A journey into the third largest wildlife refuge in the lower 48 states takes plenty of water and desert survival skills. Almost all of Cabeza Prieta National Wildlife Refuge is designated wilderness. Seven rugged mountain ranges cast shadows above valleys dotted with sand dunes and lava flows. The 1,000-square-mile refuge shares a 56-mile international border with Sonora, Mexico.

Temperatures may top 100 degrees for 90 to 100 straight days from June to October. Summer thundershowers and winter soaking rains average about 7.5 cm on the western part of the refuge and up to 20 cm on the east side, 60 miles away. The winter and summer pattern of rainfall in the Sonoran desert stimulates the growth of more plant species than in most deserts. You'll find creosote bush flats, bursage on the bajadas, mesquite, palo verde, ironwood, and an abundance of cacti, including ocotillo, cholla, and saguaro.

Endangered Sonoran pronghorn and lesser long-nosed bats call this parched land home, as do desert bighorns, lizards, rattlesnakes, and desert tortoises. Elf owls peer from holes carved in saguaros by Gila woodpeckers. Every plant and animal has adapted to life we would find uninhabitable. Far from a barren desert, Cabeza Prieta NWR harbors as many as 420 plant species and more than 300 kinds of wildlife.

Cabeza Prieta, Spanish for "black head," refers to a lava-topped, granite peak in a remote mountain range in the western corner of the refuge.

Sonoran wildlife possess a chest of tools to beat the desert's heat and hang in there for months without rain. The only water sources around are natural rock basins, called tinajas, that catch rainwater, a few artificial water storage areas, flowing washes after rains, and one intermittent seep.

Burrowing, nocturnal living, and astonishing water conservation techniques are just a few of the many ways animals adapt to life here.

The prehistoric Indians who survived here as hunters and gatherers knew how to reap the riches of the desert. They collected cactus fruit and mesquite beans and hunted bighorn and small game.