RE: Red foxes (Vulpes vulpes) were introduced to Australia for sport hunting in the 19th century, but ended up being responsible for the extinction of several native species, including the desert rat-kangaroo (Caloprymnus campestris)

[valth]

Hehe, that's true. But the thing is that the scenario you're imagining where the devils spread to most part of the island is more close to what nature was before humans intervened than what it is like now.