The visitor effect on zoo animals: implications and opportunities for zoo animal welfare

Sherwen and Hemsworth reviewed and reframed the visitor effect, drawing on human-animal interaction science from farm animals to argue that visitors are a salient and often underestimated feature of the captive environment. They synthesised evidence that visitors can be stressors, particularly through unpredictability, noise and proximity, and proposed that giving animals control, predictability and retreat options mitigates negative effects. The review emphasised rigorous experimental designs, such as manipulating visitor numbers or using barriers, to establish causal effects. It positioned visitor management as an active welfare tool rather than a fixed constraint. For cats sensitive to crowd pressure, it supports providing cover, height and the choice to withdraw from public view.