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An Immense World | Book Review

April 30, 2023

[by Chuck Almdale]

How Animal Senses Reveal the Hidden Realms Around Us
By Ed Yong
Random House, 2022. $30, 355 pages plus notes, bibliography, index

This is an excellent and fascinating book which I recommend to everyone, everywhere. If you love science, biology, psychology, philosophy, sensory awareness, fish, birds, bats, whales, insects, slugs & snails or any of 1,000 other creatures, oddities and ordinarities of earthly life, you will love this book. If you don’t love and aren’t fascinated any of these things, this book is likely to spark an interest which may bloom into love. It’s just that good.

If that’s enough for you, skip the rest of this review, go to your library, bookstore or online source and get a copy. The Los Angeles Public Library has the following copies: books 10, e-books 90, e-audio books 104. If you need a little more persuasion, read on. Book excerpts are at the end.

There are parenthetical footnotes on nearly every page. They are far too interesting to skip. Here’s two:

Footnote pg 286: If you set a clock by a black ghost knifefish’s electric field, the device would lose an hour every year.

Footnote pg 306: Robins can also be sent off course by artificial magnetic fields that simulate the effects of solar storms.

From author Ed Yong’s website

An Instant New York Times Bestseller * Winner of the Carnegie Medal for Excellence in Nonfiction * Longlisted for the PEN/E.O. Wilson Literary Science Writing Award * Finalist for the National Book Critics Circle Award in Nonfiction * Finalist for the Kirkus Prize in Nonfiction

One of the Ten Best Books of 2022 according to the New York Times, the Wall Street Journal, Slate, People, Publisher’s Weekly, Philadelphia Inquirer, Outside, Bookpage, and more.

One of the Best Books of 2022 according to Barnes and Noble, the New Yorker, Oprah Daily, the Guardian, Time, the Economist, Amazon, Kirkus, Esquire, New Statesman, the Globe & Mail, Mental Floss, Reader’s Digest, Barack Obama, and more.

Enter a new dimension—the world as it is truly perceived by other animals—from the Pulitzer Prize-winning, New York Times bestselling author of I Contain Multitudes.

The Earth teems with sights and textures, sounds and vibrations, smells and tastes, electric and magnetic fields. But every kind of animal, including humans, is enclosed within its own unique sensory bubble, perceiving but a tiny sliver of our immense world. 

In An Immense World, author and Pulitzer Prize–winning science journalist Ed Yong coaxes us beyond the confines of our own senses, allowing us to perceive the skeins of scent, waves of electromagnetism, and pulses of pressure that surround us. We encounter beetles that are drawn to fires, turtles that can track the Earth’s magnetic fields, fish that fill rivers with electrical messages, and even humans who wield sonar like bats. We discover that a crocodile’s scaly face is as sensitive as a lover’s fingertips, that the eyes of a giant squid evolved to see sparkling whales, that plants thrum with the inaudible songs of courting bugs, and that even simple scallops have complex vision. We learn what bees see in flowers, what songbirds hear in their tunes, and what dogs smell on the street. We listen to stories of pivotal discoveries in the field, while looking ahead at the many mysteries that remain unsolved. 

Funny, rigorous, and suffused with the joy of discovery, An Immense World takes us on what Marcel Proust called “the only true voyage . . . not to visit strange lands, but to possess other eyes.”

Excerpts from the book (some are paraphrased)


[Pgs 69-70] Rising high on columns of warm air, griffon vultures soar over rolling landscapes in search of food. Since they can spot carcasses on the ground, they should easily be able to see large obstacles ahead of them. And yet vultures, eagles, and other large raptors often fatally crash into wind turbines. In one Spanish province alone, 342 griffon vultures collided with wind turbines over a 10-year period. How could birds that fly by day and have some of the planet’s sharpest eyes fail to avoid structures so large and conspicuous? Graham Martin, who studies bird vision, answered this question by addressing another: Where exactly do vultures look?

In 2012, Martin and his colleagues measured the griffon vulture’s visual field—the space around its head that its eyes can cover. They got each bird to rest its beak on a specially fitted holder, and then looked into its eyes from all directions with a visual perimeter. “It’s the same device that an optician would use when you get an eye test,” Martin told me at the time. “It’s just a question of sitting the bird down for half an hour. One tried to grab at me and I did lose a bit of my thumb.”

The perimeter revealed that a vulture’s visual field covers the space on either side of its head but has large blind spots above and below. When it flies, it tilts its head downward, so its blind spot is now directly ahead of it. This why vultures crash into wind turbines: While soaring, they aren’t looking at what is right in front of them. For most of their history, they never had to. “Vultures would never have encountered an object so high and large in their flight path,” Martin says. It might work to turn off the turbines if the birds are near, or to lure the vultures away using ground-based markers. But visual cues on the blades themselves won’t work.” (In North America, bald eagles also crash into wind turbines for the same reasons.)

When I think about Martin’s study, I’m suddenly and acutely aware of the large space behind my head that I cannot see and that I seldom think about. Humans and other primates are rather odd in having two eyes that point straight ahead. The left eye gets a very similar view to the right, and their visual fields overlap a lot. This arrangement gives us excellent depth perception. It also means we can barely see things to our sides, and we can’t see what’s behind us without turning our heads. For us, seeing is synonymous with facing, and exploration is achieved through gazing and turning. But most birds (except for owl) tend to have side-facing eyes and don’t need to point their heads at something to look at it.

[Pgs 165-166] Bird beaks are made of bone, sheathed in hard fingernail-like keratin. In many species the tip of the bill contains a smattering of mechanoreceptors, sensitive to vibrations and movements. In chickens, which rely heavily on vision to forage, those mechanoreceptors are relatively rare, concentrated in a few small clusters on the lower beak. But in some ducks like mallards and shovelers, they’re spread all over the bill, upper and lower, inside and out. In some places, these mechanoreceptors are as densely packed as they are in our digits. They use this sense to find food in murky water. With head submerged and tail aloft, they swirl, strain, and dabble, rapidly opening and closing their bills. They can grab fast-swimming tadpoles in the dark, and filter edible morsels from the inedible mud. ‘Imagine being given a bowl of muesli and mild to which has been added a handful of fine gravel. How good would you be at swallowing only the edible bits. Hopeless, I suggest, yet this is precisely what ducks can do.’

[Pgs 166-167] How does a shorebird know where to stick its bill into the sand. It’s not haphazard. It’s “remote touch.” Red Knots find shell fish up to eight times more frequently than would be expected if they were doing random searches. They can detect clams buried beyond the reach of their bills. They can sense stones. It’s touch that works at a distance. As the bill descends into the sand, it pushes on the thin rivulets of water between the grains, creating a pressure wave that radiates outward. If there’s a hard object in the way — say, a clam or a rock — the water must flow around it, which distorts the pattern of pressure. The pits on the knot’s bill can sense those distortions, detecting surrounding objects without having to make contact with them. By poking the same area several times a second, pressure from the bill forces the sand grains into a denser configuration, and clarifying the picture of locations of solids.

[Pg 183] Birds in flight, to stay aloft, must continuously adjust their wing’s shape and angle. When right, air flows continuously over the wing, producing lift. If too steep an angle, turbulent vortices form and they stall, possibly drop right out of the sky. Filoplumes — small companion feather attached at the base of a feather — provide the information necessary to correct wing angle and shape. They read the air around them.

[Pgs 225-227] The fine structure of bird song: Birds can hear complexities that are imperceptibly fast to humans. Some birds can discriminate detail so fine that electronics can’t handle.

Experiment: An analog. Bird 1 hears a series of brief chunks of sound. The chunks first rise in pitch over a few milliseconds, then falls back to start. Bird 2 hears the series fall over same pitch ranged & same period. The very brief series’ average out to the same pitch and seem identical to a “slow ear” like a humans. We could distinguish between them only if each chunk was longer than 3-4 milliseconds. Canaries & budgerigars hit their limit at 1-2 milliseconds. Zebra Finches are not bothered by the shortest 1-millisecond chunks.

Zebra Finch songs consist of several distinct syllables always sung in same sequence. If one syllable is reversed (rises vs falls), humans cannot discern it but the finch can. If a gap between syllable was doubled in length, humans easily discerned but finches were oblivious. If the syllables were shuffled in order, the finches didn’t care. They care about the internal structure of each syllable, and disregard the order of syllables, even though they always sing them in the same sequence, learned from birth.

Colors: Rurple, Grurple, Yurple

[Pgs 96-98] Most birds have four types of cone cells, with opsins that are most sensitive to red, green, blue and either violet or UV. That makes them tetrachromats. Theoretically, they should be able to distinguish a multitude of colors that are imperceptible to us.

Broad-tailed Hummingbirds attracted to feeders near special lights: green and ultraviolet vs green. Not just a wider spectrum but a new dimension of colors. Dichromats see approximately 1 percent of what trichromats [e.g. humans] can see. If we see only 1 percent of what tetrachromats can see, they can discriminate 100s of millions of colors. A pyramid of colors vs a triangle. If our red and blue cones are stimulated together, we see purple, a non-spectral color not in the rainbow spectrum. Hummers with 4 cones see a lot more non-spectral colors. A bright magenta gorget looks ultra-purple. Do they see a non-spectral rurple as a blend of red & UV or as an entirely different hue?

Contact and Flow: A Rough Sense

[Pgs 140-141] Houseflies love air that’s 25°C (77°F), but avoid 30° (86°F) and 40°C (104°F) kills them. They can immediately sense temperature changes and make fast U-turns to avoid them. The chitin that makes up a fly’s antennae is very good at conducting head and the antennae themselves are tiny. They can so quickly equilibrate with their surroundings that a fly can instantly tell if it has blundered into air that’s too hot or cold. It can even us its antennae as stereo thermometers to track gradients of heat, much as a dog uses its paired nostrils for odors. It can tell if one antennae is just 0.1°C hotter than the other, and uses those comparisons to steer towards the more comfortable temperature. A fly’s weaving path may not be random at all, it may be threading its way through an obstacle course of hot and cold that we can’t perceive, don’t care about, and simply wade through.

Echoes: A Silent World Shouts Back

[Pgs 245-249] Bat sonar: In the 1790s Lazzaro Spallanzani realized bats could orient when blinded, but would blunder into objects when deafened or gagged. Other scientists scoffed. “Do they hear with their eyes?” In 1938 Donald Griffin brought a cage of little brown bats to a local physicists with a device that could detect ultrasonic sounds. They were very noisy. A year later they confirmed they make ultrasonic noises as they fly, that their ears can detect them and they need both skills to avoid obstacles. In 1944 he named it echolocation. In 1951 he learned they used it not just to avoid obstacles but to hunt prey. Their steady put-put-puts would quicken and fuse into a staccato buzz when they swooped after an insect. “No one had even speculated this possibility.” Small and delicate bat skeletons don’t fossilize well. DNA analysis recently moved echolocating Horseshoe and false Vampire Bats from the small echolocating bat branch over to the non-echolocating Fruit Bat branch. This means that either echolocation originated once and was later lost by the fruit bats, or echolocation evolved twice.

Electric Fields: Living Batteries

[Pg 286] Some electric knifefishes produce electric pulses in such quick succession that they blend into a single, continuous wave, like an endless violin note. The frequencies of these waves differ between species (and sometimes sexes), and the fish control their timing with unbelievable precision. The black ghost’s electric field usually oscillates once every  0.001 seconds, with an error of just 0.00000014 seconds. This was almost too precise for the scientist’s instruments to measure.

Magnetic Fields: They Know the Way

[Pg 306] Whales navigate geomagnetically. Solar storms send streams of radiation and charged particles at us and affect the Earth’s magnetic field. This can potentially mess us the compasses of magnetically sensitive whales. If they are close to a shoreline, even a small navigational error might send them aground. To test this idea, Jesse Granger collated 33 years’ worth of records of healthy, uninjured gray whales inexplicably stranding themselves. She compared the timing of these incidents to data on solar activity from astronomer Lucianne Salkowicz. On days with the most intense solar storms, gray whales were four times more likely to beach themselves.

Self-awareness Systems Underlie Sentience

[Pgs 325-328] All animals must be able to differentiate exafference signals (produced by others, stuff happening in the world) from reafference signals (self-produced, caused by our own actions). An earthworm must be able to different pressure on its head caused by its crawling through the soil from pressure caused by another animal poking at it. Otherwise, its totality of perceptions would be a hopeless jumble.

“This problem is so fundamental that very different creatures have solved it in the same way. When an animal decides to move, its nervous system issues a motor command—a set of neural signals that tell its muscles what to do. But on its way to the muscles, this command is duplicated. The copy heads to the sensory systems, which use it to simulate the consequences of the intended movement. When the movement actually occurs, the senses have already predicted the self-produced signals that they are about to experience. And by comparing that prediction against reality, they can work out which signals are actually coming from the outside world and react to them appropriately.** All of this happens unconsciously, and while it isn’t intuitive, it is central to our experience of the world. The information detected by the senses is always a mix of self-produced (reafference) and other-produced (exafference), and animals can tell the two apart because their nervous systems are constantly stimulating the former.

**Footnote: It’s frankly astonishing that this works. Look to your left. Your brain just sent a simple signal that told some of the muscles around your eyeball to contract. How did your nervous system then use that signal to predict how the scene around would change? We know that it did, but the actual computations that occurred are still a mystery. “How do you go from a motor command to a signal that a sensory structure can work with?” Nate Sawtell, who works with electric fish, asks me. “That’s the core problem.”

These feats [of sorting exafference signals from reafference signals] are so profound that they don’t feel like feats at all. It feels self-evident that we own our bodies, that we exist within the world, and that we can tell the former from the latter. But these are not axiomatic properties. Distinguishing self from other isn’t a given; it’s a difficult problem that nervous systems have to solve. “This is largely what sentience is,” neuroscientist Michael Hendricks tells me. “And perhaps it’s why sentience is: It’s the process of sorting perceptual experiences into self-generated and other-generated.”

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