Modern zoos have transformed their approach to animal welfare, but chronic stress remains common in many captive animals.
The transformation from menagerie to conservation institution has improved zoo animal welfare significantly, but the fundamental challenge of keeping wide-ranging, cognitively complex animals in captivity remains. Chronic stress in zoo animals manifests as stereotypic behaviors, abnormal aggression, reproductive failure, and elevated stress hormones that compromise immune function. The best modern zoo exhibits attempt to provide cognitive challenge, social complexity, and physical space approaching species needs — but financial and spatial constraints mean most fall short.