This chapter describes the Colorado Plateau Ecoregion, which is a topographically and climatically diverse ecoregion, where most mule deer migrate seasonally. Browse species play a central role in mule deer diets through the winter, whereas forbs are essential during spring and summer. Parturition (mid-Jun) commonly occurs at higher elevations. Breeding typically occurs on winter range during late-November. Threats to mule deer habitat in this ecoregion are primarily associated with human encroachment and development of natural resource extraction infrastructure. Predation is a common source of mortality for mule deer in this ecoregion, although winter range browse availability and condition, and the subsequent impacts on nutrition can be a limiting factor for mule deer. Chronic wasting disease is a concern in the northern portions of this ecoregion. Risk of mortality of young of the year is typically highest during the days and weeks following birth, and during winter. Adult females typically breed for the first time at 18 months of age. Once fully mature, pregnancy rates are generally high and twinning is normal for most adult females. Mule deer populations across this ecoregion are not at risk, although social desires dictate that managers work towards achieving higher deer densities.