Short-Term Behavioural Responses of Impalas in Simulated Antipredator and Social Contexts

International audiencePrey animals often have to trade off foraging against vigilance. However, vigilance is costly and individuals areexpected to adjust their vigilance and its cost in relation to social cues and their predation risk. To test this, weconducted playback experiments in the field to study how lions’ (Panthera leo) roars and male impalas’ (Aepycerosmelampus) territorial vocalizations affected the vigilance and foraging behaviours as well as movements of femaleimpalas. Our results show that impalas adjusted their activities in different ways depending on the vocalizationsbroadcast. After lions’ roars were played, female impalas increased their vigilance activity (in particular increasingtheir high-cost vigilance – vigilance without chewing), decreased their bite rates and increased their movements,whereas male impalas’ vocalizations caused females to decrease their vigilance (decreasing their low-cost vigilance– vigilance while chewing) and increase their movements without affecting their bite rates. Therefore, it appears thatpredators’ vocalizations stimulate anti-predator behaviours such as vigilance and movement at the expense offoraging, whereas males’ vocalizations increase individuals’ displacements at the expense of vigilance. Overall, thisstudy shows that both predator and social cues have direct effects on the behaviour of gregarious prey and need tobe considered in future studies.