I have mixed feelings about zoos. For most people, zoos may be the only place where they'll be able to see many species up close. Zoos gather a lot of knowledge about many of these animals, helping us appreciate them and perhaps understand them a bit better, and raising awareness of their plight. Unfortunately Zoos may also be the last holdout of an increasing number of species for whom natural habitat becomes increasingly scarce as our species grows and modifies the world, seldom if ever fully grasping the impact.
Despite valiant efforts to provide environments for the animals, there simply isn't enough space for them to exist in anything approaching their natural conditions, with populations sufficient for them to interact and perhaps to thrive. These animals have little to do. Those that are relatively intelligent probably suffer from terrible boredom.
While I applaud the efforts of those who work hard to make the zoos the best they can for the animals, and I appreciate the opportunity to visit such places and experience something of these animals, I am always left a bit saddened by the experience.