Feral Burro Impact on a Sonoran Desert Range

Abstract

Impact of feral burros on native desert vegetation was studied in the Havasu Resource Area, Lower Colorado River Valley, California-Arizona. Browse utilization ranged from heavy to light with increasing distance from the Colorado River. Overgrazing occurred near the Colorado River but decreased to light or moderate use at distances greater than 2.5 km from water. Overgrazing decreased the canopy cover of Ambrosia dumosa from about 2.26 to 0.04%, and decreased total canopy cover for all species from 8.64 to 2.80%. No plant species appear to act as increasers or invaders under grazing pressure by burros on the study area.