DESERT TIME -- A JOURNEY THROUGH THE AMERICAN SOUTHWEST
Chapter 15: tortoise,
Desert tortoises live in burrows, and each dark entrance has a near-Gothic arch like the shape of its maker. Between February and April -- depending on local climate, but when the desert is least like a desert -- the tortoises come out to graze on flowers: the purple phacelias and orange mallows, apple-green cactus shoots, white forget-me-nots, pink gilias, and so on, some of them perennials but most of them annuals, the growth that appears almost overnight with the chancy falls of winter rain. In the northern parts of their range their diet tends more toward grass, but in any case what they eat is soft, succulent, temporary, and in some years nonexistent.
In the heat of midsummer they return to their burrows until the monsoon brings a new crop of annuals into bloom. They go back to earth to hibernate in September or October. During the few months that food may be available everything of importance to tortoises has to be done: traveling, mating, digging burrows, laying eggs, hatching, growing, fattening for the winter and summer fasts. Because of this, the tortoise's whole life is an exercise in stubbornness.
A male tortoise matures roughly at the age we do, somewhere between fifteen and twenty, at which time he becomes irritable and aggressive. He rushes at other males, ramming them with his gular "horn," the bifurcated ridge that projects from his lower shell. The gular horn is like the medieval lance or battering ram, or the modern hockey stick, or -- given the solidity of the carapace and the verve of its inhabitant -- the bumper car. The loser of this duel retires to his shell with a clunk (a submissive signal known in the behavioral lexicon as "shell drop") or in more dignified style walks off or, often, gets tipped over. It takes a tipped tortoise some time to right himself. By then who knows where the winner's got to or what he's managed to do?
Slow by nature, a tortoise has a savvy, cautious bag-lady look from the moment it hatches from the egg. It isn't (or wasn't) uncommon for a desert tortoise to live for seventy or eighty years, and some may live more than a hundred and even as much as a hundred and fifty. In any case their feet are as thick as an elephant's and their skin is wrinkled and their mouths toothless -- the turtle clan has been toothless for the last one hundred and fifty million years -- and their shells may bump on rocks as they haul them along, but the desert tortoise is nobody's fool.
They have rules and manners to regulate life among themselves, just as we do. When one tortoise meets another they bob their heads up and down in a ritual nodding as stereotyped as our bowing or handshaking; a means of subverting aggression and of sussing out the vigor (or limpness) of an opponent or partner. An open-mouthed gape is a threat signal used by one male to another in the lists of battle or by a female defending her nest, or by a male announcing the force of his lust to his intended ladylove. Such a "courting" male may try to bite and ram a female into sexual submission, and may succeed -- his goal is simply to get her to stand still -- but females have been known to initiate courtship, too, and to do some hearty ramming of their own, forcing unwanted males to go away and leave them be.
When mating does take place it is by all reports distressing to watch. The male mounts the female from behind; with his forelegs propped on her shell he thrusts away, eyes half closed, making those moans and gusty sighs we thought were unique to our own love affairs.
Afterward, the female digs her nest in sandy soil, using her hind legs to dig the nest, arrange the eggs, and cover them up. She may make three nests of up to five eggs in a season, the season for feeding, mating, and egg laying running from late May through July. The eggs will hatch maybe a hundred days after they are laid, depending on temperature, and when the hatchlings emerge they have no bony support for their fingernail-thin shells; they are some two inches wide and flattish, roughly the size, shape, and texture of chocolate chip cookies. Numbers of young tortoises are eaten every year by coyotes, skunks, ravens, hawks, bobcats, and foxes. Especially by ravens.
By the time they are five to seven years old the flexible shell has gained underlying bone and has hardened and has grown to be some four inches long, half the length of an adult's. A five-year-old tortoise is no longer an easy snack; though eagles may take some, this is a resident animal that knows its way around. The savvy look goes more than skin-deep.
In the heat of midsummer and again during the cold months of winter, desert tortoises live in their burrows, which are deep enough so that the temperature and humidity down there are stable, comfortable, and safe. These burrows may be anywhere from ten to thirty feet in length and may have side chambers and branches; a clan of tortoises may use a common burrow and other creatures use these shelters, too. Insects and spiders, lizards, geckos, rattlesnakes, burrowing owls, packrats, roadrunners, quail, kangaroo rats, mice, even cottontail rabbits, have all been found sharing the tortoise's retreats.
Like us, a desert tortoise becomes more influential as it matures past middle age. Older larger females lay more eggs, older heavier males win more mating duels and subdue more females than their lighter-weight competitors. Besides, the old gents know from years of experience exactly where the females' burrows are and will lie in wait there, with single-minded devotion to their cause.
Most older animals have lived through several bitter droughts even before they're mature, and greater size does help an animal through lean times. A tortoise will eat to obesity if it can, becoming so pudgy that it can't retreat anymore inside its own shell, and this saving up has survival value in the desert where drought years are as much the rule as the exception. Most of the tortoises' water is absorbed from their food, and when this is low they can reabsorb water from their bladders, excreting their urine as a semisolid. When the salt buildup in their blood becomes too high they will go to earth until it rains. They have an uncanny ability to tell when it will rain. They'll come out then and stand by an empty tinaja -- a natural stone tank or catchment basin -- and wait for the rain to come and fill it up. Before there's a cloud in the sky, mind you. And when the tinaja does fill they will drink and pee at the same time, rehydrating themselves and ridding themselves of excess salts all in a rush. Once tanked up they'll go back to the business of eating well.
The tortoise's gradual nature makes it a kind of animal version of a tree; or -- here -- a desert shrub or cactus, since most of these are drought-resistant, too, and long-lived, low-profiled, durable in an environment of temperature extremes and water and food scarcity. Treelike, tortoise reproduction tends to be a year offset from climate; the year after a rainy year is when most tortoise eggs are laid, the year after a drought year is reproductively lean; the lag time here is part of the unhurried way in which a tortoise, physically, works.
In general, a tortoise's life is long and its reproductive rate is slow. This is a conservative style, a life of gradually maturing investment. The home base, the burrow, is built at some cost, lasts years, is as vital to survival as our own houses are. Smaller shallower burrows for a noon or night snooze may be built as "camps" nearby. The home range around this base is perhaps fifty yards in diameter for a youngster and as much as a square mile for a patriarch. Some males in courting trim may cover more than half a mile in a day, though a quarter mile of daily travel is more common. Either way, an animal will know its range. It will know exactly where to go for good cover and good feed, mineral licks, the tinajas where water pools after a rain. The movements and status of the neighbors can be read in the scent of their trails or feces, and the odor of threat and command is clear in the urine of the locally dominant male, an idiom understood by all. Neighbors are nodding acquaintances if not old mates or old bugaboos with whom bashing battles have been held often enough to consider them intimate enemies, undangerous because well known.
What is dangerous to tortoises is any disturbance to this status quo, "disturbance" being just those things that people seem most prone -- out of ignorant self-interest -- to do.
People pick up tortoises and take them home. After a while these captives are neglected to death, or they escape (or are loosed) into yards or parks where the food or climate is likely to be wrong, and where if they do survive they're doomed to live without mates and without community. People also let pet-shop tortoises loose in the desert under the illusion that they are giving the gift of freedom, though often enough the pet-shop critter suffers and dies of starvation or cold (or heat) but only after giving the local animals some exotic disease to which they have no resistance. Thousands of wild tortoises are now infected with an illness that is more than snotty noses and general depression; this one is as deadly as a killer strain of flu. Another plague of pet origin has infected the tortoises' shells. The result of these epidemics is that hundreds of square miles of prime tortoise range are filled with ill and dying animals.
One can plead ignorance for this state of affairs, but not for other things. Game wardens anywhere know about "plinkers" -- those gun-toting folks, mostly urban, young, and male, who will shoot at anything that moves. In the deserts, urban centers are growing. Plinkers are legion. So is the evidence: tortoise shells that have been shattered by bullets. In some places these are easier to find than used burrows, or worn paths, or the tramped circles where a pair of animals has mated, or any other sign of tortoise life.
In other places, livestock has crushed desert shrubs and introduced weeds, and as a result, much country that was once desert scrub is now a kind of weedy waste. Fires sweep through the dry stems of this waste, destroying native plants, since desert species have no tolerance for fire. Whether tortoises can adapt to this change in cover and food no one is sure.
Then there is development -- agricultural, urban, mineral, energy, anything -- which generally means the un-development of tortoise habitat. Roads bring in the collectors and plinkers, and the off-road vehicles that are quick death to all creatures not quick of foot, as well as plain old cars, and tortoises are plain slow in crossing roads, and there you are.
If one looks hard enough in the right places and at the right times the tortoises can still be found, and unlike most beasts they do not mind being watched so long as you mind your distance; tortoise wisdom says (erroneously) that once they're grown they have no enemies. There are several subspecies of them, populations separated ages ago by barriers such as the Colorado or the Yaqui River, and one or another of these tortoise varieties can be found in the desert valleys (bajadas, really; in the basins rather than the ranges) from southern Nevada and Utah into western Arizona, and through the deserts of California down into northwestern Mexico.
Sixty or even forty years ago there were parts of this country where there were as many as two thousand tortoises per square mile. You could find twenty or thirty in a half-hour walk. You might see more than a hundred in one place at one time, at a mineral lick, or on the path to a spring. Nowadays you will have to walk all day, in the same places, to see two or three.
It's the kind of desert anyway that you wouldn't think was worth much. Scrub, mostly. Creosote and burrobush, maybe some Joshua trees up in the Mojave and scattered chollas and prickly pears; the kind of place that has no sign of life except for varmint holes and a few chuckwallas in the rocks and some coyote tracks in the wash. Most of this kind of country is covered with gravel and rock and sand, exactly the bare ground that gets blanketed by flowers in certain seasons.
Whatever the reasons are for the desert tortoise's decline, it is now officially an endangered species, a flagship for the preservation of scrub desert, a rallying cry, the object of much research, a hot emotional touchstone, another flare gone up out of a crumpling relationship -- modern man to desert -- that doesn't always seem to work too well.
More to the point, it would be good to know why we cause most havoc with creatures most like ourselves, the largest predators and the most long-lived and social of beasts: the lions and wolves, gorillas and whales and elephants, and tortoises, too.
Desert Tortoise and Spring Wildflowers