Animals remain threatened or are even driven to extinction whilst resources are drained away on expensive high-profile breeding projects with no serious hope of success. Worse still, animals are still being taken from the wild and sold to European zoos. There are also dangers attached to attempts to re-introduce animals to the wild. In the wild, species build an immunity to naturally occurring disease, but in a zoo they might not develop resistance to the most commonplace of ailments. Instead they may be challenged by viruses from an animal that they would never otherwise meet.
Viruses can mutate or be transferred across the globe to devastate wildlife.
In 1991, a lethal virus was identified in a zoo-bred tamarin just 3 days before the animal was to be released into an area where the virus was unknown. Zoos also claim to be educational. Animals which have become depressed or show unnatural stereotypic behaviour are only 'educational' in showing how man can drive an animal mad by keeping it in unnatural prison-like conditions. Wildlife films which show how animals behave naturally have done far more to promote respect for animals. Studying the natural behaviour of animals in captivity will rarely give accurate information.