The spatial distributions of 20 female and 15 male Arabian oryx Oryx leucoryx, reintroduced into the fenced Mahazat as-Sayd protected area (2,244 km2) in western Saudi Arabia between 1990 and 1994, were examined from their release until the end of 1999. Over this period we observed a westward shift in home range location of most male and female founder oryx to include the Rangers' Camp within core areas of activity, despite rain falling in patches throughout most of the reserve. Sporadic and unplanned availability of water had occurred at the Camp during several years. The pre-release enclosure was also located at the Camp, and high quality shading areas could be found underneath portacabins. Oryx that maintained independence of the Camp tended to be older individuals and those released in the first years (1990–1992). Concentration of oryx in the western part of the protected area and around the Camp could potentially reduce the effective carrying capacity of the reserve, change the social structure of the population, facilitate the transmission of disease, modify habitat in the form of a piosphere (a zone of attenuating animal impact away from a watering point) around the Camp, and reduce potential genetic flow within the reintroduced population. Whereas wild-born oryx were observed at the Camp, founders were disproportionately represented, suggesting that potential problems associated with dependence on the Camp may diminish as the total population increases and ages.