Part 1/3: Which of these animals featured in An Immense World* would you rather be for a day?
Golden Mole
Asian Elephant
Red Knot
Dog (Canis familiaris)
*An Immense World: How Animal Senses Reveal the Hidden Realms Around Us is a 2022 book by Ed Yong. For context, I’ve summarised some sensory info about each of these animals below the cut. (Part 2, Part 3)
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))
Dogs are not totally colourblind but see mostly in shades of blue, yellow and grey, and they can't distinguish between red and green. Unlike light, smells can diffuse and seep out of small spaces, around corners, lingering in a way light cannot. Dogs can sniff up to six times per second, and the side-facing slits of their nostrils mean their exhalations waft more odors into their nose. A dedicated tributary in the nose allows odorants to linger and send signals to the brain even after the dog has exhaled and moved on to sniffing something else. When a dog sniffs, it is not merely assessing the present but reading the past and divining the future. ‘Nosework' classes can help reactive dogs become more tolerant and easygoing as they hone their natural olfactory sense.
