My favorite way to fix them is fried. Cut them into pieces and drop them in a zip loc bag with 1 cup of seasoned flour, shake until evenly coated, fry for 7-9 minutes then into the steamer they go for another 10 minutes max. Don't over do it or all flavor will be lost. Meat will fall off the bone, old tough ones included.
Once in a while I'll simmer them in onion gravy. Start out same as above and while they steaming drain all but a couple table spoons of oil from the pan and mince an onion or two in and cook until almost done, sprinkle in enough left over flour to absorb the oil then stir in water until the desired consistency is reached, add rats and simmer on low heat for 5 or so minutes until gravy is done. Serve over rice.
Then there's barbequed rats, but only young tender one will do. Fixed this way the old ones can probably be used as a boot to repair a blown out skidder tire.
I also have recipes for squirrel stew and squirrel perlo.