A 2015 study on the impact zoos have for endangered animals in the Journal of Applied Ecology concluded that rehabilitation programs, captive breeding and reintroduction systems fail markedly. This is not because their intentions or operations are poorly actioned, but because they simply do not construct self-sustaining populations which can reproduce with genetic diversity in the numbers necessary for success³. It is therefore argued that the most successful system for protecting and ensuring the futures of endangered animals are where the animals – or at least the parents of the animals – are taken from the wild and reintroduced after breeding⁴. This helps with the animals social and natural capacity to survive.