Back when I did a lot of trapping, I would start saving table scraps from steak, fish, sometimes chicken....freeze it and then use for bait. I had a couple of urban locations I would prebait with these table scraps a week before season, then set traps just before dark opening day, come back at 5:00 in the morning and remove the fox. Closest to a sure thing I ever had on K9's in trapping.