Things that go bump in the night!!!

[beckoes]

Im pretty sure we have rats or something living under the house. We live in a queenslander and have nothing but storage/garage underneath. I hear them running around and fighting. I think we have had one for a while but now i know there are more. im listening to them crashing about just under the floor boards now!
I dont know what to do, i dont want to kill anything, i have enough trouble killing the ants that raid my kitchen! but dont want to be over run...how can i get rid of them in a nice way or without killing anything that isnt a rat!!!

updated question.....
OK....i saw them last night,went down when they were banging around and there one was...but im pretty sure its not a rat. For a start it was light grey. It had a long thinish pink tail and its face wasnt long and pointy like a rat, more squashed. and its ears were bigger and a little more stuck out. Still quite big, about small rat sized, Is it just that im used to seeing fancy rats in the pet shop or is it a different animal?? Do you think i could trap them and then have the 'dealt with' if they were rats or relocated if they were something else, somthing native.