Here is an interesting article in Newsweek by Rabbi Marc Gelman that zoos aren't such a good thing.
From the article:
My grandpa, Leo Gellman, was a zookeeper at the Milwaukee zoo. My childhood was filled with happy days feeding giraffes and monkeys. I wanted to feed Sampson the gorilla and Tony and Cleo the hippopotamuses, but Grandpa Lepa never let me get close to them. He loved animals, but he also understood what it means to be wild. He would patiently explain to me that they did not want to be in their cages but that we put them there so that little boys like me could see up close what they look like, how they move and what sounds they make. Grandpa explained to me that this was a deal we humans made with the wild animals of the world. We capture and display some of them so that people would feel something for them and protect the wild animals that were not in cages. I asked grandpa if he thought the deal was fair. He thought and said, “It's a good deal for us, and not such a good deal for them.” I still think grandpa was right.