Zoos stir up many emotions among advocates and opponents. The issues surrounding zoo life make it hard to characterize zoos and similar exhibitions of wild animals as a homogenous entity. Zoo animals hardly ever return to the wild because the reintroduction process never works, the animal transport process fails, and the animals are exposed to disease and chemicals because of the confinement. Animals come and go at zoos, but seldom return to the wild. Reintroduction programs rarely work because captive animals no longer possess the skills for survival, and because of these poor conditions, news stories critical of zoos frequently appear around the country. The animal transport process is far from stress less and painless. Many zoos have been closed due to these horrible conditions. .
The dangers within a zoo vary from the animals being exposed to disease and chemicals to their enclosures 100 times smaller then their home range. Jordi Casamitjana, an Independent Animal Welfare Consultant with particular experience of the captive wildlife industries, compared the average enclosure size of a random sample of fifty mammals in 103 UK zoos (25% of all UK zoos) to the home range of the species in the wild. This restriction, in addition to unnatural social groupings, different climate, inappropriate diets and lack of enrichment, leads to welfare problems for wild animals in zoos, including physical and psychological problems.
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By forcing many different animals to coexist and placing them in close immediacy to humans, zoos unavoidably become a breeding ground for disease. Scientists at Johns Hopkins in Baltimore, MD and the National Zoo in Washington, D.C. recently secluded and then discovered a lethal form of the herpes virus that has killed at least 10 elephants living in U.S. zoos. The researchers said the herpes virus attacks young Asian elephants who are bred in zoos and have close contact with African elephants, who act as carriers.