Zoo visitors affect sleep, displacement activities, and affiliative and aggressive behaviors in captive ebony langurs (Trachypithecus auratus)

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Previous studies have shown that the number, noise level, and activity level of zoo visitors can negatively influence the behavior of captive animals. This study combined these three factors into a single visitor impact score and assessed whether visitor impact predicted the frequency or occurrence of displacement activities, affiliative behaviors, and aggression in a group of six captive ebony langurs (Trachypithecus auratus). This study also examined whether the amount of time the ebony langurs spent sleeping each day was correlated to the mean visitor impact score for that day. We used negative binomial and binomial models to analyze data collected during 5-min focal follows. Higher visitor impact scores predicted greater expression of displacement activities, affiliative behaviors, and aggression, suggesting that zoo visitors were a source autonomic arousal for the langurs. Similarly, the langurs spent more time sleeping on days with higher mean visitor impact scores, which may indicate learned helplessness. This study suggests that zoo visitors may be a source of environmental stress for captive ebony langurs. Nevertheless, the positive relationship between high visitor impact score and the occurrence of affiliative behavior types may indicate that the langurs use certain activities to decrease visitor-induced stress.