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

There's a vast world around us that animals can perceive — but humans can't.

Pulitzer Prize-winning science writer Ed Yong uses the example of a dark room: Though it might seem that there would be little to detect in the darkness, a bird in the room would be able to pick up on the magnetic field of the earth and would know which direction to fly if it was time to migrate. A dog would be sniffing out various odors that a human would not be able to smell. A rattlesnake would detect the presence of humans in the room by sensing their infrared radiation.

"Each of these creatures, we could all be sharing exactly the same physical space and have a radically different experience of that space," Yong says.

In his new book, An Immense World, Yong explores the diversity of perception in the animal world and the limitations of our own perception. He notes that each animal has access to its own sensory environment — called an "umwelt" — which creates its own "bespoke sliver of reality."

"Umwelt was popularized by a German biologist named Jakob von Uexküll," Yong says. "The word comes from the German for 'environment,' but von Uexküll 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."

Yong points out that humans can't sense the faint electric fields that sharks and platypuses can, or the magnetic fields that robins and sea turtles detect. Our ears can't hear the ultrasonic call of rodents and hummingbirds, and our eyes can't see the ultraviolet light that the birds and the bees can sense. But, he says, imagining the world as animals perceive it opens up a new appreciation for the everyday wonders of nature.

"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, it's in the bodies of some of the most familiar creatures around us, my dog, the pigeons on the street," Yong says. "It just makes things that felt very familiar feel newly wondrous."

Interview highlights

On what are we missing in human vision compared to insects

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. A sunflower, for example, far from looking just a matte 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 toward the pollen at their center. Some predators that eat pollinating insects, like crab spiders, 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 toward 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 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. That's exactly the opposite of what happened, because the bee eye came first, the flowers evolved later. 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.

On echolocation

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 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. ...

Bats and dolphins are the two masters of echolocation in the animal kingdom, and in some ways they use it for 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, which can only really detect a small moth within several feet in front of [them.] A dolphin's echolocation can ... [allow them] 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. 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.

On how dolphins experience sound as three-dimensional

When you think about sound, you don't think of creating this rich, three-dimensional representation of an object. 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 recreating the shape of a saxophone in my mind. But dolphins actually are doing that with sound. They can echolocate on an object. 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. 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.

On how some cephalopods experience pain

A really good example might be to turn to the cephalopods, octopuses, squid and other related animals. ... So a squid, for example, if you injure it on part of its body, it doesn't seem to understand where the pain is and it doesn't seem to have a local experience of pain. 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 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. 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, when you look at this one group of animals, you see very distinct kinds of pain. And I think that's really important. Often when we think about pain in the animal kingdom, we think of it as this yes or no thing. Animals experience pain exactly like humans do, or some people contend 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.

On how cats sense vibration

So many animals have vibration-sensitive cells in their organs of touch. I have them in my fingertips, for example. It seems that cats have that on their bellies. And one scientist I spoke to had this hypothesis, like, if a cat is laying down in a crouch, is it also sensing the vibrations caused by possible prey? 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. 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 learn incredible things about nature that you might otherwise have missed.

On how the light sculpture commemorating Sept. 11 and the attack on the World Trade Center disrupts bird migration

The light shines vertically into the heavens. It is beautiful. As an art installation, that's magnificent. But for migrating birds, it is a huge problem. The light draws them in, causes them to circle for a long time, depletes their energy, often distracts them and sends them hurtling into nearby buildings. Thousands of birds might be caught in these beams at any one time. If you're a migrating bird, you can't afford to get distracted. Migration is already an arduous process, and the birds need all the energy they can get. So for this reason, and because scientists have studied it, those lights are turned off for stretches of time if enough birds get caught in them.

There are many other examples of lights at night that confuse not only migrating birds, but also pollinating insects, hatchlings, sea turtles. All kinds of creatures get waylaid and disoriented and often fatally so by lights at night. This is a huge problem. And it's a recent one. For almost the entirety of life on Earth, animals have lived with these rhythms of light and darkness. It's really only in the last couple of centuries that those rhythms have been broken by the constant nighttime illumination that humans pour out. And we don't think of light as a problem, we think of it as a good thing, something we want, something that's safe. But it is a problem for the natural world. And the consequences can be devastating.

On how understanding umwelt has broadened the way he thinks of nature

I think that if we think of nature as something remote and distant, accessible only to someone who can go to a national park, we lose the impetus to save and to protect it. I think if you understand instead that nature is everywhere, then I can go on an adventure just by thinking about the sensory world of the sparrow that sits on the house opposite to 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. Protecting nature isn't just about saving whales or pandas or what have you. It's about protecting even things that are close to us ... because each of those things has a unique way of experiencing the world, that is worth learning about, worth cherishing and worth protecting.

Sam Briger and Joel Wolfram produced and edited this interview for broadcast. Bridget Bentz, Molly Seavy-Nesper and Laurel Dalrymple adapted it for the web.

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