There's an interesting book:
The Life of Pi by Yann Martel. The author explains at length why wild animals are happier and better off in zoos than in the wild. E.g., they don't have to worry about predators, finding food, defending their homes, disease, etc., and like humans they like the cushy life. After reading his argument, I tend to think he's right.
The book's about a boy, who, travelling, along with a number of zoo animals, by ship from India to Canada, is involved in a shipwreck and finds himself adrift in the open Pacific in a lifeboat with a zeebra, a hyena, a tiger, et al. and what he does to survive.