Sonoran Pronghorn - Cabeza Prieta NWR

The Sonoran pronghorn, a subspecies of the pronghorn, was listed as an endangered species in 1967. In 2002, it was estimated that there were only 21 left in the U.S., after a severe drought, with about 600 to the south in Sonora, Mexico. A captive breeding program was established in Cabeza Prieta NWR in 2004 to increase the number of Sonoran pronghorn. It included 11 captured pronghorn, including some from Mexico in order to broaden the genetic diversity. One square mile of desert in Cabeza Prieta NWR was fenced off just south of Charlie Bell Road west of Ajo. Beginning in 2006 some male yearlings started to be released. In 2008 27 fawns were born, bringing the captive population to about 55.  In 2012 some were introduced into the Barry M. Goldwater Range (north and east of Cabeza Prieta) and some were used to establish another captive breeding program in Kofa NWR (northwest of Cabeza Prieta). As of 2014, it was estimated that there were about 202 in the wild in the U.S., 550 in Mexico and about 115 in the captive breeding programs in the U.S., estimated at 70 in Cabeza Prieta by a ranger I talked to, which would leave about 45 in Kofa NWR.

The Sonoran pronghorn is smaller and lighter in color than other subspecies of the pronghorn. They prefer broad, open, sparsely vegetated, alluvial valleys that give them lots of space to view predators with their excellent eyesight (they can spot movement several miles away) and room to run with their blazing speed (they can run 60 miles per hour for short distances and sustain 35 miles per hour for longer distances).

Issues for their continued survival include the fact that: (a) An important part of their geographic range includes the Barry M. Goldwater Air Force Range, an active bombing site of the U.S. Air Force; (b) Illegal immigration and illegal trafficking of drugs from Mexico is prevalent in the area, contaminating water sources, leaving trash, destroying vegetation and creating illegal roads and trails; and (c) Perhaps even more destructive, the U.S. response to curtail that illegal activity by the U.S. Border Patrol and DEA means that four wheel drive vehicles and ATVs are continually moving through the range, making their own roads and trails with a highly visible and disturbing presence.

One of my goals this year in traveling to southern Arizona was to see the Sonoran pronghorn. In previous visits I'd always been in Organ Pipe Cactus National Monument ("OPCNM"). In my last visit I asked a Border Patrol agent if he'd seen any pronghorn. He said he saw them occasionally along El Camino Del Diablo, a road which starts south of Ajo and crosses BLM land, then goes through the northwest section of OPCNM and then goes through Cabeza Prieta NWR. That caused me to do further research and I learned about the captive breeding pen in Cabeza Prieta, just west of Ajo.

This is a map of Cabeza Prieta. Charlie Bell Road is top right, leading out of Ajo, going west. El Camino Del Diablo starts below Ajo and goes southwest through the corner of OPCM and into Cabeza Prieta beyond that. Note that most of Cabeza Prieta is closed from March 15 to July 15 each year to protect the pronghorn during the time that fawns are born and very young. 

Charlie Bell Road into Cabeza Prieta west of Ajo requires a high clearance, but not four-wheel drive. 

So I rented a mid-size SUV early in August and left Redlands about 11:45 p.m. on Friday night and arrived in Ajo about 5:00 a.m. Saturday morning. During the drive I'd seen incredible lightning lighting up the Arizona sky and I hit a deluge in Gila Bend that dropped buckets of rain in a very short period of time. Leaving Gila Bend I had to reduce my speed to about 40 mph to keep from hydroplaning. 

Access to Cabeza Prieta requires a permit and a waiver, which includes waivers for liability from encountering unexploded ordinance and illegal immigrants and drug dealers. The road and directions to follow the road were difficult. It crossed many arroyos that had seen substantial water earlier in the evening and had some pretty big drops, particularly in the arroyos.

The Cabeza Prieta office is in Ajo. 

The entrance to Cabeza Prieta. I had to sign in at a kiosk. 

An informational sign on the pronghorn is at the entrance.

Signs warn of the illegal immigrant and drug trade.

Beautiful scenery in the early morning light.

This one particular peak really caught my attention and I photographed it from several different angles. 

I encountered a windmill which was used to pump ground water and a large tank to hold the pumped ground water. The water appears primarily for the captive pronghorns, but it has a blue flag to attract the illegal immigrants and a spigot to allow them to drink 

The windmill is to the left and the flag and tank are to the right.

This camera was near the water tank. I'm assuming it probably got my picture as well as those of illegal immigrants, pronghorn and their predators.

I walked down this wash north of the water tank. I found this pool of water toward the bottom, courtesy of the night rain. I also saw some turkey vultures and a Harris hawk nearby. 

The fencing for the captive breeding program is about 75 yards south of Charlie Bell Road and signs forbid going anywhere near it. A 15 mph speed limit is placed on driving through the area to prevent collisions with antelope outside the enclosure. 

This blind was on top of a hill overlooking the enclosure. I'm sure it is used as an observation post for the pronghorn.

A closer look at the blind.

This structure is near the beginning of the fenced enclosure and I assume is an entry point. 

Another gate into the enclosure.

The fence is covered with black material to keep the pronghorn from running from coyotes they might otherwise see outside the fence and then from running into the fence. 

This tower is used by wildlife officials to view the pronghorn. It is particularly used in the spring when the pronghorn are giving birth and helps wildlife officials to learn more about the pronghorn. 

Closer view of the tower.

A good view of the fence.

Released pronghorn tend to come back to the enclosure area  where they were raised and it thus provides the best place to try and see them in the wild. 

I was told that a man had gone about a half mile west beyond the enclosure along Charlie Bell Road several days earlier and had hiked about a half mile north down a wash and had seen a pronghorn. I also talked to a ranger, the only other person I saw in Cabeza Prieta, who told me he'd seen some pronghorn just east of the enclosure on some small hills several days before. So I parked the SUV about a half mile west of the enclosure and started to walk down one of the washes in the area. I encountered lots of Gambel's quail, but not much of anything else. After I turned back and was almost back to my vehicle, I saw two flashes of pronghorn light brown about 50 yards ahead of me. It was only flashes of color, but I'm virtually certain I saw a pronghorn. Unlike deer that run, then stop and peer back, the pronghorn run and just keep going. That tantalizingly brief encounter further whetted my appetite to get a better view.