Wild animals don't belong in captivity

It would be difficult to believe that a wild animal kept in captivity actually thrives.Some animals seem to fare better than other in captivity while others exhibit behavioural problems and live shortened life spans. It seems that the larger and more intelligent they are the less they cope with a captivity we give them but it's often thought that somehow they are better off for having been rescued. Orcas have demonstrated quite clearly they grow to be very unhappy animals in confinement after being taken from family pods as babies then reared in a man made pool. Highly intelligent they grow frustrated and show aggression and are miserable while they are made to perform for the benefit of human entertainment. Elephants also very intelligent can't get the opportunity to be elephants, to roam, to forage and interact with their own kind when they are kept in artificial enclosures. Many rescue animals are kept this way but is it really the best thing to do I wonder if the animals are stressed and unhappy. While zoos are important if they promote better protection and understanding for wild animals, the way these animals live their lives is a dubious substitute for a wild life.