Predation risk and herd position influence the proportional use of antipredator and social vigilance by impala

摘要: Vigilance is just one of the many fitness-enhancing activities that animals do each day. However, as vigilance used for both predator detection and obtaining social information, individuals must decide how to divide their time between these two types. Yet, it unclear (1) prey species living in centre edge groups prioritize use different types (2) this prioritization varies with increasing risk. To explore this, we focused on degree which impala, Aepyceros melampus, a herd-living antelope, adjusted antipredator (looking out from herd) at herd members) across three sites guilds densities. We found densities increased, size but impala did not adjust total they spent vigilant (antipredator plus vigilance). Thus, sacrifice other (e.g. foraging) increase vigilance. overall, within herds, displayed greater social) showed proportional compared central individuals. With numbers, maintained ultimately increased In contrast, reduced As suggested elsewhere, adjustment might have been related trying foraging efficiency cohesion benefits. may also monitored conspecifics detect threats, while short- less vulnerable head-down position) long-term daily allowing more activities) Ultimately, our results highlight position differences can influence overall levels