I think it depends on how the animals are treated. I went to a zoo last week, and while some of the animals had a HUGE area, others had a very small area. The Leopards, Lions, Tigers, Bears, etc are all kept in cages and pace back and forth but the Zebras, Antelopes, and some other animals had acreage to run free and seemed happy. So, I guess it depends on how big of an area they have and also what kind of vet care they recieve, etc.