The Sonoran pronghorn is one of the most endangered mammals in North America and wildlife officials on both sides of the border are concerned about its dwindling numbers.

"This is the first time that the Sonoran pronghorn populations north and south of the border have been surveyed in the same year. The survey was a cooperative undertaking involving the Arizona Game and Fish Department, Mexico, U.S. Fish and Wildlife Service, National Park Service, and the U.S. Air Force," said John Hervert, Yuma regional wildlife program manager for Arizona Game and Fish.

Biologists estimate there are 346 Sonoran pronghorn remaining in Mexico and 99 in Arizona. A 1993 Sonoran pronghorn survey in Mexico yielded a population estimate of 414 animals. In Arizona, Sonoran pronghorn numbers have declined from a high of 246 in 1992.

"Low rainfall since 1994 has caused poor fawn survival. Adult mortality has averaged 22 percent per year, leading to a declining population trend. That trend has the Sonoran Pronghorn Recovery Team concerned," Hervert said.

Hervert explained that the current data and trends strongly suggest that within four years the Sonoran pronghorn could reach a point where it is no longer a viable, self-sustaining population. "We know that most pronghorn in the herd are older than six years and will die in the near future — two to three years. This fact has the Recovery Team very concerned," Hervert explained.

To gather further biological information about fawn survival, habitat use patterns, behavior, food habits, mortality factors and population size, four pronghorns were captured in late December and fitted with radio telemetry collars.