Generally, when we have a "mouser", I rub a F/T mouse all over a rat pup and then place it in the BPs tub. Usually works on the first time. For older BPs that we occasionally get that are mousers, if the above trick does not work, I generally hold of food for a couple of weeks and let them get hungry and then put in a rat. I know that my technique may sound a bit harsh, but sometimes tough love is needed.