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

The Umwelt

In 1909, the Baltic German biologist Jakob von Uexküll introduced the concept of Umwelt — the unique perceptual world that each animal species inhabits. A tick, he observed, has a sensory world defined by three stimuli: the smell of butyric acid (which it uses to detect warm-blooded mammals), warmth (which it uses to identify a good spot to attach), and the texture of hair or fur. Everything else in the world is, to a tick, simply absent — not perceived, not registered, as if it doesn’t exist.

The tick’s Umwelt is radically impoverished compared to a human’s. But a human’s Umwelt is radically impoverished compared to a mantis shrimp’s, which can perceive sixteen types of photoreceptor (humans have three) and see ultraviolet and infrared light. It is radically impoverished compared to a shark’s, which can detect the electrical signals produced by other animals’ muscles. It is radically impoverished compared to a bat’s, which constructs a three-dimensional model of the world from reflected sound waves with a resolution that competes with human vision.

Ed Yong’s An Immense World is an exploration of Umwelten — a tour through the perceptual worlds of dozens of animal species that reveals the universe of experience that exists outside and around the narrow band of reality that human senses access.

The Book’s Organisation

Yong organises the book by sensory modality: light, colour, darkness, echoes, touch, vibrations, electric fields, magnetic fields. Each section is structured around the specific animals that have developed extraordinary versions of the relevant sense, the evolutionary pressures that produced these abilities, and the scientific techniques that have allowed researchers to discover and understand them.

The range is extraordinary. He covers: the mantis shrimp’s visual world; the bat’s echolocation; the star-nosed mole’s nasal processing; the lateral line of fish that detects water pressure; the electric sense of sharks and rays; the magnetoreception of birds that allows them to detect Earth’s magnetic field; the spider’s ability to perceive the entire world through vibrations transmitted through their webs.

Each chapter is its own immersion — a careful build-up of evidence followed by a moment of genuine wonder at what the evidence implies. Yong has a talent for the specific analogy that makes an alien sense imaginable: he compares bat echolocation to driving in fog, electric field detection to being perpetually aware of every object in a room based on how it distorts a subtle constant signal, magnetoreception to having an internal compass that you cannot turn off.

The Writing

Ed Yong won the Pulitzer Prize for his COVID-19 reporting for The Atlantic. An Immense World reveals why: his science writing is the clearest and most accessible in the field, but clarity and accessibility are not the same as simplification. The science in this book is rigorous; the research is current and carefully attributed; the uncertainty about what is known and unknown is acknowledged throughout.

Yong is also a genuinely beautiful writer — his sentences have a quality of precision that is also pleasure, the kind of writing that makes scientific description feel like literature rather than instruction. The chapter on bat echolocation is as good as anything written about the natural world in recent years.

The Ethical Dimension

Near the book’s end, Yong turns to a question that the preceding chapters have made unavoidable: what do the Umwelten we have explored mean for how we should treat animals? If fish feel pain, if octopuses experience something analogous to curiosity, if crows have something that resembles grief — if these things are true, or even probably true, what follows?

Yong handles this section carefully, acknowledging both the strength of the case and the resistance it meets from economic and cultural interests invested in not expanding the category of morally considerable beings. He does not resolve the question — which is appropriate, because it is genuinely unresolved — but he ensures the reader cannot avoid it.

Why This Book Matters

An Immense World is the rare popular science book that genuinely changes how you perceive your environment. After reading it, a walk outside is different: the awareness that the birds overhead are navigating by magnetic field, that the insects are perceiving light in spectra invisible to you, that the ground below carries vibrations in which whole sensory worlds are conducting their business — all of this becomes not abstract knowledge but a felt sense of the hidden complexity surrounding the thin slice of reality that human senses access.

This is what the best natural history does: not merely inform but expand the imagination in ways that persist.

Our rating: 4.8/5 — One of the finest popular science books of the decade. Read it and the world will be stranger and more wondrous.