The Sound of a Wild Snail Eating Read Online Free PDF Page B

searchlights about to look for navigational marks.
While we humans have five senses, relying most heavily on vision to find our way, a snail relies almost entirely on just three senses: smell, taste, and touch, with smell being the most critical. My snail could not hear anything at all; it lived in a world of silence. Its “sight” was highly limited—just a general awareness of dark and light to help with orientation. Bright light might warn of a hotter, drier, and more challenging environment; dark suggested safer, cooler, more humid conditions. A sudden shadow might alert it to a predator.
It was its tentacles—which hold smell and taste receptors—that gave my snail its look of intelligence and purpose. So critical are they to a snail’s survival that, if injured, they can be regrown, just as a starfish can regrow an arm. In an article titled “In the Realm of the Chemical,” David H. Freedman explains:
The land snail . . . devotes about half its . . . brain to taste and smell affairs. It divides the job neatly between its two pairs of [tentacles]: one [upper] pair is waved in the air to pick up smells, while the second [lower] pair is dipped tongue-style into promising substances as a final check before ingestion.
    Using the taste buds on its lower tentacles, my snail could distinguish between salty, bitter, and sweet flavors. The thousands of chemoreceptor cells along its upper tentacles were similar to those inside a human nose. Snails “see” the world through smell, the way many insects do, and they can detect aromas from a few airborne molecules.
In its native habitat, my snail determined the source of a scent and the distance from which it wafted based on wind speed and direction. There was no woodsy fragrance blowing through my room, and the snail, especially while it lived in the pot of violets, must have been surprised by the kaleidoscope of unfamiliar smells, the scent of humans, human food, tea, soap, paper, and ink.
Unlike the human nose, infamous for its secretions, the noselike tentacles of a snail are the only mucus-free part of its body. And compared to the stationary, side-by-side nostrils of a human, the snail’s two independent tentacle-noses give it a kind of stereoscopic sense of smell. I imagined a crowd of humans with smell receptors completely covering their arms, walking down the main street of a town. As they passed coffee shops, bakeries, and restaurants, their arms would wave wildly toward the aromas. Perhaps restaurant critics so endowed could, with the wave of an arm, report not just on their own entrée but also on those of other diners at nearby tables.
Though the snail had a sophisticated method of scent tracking, I wondered how it experienced a life so devoid of sight and sound. In its native woods, my snail could not see the moss over which it glided or even the plants it climbed. It could not see the trees, nor the stars overhead. It could not hear birdsong at daybreak, nor the midnight howls of coyotes. It could not even see or hear its own kin, let alone a predator. It simply smelled and tasted and touched its world.
The closest I could come to understanding the snail’s experience of its surroundings was in reading Helen Keller’s portrayal of the richness of smell and touch from her own human experience in The World I Live In:
I am not sure whether touch or smell tells me the most about the world. Everywhere the river of touch is joined by the brooks of odor-perception . . .
. . . Touch sensations are permanent and definite. Odors deviate and are fugitive, changing in their shades, degrees, and location. There is something else in odor which gives me a sense of distance. I should call it horizon—the line where odor and fancy meet at the farthest limit of scent.
    I wondered if my snail was aware of a scent “horizon” and how far the odor of a mushroom could float through the air. A snail’s navigation is complex, based on ever-changing odors, sources of darkness