Animals in zoos are caged for life and deprived of the opportunity to develop and fulfill the full range of their interests and needs. They lose control over their lives and the environment they live in. Social animals are often forced to live in the misery of solitary confinement. Animals who would prefer to live alone are often forced into close contact with others.
If you know anyone who has a dog or a cat as a pet, ask them if the animals liked to be locked indoors and you will hear a definitive no as an answer, why can't we extend same courtesy to other animals. At least most breeds of cats and dogs are domesticated, while for the other wild animals being caged will prove to be even worse.
Animals suffer in zoos. In zoos, animals such as dolphins and sea lions are ridiculed in demeaning and embarrassing performances, animals can get extremely stressed by screaming visitors. They are subjected to camera flashes and the hordes of hundreds of people. The animals get depressed, psychologically disturbed, frustrated, they harm each other, become ill, go hungry, and are forced to endure extreme and unnatural temperatures. These animals cannot live as they would wish to live.