Ed Yong on the wondrous world of animal senses

Host: Benjamin Thompson

Hi everyone, Benjamin Thompson here. Welcome to episode one of Nature hits the books, a new show where I’ll be chatting with authors about their new science books. For this first episode, I reached out to a pal of mine, the science journalist Ed Yong. Ed is a staff writer at The Atlantic and in 2021 he won the Pulitzer Prize for Explanatory Reporting for his coverage of the COVID-19 pandemic. His second book has just been published. It’s called An Immense World, and it takes a deep dive into the sensory world of animals, and I caught up with him on the phone to find out a bit more about it. We chatted about a bunch of things, including how our human-centric view of the world has restricted our understanding of animal senses, how to conceptualise – let alone write down – what it might be like to be an electric field sensitive fish, and what bees might make of us blushing. We do cover some ground. Ed, hi. Thanks for joining me.

Ed Yong

Thanks, Ben. Good to talk to you again.

Host: Benjamin Thompson

It’s great to speak to you too. And I will say, the last time I saw you was actually at your wedding. That was, what, three years ago now? And a lot has happened since then, I think we can both agree.

Ed Yong

Yes, I mean, three chronological years, but I feel like I have aged several lifetimes in that time.

Host: Benjamin Thompson

Yeah, I mean, the pandemic has been your beat now for some time, right? But I think people who followed your work will maybe know you from covering animal oddities, I could say, which you did for a long time before the pandemic. Why is now the time for you to return to that world and write a book about, well, the vast diversity of animal senses. Was it something of a palate cleanser for you, would you say?

Ed Yong

Yes and no. So, the real answer is that this was the project that I was working on when the pandemic started. I’d come up with the idea for this book. It just totally fits with everything I’ve been interested in for the entirety of my life and career, and I went on book leave from my day job at The Atlantic in October of 2019, with the goal of writing the book in about ten months. And about halfway through that, everything went to.... and I was forced to return to work. I then went on book leave again at the start of 2021 to finish the book in the middle of two bursts of pandemic reporting. So, the book very much was a palate cleanser. Nine months of reporting on COVID is gruelling, draining, demoralising work, and returning to this topic, which is joyful and magical and wondrous, was a much-needed salve for my soul in the midst of all of that.

Host: Benjamin Thompson

I mean, I don’t know about you, Ed, but certainly for me, I would say that my world shrank in the past few years, and I guess how big your world is and what you can perceive really seems like a central theme to this book.

Ed Yong

Yeah.

Host: Benjamin Thompson

And specifically, I guess, how animals’ worlds differ according to their sensory capabilities, and this centres around the umwelt, and that was popularised in the 1900s, I guess. Maybe you could tell us a bit about that?

Ed Yong

So, the umwelt concept was popularised by a German zoologist named Jakob von Uexküll, and I’ve probably completely bastardised the pronunciation of that name, so apologies to German listeners. I did my best. So, the word ‘umwelt’ comes from the German word for environment, but von Uexküll didn’t use it to mean an animal’s physical environment – the actual tangible surroundings that it finds itself in. He used it to mean an animal’s sensory environment – the perceptual world that that animal inhabits. He recognised that every species has its own set of sights and smells and sounds and textures that it can perceive, and that might be very different from what another creature can perceive. The example that he used was the tick – a blood-sucking invertebrate – and it is sensitive to the heat of a human body, the touch of hair on the skin, the smell of butyric acid that might reveal the presence of a human. Most other things that we can sense, like light and colour, are not part of the tick’s umwelt. But similarly, there are many other things that aren’t part of the human umwelt that other animals can sense, like electric fields, magnetic fields, ultraviolet light and so on. So, the umwelt idea is about how all that we perceive – even though it feels like all there is to perceive – is in fact just a tiny sliver of the fullness of reality. And I think you’re right that over the pandemic there has been this feeling of our worlds constricting and get narrower. But von Uexküll imagined the ability to think about the umwelts of other creatures as an act of travel. The first time he wrote about it, he pitched his book as a sort of travelogue, and that’s how I think about my book too. It has allowed me to go on these imaginative adventures at a time when physically I’m moving about less in space than I used to.

Host: Benjamin Thompson

I mean, this idea back in the 1900s then seems remarkably, I don’t want to say perceptive because I’m going to have lots of these puns, I’m sure, but at the time, compared to I suppose what researchers knew about animals in the early 1900s?

Ed Yong

Right, I think a lot of people had been thinking about the senses of other animals for a long time. You can read all the way back to Aristotle about some of the ideas that people had. But, yes, I think that the umwelt concept was actually quite radical in that it really assumed that animals have these interior lives and that they are worth thinking about. von Uexküll was quite clear in saying that it wasn’t as if the human umwelt was better than the umwelt of other creatures. He recognised that each species’ umwelt is tailored to its own particular needs. It is as expansive and as limited as befits the creature in question. That ran sort of contrary to one of the dominant modes of thinking, which put humans on the sort of pedestal above all other creatures. And you can see still like the remnants of that kind of thinking today when we think about the senses. There is this like strong tendency to anthropomorphise other creatures, to assume that they sense the world in the same way that humans do. And to the extent that we know that they don’t, we tend to only value that when they exceed what we are capable of. So, there’s a lot of talk about ‘sixth senses’ or ‘super senses’, but that’s sort of not really the idea that von Uexküll had. I think his point of view was that these things are worth studying and these other sensory worlds are worth thinking about in their own right, even when they, as for example is the case with the tick, are simpler than ours.

Host: Benjamin Thompson

Yeah, that was the other thing that stood out to me, is that we are human-centric in our thinking. Things like ‘bird’s-eye view’, I suppose. A bird doesn’t see like we do. We just think of it as being from really, really high up.

Ed Yong

You’re right. If a human actually tried to take a bird’s-eye view, many weird things would happen. We would have close to wrap-around vision. Just watch a duck in a pond, like a simple duck that no one even thinks about. That duck can probably see the entirety of the sky without having to move its head, which is incredible to me. You would see a whole dimension of colours that we can’t see. So, yeah, even when we use language like ‘a bird’s-eye view’ to talk about perspective taking for other species, we radically underestimate the differences.

Host: Benjamin Thompson

And when you think about sight then, one of the stories that you tell is about ants and UV light, right? I think this speaks to the whole thing. John Lubbock, I think you write, worked out that ants could see UV, when everyone just assumed that they would see like us or just see in black and white. And then everyone said, ‘Well, it’s just ants,’ and then said, ‘Well, okay, it’s some animals, but it’s rare,’ and then, ‘But it’s just them,’ and then, ‘Actually, do you know what, it’s some mammals as well, but that’s actually rare.’ And then, ‘Hey, it’s a lot of mammals, but only really simple ones.’ And then it’s like, ‘Well, actually, do you know what, almost all animals can see UV pretty much except us.’

Ed Yong

Right, right. There’s this sort of long history in which scientists are, at every step, just only grudgingly accepting that another group of animals can see ultraviolet light. And now like, as you say, I think it's pretty clear that the majority of animals that can see colour can see ultraviolet, and we are the exceptions. But because we don't see it, we assumed that it was special and that it was rare, and it just took a long time of like pushing back the boundaries of our knowledge of other animals to realise that actually, the skill is very common. Like, there used to be a lot of talk about how UV was the key to like a secret communication channel. So, animals could use it to send like hidden messages to each other with like UV-reflective body parts that most other creatures couldn't see. And this is, of course, predicated on the fact that it's secret to us, so we assumed it’s secret to us, so it’s secret to them. But if most animals can see UV, it's really not very secret at all. Many of the people who I spoke to for this book basically said, ‘Yeah, no, to me, ultraviolet is just a different colour. It's just another colour. It just happens to be one that we can't see.’ And I write in the book, like you can imagine if bees had scientists. So, bees see a spectrum that ranges from green to ultraviolet. They don't see reds that we see. So, you can imagine that a bee scientist would be like fascinated by this colour at like the far end of the spectrum, which it might describe as something like ultrayellow, and it might ponder about like how other creatures don't seem to see ultrayellow and maybe ultrayellow is like a hidden communication channel which these weird like two-legged primates use to flash secret messages to each other whenever their cheeks like blush with ultrayellow colours. And then eventually they would just realise that, no, actually like, it's just another colour. It's just another colour. It just happens to be one that they can't see.

Host: Benjamin Thompson

And UV was actually kind of discovered, I guess, not that long ahead of when John Lubbock did his ant experiments, right? And so, it seemed like that was quite a key step, just knowing it was there at all. And I guess that sort of permeates through your book as well – these discoveries that allowed things to happen. I mean, what would you say have been some of the key leaps in our understanding of animal senses?

Ed Yong

Oh, gosh, well, so one really good example of the phenomenon you just described is the discovery of echolocation. So, people have been watching bats for millennia and centuries, and it really was only in the 1940s that pioneers like Donald Griffin realised what they were doing, which is that they're emitting high-pitch calls and then passing the echoes that return off objects around the bat to work out what's in their surroundings, and that's how they navigate in total darkness. That's how they hunt. And this was so shocking to a lot of people at the time. The idea that bats, as one person put it, like see with their ears. It just sounded so ludicrous that folks like Griffin faced intense scepticism about this idea. But, of course, it’s right, and I think he wrote about this way in which the limitations of our own senses and the dogmas that we build up because of those limitations restrict our imaginations, which restrict the kinds of questions that we ask about the world, which restrict the kinds of experiments that we do, which restrict how we interpret the results of those experiments. So, there's often this idea of sciences, this sort of very neutral, like fully objective process of understanding the world, and it's not. It's heavily influenced by all kinds of biases that we have and the biases of our senses are among them. And it's stunning that when Griffin established that bats could echolocate, it then became much easier to find examples of echolocation in other creatures. So, now we obviously know that dolphins and toothed whales can do it. We know that a lot of other animals have versions of this ability. Oil birds do, several small mammals do, and some very special humans can do it too. So, yeah, throughout the book, there is this running theme about how what we think we know limits our ability to know even more.

Host: Benjamin Thompson

I mean, you talk about the scientists’ struggle to conceptualise these ideas because they were so alien – echolocation, for example. When it comes to you actually writing about these things yourself as well, you don't echolocate, as far as I'm aware, Ed.

Ed Yong

No, I don’t.

Host: Benjamin Thompson

And you can't see outside of the visual spectrum, and all these things, right? And so, how does one go about writing these things that we can't possibly comprehend in a way that is as accurate as can be but also kind of makes sense and gives a flavour of what it is?

Ed Yong

Yeah, it's really hard. So, part of the argument that runs throughout the book is the same idea that the philosopher Thomas Nagel popularised in his classic essay What Is It Like to Be a Bat?, which is essentially that we won't know. That it is fundamentally impossible to really understand the subjective experience of another creature, which is why, firstly, you always need to make an imaginative leap. You always need this little speck of faith, this little willingness to be creative to get to that destination, and you need a bit of humility and understanding, like, ‘I actually won't ever quite get there but it's the journey that matters. It's the effort that matters.’ And so, for me writing this book, like I know I don't have all the answers, but I can give you everything we know, and I can give you informed speculations about what the animal might be going through. And that's what I tried to do. I tried to take us to like the very edge of that chasm between our subjective experience and other animals. Like let us peer over the edge, maybe do that thing where I’m like, woah, and then pull you back. And it's not easy. One thing that made it a little easier was just asking people who work in these fields and who think about these creatures, and to ask them how they think about the creatures that they study. Because all of this I've just talked about, like these imaginative leaps, they tend to not be in papers, right? They're a little antithetical to what we shove into the scientific literature. But I guarantee you that everyone who really works in this field, every sensory biologist, has thought long and hard about what the creatures they study might experience. And if you ask them, you just get some really cool stuff.

Host: Benjamin Thompson

And that’s interesting because I guess when it comes to science, I mean, we can answer maybe the ‘how’, right? We can do experiments and look at how a fish detects an electric field like at an anatomical level. But it doesn’t necessarily answer the ‘why’ or the experience.

Ed Yong

Right, so the electric field thing is a good example. So, there are lots of species of weakly electric fish which generate their own electric fields, and not enough to, say, shock a human, but enough to allow the fish to sense their environment. So, they create the field, the field gets distorted by objects around the fish, whether it's a conductive thing like a plant, or an insulating thing like a rock. The fish has receptors on its skin, which can detect the distortions in its own self-produced field, and it can map those distortions to get a sense of its environment. Now, we know all of that. The electric sense is actually remarkably well studied. Electric fish have been like model organisms for neuroscientists for a long time. We've mapped the circuitry that allows them to produce and to pass those electric fields in excruciating detail. But the question then is, what does that feel like to the fish? And the answer is, we don't know. We really don't know. But when I asked like Bruce Carlson, a neuroscientist who studies electric fish, he had some really wonderful answers. Like he imagined that if the fish is swimming past, like a rock, for example, you might imagine like a cool sensation moving down its flank that would indicate an insulating object is in the environment. So, he imagined it as something akin to touch, but operating in a distance several inches away from the fish's body. And that gives me a little portal to what it might be like for the fish. Is that exactly what it's like? Absolutely no idea. But I think this is the kind of thing that we should be thinking about.

Host: Benjamin Thompson

And it seems like there's a balance to be struck, which is something that we have to do here on the Nature Podcast as well, regardless of whether we're talking about quantum physics or molecular biology, or whatever it may be, between explaining the ‘how’, but also providing that imaginative leap to help with clarity. How do you square that circle and find out where those graphs cross over?

Ed Yong

I think partly it's just about being very clear about when you're doing which bit. I think it should be obvious to readers of the book like, when I'm telling you about things we absolutely know, things that have been established experimentally, and then when I'm taking like more than educated guess. But I think if you didn't do any of the imaginative stuff, the book would just be joyless. Whereas if you just went on like flights of fancy all the time, it would feel like almost like a work of science fiction. This is very much a non-fiction book. And I'm trying to show both what we know but also the limits of that knowledge. Look, I'll give you another example, right. So, here's a thing we know. Giant whales like blue whales make very deep infrasonic calls, and those calls can travel almost over the length of an entire ocean. And we know this because we have hydrophones that can pick up a blue whale singing near Europe from the coast of America. So, we know that the sound can travel over vast distances. Can the whales hear each other over those long distances? Maybe. Can they communicate? Harder to imagine, but not impossible to imagine. So, like, what does a pod of whales actually look like? Do they have to be right next to each other in visual proximity? Can they be separated by like miles, like tens of miles, hundreds of miles? I don't know the answer to this. But you put together what we know about how far the sound travels, you put together the intelligence of these animals, their social nature, you think about what they could do with those kinds of signals, and you can let your mind go on like slight flights of fancy in the knowledge that maybe this is wrong and maybe we won't know. But it is worth thinking about because it’s almost like what other option do we have?

Host: Benjamin Thompson

And some of these then are, I guess, to an extent, flights of fancy at the moment because those questions can't be answered yet, right? And maybe even we can't quite conceptualise what those questions are. But presumably, volume two of this, you're hoping that there'll be so much more progress that some of these questions will be asked and answered.

Ed Yong

I mean, I do hope so, but I've also made a lot of peace with the idea that some of these questions will not be answered. We've talked about whales, right? For very large animals, I think it's difficult to do the kinds of experiments that would answer these questions. And even for like smaller animal, so the bats are a classic example, right. In some ways, echolocation is one of the easiest senses to study. We have really good equipment that can detect the calls a bat is making. And because echolocation is a very unusual sense in that it is permanently active, the bat needs to create the stimulus that it then uses to sense its environment, it's actually quite straightforward to understand the bat’s intent. It will aim its sonar beam at different things around it that it's particularly interested in. If it wants more detail, it can call faster. Now, by looking at all of that, you get a pretty good sense of what a bat is trying to sense in its environment. You can get as close as you can to reading the creature’s intentions and therefore its mind. But even then, right, there's still that question of what does echolocation feel like to a bat? And we don't know. We don't know.

Host: Benjamin Thompson

I mean, what questions would you like answered, Ed? What's the maybe one thing you’re like, ‘Cor, I wish we knew why that or how that happens.’

Ed Yong

One of the chapters in the book is about magnetoreception – the ability to sense the Earth's magnetic fields – an ability that songbirds and turtles and apparently a lot of other animals have too. Magnetoreception remains one of the biggest mysteries in sensory biology. It is the only sense where we don't actually know what the sense organ is or what the receptor is – the cell that actually detects magnetic fields. We know that for everything else, right? So, vision, very obviously, is a thing that eyes do. I know exactly which cells inside my retina are responsible for detecting light. I can trace all the pathways from those cells to my brain. But with magnetoreception, we don't have any of that. We don't know what the receptor is. We don't know how they could work. There are some ideas, but no one has really nailed it down yet. It's all complicated and counterintuitive. I think I would love to know that. I wrote my first piece about magnetoreception for New Scientist in the late 2000s, so it's been over a decade now, and we still don't have answers to those questions. It's the sort of last great unknown sense.

Host: Benjamin Thompson

Yeah, we covered those molecules called cryptochromes on the podcast, which are found in the eyes of birds and might be involved with them sensing magnetic fields. That was a year ago or so. And I mean, from a purely writing perspective, is there stuff that's happened since you put down your metaphorical pen, where you were like, ‘Damn, that's the leap that I was missing,’ or, ‘That would have ended that chapter beautifully or answered that question perfectly,’ or what have you?

Ed Yong

Oh, definitely. The first book that I wrote about the human microbiome was about a science that had some history to it but it was still in its infancy. Whereas sensory biology is a field that has existed for centuries, if not longer. There's a huge volume of stuff to write about, and I had to be quite selective about which things made it into the book. But it's also an area where new things are being discovered all the time. I learned just a month ago, it was a really interesting paper about a group of mice that seemed to be able to genuinely echolocate and pretty well, that came out in Science in the middle of 2021, and I completely missed it because I was immersed in yet another round of reporting on COVID. So, there's new stuff that comes out all the time. And it is the perennial problem of writing a science book that there are always bits that are going to be a little out of date by the time the book actually comes out. But I think like because of the long history of sensory biology, I think those things are going to be few and far between, and it doesn't really change the meat of the book, like trying to actually get people to understand the basics of the umwelt concept, how it applies to the creatures around us. I think most of the book I expect to like stand the test of time, and I'm just really looking forward to finding out all the stuff that happened in between.

Host: Benjamin Thompson

Your final chapter I think is very much a lament, I guess, on how we're pushing our sensory world onto the animal world, right, in terms of fluorescent lighting and road traffic and stuff like that and the knock-on effect it's having on animal populations. What are you hoping, do you think then, that people are going to take away from this book because you have, as you described, this joyous journey on the way through, but you end it there – is that the message that you're trying to maybe get across to people?

Ed Yong

I think it is impossible to write about nature right now without writing about the ways in which we are despoiling it and our profound responsibility to protect it. And I think that last chapter does that work. It notes that we've just spent 13 chapters thinking about the sensory worlds of other animals, and we need to reckon with how we have upended those worlds with the stimuli that we flooded into the environment, with light, with sound, things that we don't normally think of as pollutants, but they very much are when they're in the wrong place at the wrong time at the wrong levels. And I think that one reason why this is important to think about is that, unlike a lot of other types of pollution, unlike a lot of other things that we're doing to the environment, sensory pollution is relatively easy to fix. You can just turn that stuff off and it will go away pretty much immediately. And that chapter is about making the case that this is worth doing, that just as we think about preserving rainforests and coral reefs, we need to think about saving the dark and preserving quiet.

Host: Benjamin Thompson

And that did happen, to an extent, over the past couple of years, of course, right, and I think I certainly noticed the difference. I'm sure you did too. But I guess there's a parallel there as well about how humanity is encroaching on the animal world and the effects that could have in the public health sphere as well, of course, with the pandemic. Was there an unconscious parallel for you there, do you think?

Ed Yong

A little bit. So, I've argued recently that the greatest problems of our time, things like climate change, the sixth mass extinction of wildlife and the rising threat of pandemics, are all part of the same problem. By fragmenting natural spaces, by heating up the world, by killing wild animals, we’re pushing them into new spaces, into narrower spaces in new combinations, allowing viruses to hop from one species to another and eventually into us. So, if we want a world in which what we've just been through for three years doesn't happen again, we're going to need to fix the other problems that we think of as separate. But I think there's another link that I think of, which you sort of got at. In the early pandemic when the world kind of shut down, a lot of people became very, very aware of like natural sounds around them. Loads of people started talking about like hearing birds. And that wasn't the ‘nature is healing’ trend. It wasn't because like birds were suddenly flooding into human spaces. It's that we could hear them because, all of a sudden, a lot of people just shut up. And we can achieve that without the debilitating effects of a lockdown. And the reason why that happened is that noise not only interferes with our ability to appreciate the natural world but also shrinks the radius over which we hear natural sounds. So, I think of sensory pollution is the pollution of disconnection. It disconnects us from the world around us, from the sounds of the birds that share our cities, from the light of the stars in the night sky. It removes us from nature and it makes nature feel like a far away and unattainable thing. Whereas what it really is, is something that exists in our backyards, in our lives, surrounding us all the time. We just need to create an environment where we can actually tap into all of that.

Host: Benjamin Thompson

Finally then, I've been back through my notes for your book. And I was going through to try to guess which animal you enjoyed writing about the most, right. Like, not what is your favourite animal, but which one did you enjoy writing about the most and I've narrowed down to three, right. One of them is snakes and I think I just wrote down ‘snake tongues, wait, what?’, octopuses and bats. They're the three. You tell me which one was it? Or was it none of those?

Ed Yong

Oh, I love them all. I mean, it's hard to pick a favourite but I'm certainly not going to fight you on any of those three. So, one thing that was interesting to me was the animals that a lot of people hate repeatedly feature the book. So, there are lots of bits about spiders, snakes, there’s stuff about scorpions and sharks. And I think there's a few reasons for this. One, like all of those weirdos also have like incredible senses, but they're also creatures I've always been drawn to. I find snakes extraordinarily beautiful. I find bats phenomenally cool. And I think I've always sort of gravitated to the under snakes, under bats, the things that get a bad rep because they just seem kind of wonderful to me.

Host: Benjamin Thompson

Well, let's leave it there then. Ed, thank you so much.

Ed Yong

Thanks for having me.

Host: Benjamin Thompson

Ed Yong there, and his book An Immense World is available now. And that's it for episode one of Nature hits the books. If you have any feedback on the show, why not ping us an email to podcast@nature.com with the subject line ‘Nature hits the books.’ Otherwise, look out for episode two later in the year. The music used in this episode was called To Clarity by Airae via Epidemic Sound/Getty Images. I’m Benjamin Thompson. Thanks for listening.