Zoos' role in conservation is divisive, but in Australia they could be critical in securing and even recovering threatened species.
Reintroduction programs can really help stop the decline of the southern ground hornbills.
When 100-year-old giant tortoise Lonesome George died in 2012, the world thought his species was lost forever. We went to the Galápagos Islands looking for 'extinct' tortoises – and we found them.
We're familiar with the idea of releasing almost-extinct species into new areas. By doing the same with common animals, we can help stop their population numbers getting into the same perilous state.