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

by Ed Yong

The human’s house might be bigger than the tick’s, with more windows overlooking a wider garden, but we are still stuck inside one, looking out. Our Umwelt is still limited; it just doesn’t feel that way. To us, it feels all-encompassing. It is all that we know, and so we easily mistake it for all there is to know. This is an illusion, and one that every animal shares.

We cannot sense the faint electric fields that sharks and platypuses can. We are not privy to the magnetic fields that robins and sea turtles detect. We can’t trace the invisible trail of a swimming fish the way a seal can. We can’t feel the air currents created by a buzzing fly the way a wandering spider does. Our ears cannot hear the ultrasonic calls of rodents and hummingbirds or the infrasonic calls of elephants and whales. Our eyes cannot see the infrared radiation that rattlesnakes detect or the ultraviolet light that the birds and the bees can sense.

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. It reminds us that there is light in darkness, noise in silence, richness in nothingness. It hints at flickers of the unfamiliar in the familiar, of the extraordinary in the everyday, of magnificence in mundanity. It shows us that clipping a microphone onto a plant can be an intrepid act of exploration. Stepping between Umwelten, or at least trying to, is like setting foot upon an alien planet. Uexküll even billed his work as a “travelogue.”

Tetrachromacy doesn’t just widen the visible spectrum at its margins. It unlocks an entirely new dimension of colors.

Plants are strong, flexible, and springy, which makes them fantastic carriers of surface waves.[*4] Insects exploit that property, filling plants with their vibrational songs. Between treehoppers, leafhoppers, cicadas, crickets, katydids, and more, Cocroft estimates that around 200,000 species of insects communicate through surface vibrations. Their songs aren’t normally audible, and so most people are completely unaware that they exist. Those who become aware often get hooked.

ears can have exceptional temporal resolution or exceptional pitch sensitivity, but not both. “The auditory system that does fast stuff is completely different from the auditory system that does frequency stuff,” Lucas tells me. And he found that birds don’t have to settle for one or the other. They can flip between the two, as the situation demands.

The majesty of nature is not restricted to canyons and mountains. It can be found in the wilds of perception—the sensory spaces that lie outside our Umwelt and within those of other animals. To perceive the world through other senses is to find splendor in familiarity, and the sacred in the mundane. Wonders exist in a backyard garden, where bees take the measure of a flower’s electric fields, leafhoppers send vibrational melodies through the stems of plants, and birds behold the hidden palettes of rurples and grurples. In writing this book, I have found the sublime while confined to my home by a pandemic, watching tetrachromatic starlings gathering in the trees outside and playing sniffing games with my dog, Typo. Wilderness is not distant. We are continually immersed in it. It is there for us to imagine, to savor, and to protect.

A bogong moth will never know what a zebra finch hears in its song, a zebra finch will never feel the electric buzz of a black ghost knifefish, a knifefish will never see through the eyes of a mantis shrimp, a mantis shrimp will never smell the way a dog can, and a dog will never understand what it is like to be a bat. We will never fully do any of these things either, but we are the only animal that can even come close. We may not ever know what it is to be an octopus, but at least we know that octopuses exist, and that their experiences differ from ours. Through patient observation, through the technologies at our disposal, through the scientific method, and, above all else, through our curiosity and imagination, we can try to step into their worlds. We must choose to do so, and to have that choice is a gift. It is not a blessing we have earned, but it is one we must cherish.