Although its climate is semi-arid, the Grand Canyon includes four distinct ecosystems, and Bright Angel trail runs the length of this ecological gamut, offering a picturesque array of wildlife.
The trail begins at the South Rim in a forest of lofty ponderosa pines, with Gambel oak plentiful as well. Colorful wildflowers bloom in warmer weather, and big-horned sheep and mule deer share the woods with ringtail cats and foxes. This area is the sole habitat of the Abert's squirrel, distinctive for its long, bristle-tufted ears. It's also home to coyotes and mountain lions, two people-shy predators (fortunately).
Descending, you wind through a juniper woodland and scrub desert. Hardy Utah juniper and pinyon pine thrive in the thinner soil, along with mesquite, sagebrush and cactus. Desert areas crawl with reptiles, including the pink rattlesnake and the chuckwalla, a large lizard that thwarts predators by wedging itself between rocks and puffing itself up for an even tighter fit. Peregrine falcons and endangered California condors nest in the cliffs.
The trail ends on the oasis banks of the Colorado River. Stream orchids and white-flowering redbud trees erupt from hillsides in hanging gardens, watered by subterranean springs. Year-round residents include raccoons and skunks, which feed on river trout and mollusks. Higher-dwelling animals come to drink and browse on willow and watercress.
More than a wildlife show, the Grand Canyon is a geological biography, chronicling North America's past. The oldest, lowest layers of rock go back nearly two billion years. They speak of volcanic activity, followed by periods of tectonic upheaval. They're studded with fossilized fish and ferns, recording the era's climate and dominant life forms. Each layer contains different iron-bearing minerals, creating deep or subtle hues as the iron oxidizes. The Canyon is also a geological work in progress, as the forces of wind and water continually erode softer minerals to create dramatic profiles.
Traveling Bright Angel Trail thrusts you into the story. Where the path hugs cliff walls, you pass beneath lobes of pearly limestone and jagged outcroppings of roseate sandstone, and sometimes through tunnels in the rock itself. Other stretches take you across open desert, amid slopes of green-hued shale. Crossing the Colorado, you'll see how its current has carved the basin to expose layers of steel-gray gneiss with pink granite streaks.