A World of Difference
Stand on the bald knob of Emory Peak and you’ll see the Chihuahuan Desert rolled out below you with wave upon wave of mesas and mountains reaching out to the rim of the world. You can see for hundreds of kilometers in all directions. Not a house, not another human being, no living thing moves. Big Bend looks round, complete, as timeless and permanent as planet Earth itself and as beautiful and barren as the Moon. But Big Bend isn’t just one world, and it isn’t lifeless. It is many different worlds inhabited by countless creatures both great and small pursuing an extraordinary variety of lifestyles. These worlds may be as narrow as the mosquitofish’s spring-fed pool, as wide as the cougar’s hunting range, as dry as the pocket mouse’s burrow, as wet as the beaver’s pond, as open as the mule deer’s golden grassland, or as canopied as the Colima warbler’s forested canyon.
And the Big Bend world is not as changeless as it seems. Over an unthinkably long span of geologic time, and sometimes overnight, Big Bend has experienced sweeping changes that carried off whole communities of plants and animals. The great order of dinosaurs died out, and no one knows why, yet the scorpion and turtle have lived on here virtually unchanged through countless ages. Other plants and animals have staked survival on the long, slow process of adaptation to a changing environment. While one ancient lily evolved into grass, for example, another became the giant dagger we see today. Cholla cactus shades itself with thorns and the kangaroo rat manages never to take a drink.
In Big Bend as elsewhere, what animals live where is largely determined by what plants grow where. This in turn depends on such variables as the type and condition of the soil, elevation, climate, temperature, humidity, amount of cloud cover and direct sunlight, exposure to the wind, availability of water, and the drastic changes for bad and for good wrought by man. Yet there is nothing clear-cut or fixed about the edges of the different plant communities. The floodplain goes green or returns to dust depending on the river’s rise or fall. The shrub desert, the grasslands, and the woodlands all crawl uphill or down, putting out skirmishers along their lines of march. Within the national park natural forces are once again free to shape and reshape Big Bend’s different worlds. The battle seesaws back and forth between drought and ponderosa pine, tarbush and tabosa-grass, the eater and the eaten, the river and the rock, and the sun and the ageless land.
Broadly speaking there are four North American deserts: the Great Basin, Mohave, Sonoran, and Chihuahuan. The park lies within the Chihuahuan. This desert is bordered on three sides by mountains; the fourth abuts vast semi-arid plains. The Sierra Madre Oriental (East Mother Range) blocks winds from the Gulf of Mexico, except as spinoffs of summer hurricanes. The Sierra Madre Occidental (West Mother Range) blocks the westerlies. How can you recognize Chihuahuan Desert? By the lechuguilla plant (see [page 32]), which grows only in this desert.
In Big Bend you can turn back your personal clock to a time when mankind was still very obviously part of nature. You can walk in the desert and drink solitude as sweet as spring water or sit on the edge of a mountain meadow knee-deep in grass. You can watch the whitetail deer drift through the forest in a silence as perfect and ethereal as song, watching you but expressing no fear. For in the park you are just one more of nature’s creatures free to live and to grow in Big Bend’s self-healing, life-renewing world.
For many people the spirit of the desert is embodied in the vulture tirelessly circling empty skies above a bleak and barren land, the harvester of death keeping watch over desolation. But the desert is far from lifeless or the vulture wouldn’t be on patrol. The meager shrubs are miracles of adaptation and those seeming barren wastes rustle under the feet of countless busy creatures. Across the eons evolutionary selection has produced a different design for living within each species, yet all are subject to the same law.
Heat and aridity are the chief factors controlling all Chihuahuan Desert life. Most desert creatures stay in hiding during the day, keeping out of the sun in underground burrows, under rocks, or in the shrubs’ sparse shade. Many birds and most larger mammals don’t even visit the desert during the heat of the day. And although plants cannot crawl out from under the sun, nature has protected them by different means.
Probably the best way to see the living desert is to get out and walk and look. Study a plot of shrub desert in a single day and night. The most obvious desert dwellers, and sometimes the only living things you will see, are the plants. These vary from one stretch of desert to another because different species prefer different living conditions. But you will likely find plants in several categories, including woody and fibrous shrubs, cactuses, and other succulents. All have their own ways of resisting heat and drought, and all provide food or shelter to one or another special animal.
If success can be judged by sheer numbers, then the most successful desert shrub must be creosotebush, an evergreen bush that can make a living on the poorest and driest soils. You cannot mistake it for any other. The ground around it is apt to be bare and the individual bushes so evenly spaced that they look hand planted. This characteristic creosotebush pattern is probably caused by root competition for scant moisture. Each creosotebush has a long taproot reaching down maybe 9 meters (30 feet) to find underground water, while a network of shallow roots spreads far and wide to capture every drop of surface moisture. The plant protects itself from moisture loss by giving its dark green leaves a light-reflecting coat of resin. In the springtime, and often after rain, it bursts into brief yellow flower. It fruits in fuzzy little white balls, and you sometimes see a plant bearing both fruits and flowers.
Fortunately for the creosotebush, its taste is so unpleasant that few large animals care to eat it. But the little creosotebush grasshopper spends his whole life living and nibbling on the shrub. You’ll hear him chirping away in a creosotebush, but unless he jumps you may never find him. He’s a great ventriloquist who across countless generations has evolved protective coloring, the same dark green as creosote leaves, marked with the same red and white of its little stems and fruits. You may never see the mottled gray and black walking-stick insect either, who sticks his front legs straight out in front of him to look exactly like a woody creosotebush twig. Creosotebush holds the desert soil as blowing sands heap hummocks around its stems, and these make favorite burrowing sites for all sorts of little desert rodents and reptiles. Look under almost any creosotebush, and you will see their holes. You may even see a busy line of ants taking bits of creosote leaf and fruit to an underground nest.
The ocotillo also goes by the name coachwhip because it so often looks like a bunch of buggy whips stuck in the ground. However, in the springtime following a wet winter, those dead-looking stalks are adorned with green leaves and topped by brilliant red flower clusters. The ocotillo is common throughout both the Chihuahuan and Sonoran Deserts.
Another curious woody shrub resembles a sheaf of coachwhips. If you see ocotillo after rain, it will look like a green fountain. If you see it during a dry spell, you may think it is dead. Not so. Ocotillo puts on a fresh close-fitting suit of green leaves whenever it rains. Then as soil and air dry out, it sheds its leaves right down to the bare brown stems. This cuts back on the plant’s water needs. Moisture loss is further reduced by resinous cells that form the inner bark. In springtime the tip of each ocotillo wand burns with a cluster of scarlet flowers.
Cactuses have done away with leaves altogether, thus reducing their surface area and cutting down on moisture loss. Although they look dry and forbidding, inside that harsh exterior their flesh is moist and succulent. The food-making function has been taken over by the thick, green, wax-covered stems. And since the stems are also used to store water, they have ballooned into a weird and wonderful assortment of shapes and sizes. You’ll find the mound-building strawberry cactus with its mass of finger-like heads, the Texas rainbow cactus with its small group of cylindrical heads topped by bright yellow flowers, the tuber-like living rock, the dog and cane cholla, and the great sprawling pricklypear that lifts its beavertails from desert flat to mountaintop.
Cactuses come heavily armed with spines so cleverly shaped that they are called “fish-hook,” “eagle’s claw,” and “horse crippler.” These spines serve a double purpose: By building a lattice work around the stem of a cactus they shade it from the sun, and in many cases they make the cactus too prickly for animals to eat. Some animals have learned to use cactus spines for their own protection. The big, ratchet-voiced cactus wren likes to build its nest in the densely spined cholla, and the packrat often piles pricklypear pads in its nest area.
Pricklypear is the commonest cactus in the park and also the easiest to identify. Purple-tinged pricklypear is just what its name suggests, and so is the brown-spine pricklypear. Blind pricklypear looks as if it has no thorns, but if you touch one of the velvety buttons on a pad, you will pick up a fingerful of almost invisible, but highly irritating little spines. Engelmann pricklypear is the most abundant species. And to human taste its fruits are delicious, although the tiny glochids, barbed spines, can hurt the mouth. Many desert creatures eat pricklypear: Flies, bees, and butterflies come to feast at the showy blossoms; birds, coyotes, peccaries, and deer eat the reddish fruits; small rodents reach between the spines to nibble on the juicy pads. In times of drought ranchers burn off the spines and feed the pads to cattle. And people lost in the desert can do as the Indians did—peel, cut, or roast the skin off the pads and the flesh yields both food and moisture. Some pricklypears are too bitter to eat, however.
Cactuses
Fish-hook cactus
Button cactus
Strawberry pitaya
Claret cup
Cholla
Pricklypear
Eagle’s claw
Rainbow cactus
Coarse strong fibers of the lechuguilla plant (top) were extracted by machine (bottom) for use in matting, ropes, bags, and household items.
The candelilla or wax plant (middle) has been used in manufacturing waxes, polishes, chewing gum, phonograph records, and candles. In the rainy season the stem fills with milky sap. In the dry season this sap coats the stem as wax by evaporation. The wax protects the plant from drought.
One of the most interesting plants in the Chihuahuan Desert is a sturdy bunch of blades called lechuguilla. This fiercely spined agave lives nowhere else in the world. When Cabeza de Vaca crossed Big Bend in 1535, the lechuguilla grew so thick that he didn’t dare walk at night. Today you find it growing singly or in colonies from the shrub desert clear up into the Chisos woodlands, its needle points still menacing hikers, horses, and deer.
Lechuguilla is a fiber plant that keeps its juicy parts underground until it blooms, which it does only once a lifetime, after ten to fifteen years. The bloom stalk shoots up like a giant asparagus spear maybe four meters (15 feet) tall, flowering from the bottom up in close-packed purplish or yellowish blooms. Then the whole plant perishes by degrees. You may find a lechuguilla whose blades have died and dried while the bloomstalk is still moist and green. Eventually the bloomstalk, too, will turn into wood strong enough for a deer to lean against when rubbing velvet from his antlers.
Lechuguilla reproduces both by seeds and by rhizomes, and you sometimes find tiny new rosettes breaking ground on the runners of a mature plant. Peccaries often root up the juicy lechuguilla rhizomes, while mule deer relish the tender bloomstalk, munching it much as a cow chews a stalk of corn. Pocket gophers eat the core right out of a standing plant by tunneling underground.
The kinds of animals you meet in the desert will differ with the time of day and the time of year. They must find food and moisture, mate, and raise their young without exposing themselves to killing heat and the risk of dehydration. Insects, spiders, scorpions, and reptiles all derive their body temperature from their surroundings. This is why they stiffen up to the point of helplessness when it’s cold, and why crawling on a super-hot surface will kill them in short order. Their temperature regulation problems are compounded by conditions in the desert, and most of them cope by modifying their behavior.
In the early morning you may see grasshoppers sunning themselves on a rock as rattlesnakes will do. They line up broadside to the sun’s rays, raising their wings and lowering their legs to expose their abdomens directly to the sun’s warmth. By noonday they line up parallel to the sun’s rays to minimize heat absorption, and they will seek shade. Also, instead of hopping over the ground, many Big Bend grasshoppers live in and fly from bush to bush. The surface of the desert may be 20 to 25 degrees Celsius (40 to 50°F) hotter than is the air just over a meter (4 feet) above the ground. This is why in the daytime you will mostly see only flying insects, such as butterflies, grasshoppers, true bugs, true flies, and bees, and why so many crawling insects stay hidden during the heat of the day. However, there are some curious exceptions: The darkling beetle scurries about over the sand throughout the day. An air-filled space under its hard outer wing-covers acts as a kind of insulation between the back and abdomen. Some darkling beetles also raise the abdomen at an angle of about 45 degrees. Speed is of the essence for this little scavenger as it scurries from cover to shade.
Some grasshoppers are ground dwellers that have lived on the desert pavement so long that they even look like stones. Many come in conventional grasshopper shape but are mottled in shades of gray and mauve. The toadhopper that inhabits wash bottoms and rocky areas has taken on the color, shape, and texture of rock. Fat and squatty, he will camouflage himself, tucking his antenna right down in front of his face and pulling his legs in close to his body. You can’t even see him when you know he is there. By comparison, the lubber grasshopper advertises his presence. He is a large black beast gaudily marked in coral-snake red and yellow. Apparently these colors warn predators that the lubber is distasteful. He is out and about from late morning on.
Whiptail scorpions, which are not true scorpions, have no stinger. They pursue insects and other invertebrates and kill them with powerful pincers.
Eleven species of stinging scorpions live in the park. Coloration varies from dull-cream through brown to shiny black.
Also seen in broad daylight is the worm-like millipede rippling its way across the desert pavement. This maroon-colored plant eater has up to 200 legs arranged in short double pairs along a 13-centimeter (5-inch), many-segmented body. He isn’t poisonous and won’t sting or bite, but he may emit a substance lethal enough to kill other insects in a confined area.
Of course, the chief daily events of life in the desert are eating and being eaten, and predators that favor a certain diet make it their business to be out when their kind of dinner is around. Thus the grasshopper-eating lizards brave the daytime heat to do their hunting. Most often seen is the quick moving western whiptail. The greenish collared lizard may be seen racing along on his hind legs like a miniature dinosaur. Lizards are about the biggest ground dwellers you scare up on a noonday walk—unless you happen on a lizard-eater like the big, pink western coachwhip snake.
At twilight you become most aware of the desert’s residents. The coolness brings them out. Some must hurry and eat before it gets full dark, while others have the whole night ahead of them. At first you may sense the desert’s coming-to-life more by listening than by looking. You hear the lesser nighthawk trilling like a toad. Then, without warning, the whole desert begins to sing, as katydids, grasshoppers, and crickets join in a tapestry of sound so rich you can almost touch it.
Soon the desert cottontail creeps from his thicket to nibble pricklypear fruit. He stays close to home and prefers brushy terrain. The blacktailed jackrabbit passes the day in a form, a basin scratched out beneath some bush. He can cover the ground in enormous jumps, and his megaphone ears help cool him by dissipating body heat. The desert mule deer, another blacktailed, long-eared browser, may also appear at dusk to forage mesquite and lechuguilla. And a band of peccaries—or javelinas as they are also called—may rattle through the brush. They have a great fondness for pricklypear and their mouths are so tough they eat roots, fruits, pads, spines, and all. The ferocity of these wild pig relatives is more fiction than fact. If you meet one face to face, he may take a few steps toward you, but not out of meanness. He’s nearsighted!
Evening can linger a long time in the desert and night can strike quickly as a cat’s paw. You watch the sun go down, turning the clouds above the Chisos red, painting Sierra del Carmen crimson, while a single golden shaft breaks through the clouds and hits El Pico like a spotlight. Then the sky goes smoky blue and mauve over the eastern mountains, and the clouds to the west turn ashen as burned out coals.
Lizards
Collared lizard (male)
Texas banded gecko (adult)
Texas alligator lizard
Twin-spotted spiny lizard
Collared lizard (pregnant female)
Texas banded gecko (young)
Marbled whiptail
Big Bend gecko
Snakes
Western hognose snake
Mexican milk snake
Blacktail rattlesnake
Trans-Pecos blind snake
Western coachwhip snake
Trans-Pecos rat snake
Western diamondback rattlesnake
Blackneck garter snake
Baird’s rat snake
Big Bend patchnose snake
Texas lyre snake
Glossy snake
Mohave rattlesnake
Longnose snake
Black-hooded snake
Bullsnake
Two Non-Drinkers
The kangaroo rat and roadrunner exemplify adaptations for desert living. Neither drinks water, as a rule. The roadrunner gets its moisture largely from its omnivorous diet, which includes lizards and small rattlesnakes. It kills them with stunning blows of its beak. Its characteristic X-track provides good traction in sand. Agile and nimble, this 60-centimeter- (2-foot) long bird can fly, but it prefers to run, at up to 32 kph (20 mph). Mexicans call the roadrunner paisano, “fellow countryman.”
The kangaroo rat metabolizes both energy and moisture from seeds that contain less than 4 percent water. It has no sweat glands and cools itself by breathing. Its nasal passages, cooler than the rest of its body, condense breath moisture for retention. Its kidneys, among the most efficient in the animal world, excrete uric wastes as a concentrated paste, not as liquid, saving further precious water. Its deep burrow has a year-round relative humidity between 30 and 50 percent. These rodents sometimes fight with each other, leaping high into the air and striking at each other with their strong hind legs.
You can see the nighthawk now against the pale and pearly afterlight, and a star pops out, then another and another. Suddenly, more stars seem to be twinkling than can possibly exist in the universe. In the absence of man-made light they are an overwhelming presence. The Milky Way stretches from horizon to horizon. Who can believe that our Sun is just a middle-sized star, and planet Earth a mere speck spinning on the fringes of that gorgeous luminosity?
On a night of no moon, in the mist of starlight, the mule deer may stay active until dawn. On mild, windless nights the hunters and the hunted come out in full force: insect-eating scorpions, tarantulas, and wolf spiders; seed-eating pocket mice and kangaroo rats; rodent-eating snakes, badgers, and owls. What a hurrying and scurrying, what popping up from holes and burrows, what slithering and digging, what squeaks and shrieks, what patient waiting in ambush. And by what ingenious means do the hunters find the hunted in the dark! Beep-beeping bats locate insects and avoid obstacles by bouncing sound waves, imperceptible to humans, off objects as they fly. The female katydid wears her ears on her knees; by waving her front legs she zeroes in on the male’s mating call. Cold-blooded rattlers heat-sense warm-blooded rats and mice. And just as an astronomer opens the aperture on his telescope, so the owl at night widens his enormous eyes for light from far off stars.
Toward dawn the morning star burns like a lamp in the east, and gradually, a pale flush spreads upward from the crest of the Sierra del Carmen. A bank of clouds hangs off the Fronteriza, and as the overhead stars wink out and the morning star burns on, the pale glow turns peach and seeps higher. Just enough air stirs to shake the mesquite. A waking bird emits one cluck. Soon the clouds below the Fronteriza go salmon pink and flare with internal fire. As the sun tops the Sierra del Carmen and spills a glare sharp as ice shards over the desert, you hear a distant bark. One yap, two, a soprano howl, an alto tremulo, then chord upon chord in wild and worshipful sounding chorus. Somewhere in the ruddy hills a pack of coyotes seems to sing the sun up.
Desert flowering plants adorn a mudflat almost as metaphors of patience. The secret lies with seeds that have adapted to remain dormant for years, if necessary, until enough rain falls to bypass their germination inhibitors.
When rains raise the water level, animals drink from natural tanks such as Ernst Tinaja. Tinajas can also be death traps when the water level falls so low that animals can’t climb back out. Mountain lion claws have etched desperation into the rims of some.