Stewart Aitchison: Living in the Desert

Stewart Aitchison is a former field biologist for the Museum of Northern Arizona and has been a naturalist/photographer/tour leader for several educational organizations.  Through Gene Foushee, Stewart became friends with the Yazzie/Holiday family in Monument Valley, which led to writing A Traveler’s Guide to Monument Valley (MBI Publishing Company). The following is a chapter of the book, republished here with Stewart’s generous permission. His latest book is The Official Guide to Grand Canyon’s North Rim (Grand Canyon Conservancy).

“There is a treeless place amid the rocks.”

Translation of an old Navajo name for Monument Valley

It is a bright, exceptionally clear autumn day.  From the lookout at the visitor center my eyes are caught by the hulking masses of red stone that make up the Left and Right Mittens.  The tiny gray-black dots of vegetation between the monuments are scarcely noticeable in this scene set on a grand scale.  The towering rocks and endless, azure sky overwhelm the visitor.

My family and I begin to descend the tourist road to the floor of the valley and notice that there are bushes, flowers, and even a few small trees.  There is life in this desert.

As we reach the valley floor, which consists primarily of an old Pleistocene-age surface of coalescing alluvial fans, we see predominantly blackbrush interspersed with a few other hardy shrubs and an occasional wildflower, the product of a recent rain shower.  As we approach a turnout for another look at the Mittens, the road skirts a large sandy hill on the left.  This past spring was a relatively wet one (perhaps an inch or two of moisture fell over a three-month period), and for a short time, the sand was covered with flowers and grasses – evening primrose, indigo-bush, dwarf lupine, crownbeard, cryptantha, prickly poppy, fleabane daisy, globemallow, phacelia, desert marigold, scarlet penstemon, western dock, desert peppergrass, sand verbena, Gray’s biscuit root, sand gilia, milk vetch, Indian rice grass, and galleta grass.  Many of these delicate spring-blooming plants are annuals, quickly producing seed and then disappearing until the next season.  Now at the end of the summer “rainy season,” mostly perennials are providing a showy display: rabbitbrush, broom snakeweed, and sulphurflower are ablaze with golden flowers.  A few purple sage plants still fill the air with their strong, minty, volatile terpene oils.  A new crop of tumbleweed, an introduced weed from the steppes of Russia, is drying out and turning brown, ready for winter winds to blow them hither and yon, spreading seeds.

The blackbrush, a member of the rose family, is well-suited to living on the clay and stony flats, as evidenced by its extensive stands.  Mormon tea, four-wing saltbush, and shadscale grow scattered among the blackbrush.  After the road crosses Stagecoach Wash and threads its way along the base of Elephant Butte and Camel Butte, the deep red clay layers of the Organ Rock Tongue form an exceptionally hostile environment for plant growth.  Amazingly, during most springs, a profusion of bent-stem (also called weakstem) mariposa lilies bloom here.  These determined perennials are closely related to the sego lily, the state flower of Utah, whose starchy, underground bulb nourished the Mormon pioneers.  On this lovely fall day, however, there is no evidence that any plant ever manages to grow at this spot.

Why this diversity of plant species on sand, as opposed to the rockier soils?  The sand quickly absorbs any rain, but as that moisture percolates downward, it encounters the impervious claystone underneath.  At this contact the water stops; the sand insulates the water from evaporating, and plants with long roots can tap this water source.  Growing directly on the claystone or in the rocky soils is a much more difficult proposition.

The importance of water is again emphasized as we drive over a wash.  Along the sides of the wash grow the shaggy-barked cliffrose, squawbush, desert ash, and wispy tamarisk, an exotic species that is native to Arabian and mideastern deserts and came to the American Southwest via transplants to California.  Against the base of a cliff, especially those walls facing north away from the sun, can be found netleaf hackberry, Utah serviceberry, and mountain privet, also known as desert olive.  Here they benefit from runoff down the rock surface.

One group of plants that is conspicuous by its absence is the cacti.  If we search, we can find some prickly pear and hedgehog cactus, but winters are too severe for most species.

We head over to the Big Dune at the northeast base of Thunderbird Mesa.  This year’s unusually rainy May and June has allowed many plants to bloom on this normally barren dune.  Acres of the dune are covered with a pale green bush one to two feet tall but unfamiliar to any of us (it is later identified as gray sand plant, a new species to us).  Amazing what a little rain can do.  Another strange plant poking here and there out of the sand like a foot-high, purplish yellow rod is the fleshy broomrape.  This odd-looking plant lacks chlorophyll which would allow it to photosynthesize its own food.  Instead, it must be parasitic on other plants such as sagebrush, cactus, and wild buckwheat.  But here, on the fairly barren dune who is its host?  Maybe a future botanist will unravel the mystery.

One of the great ways to explore a dune is to look at the patterns in the sand.  Wind-created ripples are an obvious feature, but a closer look reveals the coming and goings of a variety of primarily nocturnal creatures.  There are the tractorlike tracks of darkling or stink beetles and scorpions; the miniscule paw prints of pocket mice; the slightly larger prints of a hopping kangaroo rat; the s-curves of a snake, maybe one of the small races of prairie rattlesnake; and the thin toe prints and tail-drag of a lizard – perhaps a plateau whiptail, a strange beast in that it comes only in the female gender.  Plateau whiptails reproduce by a process called parthenogenesis, where one female plays the role of a male, stimulating another female’s body into producing hormones to cause her eggs to grow into genetic clones of herself.

Scattered across the dune are tiny quarter-inch-diameter holes, surrounded by a little fencelike structure of sticks and grains of sand all held together with a few strands of spider silk.  These are the burrows of the wolf spider, a spider that doesn’t waste its time building a web and hoping a bug flies into it but rather spends most of its days patiently sitting at the burrow’s entrance waiting to grab a passing insect.

Churned-up piles of sand near the base of the dune probably mean a pocket gopher has been busy digging tunnels in search of plant roots to eat.  A two-inch hole in the sand at the base of a rabbitbrush is the entrance to a white-tailed antelope squirrel’s burrow.  It’s not long before we see one of these squirrels running across the dune with its tail held up over its back like a parasol.  It is chipmunk-like in size and coloration and is one of the few mammals in the desert that can remain active during the heat of a summer day.  The squirrel’s body temperature can rise above 110 degrees Fahrenheit without ill affect.  If it starts to get too hot, it salivates on its fur to promote evaporative cooling or scurry into its dark, cool burrow to unload heat.

Most of the other desert rodents avoid the heat by emerging only at night.  The kangaroo rat and pocket mouse have evolved the ability to acquire most of the moisture they need from the metabolism of fats, carbohydrates, and protein found in seeds.  Furthermore, they have very efficient kidneys and no sweat glands – very handy adaptations for desert survival.

Surprisingly, only one desert bird, the black-throated sparrow, has the same ability to produce water from seeds.  All the other birds in the valley – such as ravens, rock wrens, canyon wrens, house finches, Say’s phoebe, burrowing owls – must drink liquids or eat food containing moisture.

But this high desert country is not always hot and dry.  One cold, rainy day in October, Gene and I left Susie Yazzie’s camp and drove around toward the Sun’s Eye, a large opening in the roof of a rock overhang.  Though the tops of the mesas are only six hundred feet above us, they were obscured on this day by low clouds.  The road, which isn’t that great even under the best conditions, was slippery with mud.  As we turned the last corner, we could see a shallow lake filling the valley ahead.  Floating serenely in the ephemeral pond were dozens of white pelicans.  On our approach, the birds took to the air, silently lifting off the water’s surface.  In a long line, they rose in a spiral into the low clouds and disappeared.  We looked at each other in disbelief.  Had we really witnessed pelicans in the desert?

Apparently, the inclement weather had forced the flock to land here during their annual migration south from their island breeding grounds on Great Salt Lake to their wintering areas in Mexico.

A week later, on a much warmer, sunny day, the same pond held another equally incongruous sight – freshwater shrimp.  We recognized three species: fairy shrimp, clam shrimp, and tadpole shrimp.  Amazingly, the eggs of these creatures can endure hot, dry conditions for as long as twenty-five years.  Then, when a rain fills a pool and the water becomes the correct temperature, the eggs hatch.  Males are uncommon, and parthenogenesis is the usual mode of reproduction.  If all goes well, new eggs are produced before the pool evaporates and the adults die.

Living in the desert is not easy.  Harsh conditions stress living organisms to their physiological and, in some cases, psychological limits.  The relentless sun and heat of summer bakes and sears; the bitter winds of winter freezes and cracks rocks; drought is the norm, to be broken only by a pounding cloudburst.  But the desert has a strange power to lure you in, and for those who learn to cope and adapt, the desert becomes a refuge, a home.  There is more to the desert than just rocks and sand, much more.