THE COSTS AND BENEFITS OF PREDATOR INSPECTION BEHAVIOR IN THOMSON GAZELLES

When Thomson's gazelles (Gazella thomsoni) detect stalking predators, such as cheetahs (Acinonyx jubatus) and lions (Panthera leo), they oft en approach and follow the predator for up to 72 min (average 14 min). Coursing predators are rarely approached. Gazelle groups were more li kely to approach cheetahs if the groups were larger, if the vegetation was low, or if the cheetahs came closer to the group. Immature gazell es were more likely to approach than adults, and a higher proportion o f group members participated in inspection behaviour in small groups t han in large ones. Gazelles approached closer in less risky situations : if they were in larger groups or if the vegetation was low. Inspecti on behaviour caused cheetahs to move further between rests and between hunting attempts. Approaching cheetahs was risky, particularly for yo unger gazelles (probability of being killed while inspecting a cheetah was 1 in 5000 approaches for adults and 1 in 417 approaches for half- grown/adolescent gazelles), and the risks were higher than monitoring cheetahs from a distance. The time costs of predator inspection were a lso considerable (less than 4.2% of daylight time budget), suggesting that the benefits must be substantial to offset these costs. The resul ts suggested that inspection behaviour was multifunctional, causing st alking predators to move out of the vicinity, enabling gazelles to mon itor the predators' movements, and providing an opportunity, particula rly for younger animals, to learn about predators. By approaching, gaz elles also inform predators that they have been detected and alert oth er gazelles to the predators' presence.