Pretty simple, I reckon. Animals weren't meant to be kept in cages. I know what you're thinking. "But the animals look so happy." Come on, think about it. Do you think the zoo keepers would put the sick and abused animals out on full display? No way, man. They get locked up out of sight until they get better or die.
Depending on your point of view, zoos are either sanctuaries of education and entertainment or unnecessary prisons. While some people argue that zoos play an important role in conservation and research, others counter that they do more harm than good. Not sure where you stand? Let's have a look.
Wild animals are meant to be in the wild. Does a zoo look more like the wild, or a prison?
Elephants are among the most affected. Those housed in European zoos had life spans up to three times shorter than animals from an African wildlife park or working in the logging industry in Burma. Zoo elephants were more susceptible to both mental and physical ailments such as stress and obesity and had a higher infant mortality rate.
Tigers and lions have around 18,000 times less space in zoos than they would in the wild. Polar bears have one million times less space. A captive environment can never be as large and diverse as the wild. Wide roaming animals fare worst in zoo enclosures. Many social animals are kept alone and suffer from boredom. Social animals should be kept in groups, so their behavior is as natural as possible.
Even if we could build a zoo big enough for all the animals to live happily. Why the hell would we? What a waste of space and resource. Why not just put a wall around the arctic and call it a polar bear zoo?
The zoo is not the place to learn about animals. You'd learn way more watching a tv show about animals in their natural habitat.
Let's face it, it all comes down to the almighty dollar. If there is a cheaper way to maintain a zoo: smaller enclosures, cheaper food, killing unpopular animals off in winter..., it will be done.