The place where I store my RV had mice before I started feeding them
d-Con. Since the mice cannot jump, the only way to get into the RV is up the tires. Placing a d-Con feeder at each of the 4 wheel postitions seems to have taken care of the population. They eat and then die of a stomach ache or something like that. You can tell when the problem has gone away when the pellets stop disappearing. :)
Another fairly humane method that I was going to try if the d-Con failed is the
RatZapper. In the Class B forum, several owners have written good reviews.