We studied use of habitats and diets of mule deer (Odocoileus hemionus) and feral asses (Equus asinus) by comparing vegetation (i.e., normalized-difference-vegetation index, normalized-difference-vegetation-index rate), elevation, slope, and distances to water-catchments, roads, rivers and canals, and washes used by each species. Distribution was similar with respect to distances to roads, catchments, and rivers and canals in winter, normalized-difference-vegetation index and distance to catchments in spring, distance to rivers and canals in summer, and slope in autumn. Diets (from microhistological analysis of feces) revealed biologically significant overlap during the abundant-forage season (simplified Morisita index >0.60). Diets of mule deer had high proportions of browse (76–85%) in all seasons and low proportions of grasses (1–2%) and forbs (4–8%); whereas, diets of feral asses contained less browse (65–72%) and more grasses (12–16%) and forbs (13–20%).