Grand Canyon National Park - Beneath the Rims
Below the lip of the canyon, the great trees, finding rootholds in crevices and on ledges, grow smaller, and the ponderosa forest itself is increasingly more sparse. By the time you reach the bottom of the thousand-foot cliffs of limestone and white sandstone that edge both rims of the canyon, you have entered a world where gnarled Utah junipers and pinyon pines clutch talus slopes of red shale. The pitchy, aromatic cones of the pinions contain very large seeds called pinyon nuts, and when they ripen in late summer, the trees are aswarm all day with cackling squadrons on pinyon jays, gathering as many nuts as they can to store for the winter. Nervous pinyon mice, wearing their white feet like spats, take up the same task at nightfall, alert for the threat of a gray fox, kit fox, coyote, bobcat, or owl.
This pinyon-juniper woodland gradually diminishes as you descend the ledgy slopes toward the sheer Redwall cliffs. Brittle shrubs, such as the almost leafless Mormon tea and the desert thorn with its drooping flowers and knitting-needle spines, grow in shoulder-high clumps. Mule deer pick their way past shaley ledges, where mountain lions may lie in wait.
Although little seems to grow on the exposed face of the Redwall overlooking the desert platform hundreds of feet below, it is enough to support the bighorn sheep that live there. These regal creatures, crowned with massive, coiling horns, seldom leave the precipitous rock fastness where they alone can move with ease and grace. Their lives are a constant search for scraggly patches of pungent sagebrush, trailing four-o'clocks, white evening primroses, yellow-flowered cliffroses, and other bits of greenery on shelves and ledges.
The desert at the base of the cliffs is dry because it is hot -- up to 35 Fahrenheit degrees hotter than the North Rim. Most of the rain that falls into the canyon evaporates before it hits the ground, and so only the river and its tributary streams support the kinds of life that need steady moisture. Away from these sanctuaries, plants are lean and mean, widely spaced, sparsely leaved, and often thorny. Tough blackbrush thrives, and so do shrubby catclaws, their grayish branches lined with the viciously hooked thorns for which they are named. Cactus wrens nest among the spines of chollas and other tall cacti. Grand Canyon rattlesnakes -- found only here, where their pinkish scales belnd into the colorful rock -- wait patiently for cactus mice, jackrabbits, or lizards to venture within striking range.
At dawn, when the tang of creosote bush is strong in the air, pot-bellied chuckwallas -- foot-long lizards whose blackish skin hangs like loose clothing -- lumber from their hiding places to bask in the sun. When their body temperatures reach 100°F, they begin to look for buds, flowers, fruits, and juicy plant stems to eat. Although the vegetarian chuckwalla looks ferocious, it is a timid soul; if startled it scuttles into a rocky crevice and expands its body until. It is wedged in tight. Coyotes have been known to defeat this strategy by thumping the lizards' noses until they back out of their nooks.