strangely enough, if kept properly in a good environment, animals can be happy and healthy in zoos

they have less stress, do not suffer predators, do not need to fight to keep their territory, do not die as they do in the wild from starvation and illness etc etc

essentially, as long as an animal has a good environment and has the correct diet, they will be more than happy. So criticism of zoos is often misplaced due to the critic empathising with the animals (I would hate to be locked up all my life etc).

Having said that, I prefer seeing animals in the wild, it is far more moving and dramatic