Division of Bird Habitat Conservation

Birdscapes: News from International Habitat Conservation Partnerships

Species at Risk

Taking the Hard Road
by Ben Ikenson, U.S. Fish and Wildlife Service

Reaching from Baja California Sur and Sonora, Mexico, north through the southern half of Arizona and extreme southeastern California in the United States lies the Sonoran Desert—a harsh yet beautiful environment. Human inhabitants have invented means to adapt this environment to meet their survival needs. The endangered Sonoran pronghorn, on the other hand, has not been as well equipped to adjust to the widespread consequences of human activity. Along with range fragmentation and habitat degradation, recent drought conditions are exacerbating problems for the endangered subspecies.

The some 500 pronghorns inhabiting the desert are found in three isolated populations: two in Mexico, one in Arizona. All contend with roads, fencing, and railroads. Border fencing and Mexico's Highway 2, which parallels the border, separate the U.S. population from the one in Mexico's El Pinacate Biosphere Reserve (Reserve). Farther south, the largest population (311 pronghorns) is sandwiched between the Gulf of California and Mexico's Highway 8.

For border-dwelling pronghorn, foot traffic is a disturbance. More menacing however are the makeshift roads that line the border. The movement of water in slightly sloping valleys is so slow that heavily used roads divert moisture from lower-level vegetation, killing forage. Overgrazing also has taken a toll on native vegetation, particularly in the Reserve.

A 5-year drought and dwindling access to adequate forage has significantly diminished the animal's success at raising young. Growth of their preferred nutrient-and-moisture-rich forage coincides with the rainfall the animals would instinctively follow were it not for the barrage of obstacles throughout their range. Because the pronghorn's life span is short—10 to 12 years— reproductive success is critical to species survival.

Members of the Sonoran Pronghorn Recovery Team have taken some unusual steps during the drought to save the animal. Arizona Game and Fish Department and U.S. Fish and Wildlife Service biologists, for example, have been hauling water tubs to remote areas where they've tracked pronghorn activity. The 4-mile hikes with 5-gallon jugs of water in 105-degree heat is proof of their dedication. That the animals have responded is proof of their desperation. Pronghorn typically don't drink water when the moisture content of their regular forage is adequate.

The U.S. Air Force at the Barry M. Goldwater Range, a military training ground, plans to fund a forage-enhancement project on its land. The Air Force and U.S. Bureau of Reclamation worked together to drill two test wells to provide water for the project. One well hit water, making it possible for enhancement work to begin.

Additionally, the team has proposed several action items in a recent Supplement and Amendment to a 1998 Final Revised Sonoran Pronghorn Recovery Plan, hoping its comprehensive documentation will provide guidance on increasing pronghorn survival and improving habitat.

"It may be a long, hard road to recovery ahead," said Dr. John Morgart, U.S. Fish and Wildlife Service biologist and head of the Sonoran Pronghorn Recovery Team, "but the shorter road leads only to extinction."

For more information, contact Dr. John Morgart, U.S. Fish and Wildlife Service, Cabeza Prieta National Wildlife Refuge, 1611 North Second Avenue, Ajo, Arizona 85321, (520) 387-4989, john_morgart@fws.gov.

Sonoran Pronghorn Recovery Team Members

U.S. Fish and Wildlife Service
Arizona Game and Fish Department
Organ Pipe Cactus National Monument
U.S. Bureau of Land Management
U.S. Air Force
U.S. Marine Corps
University of Arizona
El Pinacate Biosphere Reserve
Instituto del Medio Ambiente y el Desarrollo Sustentable de Estado de Sonora.