I have a few mousers that I haven't been able to trick into eating rats yet. Like you, I have tried the mouse bedding trick to no avail. I would love to know why they do this but I just figure that I will feed them what they like. I still do try to slip a rat in there every other time I feed them though. Sadly I have had some rat eaters that have never had a mouse before switch to eating mice only now. I have faith that I will get them back on rats soon.