Rodents are not man's best friend when it comes to model railroads. I had several that considered peeing on the rail of my nickel silver track was great fun. It's almost impossible to get the resulting corrosion off the rails, and mouse pee does not conduct electricity (unless it's wet - ugh!). I had to scrub the rails with baking soda, and that mostly cured the problem, but I still have conductivity problems with spots several years later.
