Modern zoos provide enrichment programs to improve animal welfare, but significant variation exists between facilities and species in the quality of behavioral opportunities provided.
Animals evolved for vast territories and complex social environments often cannot express natural behavior in zoo settings regardless of enrichment quality. Polar bears that naturally range hundreds of miles show stereotypic pacing at rates of over 25% of observation time in even well-resourced facilities. Great apes in captivity show rates of abnormal behavior correlated with inadequate social group composition. The welfare-conservation trade-off inherent in zoo keeping requires honest assessment of whether individual animal welfare costs are justified by conservation benefits.