[throaway54]

>Not every animal views a zoo (or for that matter, a farm or a pet-owners house) as a prison. For a significant population of zoo animals, life in captivity is the only life they know. For the most part, they are as happy and content, as they are well-fed.

Not if they are given a space which is too small and not stimulating enough for them, then they just pace around for their whole lives.