We had a couple rats this past fall. We laid out traps and they just ignored them.. peanut butter, meat, cheese... nothing worked. We were talking about it with a friend and he gave us his brother's perfect rat recipe. 1 tootsie roll and 1 starburst candy (we have used the orange and yellow) throw them in the microwave for 5-10 seconds. Just enough to get soft, and then mash them together into a brown ball of goo. Once you get it mixed well, heat it a bit again so that you can mold it to the trigger plate good and solid. Use as much or as little as you think is needed. I found 1 ball did 2 rat snap traps or 4 mouse sized. In 3 nights we cleared out all 4 rats. We cleared 5 mice from our basement the same way, and recently got another on the traps I left set up down there since fall. So the bait is still working!
Happy Hunting!!