Why do Cattle Egrets forage with cattle? An analysis from an anti-predation perspective

Abstract

The risk-benefit trade-off theory is a fundamental concept in the study of animal behavior strategies and remains a prominent topic in animal ecology. Cattle Egrets (Bubulcus ibis) foraging alongside ungulates has garnered considerable attention. Previous research has highlighted the impact of ungulates on disturbing grassland insects, leading to increased foraging success for Cattle Egrets. However, the risk-benefit relationship from an anti-predator perspective remains underexplored. This study, conducted in Yang County, Shaanxi Province, China, focused on Cattle Egrets and compared the foraging efficiency and flight initiation distance (FID) when foraging alongside cattle (Bos spp.) versus foraging alone. Additionally, our study analyzed the impact of increasing cattle numbers on the FID to assess whether foraging with cattle enhances the perceived safety. We hypothesized that, with more cattle, Cattle Egrets would be less vigilant if they can gain vigilance advantages from cattle. The results indicated significantly higher foraging efficiency and lower FID for Cattle Egrets when foraging with cattle compared to foraging alone, suggests that the presence of cattle enables Cattle Egrets to better tolerate potential predation risks. However, more cattle did not significantly affect the FID, indicating that the perceived predation risk of Cattle Egrets did not reduce with more cattle. The lower FID of Cattle Egrets when foraging with cattle is more likely attributed to higher foraging efficiency rather than lower perceived predation risk in their risk-benefit trade-off. This study explores the mechanism of Cattle Egrets foraging with cattle from an anti-predation perspective, enhancing understanding of this phenomenon and contributing to the risk-benefit trade-off hypothesis.