Some zoos and safari parks have supplied animals for experiments. London Zoo has experimental facilities on site, and zoo experiments have included the decapitation of conscious wallabies in research attempting to understand 'winter depression' and jet lag in humans. Not all zoo animals have been captive bred. All of the African elephants in UK zoos and most of the Asian have been imported from their country of origin. Wild animals are still captured and supplied to animal collections.
Zoos claim that they are vital to protect wild animals threatened with extinction.
About 6,000 species are either threatened or endangered. Only a handful of these are in captive breeding programmes but hardly any have been returned to the wild - about 20 have been returned to the wild with any degree of success. It is complicated and expensive, and there is little chance of captive-bred animals ever being able to adapt to the wild and survive. The only way to conserve wild animals is to protect them in their natural habitat. Less than 500 zoos register their animals on an international species database.