rat snap traps ARE working

I didn't want to use poisons,glue traps or drowning for rat control as they seemed the most cruel way of doing it and was told snap traps would do no good(most thought that anyhooo) but I have caught 3 young rats in 3 days(of course we have more,just not sure how many) unfortunately I had to finish the job on the first 2(I was there when the trap snapped) because my letting the chickens loose seems to be a cue for the rats to come out from under shed (chickens stomping on shed scares them????) It was not fun but I still think this is the best way to do it. and I have learned better how to position the trap for efficient snapping on subject. I keep the set PB baited trap covered with a weighted down milk crate and the second trap is in a wire dog kennel so only the rats will fit in. the kennel is also covered on 3 sides to encourage the rat to enter in the correct position and to keep pet paws out. plus its raining so I make the whole area more attractive (keep traps dry)by covering up cage with piece of plywood. there is STILL no evidence of rats in shed(droppings,chewed containers,urine?)