We always used small peices of fried chicken in the dirt hole sets and then sprayed some urine down the hole. If we got into too many possums and skunks, we would quit using bait and stayed strictly with urine and that pretty much eliminated the unwanted critters. I would make some new sets and clean up the traps that have already caught some of those critters. Be really careful with YOUR scent, even when checking the sets. In a weeks time you should at least be seeing foot prints in your screened dirt to show that they are visiting. If not, you may need to move your sets to more "foxy" areas.