I think of modern zoos as something far different from their sickening antecedents which displayed animals–even humans–in in awful conditions with no regard to the creatures. And they are far better–though that doesn’t mean the tension between our needs and the subject’s has disappeared. In his Aeon essay on the topic, Stephen Cave uses the death of a polar bear named Knut as a springboard. An excerpt:

“This is the paradox of the modern zoo: although they promise nature, they are necessarily unnatural. We visit them in search of the unpredictable, the vital — the sublime that cannot be found in the clockwork world we have built for ourselves. Yet they are made by humans, with all the artifice, technology and tools at our disposal. The lion and the zebra in the zoo will never meet in mortal struggle as they do daily on the Serengeti, but instead each is carefully contained, their needs met by plans, plumbing, and delivery vans.

Zoos have redefined their mission since the days of the menagerie, when people were content to show animals as spectacles and subjugates. Today, keeping wild animals behind bars demands justification beyond amazing or amusing us, and this is made on three grounds: research, education, and conservation. Each of these depends upon an idea of nature out there, beyond the city limits — a nature to be researched and understood; a nature about which we can and should be educated; and a nature that zoos want to help us conserve.”