Visitor effects on anxiety in two captive groups of western lowland gorillas

There is growing interest in examining the effects that visitors have on the welfare of zoo primates. Most recently. the importance of evaluating the combined impacts of visitors and management practices on anxiety levels of these animals has been highlighted. Studies that take such an approach have the potential not only to highlight how visitors affect the welfare of zoo primates, but also how these impacts may be mediated by management interventions, such as enrichment. The aim of this study was to explore the potential impact of visitor numbers on behavioural indices of anxiety among western lowland gorillas in two UK zoos. Port Lympne and Chessington, and to determine whether feeding enrichment mediates any such visitor effects. During fifteen minute focal watches, visitor numbers were assessed and all occurrence data collected on two behavioural indices of anxiety: self-scratching and visual monitoring of visitors. Data collected at each site were divided according to whether they were taken during periods of feeding enrichment, or during periods when no such enrichment was being given. Analyses revealed no evidence for a visitor effect at Chessington, with durations of self-scratching and visual monitoring unrelated to visitor number, either during periods of enrichment or outside of such times. At Port Lympne, durations of both self-scratching and visual monitoring were positively associated with visitor number when no feeding enrichment was taking placed no such relationships were seen, however, during periods of feeding enrichment. Potential reasons for the difference between sites in the occurrence of visitor effects, and for the absence of visitor effects during feeding enrichment at Port Lympne are discussed. The results of this study highlight the importance of assessing visitor effects on the same species at multiple sites, and also suggest that such effects may be reduced by positive management approaches. (C) 2008 Elsevier B.V. All rights reserved.