Joshua Lott / REUTERS
Supervisory U.S. Border Patrol Agent Bobbi Schad pets one of the six new mustang horses at the horse patrol training facility in Willcox, Arizona on Aug. 19.
Sturdy, highly strung mustangs from wild herds in the Rocky Mountains are playing a growing role as the U.S. Border Patrol takes its hunt for smugglers into the most rugged terrain on the Arizona-Mexico border.