Range Description

The species' range includes only southwestern Texas (central Hill Country, Trans-Pecos) and adjacent areas in northeastern Mexico: southwestern Edwards Plateau of Texas west through the dissected canyons of the Stockton Plateau and the Big Bend Region to the Davis Mountains, thence south into Mexico along Coahuila Folded Belt to the front range of Sierra Madre Oriental of Coahuila, Nuevo Leon and Tamaulipas; also the Sierra San Carlos of south-central Tamaulipas, at elevations of around 305 to 3,050 m asl (1,000 to 10,000 feet) (Lawson and Lieb 1990, Werler and Dixon 2000). Within this range, the distribution appears to be spotty (Tennant 1998), but this may in part reflect the snake's secretive behavior (Ernst and Ernst 2003).