An Immense World: How Animal Senses Reveal the Hidden Realms Around Us

by Ed Yong

Earth teems with sights and textures, sounds and vibrations, smells and tastes, electric and magnetic fields. But every animal can only tap into a small fraction of reality’s fullness. Each is enclosed within its own unique sensory bubble, perceiving but a tiny sliver of an immense world. — There is a wonderful word for this sensory bubble—Umwelt.

Umwelt comes from the German word for “environment,” but Uexküll didn’t use it simply to refer to an animal’s surroundings. Instead, an Umwelt is specifically the part of those surroundings that an animal can sense and experience—its perceptual world.

Each species is constrained in some ways and liberated in others. For that reason, this is not a book of lists, in which we childishly rank animals according to the sharpness of their senses and value them only when their abilities surpass our own. This is a book not about superiority but about diversity.

The Umwelt concept can feel constrictive because it implies that every creature is trapped within the house of its senses. But to me, the idea is wonderfully expansive. It tells us that all is not as it seems and that everything we experience is but a filtered version of everything that we could experience.

Chemicals, then, are the most ancient and universal source of sensory information.

Imagine that you’re a mantis shrimp. It is a truth universally acknowledged that you are in want of something to punch.

By this point, dear reader, you might reasonably be feeling overwhelmed by talk of photoreceptors and midbands and hemispheres and all the other absurd complications that mantis shrimps have packed into their eyes.

Nociception is the sensory process by which we detect damage. Pain is the suffering that ensues.

There are open questions about all the senses, but at least with vision, smell, or even electroreception, researchers know roughly how they work and which sense organs are involved. Neither is true for magnetoreception.

At the time of writing, magnetoreception remains the only sense without a known sensor.

Beyond complementing each other, the senses can also combine. Some people experience synesthesia, where different senses seem to bleed into one another. To some synesthetes, sounds might have textures or colors. To others, words might have tastes. This perceptual blurring is special among humans, but standard to other creatures.

Many of the other planetary changes we have wrought have natural counterparts: Modern climate change is unquestionably the result of human influence, but the planet’s climate does change naturally over much slower timescales. Light at night, however, is a uniquely anthropogenic force.

To perceive the world through other senses is to find splendor in familiarity, and the sacred in the mundane.