poop is the biggest indicator- check edges of walls. Sometimes you can hear them moving around too, but poop is the biggest thing (behind things, along walls etc). I don't think a rat could easily fit in a cage-- mice..yes, rats- unlikely. Mice are way less aggressive than rats in general.
Don't worry too much-- IDK what your house set-up is, but generally people see signs if they have a mouse problem. When I was in West Bengal, we did have mice, lizards and an occasional toad because our house had these drains in the bathroom that went straight to the outside! BUT, the house wan't well-sealed. You could have probably reached outside through the drains from inside the house if you had small hands and long enough arms...you could see the light coming in through them in the bathroom.
We also had them in our basement in the US and in both cases, there were signs.
I SHOULD have them now, because I have gotten so busy with work that I sometimes don't sweep as much as I should in a given day, and still, no issues...KNOCK ON WOOD!
