More interesting is how they got back, after the flood. How did they know, in general, to return to those areas where related forms occur as fossils? How did placental mammals know that only marsupial fossils are found in Australia, and that they shouldn't go there?
Specially adapted cave-dwelling organisms have a very strong tendency to be closely related to above-gound living ones in the same locality (comprising, say, different but clearly similar genera). At the same time those that are obligatory cave dwellers are seldom widely distributed, with each cave system having its own particular species and genera. IOW they are more closely affiliated with local terrestial organisms inhabiting very different environments then they are with those inhabiting nearly identical environments in other cave systems. How did they manage to sort themselves out so post flood?
In South America they are trees or shrubs and ants that are co-adapted in such detailed and specific ways that they are classed as single "ecological species," so called "ant-plants". How did those get all the way to S.A. from Ararat?
However medved will be here shortly to explain how the earth was orbiting Saturn at the time which ment there was far less gravity making it possible to all animals to fly to their present habitats