LIFE SATURATES THE POROUS SURFACE OF THE EARTH. Indeed, life’s fundamental property seems to be that it spreads. Disseminating its information in the form of discrete creatures, it entails the power both to adapt to new environments and to reproduce both rapidly and fully to occupy suitable ones. Hans Jenny once added up all the estimates of microbial, invertebrate, and vertebrate life underground. The calculation showed that under each acre was a biomass equivalent to at least ten draft horses. There was more living matter beneath the surface than upon it.
A great deal of this pulsing life is invisible to the human eyes. The several billions of bacteria per average square yard escape our notice, though they are responsible for the maintenance and healing of the soil.
Even the comparatively outsized invertebrates may go unheeded, until they prick us somehow. People working in peat soils around the world often complain of a persistent itch or prickle where their bodies come in contact with the soil. Chemical explanations were common—it was thought that some sort of alkali irritant was present—until someone bothered to put the offending soils under the microscope. It turned out that they were full of tiny spears excreted by freshwater sponges whose presence had until that time not been suspected.
Just as annoying but a great deal more visible than such mini-varmints are the giants of the soil world. Biologists picturesquely refer to them as the “fossorial species,” meaning the hole diggers. They include moles, ground squirrels, rabbits, marmots, badgers, mice, shrews, armadillos, certain tropical rats, marsupial moles, prairie dogs, and gophers.
The majority of these are rodents, whose adaptation for digging is extraordinary. Their compact, short-legged bodies are like augers with paws, centrally powered and headed by a set of jaws that must chew to live. As anyone who has kept a hamster knows, the large front teeth never stop growing. It is not that rodents necessarily like to gnaw, but if they fail to gnaw, their teeth grow round until the jaws are sutured shut. Therefore, they gnaw. Furthermore, their teeth have the interesting property of growing enamel only on the front side, so that as they gnaw, they maintain an excellent chisel edge, perfectly adapted for more and more efficient. . . gnawing.
A rabbit or a mouse is quite content to gnaw in place. Once it has dug its burrow, it is satisfied. Not so the gopher. Back in the mid-1960s, a correspondent sent the Journal of Mammalogy a three-page report that should have won him the Nobel Prize for effort. Not only did he succeed in starting and ending a six-month, open-site experiment with only one gopher, he also managed to follow the gopher around.
On capture the beast weighed five ounces, about the weight of an average peanut-butter sandwich. On a nice fall day, the correspondent set the diminutive gopher down in his vegetable garden near Logan, Utah, gave it a pat on the haunches, and sat back to observe.
He might as well have released a chainsaw. Within fifteen minutes, it had drilled through eighteen inches of soil. An hour later, it pushed up a mound three feet away. After a week, it appeared on the other side of the road, about a hundred feet from the start. And so it went. With the mammalogist in hot pursuit, the gopher covered 390 feet underground before the soil surface froze solid in December.
Undaunted, the gopher waited in his warm underground burrow until the thaw, while the scientist presumably sipped hot chocolate. In February, fresh mounds began to appear two hundred feet from where the animal had last left off The experiment ended on the twenty-eighth of February, when the gopher was found dead on the surface.
It might be speculated that the varmint spent all his energy looking everywhere for another gopher with whom to create still more gophers, finally abandoning himself to despair. Nevertheless, the digging statistics are impressive. Almost five hundred feet of near-surface tunnels alone, in a free digging time of a little less than three months. In his most active month, he had pushed up seventy mounds of soil, amounting to about five hundred pounds.
Doing some quick calculations to approximate per-acre gopher density, the mammalogist came up with a figure of thirty. Multiplying that number of active gophers by his prize gopher’s statistics, he estimated that a good field full of gophers would move about thirty-eight tons per acre per year. In short, under the influence of a good population of motivated gophers, it would theoretically be possible to move all of Utah into Colorado within a century.
An exaggeration? There is a whole kind of landscape in the western United States (also in South Africa, Argentina, and East Africa) called Mima Mound topography. These mounds are up to six feet high and from seventy-five to 150 feet in diameter, sometimes extending over areas of several hundred acres. Once, it was thought that geological agents had caused this distinctive terrain.
Wrong. It was gophers. Like their cousins, the prairie dogs, certain pocket gophers tend to pile all the soil that they move into these large mounds. Students whose job is to examine this “soil translocation” suggest that the animals only stop moving soil when there is no more soil to move, that is, when they hit bedrock. The size and topography of the mounds themselves suggests that a gopher will keep digging until he has moved all nonmound soils into his regular heaps.
The extraordinary beauty, power, and determination of the gopher cannot be denied. But, as every gardener is then prone to ask, how do I destroy them? By “them,” he means not only gophers but also the moles, who, from the horticultural point of view, are simply gophers in Halloween costumes. Both are distinguished by the spongy-to-the-touch tunnel lines that they leave crosshatching the lawn and emerging every twenty feet or so in a nice brown pile of earth.
From one point of view, it is a testimony to the gardener’s skill at making fine pasturage that the gophers have favored his lawn with their presence. On the other hand, it is inconvenient and ultimately destructive to the lawn.
The soil defends its inhabitants. I remember hours spent filling gopher holes with water in the vain hope of drowning the animals. One could indeed make the hole overflow, but soon the water would percolate away. We succeeded only in fractionally elevating the water level in the creek. Then, there were the little guillotine traps that promised to impale the beasts in a nest of sharp metal rods the moment they emerged from the burrow. Once we caught a gopher by this means, though mainly we acquired my father’s anxiety at having these deadly instruments exposed on the ground, where the curious dog or child might receive a memorable surprise.
Catch ’Em Alive traps never caught ’em at all. Perhaps poisons had some effect, but we never knew. The gophers would come and go punctually, like the rain. In other words, we might have a plague of them one year, and hardly any the next. All the control measures seem to have been executed largely for our own amusement.
Indeed, as children we were always secretly on the gophers’ side, and it was with real delight that on occasion we actually saw one poke up his head above the soil, while the adults were setting traps for them in another quarter of the garden. When we filled the hole with water, I often imagined that I was surfing along the front of the advancing water, exploring the underground realm that belonged to gophers, moles, and ants.
The only real specific against gophers is nature. To control the gopher, prosper his enemies. But it is just his enemies that have so much trouble surviving the suburbs. The whole tribe of snakes is marvelously adapted for gopher consumption, and indeed in the wild, they are often the residents of former gopher homes. The favorite constrictor in our part of the world was known as the gopher snake. But while we could easily find the snake in the untouched regions of the coastal hills, there was never a single one in our garden.
Perhaps the best thing to do if you have gophers is to be grateful that you don’t have prairie dogs. On the other hand, plagues are often scaled so that they are suitable for us to bear them. A friend lives on a 24,000-acre ranch in South Dakota. He has fields of prairie dogs. Each prairie-dog town is about the size of a small suburban sub-development: acre after acre of mounds, each topped with a vigilant whistling demon.
My friend has tried a number of forms of prairie-dog control. One was to place salt licks in their cities, so that buffalo would come and trample them. But the bison don’t like the terrain and the prairie dogs don’t mind the trampling. Another idea was to try to surround the mounds with quick-growing grasses, to give the predators a way to creep close to the mounds. (Prairie dogs are always sure to denude the surrounding area, probably for precisely that reason.) But prairie dogs are not rodents for nothing.
In the end, my friend’s best line of defense has been to talk to all of his neighbors about the importance of ceasing to shoot and trap coyotes and hawks. The rancher’s traditional hatred of the coyote has only served his subtler but more powerful enemies. A coyote may take the occasional young animal, but the prairie dog, because of the way it clears large tracts of land, is the occasion for erosion that destroys the life-giving basis of the ranch: the grass.