Location: 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.