LANDSCAPE-SCALE FORAGING DECISIONS BY REINTRODUCED ARABIAN ORYX

We evaluated landscape-level movements of reintroduced Arabian oryx (O ryx lycorexia) in relation to rainfall for 8 years (1982-89). For the first 4 years (1982-85), captive-bred oryx released into habitat devoi d of conspecifics demonstrated a distinct shift in movement patterns a s foraging conditions deteriorated. Based on mean monthly estimates, d uring the first 2 months after rain, oryx used large areas (297-724 km (2)), exhibited low site fidelity (15-32% overlap between consecutive months), high range expansion (45-62%) new area used each month), and undertook more long distance journeys than expected (P < 0.01) From 2 to 3 months after rainfall, oryx reduced the amount of area used by 86 %, increased site fidelity by 72%, reduced range expansion by 29%, and gradually suspended long distance forays. We related this shift to th e low nutritive quality of the oryx's primary forage species (Stipagro stis spp.). Once Stipagrostis declined to extremely low levels of crud e protein, copper, and phosphorus, the oryx apparently suspended their nutritionally costly searching activities, and instead remained in ar eas where Stipagrostis was most palatable. In contrast, in years 6 thr ough 8 following their release, the oryx responded to rain with no app arent shift in foraging patterns. Instead, they exhibited less variabl e and reduced levels of range expansion (10-42%) and area use (180-211 km(2)). In addition, site fidelity was more consistent on a monthly b asis (45-65% overlap), and long distance movements were more random re gardless of the influence of rainfall on the nutritive value or palata bility of Stipagrostis. The changes in movement patterns over time wer e attributed to: (1) a reduction in the oryx's threshold of acceptance for low-quality Stipagrostis; (2) decreased consumption of Stipagrost is and a concomitant increase in browse consumption, and (3) greater k nowledge of the landscape. Captive-bred oryx released in years 7 and 8 into the existing reintroduced population reacted to changes in forag e nutritive quality caused by rain with a similar shift in foraging pa tterns as exhibited by the first releases during their first 4 years i n the desert. This result emphasizes the relative importance of learne d foraging behavior in explaining changes over time in the movement pa tterns of the oryx. Results of this study indicate that reintroduction s of social herbivores should be implemented in ways that enhance the transfer of knowledge from experienced to naive individuals.