Desert ungulates live in adverse ecosystems that are particularly sensitive to degradation and global climate change. The morphological, physiological and behavioural adaptations of ungulates towards heat and drought stress are relatively well studied. However, only little work focused on their dietary and spatio-temporal strategies to overcome severe shortages of food resources in deserts. The aim of this thesis was to investigate the dietary and spatial flexibility of two ungulate species that live in the xeric Kunene Region of Namibia; grazing gemsbok (Oryx g. gazella) and browsing springbok (Antidorcas marsupialis). The diet of these two ungulates was investigated using stable isotopes analyses of animal and plant tissues. The results suggested that the gemsbok population was more flexible in its diet than previously suggested in the literature (Chapter II). Individual gemsbok had a mixed diet of grass and succulent plants (60%), shrubs and trees (30%) during the broad dry periods (including 10% of uncertainty), whereas they focused primarily on fresh sprouts of grasses during periods of rainfall. Interestingly, isotopic data also indicated that gemsbok relied also on Euphorbia damarana during dry periods, an endemic plant that is rich in toxic secondary plant compounds. In contrast, springbok maintained a predominantly browser diet, independent of dryness. Keywords: Antelopes, diet, spatial movement, desert, drought, population, individual.