Sensory Worlds Beyond Our Imagining

An Immense World; How Animal Senses Reveal the Hidden Realms Around Us, Ed Yong, Random House/Bodley Head, June 2022

This book is an enormous achievement. A thrilling read, taking us into the Umwelt, or perceptual world, of numerous mammal, fish, reptile and insect species. A major work of scholarship, with over a thousand references to a 45-page bibliography, as well as accounts of interviews with numerous researchers and visits to their laboratories. An exploration of many ways of sensing the world, some of which we share, while others are beyond our imagining. The evolving interplay of perception and action, communication and deception, environment and response. And an enhanced insight into what it is like to be a bat, a bird, a blue whale, a beetle, or a human.

From the wealth of detail in the book, a consistent grand narrative emerges. Some physical process interacts with living matter. This is the raw material for sensation. Sensory abilities then shape a creature’s Umwelt, being developed according to the demands of its environment. But every perceiver is itself an object of perception to others, and we have colour displays and camouflage, smells as signals and identifiers, sound as communication to others and, by echolocation, back to the creature who generates it, and the same is true of other senses that we do not share, such as the detection of tiny electrical fields. Senses combine and even, we suspect, merge, and what we ourselves perceive is but part of an immense pattern. But the heedlessness with which we amplify our own signals disrupts this pattern, contributing to our destruction of nature, and we ourselves are the poorer for it.

Let me offer a few samples from the book’s wealth of detail.

Yong starts with taste and smell, two ancient senses that operate by direct molecular contact. It is not long before he surprises us. Snakes use their forked tongues to smell in stereo. Humans are poor compared with other mammals at detecting smells at low levels, but are rather good at telling different smells apart. No one knows how smell relates to chemical structure (contrast this with how seeing relates to the wavelength of light, hearing to frequency, or touch to pressure). As every well-trained dog-owner knows, smell is central to the Umwelt of dogs, but I would never have guessed that the same is true of elephants. And the molecules involved in smell include opsins, which are central to vision. As Yong puts it, in a way we see by smelling light.