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

by Ed Yong

an Umwelt is specifically the part of those surroundings that an animal can sense and experience—its perceptual world.

This is a book not about superiority but about diversity.

“They move finished and complete, gifted with extensions of the senses we have lost or never attained, living by voices we shall never hear,” wrote the American naturalist Henry Beston. “They are not brethren, they are not underlings; they are other nations, caught with ourselves in the net of life and time, fellow prisoners of the splendour and travail of the earth.” —

The senses transform the coursing chaos of the world into perceptions and experiences—things we can react to and act upon. They allow biology to tame physics. They turn stimuli into information. They pull relevance from randomness, and weave meaning from miscellany. They connect animals to their surroundings. And they connect animals to each other via expressions, displays, gestures, calls, and currents.

Senses that seem paranormal to us only appear this way because we are so limited and so painfully unaware of our limitations.

Ant civilizations are among the most impressive on Earth, and as ant researcher Patrizia d’Ettorre once wrote, their “genius is definitely in their antennae.”

Female lobsters urinate into the faces of males to tempt them with a sex pheromone.

wedge-tailed eagle of Australia.[*11]

With these svelte cells, the eagle effectively sees the world on a screen with over twice as many pixels as ours. It can spot a rat from a mile away.

(There are no nocturnal eagles.)

“The human visual world is in front and humans move into it,”

But “the avian world is around and birds move through it.”[*19]

the bird can spot food grains among a bed of pebbles if it uses its right eye (directed by its left brain), but not its left eye.

many birds use their left eyes (directed by their right brains) to scan for predators, and are quicker to detect a threat when it approaches from the left.

seal that swims upside down might look relaxed to a human observer, but is actually scanning the seafloor for food.

A cow can simultaneously see a farmer approaching it from the front, a collie walking up from behind, and the herdmates at its side. Looking around, which is inextricable from our experience of vision, is actually an unusual activity, which animals do only when they have restricted visual fields and narrow acute zones.

cock-eyed squid, whose left eye is twice the size of its right. It hangs in the water column with the small eye pointing downward to spot bioluminescent flashes and the big eye pointing up to spot silhouettes.

Dogs have two cones—one with a long, yellow-green opsin and another with a short, blue-violet one. They see mostly in shades of blue, yellow, and gray.

Most “color-blind” people are also dichromats, because they’re missing one of the three usual cones. They still see colors, albeit in a narrower range.

Their world is painted in yellows, blues, and grays, while reds and greens are hard to distinguish.

thanks to their UV patterns, males and females look very different from each other. The same is true for more than 90 percent of songbirds whose sexes are indistinguishable to us, including barn swallows and mockingbirds.

The emerald jewel wasp also has a long, probing organ with a touch-sensitive tip, but its goals and methods are far grislier than a red knot’s. The wasp—a beautiful inch-long creature with a metallic green body and orange thighs—is a parasite that raises its young on cockroaches. When a female finds a roach, she stings it twice—once in its midsection to temporarily paralyze its legs, and a second time in its brain. The second sting targets two specific clusters of neurons and delivers venom that nullifies the roach’s desire to move, turning it into a submissive zombie. In this state, the wasp can lead the roach to her lair by its antennae, like a human walking a dog. Once there, she lays an egg on it, providing her future larva with a docile source of fresh meat.

This goes against every stereotype one might have about crocodiles as brutish, unfeeling animals. With jaws that can crush bone and thick skin that’s heavily armored with bony plates, they seem like the antithesis of delicacy. And yet, they are covered head to tail in sensors that, as Ken Catania and his student Duncan Leitch showed, are 10 times more sensitive to pressure fluctuations than human fingertips.

The fly only becomes recognizable as food if it shakes the web.

To date, “the only sonar that the Navy has that can detect buried mines in harbors is a dolphin,” Au says.

echolocating dolphins can detect targets from over 750 yards away.

dolphins can peer inside theirs. If a dolphin echolocates on you, it will perceive your lungs and your skeleton. It can likely sense shrapnel in war veterans and fetuses in pregnant women.

Corollary discharges explain why you can’t tickle yourself: You automatically predict the sensations that your writhing fingers would produce, which cancels out the actual sensations that you feel.

soft whisper is usually 30 decibels, normal conversation is around 60, and a rock concert is about 110. Every extra 3 decibels can halve the range over which natural sounds can be heard.

On a random schedule, they stuck up signs that declared one of the most popular parts of the park a quiet zone and encouraged visitors to silence their phones and lower their voices. These simple steps, with no accompanying enforcement, reduced the noise levels in the park by 3 decibels, equivalent to 1,200 fewer visitors.