There was an amusing article in the paper today, about a plan to reintroduce Australian bush rats to a posh Sydney suburb. There's more native vegetation now than in the period immediately after European settlement when the land was cleared, so the bush rats might be able to make a comeback. Only in Mosman would people worry about having a better class of rat.
The ecologists even speculate that the bush rats might displace the introduced black rats, but that's where I beg to differ. The native animals might thrive in the bushland and it would be great if they did, but my money's on the black rats in the residential areas.