Zoos also claim that they are conserving endangered special in the hope of returning them to the wild in the future. Out of about 10,000 zoos that exist around the world, only about 500 register their animals with an international species database, and only about five or ten percent of these actually work with endangered species. Zoos have projects where they breed animals in zoos for the purpose of conservation. However, most animals do not need help in breeding they have been doing it for a long time without any help. Animals have been endangred because their natural surroundings have been destroyed by humans. It is true that zoos have had several success stories with zoo-bred animals. One was the golden lion tamarin, a species of monkey, which had almost become extinct because humans destroyed its natural habitat and too many were captured for pets and zoos. Over 100 tamarins were bred in zoos, Some were unable to live life in the wild-they were not even move some were not used to a natural diet. It is a riskey business to re-introduce zoo-bred animals to the wild, because if they have lost their instinct for survival and cannot adapt quickly enough, they will die.