This is for all your greats posts that I have learned something from.

Go to home depot/lowes/etc. Buy a mousetrap.. don't be cheap. Make sure it is along side a wall and close to where you know it is or travels. Most will have instructions on how to place it. Any animal will do anything to free itself so it you want something it can't get out of. Bait it with something good.

P.S. It is probably a rat and has the bubonic plague. Rabies suck the black death blows.