The food supply of Arabian oryx (Oryx leucoryx) in the desert of Oman

The crude protein content, water content and in vitro digestibility of gras ses in the diet of the Arabian oryx Oryx leucoryx were investigated. In the main food species, Stipagrostis spp., levels of crude protein, water conte nt and digestibility were generally highest in the flower component while i n other species, leaf was the best quality food. Crude protein content, wat er content and digestibility were highly correlated and all declined expone ntially following rainfall. Levels remained comparatively high, even during extended drought, largely because fog and dew-fall enabled some plants to continue to produce green leaf material. The crude protein content of rumen material from oryx that died during drought was negatively correlated with time since rainfall. Estimates of dietary crude protein derived from the p rotein content of rumen material were comparable to those predicted for ava ilable grass forage. The results are discussed in the context of the food a nd water requirements of oryx. It is suggested that during drought some gra sses continue to be a source of adequate crude protein and water and of suf ficient digestibility but that levels are close to minimum maintenance requ irements. This and the decreasing biomass of available forage of sufficient quality lead to condition loss and death, particularly of the most vulnera ble animals. Crude protein may become limiting sooner than does water.