Mice/rodent proofing a camper

I use mouse bait... 1 trap inside right in the middle of the floor. 1 trap behind each tire on the ground, and 1 on the tongue. The little boogers have to walk past one to get in. I'm hoping the temptation is too much. The instructions on the traps indicate that the bait causes internal bleeding - they get thirsty and exit the trailer before dying. The trap is designed so that the bait is protected within a box that dogs and cats cannot get into.

I have yet to find a mouse or any evidence in the trailer. I have found the bait nearly devoured in the outside traps!