Solution if you have the stomach!
Rat Fishing & Killer Rat
Rat Fishing is much like real fishing, Rod/Bait and time to kill, just put bait on a hook and drop down one their holes and wait. You will have to kill them when you drag them out. (check out Rat Fishing on Youtube)
Killer Rat, rats are cannibals under the right circumstance, hunger!, if you trap two live rats put both in one cage and eventually one will kill the other, once this happens release the survivor and he will attack and kill other rats.
Killer Rats also will do their job when they have no food in the wild, clean food free environments will force larger rats to kill smaller ones to survive.