Currently classed as extinct in the wild, it has been reintroduced and the wild population is currently thought to be around 10,000. These are all descended from deer that the 11th duke of Bedford had bred from a small number that he was given.
Currently, there are thought to be around 10,000 in the wilds of China, in a variety of reserves. Given a wild population of 10,000 in the wild, one might wonder why the are still classed as extinct in the wild. I suspect that at some point this classification will be reduced. After all, a population of 1000 is far higher than many other endangered species. Historically, the deer would have been prey for tigers and leopards, though whether there are any left in its former range is unknown (historically, China had significant populations of both tigers and leopards). It is quite possible that when it is reassessed, that it will move several steps up the classification list in one go.
They do breed willingly, with red deer, though it is unlikely that they would encounter each other in the wild.