We used stable carbon isotopes from faeces to investigate the proportional contribution of C₃ and C₄ plant forms to the diet of the herbivores in Mkambati Nature Reserve, a grassland dominated ecosystem on the east coast of South Africa. Our results indicate that Equus burchellii, Damaliscus pygargus phillipsi, and Alcelaphus buselaphus utilize mainly C₄ grasses. Tragelaphus oryx, Potamochoerus larvatus, Tragelaphus scriptus and Antidorcas marsupialis utilized mainly C₃ plant forms but Redunca arundinum utilized an approximately equal amount of C₃ and C₄ plants. The results indicated similar trends compared to the more arid savanna systems (i.e. Kruger National Park in South Africa and several national parks in Kenya) with a few notable differences in some species (i.e. red hartebeest, southern reedbuck, eland, bushbuck and bushpig).