Scott, rather than myself going into a lot of detail, there is quite bit of information on the net on mouse plagues in Australia.
I would only be repeating a small part of that information so I suggest you google or Bing, "Mouse Plagues" or "Mouse Plagues in Australia" and maybe a paper such as this one;
There are a number of photos around from the 1930's showing heaps of plague mice 4 and 5 feet high that were killed in the haystacks and grain stacks of that time.
An experiment set up a few years ago in a walled area of some 5 acres or thereabouts to confine mice just to watch and record mice in their natural habitat so that control systems could be developed came unstuck when all the local raptors like hawks, falcons, owls and etc very quickly figured out that if you sat in the surrounding trees for a few minutes you got a meal without having to bother about spending hours of flapping around trying to track a meal down as those mice weren't going anywhere inside of that walled compound.
The mice are quite territorial and don't roam far but one randy buck mouse fitted out with a radio transmitter to track him in another trial disappeared out of range of a half a kilometre for a couple of weeks before turning up again for R and R and a bit the worse for wear after, it was assumed, working the available district female mouse population over and dodging the harem owners.
And for those who have not yet seen this quite vividly real video of a very bad Australian mouse plague;