As predicted, based on the limitation of food quality for small body size ruminants, the Cape grysbok (Raphicerus melanotis) is a selective browser, with relatively few plant species eaten. The alien Australian acacia (Acacia cyclops) is, however, prominent in their diet at this study site. We suggest that the grysbok's use of this alien species and the lack of their population response to clearing of acacias shows that they are able to switch diets as resources change.