The trail to Palm Canyon: set aside for sheep, an Arizona refuge also shelters some unexpected plants

Natural History, Sept, 2002 by Robert H. Mohlenbrock

About fifty miles northeast of Yuma, Arizona, and largely surrounded by an army proving ground, the Kofa National Wildlife Refuge embraces a thousand-square-mile area, most of which is classified as wilderness. The terrain includes the dry, brown, rugged Kofa Mountains and portions of other nearby ranges, along with surrounding Sonoran Desert flats. The only roads are unpaved, left over from past mining operations. The name "Kofa" in fact, is an abbreviation of the name for the area's largest abandoned mine, the King of Arizona. One rough road that runs through the northern end of the refuge provides access to Crystal Hill, where rock hounds may collect a limited quantity of rocks and minerals.

Managed by the U.S. Fish and Wildlife Service, the refuge was established in 1939 to protect the area's dwindling population of desert bighorn sheep, at that time estimated to consist of as few as a hundred animals. Here, as in other regions of the Southwest, this subspecies of bighorn sheep had been decimated by diseases, excessive hunting, loss of habitat, and competition with livestock. Since the sheep may need to drink water every three days during the summer, numerous artificial water holes and water tanks were constructed to aid in this population's recovery. Today, systematic surveys show there are more than 800 bighorns in the refuge.

Possessing remarkable climbing skills, the sheep usually stay in the upper reaches of the mountains, the highest of which is 4,877-foot Signal Peak. As ruminants, they are able to subsist on dry, often spiny vegetation that would seem to have little food value. Both males and females have horns, but the males' horns boast an amazing full curl and may measure more than thirty inches from base to tip.

Although the Kofa National Wildlife Refuge was created to protect the sheep, it also protects two stands of the rare California fan palm. The best time to visit the refuge is between October and March, when the temperatures are cooler. A gravel road off U.S. Route 95 crosses seven miles of desert to the Palm Canyon trailhead. The rocky, narrow trail to the palms goes through Sonoran Desert habitat, crossing several dry washes that carry water only after a torrential downpour--an infrequent occurrence. After a gradual climb for half a mile, hikers reach a vantage point offering a view of Palm Canyon and a few of its trees. Only hardened hikers should tackle the remaining half-mile up to the palms. For most people, the view from down below is satisfying enough.

Fishtail Canyon, the next canyon southeast of Palm Canyon, harbors a few more California fan palms. The only other stand in Arizona is in the Hieroglyphic Mountains, near Phoenix. These isolated populations are apparently remnants from a time when Arizona was wetter and cooler. Other stands exist in Nevada, California, and Mexico. In California the trees may reach a height of sixty feet, and as their lower leaves die, they hang down to the ground in a dense mass, forming what looks like a petticoat or skirt around the trunk. In Palm Canyon and Fishtail Canyon, however, the palms are only twenty to thirty feet tall and sometimes do not form petticoats of dead fronds. Botanists have not yet determined the reasons for these differences.

HABITATS

Canyon. Although the California fan palm is the major attraction, another rarity is the Kofa barberry, a three-foot-tall shrub known only from the Kofa Mountains and from the Ajo Mountains, farther south. Its leaves are divided into three shiny, spiny-toothed, hollylike leaflets; clusters of small, yellow-green flowers appear in June and July. Other canyon plants are desert-olive and skunkbush--both small shrubs--and bear grass, a robust plant related to yucca.

Desert flat. Saguaro grows here, along with numerous smaller cacti, including teddy-bear cholla, beaver-tail cactus, California barrel cactus, hedgehog cactus, and various prickly pear cacti. The most common shrubs are creosote bush, ocotillo, and bur sage. Others are catclaw acacia, whitethorn acacia, rigid spinyherb, white ratany, and two extremely spiny species known as crucifixion thorns. Wildflowers: gold poppy, whitestem milkweed, fiddleneck, Douglas nightshade, brittlebush, trixis, horsfordia, California buckwheat, various species of phacelia.

Desert wash. Foothill palo verde and ironwood--two small trees in the legume family--almost always dominate the dry streambeds. Shrubs are desert holly and Anderson wolfoerry. Wildflowers: coyote tobacco, yellow paper daisy, Emory's rock daisy.

For visitor information, contact: Kofa National Wildlife Refuge 356 West 1st Street Yuma, Arizona 85364 (928) 783-7861 http://ifw2irm2.irm1.r2.fws.gov /refuges/arizona/kofa.html

Robert H. Mohlenbrock, professor emeritus of plant biology at Southern Illinois University, Carbondale, explores the biological and geological highlights of U. S. national forests and other parklands.