try to use what they have been feeding on where you are setting the trap
i use cages but i only do domestic type jobs mainly when the chickens in the back garden have been had, if possible i use any dead chickens or parts of that are left but i have caught them on rabbit, pigeon, fish, cat/dog food, tuna fish(can of) i even had one that was digging up the garden where the customer had put blood,fish and bone fertilizer down and i caught him by using this at the back of the trap.
just keep changing baits and you will get him