A thriving cat colony where the RV is parked works well for me. Nothing like seeing a feral cat with a plump rat in its mouth.
I also have had decent luck with the ultrasonic pest repellers, but they need electricity to function.
Of course, there are sticky pads and other traps... the trick is to find the paths where the rats run, and lay traps there, rather than assume they will go for bait. One generation of rats may not bother with peanut butter, another will.
In all cases, I avoid poison... it can do a number on the local ecosystem, from the local barn cat to the owls to the vultures, maybe even the chickens that eat dying/dead rodents.