Prairie Ghosts

Photo taken by John Kulberg, AZGFD Volunteer

Most people usually do not think of pronghorn antelope when they think about the animals of the Sonoran desert. Instead images of Gila monsters, rattlesnakes and desert big horn sheep come to mind. This is no accident because all those animals live in healthy populations throughout the Sonoran desert. Unfortunately the same cannot be said for the Sonoran pronghorn. It is believed that this majestic animal, a distinct subspecies of pronghorn, once ranged from Sonora, Mexico to the south and north to the Gila River in Arizona. Sonoran pronghorn were observed as far east as the San Pedro River and west to southeastern California. The land composing the Sonoran Desert National Monument once had Sonoran pronghorn roaming it valleys and plains.  It is listed by the U.S. Fish and Wildlife Service as endangered. Today about 400 Sonoran pronghorn can be found in southwestern Arizona and northwestern Sonoran. Most of the American Sonoran pronghorn live on the Cabeza Prieta National Wildlife Refuge, Organ Pipe Cactus National Monument and the Barry Goldwater Bombing Range southwest of Gila Bend, AZ. Most Sonoran pronghorn live in Sonora, Mexico south of Mexican Highway 2. Occasionally Americans traveling to Rocky Point, Puerto Penasco, have the opportunity to see this animal feeding alongside the road.

Pronghorn-3yr-buck-Greg-Joder-r2010

3 year old pronghorn buck, photo taken by Greg Joder, AZGFD

Threats

As with most species facing extinction habitat destruction and fragmentation are the main threats to this species’ survival. From about 1700 to the late 20th century competition with livestock on public lands had its effects upon the Sonoran pronghorn population, but this threat dwarfs the effects of roads, fences and canals have had on this animal.

Over hunting in the past and illegal hunting in Mexico have had an impact on this species.

Before Interstate 8, Mexico 2 and several other roads and highways and canals were built Sonoran pronghorn were free to roam an area millions of acres in size to search for forage and water. Even though the Sonoran desert is perhaps the most productive desert in the world, forage availability can be sporadic because of the periodic nature of precipitation characteristic of this region. It may rain two inches in one desert valley resulting in a flash flood whereas the valley three miles away will receive no rain at all. Forage in the wet valley will grow and pronghorn and other mobile desert wildlife will travel to take advantage of the relative abundance found there. Roads, canals and fences are barriers to wildlife such as pronghorn, deer and desert bighorn sheep. If they cannot reach the area where it rained and forage is available they can perish. Nursing fawns are especially threatened.

All pronghorn are especially susceptible to roads with right of way fences that are meant to keep animals from wondering on to roads. In general pronghorn do not like to jump fences. They prefer to go around or under the fence if they are able to. Pronghorn friendly wire fences have a smooth bottom wire raised 18 or more inches above the ground to allow them to easily pass under.

So each time a road was built, a fence stretched or a canal was dug the Sonoran pronghorns habitat was whittled away and individual herds were left isolated from other pronghorn reducing genetic variability and from food and water.

 

Pronghorn Recovery and the Sonoran Desert National Monument

Presently the U.S. Fish and Wildlife Service, Arizona Game and Fish Department and the National Park Service at Organ Pipe Cactus National Monument, the Department of Defense and others are working to recover the Sonoran pronghorn. The Sonoran pronghorn recovery plan calls for the establishment of additional populations of pronghorn in order to buffer this species from future loss. A captive breeding program is in place at the Cabeza Prieta and Kofa National Wildlife Refuges.

The Sonoran Desert National Monument has been named as a possible location for future Sonoran pronghorn population.  The Friends of the Sonoran Desert National Monument considers recovery of the Sonoran pronghorn a priority and will continue to advocate for this animal and for its future reintroduction back into the Sonoran Desert National Monument.

To facilitate a real and sustainable recovery the Friends of the Sonoran Desert National Monument is working to establish wildlife travel corridors to link various protected habitats together. This involves planning and eventually the construction of wildlife overpasses where Sonoran pronghorn, desert bighorn sheep and deer as well as other animals travel safely to areas where they can forage and breed safely.

This article is courtesy of Friends of the Sonoran Desert National Monuments

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