The region contains sky island mountain ranges, called the Madrean Sky Islands, some separated from the Sierra Madre Occidental proper, and occurring in the northeastern Sonoran Desert, and extreme west-northwestern Chihuahuan Desert.

The mountain range and the range to the north, the Peloncillo Mountains of Hidalgo County, New Mexico, can be viewed from the west at the Leslie Canyon National Wildlife Refuge and the San Bernardino National Wildlife Refuge.

Sky islands often lead to geographic isolation; (the tepuis of north-northeastern South America).

The Madrean Sky Islands are being studied for mammal movements, the cats especially, bobcats, mountain lions, etc.

It is being studied in 3 sky island ranges: Animas Mountains, the Peloncillos, and Sierra San Luis.