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

Vigilance is just one of the many fitness-enhancing activities that animals do each day. However, as vigilance is used for both predator detection and obtaining social information, individuals must decide how to divide their time between these two vigilance types. Yet, it is unclear (1) how prey species living in the centre and edge of groups prioritize their use of these different vigilance types and (2) how this prioritization varies with...