Introduced by landowners in 1957, the species has since flourished and competes with native wildlife for precious food and water resources. Though their existence is controversial, mature aoudads are an impressive sight. Mule deer and white-tailed deer, their chief rivals for food, also are seen frequently, along with raccoons, bobcats, coyotes, porcupines, opossums and foxes. Birders have observed more than 175 species, including bobwhite quail, turkeys, several different types of hawks and golden eagles. Listed on the National Register of Historic Places, Clarity Tunnel was the last active railroad tunnel in Texas and now is home to a colony of Brazilian free-tailed bats.
Farther west are the remains of a second tunnel.
Although the tunnel is no more, the trail is littered with huge rocks that have tumbled down over time after being loosened by the excavation, making for a dramatic setting. The trailway's 46 bridges pass over everything from small washes only a few feet from the ground to creek and river beds almost 100 feet below. Perhaps the most photographed bridge on the trail spans more than 200 feet, over often-dry Los Lingos Creek. People planning a trip on the trailway should call park headquarters. Park personnel know the trailway well and have plenty of suggestions for starting and stopping points.