about animal senses, check out his book, An Immense World. Or to hear him tell me about all the types of sense that humans don't have at all, head over to Instant Genius Extra, available only on Apple Podcasts. The June issue of BBC Science Focus magazine is out now.

Pick up a copy in store or visit ScienceFocus.com. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analog warmth. Alongside French acoustic specialist vocal, Name creates high-end audio systems combining innovation with craftsmanship so you can listen to music,

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