The golden mole, native to the Namib Desert in Southwestern Africa, forages at night by trundling over the dunes or “swimming” through loose sand with paddle-like feet. It is mostly insensitive to airborne sounds, but highly sensitive to vibrations thanks to its malleus, the hammer bone of its middle ear. This bone is relatively enormous; Even though the golden mole weighs just an ounce and would fit in your palm, its malleus is bigger than yours.

It searches for sparse mounds of dune grass, where delicious termites might nest. Peter Narins has suggested that wind blowing over these mounds produces gentle low-frequency vibrations, which the golden mole can detect by dipping its head and shoulders into the sand. This seismic sense is so acute that, though blind, it can walk between distant mounds in virtually straight lines.

Elephants can call to each other over distances of several miles using infrasound - low pitched sounds inaudible to humans. This explains how elephant families seperated by great distances sometimes travel in the same direction for weeks, or converge on waterholes at the same time. They respond to seismic cues from other far-away groups, vibrations which travel through the ground and up their legs, much the same as treehoppers.

Their lives are also dominated by smell. After only brief training, they have been known to outperform highly trained detection dogs, and few sources of odor are as interesting to them as each other. They regularly inspect each other with their trunks, smelling glands, mouths and genitals. Urine, dung and other bodily fluids are full of pheromones and thus full of meaning.

Red knots** and other shorebirds use ‘remote touch’ to sense the exact position of worms, shellfish and crustaceans buried in wet sand, even ones out of reach of their long beaks. The tips of their bills have microscopic pits, which contain mechanoreceptors similar to those in our hands. As the bill repeatedly probes the sand, it pushes on thin rivulets of water between the grains, creating a pressure wave that radiates outward, and if there is a hard object in the way, the water must flow around it, distorting the pattern of pressure. The knot stabs its beak up and down several times a second to stir up the sand grains and make these distortions more obvious, as if it were using a kind of sonar based on touch instead of hearing.

Many distantly related birds use this sense to forage; Ibises use remote touch to probe through muddy wetlands, and Kiwis do the same with leaf litter.

(**Although it’s not stated explicitly about this species, most birds have tetrachromatic vision, meaning their eyes can detect red, green, blue and ultraviolet wavelengths. UV can combine with the others to create colours which are hard for us to conceptualise, like UV-red (rurple) or UV-green (grurple))

Big brown bats hunt in total darkness using echolocation; they unleash a stream of short, ultrasonic pulses, and listen to the returning echoes. The sonar call of the big brown bat leaves its mouth at around 138 decibels, roughly as loud as a jet engine. To make sure the bat is not deafened by its own scream, muscles in the inner ear contract in time with their calls, temporarily desensitizing their hearing before restoring it in time for the echo. In the final moments of a hunt, the pulses grow shorter and closer together, creating a so-called ‘terminal buzz’ as it gathers information as fast as possible. In this final stage, their vocal muscles can contract up to 200 times per second.

Since the bat needs to match each outgoing call to its returning echo, there is no overlap between calls and echoes, even during the terminal buzz. It produces a wide range of frequencies in its sonar which bounce off a moth’s body in different ways, telling the bat the exact size, shape, texture and position of its prey down to distances of half a millimeter or less. It’s worth noting that using echolocation, the bat hears in snapshots much like the framerate of a film, rather than a continuous moving image.

Loggerhead turtles have two magnetic senses that help them navigate: one that senses inclination (the angle at which geomagnetic field lines meet the Earth’s surface) and one that senses the intensity of that magnetic field. These two properties vary across the globe, acting like coordinates on a map, and turtles can read that map innately.

Even hatchlings, when moved to points in the Atlantic along their future migration route, would swim in the direction that would keep them within that migration route. If they survive long enough to ‘settle down’ as an adult, they learn the geomagnetic topography of their home waters best; when older turtles were exposed to magnetic fields from different parts of the Florida coastline, they would always swim in directions that would lead them home.

Manatees are the only known mammals that have no hair except for vibrissae, a type of specialised whiskers. 3,000 of them are scattered over their large bodies, but another 2,000 are concentrated on their oral disk, the part of their face between the upper lip and nostrils. This disk is muscular and prehensile, and by flexing it a manatee can investigate objects with the same dexterity and sensitivity as a hand. This is called oripulation. They explore everything in their path face first, and whenever they meet, they’ll oripulate each other’s faces, flippers and torsos. Their eyesight is ‘notoriously bad’, but their vibrissae allow them to perceive their surroundings through a distant version of touch.

a moment of appreciation for one of my favourite lines in the book:

The black ghost knifefish produces an electric field from an organ in its tail that wraps around its whole body; it senses distortions in this field using over 14,000 electroreceptors scattered across its skin. Like echolocation, this electrosense works a little like 'touch at a distance; it investigates objects by swimming back and forth against them, just like we run our fingers over things to feel their texture. The sense is omnidirectional, and so reliable that the knifefish can swim backwards and upside-down just as well as forwards.

Treehoppers are a group of sap-drinking insects which communicate by sending vibrations through the plants on which they stand, and recieve these messages through their legs. The vibrations are not audible, but can be converted into sound using a vibrometer.

Yong compares some of these sounds to cows mooing, the beep of a truck reversing, the calls of birds, apes, mechanical clicks and ticks, a 'startlingly deep' cat's purr, a scratchy didgeridoo, drumming and more. They use these vibrations to find each other in a jungle of plants; some baby treehoppers synchronise their vibrations to summon their mother when they sense a predator, and adults have call-and-response courting rituals.

Hammerhead sharks do not have colour vision (their eyes have one cone, in contrast to most humans' three and most birds' four, but rely on other senses at different points during hunting. Over distances of miles, the shark can sniff out its food. As it draws near, vision takes over, followed by the lateral line, a rich and ancient sense which fish use to detect currents, flow and objects around them.

Once the shark gets within an arm's length, its passive electric sense - concentrated around the snout - allows it to pinpoint the exact position of its prey. The underside of hammerheads snouts are packed with ampullae, the sensors that give them their electric sense, and they sweep their snouts across the seafloor like metal detectorists, in search of buried (edible) riches.

Octopuses, like cuttlefish and other cephalopods, have photoreceptors dotted throughout their skin which might help to control their color-changing abilities. But since they are monochromats, they are unable to see their own shifting colors. Around two thirds of the octopus’ neurons are in the arms, and each arm has a relatively complete nervous system which barely seems to communicate with the other arms. A single octopus arm contains roughly as many neurons as a lobster. Even the 300 suckers on each arm are somewhat independent, each with its own mini-brain (a cluster of neurons called the sucker ganglion) which can decide whether to stick onto something or let it go. The central brain can control the arms if it needs to, but it mostly lets them sort themselves out.

It also tastes with these suckers; whereas our tongues perceive flavor and shape as different, an octopus’ sense of touch and taste are probably inexplicably fused, which Yong describes speculatively as a single unified sense of taste-touch.

Albatrosses**, like other seabirds known as tubenoses, navigate the open ocean partly by smell. When swarms of krill eat blooms of plankton, the plankton release a chemical called DMS, which seeps into the air and, if it rises high enough, seeds clouds. In the varying levels of this chemical, the seemingly featureless ocean has a secret topography invisible to the eye but evident to the nose. Albatrosses can soar for thousands of miles, searching for diffuse plumes of scent that betray the presence of krill beneath the surface, which in turn means an ocean teeming with prey.