The Sound of a Wild Snail Eating (6 page)

Part 4
THE CULTURAL LIFE

[Snails are] found to be furnished with the organs of life and
sensation in tolerable perfection; they are defended with armour
that is at once both light and strong; they are as active as their
necessities require; and are possessed of appetites more poignant
than those of [other] animals . . . In short, they are a fruitful
industrious tribe . . . [They have their] . . . powers of escape and
invasion; they have their pursuits and their enmities.

— O
LIVER
G
OLDSMITH
,
A History of the Earth and Animated Nature,
1774

11. COLONIES OF HERMITS

Where’er he dwells, he dwells alone,
Except himself has chattels none,
Well satisfied to be his own whole Treasure.

— W
ILLIAM
C
OWPER
, from “The Snail,” 1731

A
DIET OF NOTHING
but portobellos seemed monotonous, so I offered my snail a concoction of wetted-down cornstarch and cornmeal. This was the diet suggested in a pamphlet sent to me by the local Cooperative Extension office. It was a big mistake: the snail overate. It climbed in a staggering sort of way to the top of the terrarium. Clearly suffering from a severe case of indigestion, it stayed there for hours, excreting wastes from all orifices.

I was terribly worried. If the snail didn’t recover from cornstarch indulgence, then how, I wondered selfishly, could I survive my illness without the snail for a companion? It was a miserable night for both of us, and I resolved never again to feed it anything unnatural. The next morning I was relieved to find the snail moving about normally, and following its usual routine, it went off to doze in a soft mossy corner of the terrarium.

A woodland snail is most at home in the soft layer of debris, leaf litter, and duff that carpets the forest. Snails are known as decomposers because they feed primarily on dead matter, thus filling a niche in the ecosystem by returning nutrients to the soil. A special enzyme allows them to digest cellulose, which explained my snail’s penchant for eating paper. It is rare for native woodland snails to feed on live plants, but if they do, they usually eat older deteriorating leaves. Many species love to graze on algae and will munch contentedly on mushrooms, even those toxic to humans. The mycelium, the threadlike part of a fungus that often grows underground, is a favorite food.

The foraging of snails is complex; they vary their diets to balance their nutrient intake. Two snails of the same species in the same location may make different dining arrangements. They are intrigued by a new food but proceed cautiously: After inspecting it with the lower tentacles, they take a small taste. If there are no unpleasant side effects, they will return for a larger portion.

Soil is also part of a snail’s diet, providing muchneeded nutrients such as calcium, which is essential not only for shell growth and repair but also for egg production. So critical is this mineral that the snail is the only known land animal able to find it by smell. When my caregiver placed a little pile of crushed eggshells in the terrarium, my snail waved its tentacles as rapidly as a snail can, setting off at once to investigate and eat. From then on, the eggshell site was one of its regular hangouts.

The mussel shell of fresh water was another of the snail’s favorite spots. Usually, it drank straight from the small basin, but sometimes it climbed right inside, flattening its foot into the shell’s pearly contours and absorbing water directly through its skin, a hydration method known as foot drinking.

Most snail activity occurs with nightfall’s cooler temperatures, or just after a daytime rainstorm, when humidity improves locomotion and replenishes the supply of fungi. Even in the house, my snail increased its activity on a rainy day. When it lived in the flowerpot and I watered the violets, it must have been perplexed by the highly localized rainstorm that never resulted in any fresh vegetation or mushrooms.

In the wild, snails generally travel downwind from their daytime hiding places, then find their way home in the morning by following familiar smells. While exploring the crate, my snail had used its homing skills daily to return to the flowerpot, which had offered the only decent sleeping place. The terrarium, however, offered it numerous hiding spots, and it made use of them all.

Older snails may spend their evenings foraging within an area of several square yards, while juveniles might roam five times as far, searching, perhaps, for new food sources or their own territory in which to start a colony. Many snails live out their lives in such close proximity to where they hatch that the botanist A. D. Bradshaw once remarked, “All I can say is, you’ve convinced me [that this snail species] is a plant.”

Colonies of snails are often confined by the natural contours and terrain of their location. A species’ micro-environment might be as site specific as a hillside or a valley, or even a clump of leaves drifted against a log, or a damp area between rocks. Populations may number a hundred individuals, though they can be much smaller or, if the habitat is contiguous and extends for miles, much larger. I envisioned a colony of hermits, each off on their individual forays by night, each sequestered, asleep, by day.

W
HEN I THOUGHT OF
the distance my snail could travel in relation to its size, my own immobility was stark in comparison. And my life was becoming nearly as solitary as my snail’s. As the months drifted by, it became harder for friends to give up weekend time to make the long drive to visit. There were many days when I saw a caregiver for just a half hour at mealtimes, and I was becoming more and more cut off from the world.

My bed was an island within the desolate sea of my room. Yet I knew that there were other people home-bound from illness or injury, scattered here and there throughout rural towns and cities around the world. And as I lay there, I felt a connection to all of them. We, too, were a colony of hermits.

12. MIDNIGHT LEAP

little snail
facing this way
where to now?

— K
OBAYASHI
I
SSA
(1763 – 1828)

I
REMEMBER A SUMMER
of better health. Deep into a humid night I half woke from thirst. Keeping my eyes almost closed to maximize sleepiness, I made my way by moonlight, barefoot, across the wood floor toward the kitchen sink and water.

Suddenly I was high in the air, my body springing up of its own accord, my legs zooming into my nightgown, knees bent. I stayed suspended this way for a long moment, my mind still focused on water, unaware that it had been hijacked.

I had stepped on a slug.

Landing back on my feet, I was now fully awake, and it didn’t take long to figure out why a slug was on the loose. Earlier that day, my orange coon cat, Jasione, must have taken a nap in a cool, damp garden spot. A slug had stuck in the cat’s fine, soft fur, as occasionally happened. Well camouflaged, it rode its feline mount into the house at a trot. During her evening bathing ritual, Jasione must have managed to extract it from her fur. A spider she would have pounced on and eaten, but the slug, saved by its slime, was discarded alive.

As the sun set, the humidity in the house increased, improving conditions for gastropod travel. The slug made its leisurely way across the floor, unaware that I, a large mammal, was coming toward it through the dark. Though its own weight was less than a sixth of an ounce, it easily and passively repelled my one hundred pounds with its slime and, unperturbed, continued on its way.

Were I to encounter an animal as large to me as I was to the snail—Highsmith’s giant carnivorous snails of Kuwa come to mind again—what would I do for defense, and how would I escape? I could not think of a single passive human defense method as brilliant as slime.

In terms of size, mammals are an anomaly, as the vast majority of the world’s existing animal species are snail sized or smaller. It’s almost as if, regardless of your kingdom, the smaller your size and the earlier your place on the tree of life, the more critical is your niche on earth: snails and worms create soil, and blue-green algae create oxygen; mammals seem comparatively dispensable, the result of the random path of evolution over a luxurious amount of time.

T
HREE AND A HALF
billion years ago, when life on earth began, the snail and I shared a common ancestor, some kind of simple worm that over time evolved into two animal groups. The protostomes, which in the embryotic stage develop a mouth first and then an anus, branched off into gastropods and the species of snail at my side. And the deuterostomes, which develop the same characteristics, though somewhat embarrassingly in reverse order, anus first and then a mouth, branched off into mammals, including
Homo sapiens.

The snail and I both had a gut and a heart and a lung, though I had two lungs to its one. There the similarities ended. Observing its quirky telescoping eye-noses, ribbonlike teeth, slimy skin, and movable house, it was hard to believe that we originated on the same planet. In 1862, Charles Darwin wrote to the geologist Charles Lyell, “I should think mammals & molluscs rather too remote from each other for fair comparison.”

The evolution of a species is shaped, in part, by its unique history of viral and bacterial pathogens. By rearranging cellular DNA, pathogens can switch genes on or off and thus impact the traits of a species’ future generations. Luis P. Villarreal, director of the Center for Virus Research, proposes that even common, seemingly benign viruses may have shaped human cognition and socialization. And the virologist Thierry Heidmann, as well as Villarreal, links viruses to the development of the placenta—without which we humans would still be egg layers. I wondered if there was DNA for other animal traits buried in my own genetic code. We all have some genes that for unknown reasons are in the “off” mode; perhaps scientists will someday figure out how to flip these switches, and we’ll each be able to choose other interesting animal traits: a tail, striped fur, wings, or even gastropod tentacles.

And how, I wondered, did the mysterious virus that had felled me change life inside the cells of my own body? Would there ever be a switch I could flip to instantly restore my health? This was a most tantalizing idea.

A
S I GLIDED FURTHER
into the dusty mollusk volumes, I discovered that gastropods—which account for 80 percent of all mollusks—are one of the most successful animal groups. They have existed for half a billion years, surviving or reevolving through several mass extinction events. They make their home in nearly every habitat on earth. While thirty-five thousand living terrestrial snail species have been documented, tens of thousands are not yet identified. The majority of these are microscopic, as Ernest Ingersoll points out in his 1881 essay “In a Snailery”: “Some [snail species] are so minute that they would not hide the letter
o
in this print.”

If we
Homo sapiens
thought we were in charge of the planet, here was clear evidence to the contrary. The humble snail and its clan have a far older, and stickier, foothold on the earth than we more recent creatures. It was clear to me that gastropods should make front-page headlines in the
New York Times,
and mammals, particularly the human sort, should be relegated to the back sections. But then, with its many-toothed radula, cellulose-digesting enzyme, and lack of vision, my snail was more likely to eat the
Times
than read it.

With a home range measured in yards and a locomotive speed of a few inches per minute, how did terrestrial snails colonize the world’s continents? As it turned out, it was not just my cat that provided high-speed gastropod transport. Tim Pearce, a malacologist (a person who studies mollusks), specializes in gastropods. He tracked the nighttime jaunts of a group of snails by attaching a thread to each of their shells. He discovered one snail was moved, alive, twenty-seven yards by a shrew, its journey ending more than three feet below ground in a burrow.

One hundred and fifty million years ago, my snail’s ancestors probably caught unexpected rides on fifty-ton dinosaurs. These largest of steeds may have provided fine dining, as fossil evidence suggests that snails enjoyed banquets of dinosaur dung. During North America’s megafaunal period, which ended thirteen thousand years ago, snails may have hitchhiked on giant tree-eating sloths, elephants, and perhaps the fastest of their mounts, the lions, cheetahs, and powerful saber-toothed cats.

Yet none of these transport methods explained how terrestrial snails came to colonize islands far out to sea, and this was a problem that greatly vexed Charles Darwin. On September 28, 1856, he wrote to the naturalist Philip Gosse, “The means of transport . . . of land mollusca utterly puzzle me.” A few days later, writing to his cousin, the naturalist William Fox, Darwin states, “No subject gives me so much trouble & doubt & difficulty, as means of dispersal . . . to oceanic islands.—Land Mollusca drive me mad.” And clearly they did, for that December, Darwin wrote to the botanist Joseph Hooker, complaining “I have for [the] last 15 months been tormented & haunted by land mollusca.”

As he later recorded in
The Origin of Species,
in 1859, Darwin wondered if a hibernating snail “might be floated in chinks of drifted timber across moderately wide arms of the sea.” This set him off on his usual method of scientific inquiry: experiments. He filled containers with ocean water and obtained a collection of live, hibernating snails:

[One snail] was put into sea-water for twenty days, and perfectly recovered. During this length of time the shell might have been carried by a marine current of average swiftness, to a distance of 660 geographical miles.

Greatly relieved by this possible explanation, Darwin confided to Joseph Hooker, “I feel as if a thousand pound weight was taken off my back,” though he concludes in
The Origin of Species,
“It is, however, not at all probable that land-shells have often been thus transported; the feet of birds offer a more probable method.”

Darwin’s dispersal theories turned out to be right: a snail might attach itself to a bird, settling into the plumage as a stowaway on a long migratory flight. For aerial travel closer to home, a tiny snail has been known to catch a ride on the leg of a bee or may adhere to materials picked up by an avian nest maker.

Stuck to an autumn leaf, a snail may blow along in a storm, its magic carpet eventually landing in faraway terrain. It is even thought that microscopic snails may be swept up by the wind, rising on air currents until they join the fertile bank of animal and plant minutiae that inhabit the earth’s atmosphere. They may float undreamed-of distances, finally descending within a rainstorm, the perfect humid landing condition for slime travel and a search for fresh fungi.

Millions of centuries of voyaging via animals, water, and wind brought my snail’s family to colonize the woods near where I was staying. It was by chance that my snail’s path had intersected with a human trail, just as a friend—the sort of friend who stopped for a snail—was passing by. The history of gastropod travel now included the unexpected journey of my own snail, which had arrived at my bedside by human transport.