CIBOLA-TRIGO HERD MANAGEMENT AREA
Spreading across the border of Arizona and California, the Cibola-Trigo Herd Management Area (HMA) extends from Imperial Dam, west of the Colorado River, to Walters Camp in California. Located primarily between US 95 and the Colorado River and Interstates 8 and 10, the HMA is about 20 miles north of Yuma, Arizona. The Cibola-Trigo HMA is comprised of nearly one million acres of the lower Sonoran Desert.
The HMA supports both wild burros and horses. While in southwestern California, only the wild burro roams between the river and the Chocolate/Mules and Picacho Herd Management areas. The HMA in California is dominated by intricately dissected alluvial fans and bajadas adjacent to the Colorado River. The uplands support sparse stands of Creosote, Ocotillo and Palo Verde. The many drainages emptying into the river support dense stands of desert trees including Palo Verde, Ironwood, Catclaw Acacia and Mesquite. Immediately adjacent to the river are thick stands of Salt Cedar, Phragmites and Arrow weed. Further from the river, the bajadas give way to rugged volcanic mountains. Winters in the HMA are typically mild, but summers can be brutal with temperatures exceeding 125 degrees. Wild burros share this habitat with desert bighorn sheep and desert mule deer. Other animals that can be found in the area include desert tortoise, several species of rattle snakes and a variety of birds and lizards.
Wild burros were likely introduced into this area in the mid-1800s. As mining booms played out and alternate transportation became available, the wild burros were left to fend for themselves as the miners moved on to other areas. Wild horses have a more recent introduction to the area. These animals probably escaped, or were released, from ranch horses when the river was channeled in the 1940s. There are several Appaloosa studs, in the Arizona portion, of the HMA that contribute to the color diversity of the herd. This line may be a continuation of the first Appaloosa stud in the area.
Burros (Equus asinus) evolved in the harsh deserts of North Africa and are very well adapted to a dry desert environment. Left alone in this remote region with few natural predators, the wild burro population flourished. Today the population of burros is about 300. The burros in this area are typically grey in color and are fairly fine boned. They average about 350 to 400 pounds and 40 inches (10 hands) in height. During the summer months, the burros are concentrated along the Colorado River, or other permanent water source. In late fall or early winter, depending upon rainfall, they disperse throughout the HMA. They begin their movement back to the river about May or June as the temperatures rise and the Mesquite beans mature. The wild horses remain near a permanent water source year round. There are approximately 130 wild horses the HMA.
The wild burros and horses of Cibola-Trigo Herd Management Area are managed in an ecological balance within their habitat to protect the forage plants. This ensures that there is plenty of feed for the burros, as well as for the other wildlife species. When the population exceeds the Appropriate Management Level, as determined through vegetative monitoring studies, the Bureau of Land Management will remove some of the animals and offer them to the public through BLM's Adopt a Wild Horse or Burro Program.