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The human sensory experience is limited. Journey into the world that animals know

DAVE DAVIES, HOST:

This is FRESH AIR. I'm Dave Davies, in for Terry Gross. After reporting on the first year of the pandemic for The Atlantic, for which he won a Pulitzer Prize, science writer Ed Yong decided he needed to take a break. He wanted to shift his focus from the catastrophes and tragedies caused by COVID to a facet of the natural world he hoped would bring some joy to his life and to his readers. The result is his book "An Immense World: How Animal Senses Reveal The Hidden Realms Around Us." It's almost like science fiction or the supernatural, in that it describes the worlds that animals, birds and insects perceive which humans can't - the sounds, smells, colors, vibrations, echoes and magnetic fields that exist beyond the limits of our own senses. He writes about animals with eyes on their genitals, ears on their knees, noses on their limbs and tongues all over their skin. As he puts it, every animal, including humans, can only tap into a small fraction of reality's fullness. The book is about the diversity of perception in the animal world and the limitations of human perception. Ed Yong spoke with Terry Gross.

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TERRY GROSS: Ed Yong, welcome back to FRESH AIR.

ED YONG: Hi. Thanks for having me.

GROSS: So your book is about how every animal, including us, is enclosed within its own sensory bubble, as you put it, perceiving but a tiny sliver of an immense world, which leads to the word umwelt, which is a word I'm sure you'll be using. So why don't you describe what it is?

YONG: So umwelt was popularized by a German biologist named Jakob von Uexkull. The word comes from the German for environment, but von Uexkull wasn't using it to mean the physical environment. He meant the sensory environment, the unique set of smells, sights, sounds and textures that each animal has access to and that might be unique to it, its own little bespoke sliver of reality. So I'll give you an example. Like, humans can see colors ranging from red to violet, but we don't - we aren't able to see the ultraviolet colors that actually most sighted animals can perceive. We can't detect the magnetic fields of the Earth that songbirds and sea turtles can. We can't detect the ultrasonic frequencies that bats use to navigate around them or that rats and mice used to send messages to each other that we can't hear. So every creature has these sensory limitations and is enclosed in its own particular sensory bubble. And that's what the umwelt is.

GROSS: Where are you now?

YONG: I am in my home in D.C. I am in the recording studio/shoe closet of the bedroom or, as my wife calls it, our shoedio (ph).

GROSS: OK. So it's not exactly a rich sensory environment. But if...

YONG: It is not.

GROSS: If you were one of the animals you were writing about or insects or birds, what might you perceive in this studio/closet that you can't perceive now?

YONG: So at the start of the book, I do this - exactly this thought experiment, right? I imagine that I'm - a human is sharing a physical space with a bunch of creatures - say, a rattlesnake, an elephant, a mouse, a dog. It's hard to imagine all of those in this shoe closet with me. But if we do, then the rattlesnake, for example, will be able to sense my body heat. Even if I switched off the light in this closet, it would be able to detect my presence from the infrared radiation I was giving off. A bird in this closet, even though we're surrounded by walls, would be able to detect the magnetic field of the Earth and would know which direction to fly if it was time to migrate.

A dog - if my own dog, Typo, whose a corgi, was in this room, he'd almost certainly be sniffing around. He'd be picking up the odors that are abounding in this space and that I cannot detect. So each of these creatures, we could all be sharing exactly the same physical space and have a radically different experience of that space. And that's what "An Immense World" is about. It's about going through these adventures, these sensory voyages, by considering the umwelten of other animals.

GROSS: Let's talk a little bit about vision. You mentioned ultraviolet light, which we cannot see. All the colors we see are based on three colors - blue, yellow and red, although I really don't understand exactly...

YONG: Red, green and blue.

GROSS: Red, green and blue. Wait, I thought green was blue and yellow.

YONG: So you're thinking about primary colors, like, with paints. For light, it's different. So for light, it's based on red, green and blue.

GROSS: No kidding Really? Oh, I didn't know that (laughter). OK. So we see red, green and blue.

YONG: Yes. We have three kinds of color-sensitive cells in our eyes that are most sensitive to red, green and blue.

GROSS: So what are we missing? Like, for insects that can see or butterflies, I guess, that can see ultraviolet light, what are we missing, for instance, in flowers, which are beautiful enough with what we can see? But what are we missing?

YONG: So flowers, absolutely, are extraordinarily beautiful. But if you had the ultraviolet vision that a bee has, you'll be able to see patterns on those flowers that we can't see. So a sunflower, for example, far from looking just a matte - a uniform yellow would have a stark ultraviolet bullseye at its center. A lot of flowers have these ultraviolet shapes, like arrows and bullseyes, to guide insects towards the pollen at their center. Some predators that eat pollinating insects like crab spiders blend in when - blend in against the flowers to our eyes but really stand out when viewed in ultraviolet. And that acts as a lure to insects. It draws them in towards the waiting spider.

One of my favorite things about the relationship between insect vision and flowers is that if you took all the colors in all the flowers that were out there and you asked what kind of eye, what kind of color vision is best at discriminating between these colors, what you get is an eye that's basically almost what a bee has, an eye that is maximally sensitive to blue, green and ultraviolet. And you might think then that the bee eye has evolved to see the colors of flowers really well. And that's exactly the opposite of what happened because the bee eye came first; the flowers evolve later. And so the colors of flowers have evolved to ideally tickle the eyes of bees. And I think that's a truly wondrous result. It means that beauty, as we know it, is not only in the eye of the beholder. It arises because of that eye. Eyes in viewing nature's palette also affect its paintings.

GROSS: Oh, it's really form follows function.

YONG: Yes. Right.

GROSS: So what exactly is UV light? I mean, we know it's used to, like, sanitize things. And, you know, like my electric toothbrush has a UV light in the little cleanser unit. But in terms of vision, like, what is it? And why can't we usually see it? Like, the UV light in my toothbrush thing, when I turn it on to clean the toothbrush, I see blue. Maybe that's just a blue lightbulb. I don't know.

YONG: Yeah, right. That's the blue part of the light that you can see. So our - we can see light ranging from red to violet, right? It's the classic rainbow of colors that we can perceive. Ultraviolet - literally beyond violet - exists beyond the violet end. It's just off its edge. Now, there's a huge range of UV light that includes the stuff that causes sun burn and that, you know, we use to sanitize our world. But there's also a section of it near UV that exists quite close to that violet that we can see that effectively paints nature. You know, it's there in flowers, like we've said. It's there on the feathers of birds. And most other animals that can see color can see that UV. We didn't used to think that. We used to think that it was special, that seeing ultraviolet was rare.

And that, I think, reflects how much the limits of our own senses affect our view of the world. We think of things that have different umwelten, that see differently to us as being extraordinary, whereas, in fact, often, they are very typical. So, you know, most birds can see ultraviolet, most insects can do it; a lot of other mammals can do it. We're actually quite weird in not being able to see ultraviolet. For a long time, scientists used to think that ultraviolet was a sort of secret communication channel that animals used to send coded, like, hidden messages that other creatures could not see. Sometimes that is the case.

There are, for example, fish that look completely uniform yellow. But if you look at them through ultraviolet, you see that they have, like, distinct patterns on their faces, almost like running mascara. But in the main, those messages aren't secret because most animals can actually see them. Ultraviolet abounds in the world around us. And there's just a ton of stuff that we're missing. You know, there are loads of birds, for example, including common backyard birds, where we think the males and females look exactly the same, but they all look very different to each other because they can see the ultraviolet patterns that distinguish the sexes.

GROSS: So scallops have a lot of eyes. I never thought about whether scallops even had eyes, but they have an eye at the end of each of their mobile tentacles. So how do they work, and how do they coordinate? It sounds very, like, sense surround.

YONG: Yes. It is and it isn't. So for most of us, our experience of scallops is just - is going to be a tasty puck of flesh, you know, seared in butter and garlic. That's just part of the entire animal. If you look at the entire animal and its beautiful shell, on the rim of that shell, there'll be dozens of eyes, possibly hundreds in some species. For some scallops, those eyes are really beautiful. They look like neon blueberries. And you would think then that the eyes give scallops this beautiful vision of the world so that they would have this image that's the sum total of what their dozens or hundreds of eyes see. But it's not quite like that. Scallops have very simple brains and too simple to really create this composite view from what their eyes do.

Trying to imagine the visual world of scallops is quite difficult. The way I imagine it, imagine that the scallop is like a security guard looking at a bank of monitors. Each of those monitors represents the view from one single eye. And that eye is good. It has good optics. It's a decent state-of-the-art camera, but what it feeds to the monitor is the simplest possible information. It's just, have I detected something interesting or not? So the scallop, the security guard, doesn't see a bank of dozens or hundreds of images. It just sees like, say, maybe a green light, so something that says, yes, there's something interesting over here that I can then explore with my other senses, like touch or smell.

It effectively sees without scenes. And that's, I think, very difficult for some - for, you know, a species like us to imagine. For me, vision is completely inextricable with this, like, movie-like representation of the world around me. I can see in rich detail everything that's in this weirdly small closet. But if I was a scallop, I wouldn't be able to do that. I would have some visual awareness of the world around me, but I wouldn't have this detailed image that is so synonymous with vision for a human.

GROSS: Well, let's take a short break here, and then we'll talk more about some of the things that humans cannot perceive. My guest is Ed Yong, who writes about science at The Atlantic. His new book is called "An Immense World: How Animal Senses Reveal The Hidden Realms Around Us." We'll be right back. This is FRESH AIR.

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GROSS: This is FRESH AIR. Let's get back to my interview with Ed Yong, a science writer for The Atlantic. He won a Pulitzer Prize for his coverage of COVID. His new book is about how animals' senses allow them to perceive sounds, smell sights, echoes, magnetic fields and more that humans are incapable of perceiving with their senses. It's called "An Immense World: How Animal Senses Reveal The Hidden Realms Around Us."

Let's talk about echolocation. Why don't you explain what it is?

YONG: Echolocation is a very advanced form of hearing that a lot of animals, like bats and dolphins, use to perceive the world around them. So they make high-pitched, ultrasonic calls beyond the range of human hearing. And they listen out for the echoes of those calls after they've rebounded off objects around the animal. And by listening for those echoes and passing those echoes, they get a sense of the world around them. A bat in complete darkness can find, track and swoop upon a flying insect. It can navigate through the darkness of a cave. It can wend its way around obstacles, all by using this incredibly sophisticated type of hearing.

GROSS: So I want to talk about another side of bats for a moment, because on the one hand, like, that's so remarkable. They have echolocation. It's something we don't have. We don't have this ultrasonic sound ability. At the same time, now when we think of bats, we're thinking bats may have been the origin of COVID. Bats may have been one of the origins of monkeypox. It's named monkeypox because it was discovered first in a monkey, but it spread initially by rodents. At least that's what scientists think now. So when you think of bats, do you think like, oh, they're amazing, or like, oh, they're real trouble?

YONG: Right. Bats do act as reservoirs for viruses. I don't think that they deserve a bad reputation because of that, though. You know, they are extraordinary creatures with extraordinary senses. You know, it's - the fact that we are in trouble now with COVID and multiple other diseases isn't the fault of bats. In many ways, it's to do with how we have reshuffled the natural world around us and kind of crunched down the amount of space that other animals have. You know, we've sort of intruded upon their worlds. And, you know, I've written before that it's like humanity has crushed the world's wildlife in a tight fist, and viruses have spilled out of that as a result.

You know, in many ways, this book is a chance to talk about the incredible things that bats do and the wonderful ways of perceiving the world that might be lost if we persecuted bats or if we continued the practices that reduce the habitats and harm them. Even the kinds of bats that are the most likely reservoirs of SARS and other related viruses have this absolutely extraordinary skill. They have taken echolocation to extreme heights.

So a bat typically creates a high-pitched call that covers a range of frequencies, and it's listening out for the echoes that come back. These specific kinds of bats, the horseshoe bats of Asia, create a call that is very much like a single tone. Like, they just hold a note. And their ears are tuned to the very specific frequency that they put out. That allows them to detect very specifically the fluttering wings of insects. As an insect beats its wing, there comes a point where the wing is exactly angled to the bat as to return a very sharp echo. And that's what the bat is looking for with this very specifically toned call.

GROSS: Can we compare the bat's echolocation with an animal that is really, really different - dolphins? 'Cause they use echolocation, too. They're different in terms of the environment they live in, their size, their needs. So could you compare them?

YONG: Yes. Bats and dolphins are the two masters of echolocation in the animal kingdom. And in some ways, they use it to similar purposes. But the difference between them is mostly because dolphins are echolocating in the water. Their calls travel much further. And so for them, echolocation is a much longer-range sense than it is for bats. You know, a bat can only really detect a small moth within several feet in front of it. A dolphin's echolocation can extend much, much further, and that allows dolphins, for example, to use echolocation to coordinate their movements, to coordinate their hunting strategies over the distance of an entire pod.

Dolphins can also use echolocation kind of like a medical scanner. They can detect hard surfaces that exist inside other animals. You know, a dolphin echolocating on a human could likely see your skeleton, could likely see your lungs. Dolphins can, through echolocation, detect the swim bladders inside the fish that they hunt. They can probably tell the difference between different kinds of prey by the shape of their swim bladders. So they have this incredible see-through ability, but - except it's not really to do with vision, right? It's to do with sound.

GROSS: So this was amazing to me. You write that dolphins can visually recognize objects that they first identified through echolocation. They can even identify the object on a video screen. That seems implausible to me.

YONG: Right. Absolutely - because when you think about sound, you don't think of creating this rich, three-dimensional representation of an object. You know, if I heard this - if I heard a recording of someone playing a saxophone, I would appreciate it. But there's no way I could go from that to, like, recreating the shape of a saxophone in my mind. But dolphins actually are doing that with sound.

They can echolocate on an object. They can then work out - it seems as if they build a physical model of what that object looks like - its shape, maybe its texture - which they then can use as fodder for their other senses. So they can recognize, say, on a screen, the shape of an object that they previously echolocated upon. And that is extraordinary. I think that speaks to not only their weird sensory worlds, but how those extraordinary senses can be deployed by an extremely intelligent animal.

GROSS: Well, let's take a short break here, and then we'll talk some more. If you're just joining us, my guest is Ed Yong, who writes about science for The Atlantic. His new book is called "An Immense World: How Animal Senses Reveal The Hidden Realms Around Us." We'll be right back. I'm Terry Gross. And this is FRESH AIR.

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GROSS: This is FRESH AIR. I'm Terry Gross. Let's get back to my interview with Ed Yong, a science writer for The Atlantic. He won a Pulitzer Prize for his coverage of COVID. His new book is about how animals' senses allow them to perceive sounds, smells, sights, echoes, magnetic fields and more that humans are incapable of perceiving with their senses. The book is called "An Immense World: How Animal Senses Reveal The Hidden Realms Around Us."

I want to talk with you about pain, which you describe as the unwanted sense. I heartily agree. And I found this chapter really interesting. As somebody who's very pain averse, I was surprised to hear that not all animals experience pain - or at least the things that might hurt us and cause us to perceive pain, some animals don't perceive it as pain. Give us an example of that.

YONG: So a really good example might be to turn to the cephalopods - so octopuses, squid and other related animals. There, what you find is that these creatures' experience of pain varies significantly. So a squid, for example, if you injure it in part of its body, it doesn't seem to have a local experience of pain. You know, if I stub my toe, I know, oh, my toe hurts. For a squid, it seems that its entire body becomes hypersensitive. So it's not as if it's like, oh, my third arm hurts. And that might be because a squid's arms are short. It can't really explore a lot of its body. If it knew that part of its body was injured, it might not be able to do anything about it. That's not true for octopuses, which have much longer and dexterous arms, and they do seem to be able to understand - they do seem to have an experience of pain. They do seem to understand exactly which part of their body has been injured. And they will cradle and tend to an injury, much like a human would.

So even here, I think, you know, when you look at this one group of animals, you see very distinct kinds of pain. And I think that's really important, right? Often when we think about pain in the animal kingdom, we think of it as this yes-or-no thing. Either animals experience pain exactly like humans do, or some people contend that they don't experience pain at all. I think in most cases, it's likely to be something in the middle, and their experience of pain is going to vary just as our experience of color or sound or other sensory information might.

GROSS: But you write, for instance, about the mole rat, which you said doesn't experience pain from certain acids, like those really hot acids in chili peppers.

YONG: You know, if you - if I ate a chili, if there was tons of capsaicin, in it my eyes would water. It would feel really hot. A naked mole rat - it wouldn't bother them at all. Birds also seem to be largely insensitive to capsaicin, so they don't care about the sting of chili peppers. You know, I write about a type of mouse that is insensitive to the extremely painful chemicals found in scorpion venom. And indeed, it can use those chemicals as a kind of pain killer, as the opposite of what I think the scorpion evolved them to be. So there doesn't seem to be anything that universally across the animal kingdom is painful. Even things that we think of as being extremely painful, like capsaicin, like acids, like extremely hot or cold temperatures, might feel like nothing to a lof of other creatures.

GROSS: Yeah, including, as you say, some hibernating creatures don't experience extreme cold as pain. I mean, they just sleep through it. So what are some of the explanations for why some animals don't perceive pain from some of the substances or things that cause pain in humans?

YONG: It varies a lot. In terms of temperatures, animals have thermal sensors in their nerve cells that open and cause those cells to fire at specific temperatures. The thresholds for firing might differ from one species to another so that what to us might be painful heat, might be extremes of temperature, to them feel like nothing. And I think that's important to think about. You know, when we look at a hibernating animal in the dead of winter, we think that maybe it's sort of suffering through its experience. But in reality, I think most of those animals don't care. They simply don't feel to the cold in the same way that we do. They tolerate it because their senses are calibrated to different conceptions of what cold and hot might be.

GROSS: So I have a cat, and a really interesting thing I learned about cats is that they have muscles in their bellies that sense vibration. Can you elaborate on that?

YONG: Right. So many animals have vibration-sensitive cells in their organs of touch. You know, I have them in my fingertips, for example. It seems that cats have that on their bellies. And one scientist I spoke to, you know, had this hypothesis - like, if a cat is laying down in a crouch, you know, is it also sensing the vibrations caused by possible prey? You know, when we see a lion watching a herd of antelope in the distance, is it also getting information through the crouch about the footsteps of those prey?

Now, I want to be very clear. We don't know the answer to that question, and it might be entirely far-fetched speculation. I write about it in the book specifically because I think it's the type of question we should be asking because a lot of people, including scientists who work on the senses, neglect the world of vibrations, the world of seismic tremors that course through the ground and surfaces along us. You know, we care when those vibrations move through the air. We call them sounds. But when they move through surfaces, we tend to ignore them. Except a huge number of animals - scorpions, moles, elephants - many insects seem to pay attention to that vibrational world. And I think if you really start thinking about it and looking at it, you know, you learn incredible things about nature that you might otherwise have missed.

GROSS: You say you got a puppy during COVID...

YONG: I did get a puppy.

GROSS: ...Named Typo. Great name.

YONG: Thank you.

GROSS: And you write that you've been spending more time on the ground, you know, on the floor with your dog. Have you noticed vibrations that you never noticed before?

YONG: I have, very much so. You know, I can sense the vibrations of our downstairs neighbors coming in to the door - coming in through the front door and walking around. I can tell when cars are driving past in the streets next to me, when big trucks are. And I can feel them in a different way than I could if I was just sitting up and hearing them. And that's what I mean. You know, we pay attention to vibrations moving through the air in the form of sounds, but those moving through the ground, we're a little oblivious to. That's not the case for many animals. I don't think it's the case for my dog, and I don't think it's the case for a lot of other creatures around us.

I can give you one of my favorite examples - right? - from the book about the vibrational worlds of other animals. There are little insects called leafhoppers that sit on plants. You probably haven't heard of them. But if you've ever been, like, in a garden or a park, you will almost certainly have walked past or sat next to one of them. They send - make vibrations with their abdomens that course through the plants so that other leafhoppers can detect but that are inaudible. If you clip a small microphone onto the plant and try and transform those sounds into things we - and transform those vibrations into things we can hear, what you get is just out of this world. The songs of these insects sound like birdsong. They might sound like musical instruments. They might sound like a machinery. They sound entirely unlike what an insect would make. They are beautiful and haunting and clearly everywhere around us without - you know, below - it - to a degree that we cannot sense.

GROSS: And you think that the other leafhoppers aren't hearing it. They're feeling the vibrations of it?

YONG: Exactly, yep. I think that they are feeling those vibrational songs, and I think that the plants around us just course with those vibrational signals.

GROSS: All right. Time for another break. Let me reintroduce you. If you're just joining us, my guest is Ed Yong, a science writer for The Atlantic. His new book is called "An Immense World: How Animal Senses Reveal The Hidden Realms Around Us." We'll be right back. This is FRESH AIR.

(SOUNDBITE OF MUSIC)

GROSS: This is FRESH AIR. Let's get back to my interview with Ed Yong, a science writer for The Atlantic. He won a Pulitzer Prize for his coverage of COVID. His new book is about how animal senses allow them to perceive sounds, smells, sights, echoes, magnetic fields and more that humans are incapable of perceiving with their senses. It's called "An Immense World." Let's talk about electricity. There's around 350 species of fish that produce their own electricity. How do they use that electricity to communicate and to size up the world around them?

YONG: Yeah. So they produce weak electric fields that mostly are too weak for us to detect but that can - but that form the basis of this extraordinary sense. So those fields get distorted by the objects around them, whether those objects are conductive like plants or insulating like rocks. And by detecting these distortions, the fish can get a sense of their surroundings. This allows them to exist and navigate through incredibly murky water where vision would be useless. It allows them to detect hidden prey. It is very difficult - almost impossible - to hide from the electric sense in the way that you could from a hunter that uses vision. And these fish also use their electric senses to communicate with each other. The pulses that they create to map their surroundings are also the basis of signals that they send to one another. And, you know, in many rivers in South America and Africa, the water is full of these electric messages.

GROSS: I mean, that’s such a theme of science fiction that you could have this, like, superpower of emitting electricity. It really is remarkable how animals have all these things that we attribute in a way to the supernatural or superpowers.

YONG: Absolutely. And I think one of the big themes about - or one of the big themes of An" Immense "World is that these abilities can seem supernatural, but they are actually just natural. It’S just that the limitations and the expanse of the natural world is so much larger than what we give it credit for. When we perceive the world through our own senses, we get this incredibly powerful illusion that we are perceiving all that is because our sensory information feels total and complete. It’s not, though. We are only really getting a thin slice of all there is to perceive. And I think if you look at what other animals can sense, whether it’s electric fields or echoes or ultraviolet as we've talked about, you understand that the world is so much broader than what our limited sensorium gives us.

GROSS: It’s very humbling.

YONG: Thank you. Yes, it is. It very much is.

GROSS: Now that you've immersed yourself in worlds that you can read about but you can't perceive, how has it changed your sense of the world around you?

YONG: I think it does two things. First, it just makes things that felt very familiar feel newly wondrous. So when I walk Typo along the streets of my neighborhood, those streets look exactly the same to me from one day to the next. But they change on an almost hourly basis to his nose so that every walk, he's exploring really intensely. He's sniffing new patches of sidewalk, and he clues me in to the fact that the world around me that I think of as boring is actually in constant flux. And I think that's a gift. I think I see the parks around me in a new light because I know that the plants there are thrumming with the vibrational songs of leafhoppers. You know, if I look at a body of water, if I look at, you know, the featureless ocean, I understand that it's full of currents that fish can sense. It's full of smells rising from the surface that a seabird can sense. The world just feels richer to me.

And I also see the animals themselves in a different way. You know, I understand that their lives are magnificent and spectacular even when they don't seem to be doing very much at all. You know, if I popped my head out the door of this closet and I looked out my back window, I guarantee you I could see a robin or a sparrow perched there. And it's the most common of birds. And yet, those are animals with incredible color vision. They can see an entire dimension of colors that I can't see. They can hear - their hearing is so finely tuned to fast changes in sounds that they can hear qualities in their own notes that I can't perceive. They are extraordinary even in the mere act of existence. And I think understanding that has been a truly profound gift that writing this book has given me and that I hope that it gives to readers.

GROSS: Your book deals with what animals' senses can perceive. It doesn't, I don't think, really raise the question of consciousness. Do you feel like you've learned anything through researching this book about whether animals and fish and butterflies have consciousness?

YONG: Yeah, that's a difficult and different question. But I think that the senses provide the foundation for starting to think about - thinking about consciousness. You know, they are like the building blocks of whatever subjective experiences we have. And I think they hint at why that world is so difficult for us to get at. You know, even when you think about the senses, even when you think about what an animal might be seeing or feeling or hearing, there's always going to be this gulf between what we experience and what they experience that no amount of scientific research can fully bridge. Alexandra Horowitz, a dog cognition researcher, talks about making these informed, imaginative leaps into the umwelten of other animals, that we always need to speculate a little bit, to go on a voyage of creativity and imagination, to enter those other subjective worlds. That's true for the senses. It's even truer when it comes to thinking about consciousness.

GROSS: I really like the way you end the book, and you write about how most people think of, you know, the majesty of nature as being like canyons and mountains. But you write, equating wilderness with otherworldly magnificence treats it as something remote, accessible only to those with the privilege to travel and explore. It imagines that nature is something separate from humanity rather than something we exist within. Can you talk about that realization?

YONG: Yeah. This speaks to my earlier point that if you start thinking about the umwelt of other animals, you understand that nature's magnificence is all around us. It's in our backyards. It's in our gardens. You know, it's in the bodies of some of the most familiar creatures around us - my dog, the pigeons on the street. I think that if we think of nature as something remote and distant, you know, accessible only to someone who can go to a national park, we lose the impetus to savor and to protect it. I think if you understand instead that nature is everywhere, that you can go - I can go on an adventure just by thinking about the sensory world of the sparrow that sits on the house opposite me, I think then nature feels like something close to me, close to my heart and close to my life. And I feel like if that's the case, people will be more motivated to try and protect it.

You know, protecting nature isn't just about, like, saving whales or pandas or what have you. It's about protecting even things that are close to us. And - because each of those things has a unique way of experiencing the world that is worth learning about, worth cherishing and worth protecting.

GROSS: Ed Yong, it's been a pleasure to have you back on the show. Thank you so much.

YONG: Thanks, Terry. Always a pleasure talking to you.

DAVIES: Ed Yong is a science writer for The Atlantic. His book is called "An Immense World: How Animal Senses Reveal The Hidden Realms Around Us." Coming up, John Powers reviews "Magpie Murders," the new Masterpiece mystery series on PBS. This is FRESH AIR.

(SOUNDBITE OF BENJI MERRISON AND WILL SLATER'S "BETWEEN FEEDS/AMOROUS PEACOCK") Transcript provided by NPR, Copyright NPR.

Combine an intelligent interviewer with a roster of guests that, according to the Chicago Tribune, would be prized by any talk-show host, and you're bound to get an interesting conversation. Fresh Air interviews, though, are in a category by themselves, distinguished by the unique approach of host and executive producer Terry Gross. "A remarkable blend of empathy and warmth, genuine curiosity and sharp intelligence," says the San Francisco Chronicle.