FALFURRIAS, Texas (AP) — Some migrants are willing to risk walking through a dangerous stretch of rough terrain in a vast valley of Texas ranchlands and brush to avoid detection by border authorities. This elusive group is usually single adults who may walk long distances through the shrub-invaded grasslands on sprawling ranches to circumvent U.S. Border Patrol checkpoints where agents verify people’s immigration status. They’re less likely to surrender to U.S. authorities to seek asylum than families and children. Many have died on these journeys in the Rio Grande Valley, and aid groups are working to help them by leaving water and helping with rescues.