Desert bighorn sheep, for which the refuge was founded in 1939, and the endangered Sonoran pronghorn receive protection here. Much of the refuge has wilderness designation. Twelve small mountain ranges rise above the desert floor. Wildlife and vegetation are similar to those in Organ Pipe Cactus National Monument, but the climate is harsher. Cabeza Prieta's annual rainfall averages about nine inches in the east and three inches in the west.
Some areas go for more than a year without rain.
The Smithsonian Institution studies the heavens with a variety of telescopes on Mt. Hopkins. The famous Multiple Mirror Telescope, one of the world's largest, has been replaced by a new telescope with a single giant 6.5-meter mirror using the latest optical and electronic technologies. From March to November, six-hour tours begin at the Whipple Observatory's visitor center at the base of the Santa Ritas. The tour begins with a short video presentation at 9 a.m., then you have a narrated bus ride high into the mountains. The outstanding views are almost as good as those from nearby Mt. Wrightson.