The Chisos Mountains make a perfect backdrop for this Prickly Pear Cactus - Opuntia engelmannii. The Chisos are volcanic in origin - lava and ash are evident all around the park - and are the second highest mountains in Texas at about 8,000 feet. They also harbor some decidedly "non-desert" species at higher, cooler, moister elevations. Black bear, mountain lions, and white-tail deer are found in the aspen, spruce and pine forests of these unique mountains. March 29, 2001.