by Brent Eades
Dolphins can use their echolocation sense to identify food targets as far as 750 yards away — not only the shape of them but what’s beneath their skin, such as internal organs, or fish hooks inside tuna that they can then avoid. Ticks are blind and deaf, but have sensors on their front legs that can detect your body heat from a dozen feet away.
These are two of the fascinating things I learned from reading Ed Yong’s latest book, An Immense World: How Animal Senses Reveal the Hidden Realms Around Us. Yong is a science writer with The Atlantic, where his reporting on COVID won a Pulitzer Prize and many other awards. He has a graduate degree in biochemistry.
An Immense World explores the umwelt of animals – essentially, the particular sets of senses that shape their experience of the world. Umwelt is German for ‘environment’ (plural umwelten) and was coined by the biologist Jakob von Uexküll in 1909. (As an aside, this is one of the few technical terms the reader will need to absorb in order to understand and enjoy the book.)
As the 450 pages of An Immense World make abundantly clear, those umwelten are almost inconceivable in their variety and — to us — strangeness. Other creatures see things we can’t see and hear things we can’t hear. They have senses and sense organs that we don’t have. As Yong writes, “Our umwelt is limited; it just doesn’t feel that way. To us, it’s all-encompassing. It is all that we know, and so we can easily mistake it for all there is to know.”
He sets the scene in his introduction, where he imagines the proverbial elephant in a room, together with a human and various other species. The elephant makes an infrasonic rumble that we can’t hear but the snake detects through its vibration-sensitive underside. The mouse utters a squeak we can’t hear but the bat can. The mosquito smells the carbon dioxide on the human’s breath. The room goes dark, but the mouse can navigate by waving its whiskers about; the owl’s super-acute ears detect the mouse’s tiny footsteps, while the spider waits for some entangled prey to tug on its web – a “trap that acts as an extension of its senses.” And so on.
Yong is a skilled and engaging storyteller with a pleasantly light touch. His reporting is impeccable; through the course of the book he interviews scientists around the world, often visiting them in their labs and in the field. His bibliography runs to 34 small-print pages.
The stories he tells of the vast variety of animal senses are entirely absorbing; I found myself saying “That’s amazing!” every few pages. The concepts were a little hard to grasp at times – since, by definition, Yong is explaining sensory experiences we simply can not have.
Many birds, for instance, can hear faster than we can. Although they and we can hear roughly the same range of sounds, from lows to highs, they can hear intervals in sounds that we can’t. A note in a birdsong that sounds like a single unbroken tone to us might sound much more complex to the bird – “full of jagged bumps, which represent extremely fast shifts within the span of a single note.” (Most insects, on the other hand, can’t hear anything at all.)
Some species use electricity to sense things — bumblebees can detect the unique electrical patterns of the flowers they want to drink from, while sharks and rays can sense the faint electrical fields of their prey. Other species use vibrations or the earth’s magnetic fields as sensory input.
Fascinating as all this may be, does it really matter? Does a better understanding of the myriad kinds of umwelten change anything? It does, as it turns out.
Yong notes that even the world of science has been slow to discard an anthropomorphic bias – “to frame animals’ live in terms of our senses rather than theirs.”
This can lead to bad outcomes for those animals. We place bright lights by seashores that deceive hatchling turtles into thinking they’re seeing the moon and lure them to their deaths. Noise pollution in the oceans drowns out communication between whales, and clear windows kill millions of birds each year.
It can even be hard on our dogs: their sense of smell is exceptionally sophisticated and their constant sniffing of everything around them is fundamentally important to them. Yet when we walk them, we very often yank at their leashes every time they stop to sniff, depriving them of essential data about their canine world.
An Immense World is an excellent read and I highly recommend it, not just to nature lovers but to anyone wanting to look at the world around them from a fresh perspective.