Sonoran pronghorn continue to thrive

by Teresa Walker
56th Range Management Office

2/22/2013 - LUKE AIR FORCE BASE, Ariz. -- An estimated 85 percent of the U.S. population of Sonoran pronghorn died during a severe drought in 2001 and 2002. They inhabit the Barry M. Goldwater Range, an active military range.

Drastic measures were taken to sustain the remaining 21 animals and recover the species. These measures included provision of emergency water sources, developing forage enhancement plots, and building two semicaptive breeding pens, one on the Cabeza Prieta National Wildlife Refuge built in 2004, and another in King Valley, on the Kofa National Wildlife Refuge, built in 2011.

The Sonoran pronghorn is federally listed as an endangered species in 1967, is the fastest land mammal in North America, clocking speeds up to 60 miles per hour. A desert sub-species of the antelope family, the Sonoran pronghorn is smaller and lighter in color than other pronghorn subspecies and is uniquely adapted for survival in harsh desert conditions.

The Sonoran pronghorn population is currently estimated at more than 150 animals, due to the specific actions of many state and federal agencies to bring the animal back from extinction.

Aaron Alvidrez, 56th Range Management Office wildlife biologist said it's been a long road to recovery but the results of all the labor are coming to fruition.

"A lot of hard work and teamwork is needed to implement pronghorn recovery actions," Alvidrez said. "Through teamwork and persistence, we are beginning to see our efforts pay off."

To minimize operational impacts and gain a better understanding of the animals, the 56th RMO goes to great lengths to ensure the safety of the animals.

Contracted biologists are used to survey and monitor for Sonoran pronghorn in known habitat areas prior to any missions taking place on the range. The pronghorn monitors establish the proximity of the animals to target arrays to ensure their safety.

When pronghorn are present, targets are closed based on their type and proximity to the animals; training and inert ordnance targets within 1 kilometer of sightings are closed for the day; and high explosive hills within 1.5 kilometers of sightings are closed for the day. Typically, scheduled missions are diverted to other targets if available, or canceled if no alternate targets are available.

The RMO employs a modified range maintenance schedule to further reduce potential effects on the Sonoran pronghorn during fawning season.

The annual Sonoran pronghorn capture and release operation in December 2012 was a success due to assistance from many agencies including Arizona Game and Fish, U.S. Fish and Wildlife Service, Luke Air Force Base, Marine Corps Air Station Yuma; the Ajo, Yuma, and Wellton Border Patrol Sectors; Bureau of Land Management, National Park Service and the Phoenix Zoo.

According to Alvidrez, the pronghorn capture and release process has evolved and the team continues to improve each year.

"For me, the captures are an exciting event with a lot of moving parts," he said. "The use of two helicopters and a large veterinary staff helped to transport multiple animals in a relatively short time. During the three-day event, we handled more than 60 animals and reached our goal of relocating 22 target animals."

The United States and Mexico are currently engaged in an international effort to capture and breed the Sonoran pronghorn for reintroduction into suitable habitats. Capture-breed-transplant actions are considered essential to the survival of the Sonoran pronghorn (commonly referred to as 'antelope') as they are one of the most endangered mammals in the world.

The BMGR is primarily used to train pilots but over the years has expanded its scope to allow some limited ground training. In land mass, the range encompasses more than 1.7 million acres, with the Air Force retaining land management responsibilities for more than a million acres on the eastern portion and the Marines approximately 700,000 acres on the western side. The range stretches from Yuma to beyond Gila Bend and from Interstate 8 south to the Cabeza Prieta National Wildlife Refuge.

Portions of this article were contributed by Arizona Game and Fish Department.