I only have one bp that has not switched to rats with 4 years of trying, but all the others took to it with no problems. What I would do is start with a rat crawler that is alive if possible and feed it to him at night. I have only had to try one other method then this. I actually fed one live adult mouse and while the bp was still fired up it took the rat right after with no problems. Like I said before it has been a pretty easy process for me except for the one large female that has utterly refused, but since we breed tons of mice its no problems just takes a bunch of mice per feeding. Good luck and keep us posted.