Fencing conservation areas is ubiquitous in South Africa, however, the impact of these on predator ecology has not been tested. We used relationships between prey abundance and predator space use to create equations to predict the home range size of lions Panthera leo and leopards Panthera pardus. We then successfully tested these predictions using published data (Phinda, Makalali) and home range estimates from radio collared individuals reintroduced to Addo Elephant National Park. Spotted hyaena Crocuta crocuta ranges also seem food dependent. Lion home ranges in Addo (114 ± 5 km²) required 180 fixes to be accurately estimated, spotted hyaena ranges (91 ± 10 km²) required 200 fixes, and the solitary leopard had 295 fixes for a range of 38 km². There were no sexual differences in home range sizes of lions or hyaenas. The daily food intake rate of lions, measured during continuous follows, was 9.8 kg per female equivalent unit. Dominant male lions (14.3 km for 8.3 kg) traveled furthest but obtained the least amount of food per day compared to subordinate males (8.9 km for 16.0 kg) and females (5.8 km for 17.9 kg). Subordinate males traveled the fastest and during the day, to avoid competition and harassment from the dominant males. From an evolutionary viewpoint, the use of fences for conservation has not affected the natural behaviour of the predators as they still conform to predictions derived from unfenced reserves; that is, prey abundance is the key factor in determining space use of large predators. Keywords: Behavioural ecology, Competition avoidance, GPS/GSM radio collars, Home range, Food intake, Intra-specific competition, Optimal foraging, Reintroduction, Resource dispersion hypothesis.