The Mary Valley Cattle Station, a ramshackle collection of buildings and trailers on the Cape York Peninsula about 100 miles inland from the Queensland coast, is home to one of Australia’s largest colonies of bats. The bats are little red flying foxes, a type of fruit bat, and there, in this remote sliver of the Outback, one can sometimes see five million of them, clustered upside down and on top of each other, hanging in the trees.