Siamangs (Hylobates syndactylus) and white-cheeked gibbons (Hylobates leucogenys) show few behavioral differences related to zoo attendance.

The effect of visitors on behavior and welfare of nonhuman animals in the zoo has been an active research topic during the last few decades. Although research has variously shown negative or positive impacts of zoo visitors on animals in captivity, previous primate research at Disney's Animal Kingdom suggests the importance of visual barriers in allowing animals to cope with large crowds. Examining this further, this study monitored the behavior of white-cheeked gibbons (Hylobates leucogenys) and siamangs (Hylobates syndactylus) in large, open exhibits. Behavioral data showed rates of social behavior and percentage of time engaged in solitary behavior did not differ between low and high visitor-attendance days. Both gibbons and siamangs spent more time in areas away from the public on high attendance days. Supporting previous findings, results imply visual barriers and ability to retreat from crowds may have provided these animals with choice and minimized potential negative visitor impact. Future research should focus on the relationship between attendance and actual crowds at exhibits; it should utilize multi-institutional methodologies to control for variance and look for individual and demographic differences between individuals.