Vigilance behaviour in African ungulates: The role of predation pressure

Impala Aepyceros melampus and wildebeest Connochaetes taurinus vigilance behaviour was concurrently monitored in two adjacent sites where re-introduction of large felids at one site gave rise to increased predation pressure. In the high predation site, rate of looking and proportion of time spent looking by both species was significantly greater than in the low predation site. Vigilance behaviour also showed an increase over time following felid reintroduction: there was no increase where re-introduced felids were absent. The relationship between vigilance and herd size, position in herd and presence of juveniles was compared for high and low predation conditions. Herd size and vigilance behaviour showed a negative correlation for both species regardless of predation conditions. Mothers with juveniles were always the most vigilant members of the herd and central animals were always the least watchful in both predation conditions. The interplay between vigilance behaviour and predation pressure, herd size, position in herd and presence of juveniles is discussed. It is suggested that predation pressure is the principal influence on vigilance behaviour in ungulates and even very low risk of predation appears to contribute to vigilance. Impalas and wildebeest spared the risk of predation devoted very little time to vigilance, suggesting it played a minor role in intraspecific interactions and finding food.