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BLM > Arizona > What We Do > Wild Horses & Burros > Herd Management Areas > Cibola-Trigo HMA
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Cibola-Trigo Herd Management Area

cibola-trigo hmaLocation: Reaching 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 U.S. Highway 95 and the Colorado River, and Interstates 8 and 10, the HMA is about 20 miles north of Yuma, Arizona.

Size: This area is large, with the HMA comprised of nearly one million acres in the lower Sonoran Desert.

Habitat: In Arizona, the Cibola-Trigo HMA supports both wild burros and horses. Meanwhile in southwestern California, only the burros roam between the river and the Chocolate/Mules and Picacho HMAs. In California, the HMA is dominated by intricately dissected alluvial fans and bajadas adjacent to the Colorado River. The upland soils support sparse stands of creosote, ocotillo and palo verde. The many waterways emptying into the river provide life to dense stands of desert trees including palo verde, ironwood, catclaw acacia and mesquite. Sitting along the river are thick stands of salt cedar, phragmites and arrowweed. Moving away from the river, the bajadas give way to rugged volcanic mountains.

Winters in the HMA are typically mild, but summers can be dangerous, with temperatures exceeding a thermometer-breaking 125 degrees. Wild burros share this habitat with desert bighorn sheep and desert mule deer. Other animals living here include the desert tortoise, rattlesnakes and a variety of birds and lizards.

History: Wild burros were most likely introduced into this area in the mid-1800s. As mining booms went bust and alternate transportation became available, the wild burros were left to fend for themselves.

Wild horses have a more recent history. These animals probably escaped or were released as ranch horses when the river was channeled in the 1940s. There are several Appaloosa studs thriving in the Arizona portion of the HMA, contributing to the color diversity of the herd.  In fact, this line may be a continuation from the first-ever Appaloosa stud in the area. 

Program Information

Burro Information


Population:  Burros evolved in the harsh deserts of North Africa and are very well adapted to the dry desert environment. Let alone in this remote region with few natural predators, the wild burro population flourished. Today, the burro population here numbers approximately 527. The burros found here are typically grey in color and are fairly fine boned. They average about 350 to 400 pounds and 40 inches in height. 

During the summer months, the burros congregate along the Colorado River or other water sources. In late fall and early winter, depending upon rainfall, the burros disperse across the HMA. They begin their move back to the river in May or early June, and temperatures rise and the mesquite beans ripen. The wild horses remain near a permanent water source year round. Presently there are about 319 wild horses within the HMA.

Management: The wild burros and horses living in the Cibola-Trigo HMA 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 other wildlife species. When the population exceeds the Appropriate Management Level, determined through vegetative monitoring studies, the BLM removes some of the animals and offers them to the public through its Adopt a Wild Horse or Burro Program.

  Yuma Field Office
2555 East Gila Ridge Road
Yuma, AZ 85365-2240
Phone: (928) 317-3200
Fax: (928) 317-3250
Field Manager:  John MacDonald
Hours:  7:45 a.m. – 4:30 p.m., M-F